Abstract
Background
Strength and power represent two crucial physical qualities for the attainment of a high level of performance considering the frequency and the importance of explosive actions occurring during elite soccer match-play. Evaluation of strength and power is a multifaceted concept involving a vast array of tests and outcome variables. Nevertheless, a comprehensive and systematic search of strength and power assessment procedures in elite soccer has yet to be undertaken.
Objectives
The aims of this systematic review were to: (1) identify the tests and outcome variables used to assess strength and power of elite male soccer players; (2) provide normative values for the most common tests of strength and power across different playing levels; and (3) report the reliability values of these strength and power tests.
Methods
A systematic review of the academic databases MEDLINE, CINAHL, SPORTDiscus, Web of Science and OVID for studies published until August 2023 was conducted, following the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were eligible for inclusion if they: (1) were original research studies, published in a peer-reviewed journal, and written in English language; (2) had the primary aim to assess strength and/or power; (3) players were male and older than 17 years of age (i.e., mean age of the group); and (4) their playing level was defined as “professional”, “international” or “elite”.
Results
Regarding strength testing, 115 studies and 29 different tests were identified. The three most frequent strength tests were the knee extensor isokinetic strength test (58 studies), the knee flexor isokinetic strength test (55 studies) and the Nordic hamstring strength test (13 studies). In terms of power testing, 127 studies with 31 different tests were included. The three most frequent power tests were the countermovement jump with hands fixed on hips (99 studies), the squat jump (48 studies) and the vertical jump with arm swing (29 studies).
Conclusions
The wide range of different tests and outcome variables identified in this systematic review highlights the large diversity in the employed testing procedures. The establishment of a hybrid testing approach, combining standardised and widely accepted tests for establishing normative standards and enabling comparisons across different contexts, with flexible context-specific testing batteries, has the potential to maximise the impact of testing information for practitioners. In addition, the limited reporting of reliability data across studies highlights the need for practitioners to establish their own reliability measure within their specific contexts, informing the selection of certain tests and outcome variables.
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Avoid common mistakes on your manuscript.
Twenty-nine different strength tests and 31 different power tests were identified in elite soccer. |
Isokinetic knee extensor strength, isokinetic knee flexor strength and Nordic hamstring test represent the three most frequent strength tests. |
Countermovement jump, squat jump and vertical jump represent the three most frequent power tests. |
1 Introduction
Soccer is an intermittent sport in which high-to maximum-intensity bouts (i.e. jumping, passing, shooting, tackling, turning, sprinting and changing pace) are interspersed with low-intensity activity [1]. Despite the fact that the explosive actions executed during a soccer match account for only a small percentage of the total distance covered, their role is pivotal given many of them are deemed to be key determinants of success, both at an individual and team level [2]. Specifically, male individuals competing in the top European leagues cover distances of approximately 9–14 km, with approximately 900 m at high speed (> 19.8 km/h), and 300 m at sprinting speed (> 25.2 km/h) [3,4,5]. In addition, it is common for over 700 changes of direction to be performed in a single match, although some variation exists between playing positions [6]. Furthermore, the physical demands of elite soccer are becoming more demanding, placing increased demands on the players in terms of the quantity and quality of explosive actions [7, 8]. Consequently, possessing a well-developed set of physical attributes such as strength and power is essential for optimising performance and increasing the chances of a long and successful career at the elite level.
Strength and power are key components of an elite soccer player’s physical profile as they largely underpin the successful completion of many of the crucial actions that occur during the game, such as sprinting, jumping, turning, winning physical duels and scoring goals [9,10,11]. The effectiveness of strength and power interventions in improving the effective execution of various explosive actions such as acceleration, top speed, jumping ability and change of direction has been well documented in elite soccer [12,13,14,15]. In addition, previous research has revealed differences in strength and power levels of starting and non-starting, senior and youth, and professional and amateur soccer players [16,17,18]. Nevertheless, the significance of strength and power is not confined to the concept of performance enhancement. Multiple studies have shown that strength and power can help mitigate against injury [19,20,21,22]. Given the fact that elite soccer players are regularly exposed to a congested match and training schedule, maintaining a sufficient level of strength and power is likely to have an influential role in ensuring players are physically robust, thus also reducing the chance of non-contact injuries. Therefore, special consideration needs to be paid to optimising the strength and power outputs of soccer players, which can have a significant impact on both performance and availability to train and compete.
With this in mind, fitness testing constitutes an integral component of the physical development process, as it facilitates the objective assessment of individual and team fitness levels, the comparison of athlete’s performance to normative data, the identification of strengths and weaknesses, and the effectiveness of a training intervention [23, 24]. This can inform decision making on whether to continue or modify a training programme, helping to promote an individualised approach to training prescription [25]. A recently performed survey examining the practices of strength and conditioning coaches in professional soccer settings revealed the importance placed by practitioners on strength and power assessments [26]. However, despite the well-established role of using testing to determine the efficacy of a training programme [24, 27, 28], no large-scale scoping or systematic review has been conducted on the most appropriate and reliable strength and power protocols for soccer. This is somewhat surprising given the popularity of soccer and the vast quantity of assessment methods available to practitioners. Such assessment methods include, but are not limited to: isokinetic dynamometry, repetition maximum (RM) back squat, a variety of isometric strength testing protocols, use of barbell velocity for 1RM estimation, eccentric knee flexor strength via the Nordic hamstring exercise and a plethora of different jumping protocols [24, 29]. This lack of uniformity poses a significant challenge to practitioners, as inconsistent test selection and administration do not allow for the establishment of normative standards. While a standardised testing battery could be valuable for benchmarking purposes, its realisation can be difficult owing to practical constraints, such as time scarcity and equipment availability. As such, testing selection and implementation must be tailored to the specific needs and resources of each setting [30]. In addition, the testing selection process should be influenced by the reliability or repeatability of a test [31], as well as its sensitivity, which refers to the ability of a test to detect small but important changes in performance [32]. If a test cannot be reliably reproduced, practitioners cannot be confident that the test score is an accurate reflection of an athlete’s ability, and whether any subsequent performance changes are true. Hence, practitioners must have a good understanding of these core concepts.
Although previous work has shed light on strength and power testing in soccer [24, 29], a comprehensive and systematic search of strength and power testing in elite soccer is still missing. A systematic review of the literature could offer valuable insights to practitioners working in elite soccer on testing selection, by providing a clear and comprehensive picture of all the available options for strength and power assessments. Furthermore, a potential investigation of the reliability and sensitivity of these tests can support evidence-informed decisions on the strength and power assessments to be used. In addition, as one of the main responsibilities of soccer practitioners is to prepare physically robust athletes that can withstand the demands of the contemporary game, reporting and summarising normative data from studies performed in elite soccer settings could further facilitate the process of strength and power benchmarking. With this in mind, the aims of this systematic review were to: (1) identify the tests and outcome variables used to assess strength and power of elite male soccer players; (2) provide normative values for the most common tests of strength and power across different playing levels; and (3) report the reliability values of these strength and power tests.
2 Methods
2.1 Design and Search Strategy
A systematic review was conducted in accordance with the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) statement [33]. A search of the academic databases MEDLINE, CINAHL, SPORTDiscus, Web of Science and OVID was performed from the earliest record to August 2023 to identify English-language, peer-reviewed, original research studies that evaluated strength and/or power ability in elite male soccer players. Keywords employed for the identification of the studies are shown in Table 1. Search levels 1–5 were all linked by the Boolean operator ‘AND’, whereas search terms within each search level were joined with ‘OR’ or ‘NOT’. All search results were extracted and imported into a reference manager software (RefWorks, ProQuest LLC, Ann Arbor, MI, USA).
2.2 Study Selection
Following the removal of duplicates, two reviewers (NA and CB) independently screened all titles and abstracts against the inclusion and exclusion criteria of the review. Studies that did not meet the inclusion criteria were removed. Conflicts were resolved through discussion, or via a third reviewer (AT). The full text of the articles that were not excluded during this process were subsequently reviewed for eligibility. Supplementary to the systematic search, the reference lists of the included papers were reviewed for the identification of potentially eligible articles. With regard to the first objective of the review, studies were eligible for inclusion if they: (1) were original research studies, published in a peer-reviewed journal, and written in English language; (2) had the primary aim to assess strength and/or power; (3) players were male and older than 17 years of age (i.e. mean age of the group), in line with a previous systematic review on fitness testing (Altmann et al., 2019) and to minimise any potential influence of maturation; and (4) their playing level was defined as “professional”, “international” or “elite”. In contrast, studies were excluded from the review if they: (1) were narrative or systematic reviews and/or meta-analyses; (2) assessed physical characteristics as a result of other research aims (i.e. fatigue, recovery, nutrition and genome); (3) the sample consisted of different team sports; (4) players were semi-professional; and (5) players were younger than 17 years of age. For the second objective, studies were eligible if they reported the mean result of the tests under consideration and clearly distinguished between different groups (i.e. professional vs amateurs, men vs youth, male vs female). As such, only normative data for elite male soccer players older than 17 years old were recorded. For the third objective, studies were included if they provided information about reliability statistics (i.e. within-day and/or between-day).
2.3 Assessment of Methodological Quality
A modified version of the Downs and Black [34] assessment scale was used to evaluate the methodological quality of included articles. This checklist has been used previously in systematic reviews with similar research aims [35, 36] and can be adapted to the scope and the needs of the systematic review [37]. More specifically, 11 questions (1–4, 6, 7, 10, 11, 16, 18, 20) from the traditional version of the checklist were considered relevant with the specific aims of this systematic review, and therefore used to grade the methodological quality of the included studies (Table S1 of the Electronic Supplementary Material [ESM]). For the purposes of this review, question 4 was directed to whether the testing procedures in each study were clearly described. Each question was scored as either a ‘1’ (yes) or a ‘0’ (no or unable to determine). Scores were summed for each study with a total score of ‘11’ representing the highest possible score.
2.4 Data Extraction
Data were extracted and documented using a Microsoft Excel 365 spreadsheet (Microsoft Corporation, Redmond, WA, USA). Extracted data from each study included research design, publication details (authors and year of publication), sample information (number of participants, age of the sample, playing level), tests performed to evaluate strength and/or power ability, outcome measures derived from each test, as well as normative values for each test including reliability values (i.e. intraclass correlation coefficient [ICC], coefficient of variation [CV], standard error of measurement [SEM], minimal detectable change [MDC], Pearson’s r and Cronbach’s alpha [α]), where available. Playing level was classified into two distinct categories: (a) senior professionals (i.e. players that were regular members of the first team of a professional soccer club and/or a national team’s senior squad) and (b) elite youth (i.e. players over 17 years of age who were members of the youth department of a professional soccer club, yet not regular members of the first team, were members of a junior national team squad or defined as “elite” by the authors of the study). This distinction was made to account for physiological and training age differences, which is crucial for contextualisation of normative data and more accurate benchmarking. If more than one group of players were investigated in a study, only the groups with a mean age of 17 years or older were considered. To fulfil the purpose of reporting normative values, the mean of each group (i.e. senior professionals vs elite youth) was recorded. When a study consisted of multiple groups of the same playing level, the average of the mean and the pooled standard deviation were recorded. In intervention studies, the baseline values were recorded to eliminate any intervention bias. When a repeated-measures with no intervention study design was implemented (e.g. during seasonal variation studies), the most recent testing point was recorded (except when the most recent point was after a congested fixture period).
3 Results
3.1 Identification and Selection of Articles
The selection process flowchart is presented in Fig. 1. The initial search of databases identified 4217 articles. After removing the duplicates (1468 articles), the titles and the abstracts of 2749 articles were screened. This resulted in the selection of 224 articles to be assessed for eligibility through full-text review. Furthermore, 13 studies were identified through reference lists for full-text eligibility assessment. Following full-text screening, 194 were included for the aim of identifying the tests and outcome variables used to assess strength and power in elite male soccer. Additionally, 139 of these were included for the purpose of reporting normative values for the most common strength and power tests.
Flow of selection process of eligible studies for a qualitative and quantitative synthesis
3.2 Evaluation of Methodological Quality
Assessment of quality scores can be found in Table S2 of the ESM, with an observed range from 4 to 10 for the 11 items assessed.
3.3 Characteristics of Included Studies
Table S3 of the ESM provides a summary of characteristics of the studies included in this systematic review. The range of sample size was 10–939, with a median of 29 participants. A total of 120 studies included senior professionals as participants, 56 included elite youth, while 18 studies involved a group of both. The age range of the samples involved in the studies was 17.0 to 28.3 years, with a median age of 20.7 years. From a study design standpoint, 100 (52%) studies used a cross-sectional design, 44 (22.9%) were intervention studies, 43 (22.4%) used a repeated-measures design, 5 (2.0%) were reliability studies and 2 (1%) were validity studies. The studies took place in 39 different countries, with Brazil, Spain, Qatar, England and Portugal being the countries with most occurrences.
3.4 Tests and Outcome Variables Used to Assess Strength
Evaluation of strength was performed in 115 studies (59.2%) [Table 2]. A total 29 different tests were used to assess strength, further illustrating the wide range of assessment methods for the evaluation of this physical characteristic. Four different types of strength were evaluated (i.e. isokinetic, isometric, dynamic and eccentric). Isokinetic strength was the most frequently evaluated, being present in 62 studies (54.9%), followed by isometric strength in 29 studies (25.7%), dynamic strength (i.e. the ability to produce force during dynamic movements that include both the eccentric and concentric part, such as squat or bench press) in 27 studies (23.9%), and eccentric strength in 19 studies (15.9%). Isokinetic strength was evaluated by eight different tests, isometric strength by 11 different tests, dynamic strength by seven different tests and eccentric strength by three different tests. The three most frequently occurring tests were: (1) knee extensor isokinetic strength (58 studies); (2) knee flexor isokinetic strength (55 studies); and (3) knee flexor eccentric strength (14 references). It is noteworthy that the hip adductor strength test and the half-back squat test were also frequently employed (12 studies each). Of note, the total number of studies that assessed eccentric hamstring strength with the Nordic hamstring exercise, as well as those that assessed isometric and eccentric strength for the hip adductors and abductors, were all performed during the last decade. Isokinetic dynamometry was the predominant measurement method in the overall number of studies that assessed knee extensor and flexor isokinetic strength. In contrast, Nordic hamstring exercise was the primary measurement method to assess knee flexor eccentric strength (13 studies). For knee isokinetic strength, peak concentric torque (48 studies), conventional strength hamstrings/quadriceps ratio (28 studies) and relative peak concentric torque (17 studies) were the main outcome variables. In terms of knee flexor isokinetic strength, the three main outcome variables were peak concentric torque (46 studies), peak eccentric torque (28 studies) and relative peak concentric torque (16 studies). Last, peak force (13 studies) was the main outcome variable in the assessment of eccentric knee flexor strength via the Nordic hamstring exercise.
3.5 Tests and Outcome Variables used to Assess Power
Evaluation of power was performed in 127 studies (65.4%) [Table 3]. Thirty-one different tests were used to assess power in elite soccer players, employing primarily various types of jumps (24 different in total). The countermovement jump (CMJ) with hands fixed on hips (99 studies), squat jump (SJ) (48 studies) and vertical jump with the use of an arm swing (VJ) [29 studies] were the most frequently utilised. Among these, jump height was by far the most common outcome variable reported in 95 studies in the CMJ, 47 studies in the SJ and 27 studies in the VJ. However, it is important to note that the calculation of jump height was based on different methods (e.g. impulse-momentum method, flight time method) owing to the different equipment used. Furthermore, two additional commonly reported outcome variables in CMJ were relative peak power (W/kg) [nine studies] and peak power (W) [five studies]. Among unilateral tests, the single-leg CMJ test (SLCMJ) was the most frequently implemented, featuring in 12 studies. It is noteworthy that all of those studies were performed during the last decade. Finally, the drop jump test (used to assess reactive strength ability) [38] was reported in eight studies.
3.6 Reliability Data
Reliability statistics reported for the strength and power tests can be found in Tables S4 and S5 of the ESM, respectively. For strength tests, reliability statistics were reported in 15 studies (13%). Intra-day reliability was the most common reliability type reported in nine studies, while inter-day reliability was determined in five studies. One study also assessed inter-season reliability. In terms of specific reliability metrics, the reported metrics were ICC (13 studies), SEM (seven studies), CV (four studies), MDC (two studies) and Cronbach’s alpha (one study). Knee extensor isokinetic strength (four studies), knee flexor isokinetic strength (four studies), half-back squat (four studies) and Nordic hamstring testing (three studies) were the tests for which reliability values were most reported. Intra-day reliability values (i.e. ICC, CV, SEM) were higher compared to inter-day and inter-season reliability for all these tests. In terms of power tests, reliability values were reported in 34 studies (27%). Intra-day reliability was the most reported type with 30 studies, whereas a considerably lower number of studies reported values for inter-day (three studies) and inter-season (one study) reliability. The ICC (29 studies) and CV (22 studies) were the most reported metrics, followed by SEM (four studies), Cronbach’s alpha (three studies), Pearson’s r (two studies) and MDC (one study). Countermovement jump (27 studies), SJ (15 studies) and SLCMJ (five studies) represented the tests with the highest availability of reliability values. Specifically, intra-day reliability for CMJ height ranged from 0.80 to 0.99 (ICC) and from 1.8 to 15% (CV), with a SEM that ranged from 0.6 to 1.4 cm. In contrast, the only study that investigated the inter-day reliability in CMJ height reported values of 0.83 (ICC) and 4.3% (CV), with a SEM of 1.7 cm. With respect to SJ height, intra-day reliability ranged from 0.75 to 0.99 (ICC) and from 2.12 to 13.2% (CV), with a SEM of 0.6 cm. Similar to CMJ, only one study examined inter-day reliability, reporting an ICC value of 0.89, a CV of 3.7% and a SEM of 1.4 cm. Last, only intra-day reliability was reported for SLCMJ height. In particular, ICC exhibited a range from 0.74 to 0.99, a CV from 1.98 to 9.63% and a SEM from 0.3 to 1 cm.
3.7 Normative Values for Strength in Elite Male Soccer Players
3.7.1 Knee Extensor Isokinetic Strength via Isokinetic Dynamometry
Table 4 provides the normative values for the knee extensor isokinetic strength test. A range of different angular velocities was observed in the studies that reported normative values in the knee extensor isokinetic strength testing. However, the majority of the studies that reported normative values were conducted at 60°/s. In senior professionals, the mean values ranged from 212.9 to 364 Nm in peak concentric torque (32 studies), from 2.45 to 3.62 Nm/kg in relative peak concentric torque (15 studies) and from 54.0 to 65.5% for the conventional strength hamstrings-to-quadriceps ratio (17 studies). In elite youth, the mean values ranged from 208 to 331 in peak concentric torque (six studies). In terms of relative peak concentric torque, only one study reported normative values, with a value of 3.14 Nm/kg. Finally, the mean values of conventional strength hamstrings-to-quadriceps ratio ranged from 50 to 60.5 in elite youth soccer players (three studies).
3.7.2 Knee Flexor Isokinetic Strength via Isokinetic Dynamometry
Normative values reported for the knee flexor isokinetic strength test can be found in Table 5. As with knee extensor isokinetic strength testing, a variety of different velocities were used in the studies that reported normative values for knee flexor isokinetic strength test. Angular velocity of 60°/s had the greatest number of available normative data. For senior professionals at 60°/s, the mean values for peak concentric torque ranged from 113.2 to 190.5 Nm (30 studies), from 153 to 213.4 Nm for peak eccentric torque (15 studies) and from 1.2 to 2.1 Nm/kg for relative peak concentric torque (11 studies). Conversely, elite youth players had average peak concentric torque values that ranged from 114 to 187.4 Nm (four studies). Only two studies reported a normative value in elite youth for eccentric peak torque (range 149–177.1 Nm). No study reported relative peak concentric torque values for elite youth soccer players.
3.7.3 Knee Flexor Eccentric Strength via Nordic Hamstring Exercise
Results of the peak force (N) attained by elite soccer players can be found in Table 6. As can be observed, different equipment has been used to assess eccentric knee flexor strength. More specifically, the range of the average values in senior professionals was from 277.5 to 403.7 N (seven studies). Only two studies reported values for peak force in elite youth soccer players. The different devices employed yielded extremely different values, with one reporting a value of 338.2 N and the other 636.5 N.
3.8 Normative Values for Power in Elite Male Soccer Players
Normative values for the CMJ, SJ, and VJ test are presented in Tables 7, 8 and 9, respectively. For CMJ, the average values of jump height observed in senior professional soccer players ranged from 33.6 to 57.2 cm across 54 studies, while the mean values ranged from 34.8 to 58.6 cm across 33 studies in elite youth soccer players. In terms of relative peak power during CMJ, the average values in senior professional soccer players ranged from 26.3 to 54.5 W/kg across four studies. However, only one study reported the relative peak power value in elite youth, which was 55.1 W/kg. In addition, the average peak power values in senior professionals ranged from 3474 to 5029 W (range 3474–5029) [four studies], while the only study that reported a value in elite youth yielded a value of 3778 W. For SJ, the average jump height in senior players ranged from 29.8 to 44.1 cm (23 studies), whereas it ranged from 34.3 to 52.8 cm in youth (16 studies). Last, the average VJ jump height values in senior players ranged from 41.1 to 56.4 cm across 13 studies, while the mean values in elite youth ranged from 41.6 to 65 cm across 13 studies.
4 Discussion
The aims of this systematic review were to: (1) identify the tests and outcome variables used to evaluate strength and power in elite male soccer players; (2) provide normative values on the most common strength and power tests; and (3) report the reliability values of strength and power tests used in elite soccer. In summary, the large volume of studies included in this review (194 studies) is indicative of the high level of interest in strength and power assessment in soccer within the scientific community. A wide variety of tests were employed to assess strength and power, which was to be expected given the various time and financial constraints, as well as the different approaches to training and testing in soccer. A considerable amount of variability was also evident in the methods used to calculate the outcome variables of a test, as well as in the terminology used to describe the test. For instance, two distinct methods were identified in the calculation of the jump height (take-off velocity and flight-time method), while the terms “back squat” and “half-back squat” were used sometimes interchangeably. A total of 29 different tests were identified for strength assessment, of which the isokinetic strength test for knee extensors, the isokinetic strength test for knee flexors and the eccentric strength test for knee flexors were the most commonly used. However, 31 different tests were utilised to assess power, with CMJ, SJ and VJ being the most frequently employed. However, it is noteworthy that the majority of the studies included in this review failed to report reliability values, concealing valuable information that could assist in determining test accuracy and consistency.
4.1 Testing Methods and Outcome Variables
As strength and power can support both performance enhancement [2, 9, 18] and injury risk minimisation [19,20,21], a valid and reliable assessment of strength and power ability can form the basis for effective prescription of training interventions. A plethora of strength and power tests were identified in our systematic review, reflecting a high level of interest in researching these attributes. However, this large disparity highlights the inherent complexities in the assessment of strength and power, as well as the lack of consensus on the optimal testing protocols for strength and power profiling in elite soccer players. This variation can be attributed to several factors, such as equipment availability and facilities, time constraints, safety and a competitive schedule among others [24]. Finally, cultural and philosophical differences may also have contributed to the wide range of different tests observed, as the included articles originated from 39 different countries.
4.1.1 Strength Assessment
Based on the results of this systematic review, isokinetic strength assessment of the knee extensor and flexor muscles represent the most popular testing methods to assess strength (58 and 55 studies, respectively). The large number of studies that have evaluated the strength of the knee extensors and flexors highlights the importance of these muscle groups in the execution of fundamental soccer-specific actions as well as in the prevention of common soccer injuries. In particular, knee extensors are involved in many soccer actions such as acceleration, deceleration, jumping and kicking, while knee flexors are highly recruited during running at higher velocities and provide additional support to the stabilisation of the knee joint during landing, deceleration and cutting actions [39]. In addition, the anterior cruciate ligament and the hamstring muscle group represent two of the most affected areas in soccer injuries [40, 41], which further highlights the necessity to assess knee extensor muscle function in soccer. The combination of the two measurements can be used for the calculation of the conventional strength ratio, enabling the determination of strength imbalances between knee extensor and knee flexor muscles. The conventional strength ratio is typically calculated by dividing the concentric peak torque of knee flexors by that of knee extensors [42, 43]. Its use is further supported by the findings of this systematic review, as it represents the second most frequent outcome variable in the isokinetic assessment of knee strength. It has been suggested that greater strength imbalances are associated with an increased risk of injury in the anterior cruciate ligament and hamstring muscle groups, although the overall research findings are inconsistent [20, 42, 44]. The assessment of peak concentric torque during knee flexor isokinetic strength and, subsequently, the conventional strength ratio, may fail to consider the main mechanism of hamstring strain injuries, where an eccentric muscle action occurs. This is further linked with increased demands of high-speed running (> 19.8 km/h) in modern soccer, where the hamstring muscles are subjected to additional eccentric loading. This appears to be the reason why the assessment of peak eccentric torque is another variable of interest (i.e. the second most investigated) in relation to the isokinetic strength of the knee flexors. Furthermore, peak eccentric torque is used for the calculation of the functional ratio, where the eccentric knee flexors torque is evaluated in relation to the concentric knee extensors torque. However, obtaining the functional ratio can significantly extend the duration of an already time-demanding test. Indeed, a recent systematic review [44] demonstrated no difference in association with anterior cruciate ligament and hamstring injuries between the conventional and functional ratios. Although isokinetic testing represents a valid and reliable method of assessing muscle strength at both slow and high contraction velocities, it is not without issues. Isokinetic testing necessitates the use of isokinetic dynamometers, which are costly, lack portability and demand a significant amount of time to complete their various testing protocols. Consequently, clubs with limited resources may not have access to this equipment. This has led to the search for alternative and more practical solutions, and as such, the eccentric knee flexor strength test via the use of the Nordic hamstring exercise has emerged [45]. Nordic hamstring testing enables the functional assessment of eccentric hamstring strength — a critical factor given the high prevalence of hamstrings injuries in soccer as well as the constantly increased demands of the modern game in the amount of high-speed running performed. Nordic hamstring testing is gaining popularity and currently represents the third most common method to assess strength in elite soccer based on the results of our systematic review. Its simplicity of use, the growing availability of Nordic measurement devices in elite soccer environments (e.g. Nordbord), and the ability to assess large groups of athletes in a time-efficient manner may have contributed to its rise. Furthermore, the Nordic hamstring exercise is a staple exercise in many strength and conditioning programmes in elite soccer [26, 46], and therefore no additional time for familiarisation is typically required. Finally, its well-established effectiveness in reducing the incidence of hamstring injuries [47] further validates the increased interest in assessing the amount of force produced in this exercise.
The review of the literature revealed a growing interest in the assessment of isometric and eccentric hip adductors and abductors strength over the last decade in elite soccer players. The rise in their popularity may be attributed to several factors. In addition to hamstring injuries, hip and groin injuries are also common in professional soccer, and result in long absences from training and matches [48]. The assessment of hip muscle strength, especially in the hip adductor and abductor muscle groups, plays a critical role in the clinical evaluation of groin-related issues. In fact, lower hip adduction isometric and eccentric strength values, as well as lower isometric hip adduction/abduction ratios, have been reported in athletes with groin pain [49,50,51]. Furthermore, hip adductors and abductors have an important function as frontal plane stabilisers, as they facilitate the prevention of excessive knee valgus during landing and cutting tasks [52]. These muscles have a significant contribution to the effective execution of COD tasks, potentially by assisting in the generation of propulsion in the lateral plane [53]. In addition, the increased availability of specialised equipment (e.g. ForceFrame, GroinBar, Kangatech KT360) in the field has led to an easier assessment of these muscles. However, the available literature suggests a lack of standardised protocols in isometric adductors and abductors strength testing. Different joint angles (hip: 0–60°, knee: 0–90°), duration of force application (3 vs 5 s), measurement devices (hand-held dynamometers, ForceFrame, GroinBar), limb engagement (unilateral vs bilateral) and outcome variables (e.g. peak force vs peak torque) have been identified in the examined literature. In view of these inconsistencies, standardisation of the overall process of assessing isometric hip adductor and abductor strength seems to be necessary.
While the aforementioned strength tests offer valuable insights into the function of specific muscle groups, they fail to provide an indicator of overall system strength. In this regard, the squat test provides a more holistic assessment of lower-body strength. The investigated literature revealed distinct squat testing methods such as the half-back squat (11 studies), back squat (eight studies) and isoinertial loading squat (three studies). However, when delving deeper into the testing protocols, a lack of clear and consistent nomenclature is evident, especially when differentiating between the half-back squat and the back squat. More specifically, in the studies that reported the “back squat” as the selected testing method, the depth of the squat varied (i.e. 90° vs thighs below parallel vs no information provided on the depth of the movement). Different squat depth has been shown to result in varying levels of muscle activation in the lower limb muscles, with greater depths leading to an increased activation of quadriceps, hamstrings and glutes muscles [54, 55]. Furthermore, individuals are able to lift heavier loads when the range of motion is shorter [56]. This can lead to inconsistent testing results and an inability to perform reliable comparisons. In addition, this discrepancy can have significant implications for the findings of this review by affecting the ranking in test frequency. In fact, better defined and standardised protocols could place either the “half-back” squat or the back squat among the three most popular testing methods in elite soccer. Overall, further standardisation of the squat test is necessary, taking into account the various 1RM calculation methods (direct assessment of 1RM vs estimation of 1RM [i.e. 6RM] vs assessment of barbell velocity using linear position transducers) and setups (barbell vs Smith machine vs Keiser) observed in our systematic review.
Finally, a lack of emphasis on upper body strength and multi-joint isometrics assessment seems to exist in elite soccer. The limited number of studies evaluating upper body strength, using exclusively the bench press test, may be possibly attributed to the specific demands of soccer, where the involvement of the upper body is minimal compared with the lower body. In contrast, similar previous work in rugby and basketball reported that the bench press test is one of the key tests in the assessment of strength [35, 36]. Isometric testing can serve as a quicker and less exhaustive alternative to dynamic testing, and both the isometric midthigh pull (IMTP) and isometric squat have been shown to be reliable options [57]. A recent survey investigating the fitness testing practices of elite male soccer practitioners identified the IMTP as the most commonly used test to assess strength [58]. Nevertheless, this systematic review identified only a single study utilising the IMTP [59], illustrating a discrepancy between research and practice. The specialised equipment required (i.e. force plates) to administer the IMTP may have rendered this test less viable in smaller clubs, accounting for the lower prevalence of the IMTP in this systematic review. In addition, isometric tests have the potential to be used in conjunction with other strength and power assessments to provide a more comprehensive picture of an athlete’s strength and power capabilities, as well as informing the training prescription; for example, with the CMJ for the assessment of a Dynamic Strength Index [60]. However, this systematic review failed to identify any studies in elite male soccer using a Dynamic Strength Index. Furthermore, the IMTP offers the ability to record multiple variables such as peak force, force at specific timepoints, rate of force development and impulse, as well as enable the identification of interlimb asymmetries. Therefore, more nuanced insights on force production can be provided. However, caution should be exercised in the use of time-dependent metrics such as rate of force development and impulse, as it has been demonstrated that their reliability is lower compared with non-time-dependent metrics, such as peak force [57, 61].
4.1.2 Power Assessment
Jump tests represent the main method for assessing power in elite soccer, with the CMJ, SJ and VJ being the most popular protocols. Jump height, measured in centimetres, was the primary outcome variable in these tests and the CMJ was by far the most commonly employed method for assessing power in elite soccer, having been featured in 99 studies. The CMJ is an easy to administer and time-efficient test that requires minimal familiarisation. Furthermore, it provides valuable insights into an athlete’s ability to utilise the stretch–shortening cycle. As hands are typically fixed on the hips during the execution of the test, this elimination of arm swing adds further standardisation to the test in assessing lower body power. A range of different equipment types, including force plates, photoelectric systems and jump mats has been employed in CMJ testing in the examined literature [62,63,64,65,66]; however, force plates are considered the gold-standard equipment for measuring vertical jump height [67]. In terms of calculating jump height, take-off velocity and the flight-time methods constitute the two primary methods [68]. Overall, practitioners are encouraged to use the take-off velocity method with the use of force plates [69], which are often inaccessible in the applied settings. As a result, flight time represents the most frequently used method in the calculation of jump height. However, this approach is not without its limitations. In particular, the flight-time method requires an individual to maintain the same position at take-off and landing, yet the landing position is different owing to the preparation with the ground contact mechanisms (i.e. ankle dorsiflexion and hip and knee flexion) [69]. This leads to an overestimation of the jump height. As a result, jump scores obtained using the flight-time method should not be compared with those obtained using the take-off velocity method, unless a correction equation is implemented [70]. Recently, there has been a call in the field to move beyond jump height and delve deeper into more nuanced metrics, in order to assess and report the movement strategy of the jump [71]. In this way, a more comprehensive understanding of the specific factors underlying a jump can be achieved, thereby leading to more targeted and individualised training interventions. Our literature search identified 12 additional variables, with peak power, both in absolute and relative terms, being the most frequently reported. However, similar to jump height, peak power is classified as an outcome variable that does not reveal the underlying kinetics and kinematics of the jump. Interestingly, the vast of majority of these metrics have been reported in studies conducted within the last 10 years, possibly indicating the increased availability of force plates, as well as a shift towards a more holistic assessment of jumping ability. However, given the high degree of variability found within some strategy metrics compared to jump height [72, 73], careful consideration is warranted in the selection of these.
Power is a multi-faceted concept, and as such, a single test is unlikely to provide a comprehensive assessment of power ability. This is further supported by the different types of jumps identified in this literature review. One such example is the SJ, which theoretically evaluates an athlete’s explosive ability in the absence of a stretch–shortening cycle, as no countermovement is allowed. Based on our systematic review, there is a high prevalence of SJ testing in elite soccer, with 48 studies utilising this test to assess power. The different insights provided compared to CMJ may contribute to a more comprehensive profile of power ability. Nevertheless, strict compliance with the SJ protocol (i.e. isometric hold of 2–3 s prior to the jump) is necessary, as a small-amplitude counter-movement has been shown to affect the jump height achieved [74]. In particular, the authors found that 55% of the SJ trials in their study consisted of a small-amplitude counter-movement when a gross observation was used. However, the occurrence of a small-amplitude counter-movement was increased though to 89% when the trials were analysed using force plates and to 99% when using linear position transducers. This can have significant implications in practical settings, where access to specialised equipment and resources to analyse each jump are limited. In light of these considerations, practitioners should critically evaluate the value of the information provided by the SJ. In addition, a number of studies performed the assessment of SJ under loaded conditions, which is commonly referred to as the jump squat test, using linear position transducers. In this way, an individual’s force–velocity profile and theoretical optimum power zone can be determined [75], subsequently informing targeted training interventions. Last, the VJ is another test commonly performed in elite soccer, featuring in 29 studies in this systematic review. The VJ has many similarities to the CMJ, except that an arm swing is allowed. This inclusion of the arms introduces a coordinative element to the movement and can facilitate the attainment of a higher jump height owing to the increased work output of the lower limbs that results from the use of the arm swing [76].
In recent years, the SLCMJ has garnered an increased amount of attention as a method to evaluate unilateral power in elite soccer. In fact, all 12 studies that used SLCMJ testing were conducted within the last 9 years, further highlighting the growing popularity of this test. Compared with other popular jump tests, the SLCMJ enables the assessment of power in a unilateral manner, something that can be of value given the requirement for unilateral movement competency in soccer. Moreover, the detection of interlimb asymmetries can support injury prevention and return-to-play strategies [66, 77]. Jump height, measured in centimetres, was found to be the main outcome variable obtained from the SLCMJ test. More importantly, jump height (when assessed unilaterally) has been shown to be a sensitive measure for assessing changes in performance of elite soccer players when in a fatigued state [64], encouraging the use of the test in settings where there is lack of specialised equipment such as force plates.
Interestingly, our systematic review revealed that the assessment of reactive strength ability, which represents the ability to transition rapidly from an eccentric to a concentric muscle action, does not appear to be prioritised in elite soccer players. The drop jump represents one of the most popular tests to evaluate reactive strength and provide insights into an athlete’s fast stretch–shortening cycle ability [37]. However, it was reported in only eight studies of elite soccer. In terms of outcome variables, jump height (six studies) and contact time (four studies) were the most frequently reported. The combination of these can be used to calculate the reactive strength index, which was reported in three studies and provides a measure to evaluate an individual’s reactive strength ability. Nevertheless, the fact that the reactive strength index is a ratio and is deemed as an outcome variable points to the need to examine each component separately and delve deeper into metrics that provide insights into the strategy used, such as ground contact time and leg stiffness [71].
4.2 Normative Values for Strength and Power Tests
Normative standards can serve as an important tool in the athletic development process, enabling benchmarking and a data-informed approach to athletic development. Given the potential of strength and power to distinguish between different playing levels [16, 17], availability of normative data can provide multiple benefits to key stakeholders such as coaching and management staff. In particular, normative values for elite soccer players can support practitioners in setting training priorities and objectives, which can lead to the implementation of targeted training interventions. In addition, knowledge of the strength and power outputs of soccer players competing at the highest level can be of great value, including for practitioners working with developmental players. This can enable the reverse engineering of the strength and power development process so that players are ready to cope with the physical demands of elite soccer. Therefore, this review also provides a summary of normative values of strength and power. Owing to the large discrepancy in testing methods identified, only normative values of the most commonly implemented tests and outcome variables were reported. Overall, the biggest challenge encountered in the establishment of normative standards lies in the wide variability of testing protocols and measurement devices. Therefore, readers are referred to Tables 4–9 for more in-depth information on the values reported by each study for each test.
A variety of angular velocities, with a range from 30°/s to 300°/s, have been used in isokinetic strength testing, enabling practitioners to gain insight into muscle strength capabilities at different speeds. As the majority of isokinetic strength values were reported at 60°/s in this literature review, the mean values reported correspond to this angular velocity. The substantially smaller number of studies reporting isokinetic strength values in elite youth soccer players could possibly indicate a research area where more work needs to be performed in the future. In terms of Nordic hamstring strength, the difficulty to draw conclusions was arguably greater. More specifically, the range of mean values of peak force is large (338.2 vs 636.5 N) in the two identified studies performed in elite youth soccer players, perhaps in part as a consequence of the different equipment used (Nordic assessment device vs acceleration leg curl/extension, neuroexcellence) or the training approaches adopted by the club. In a similar manner, the variety of equipment used in jump testing such as force plates, jump mats and photoelectric cells can introduce a varying degree of measurement error during a jump assessment. In addition, readers should take into account the detailed discussion on the intricacies of jump height calculation provided in Sect. 4.1.2. The range of values observed for SJ, CMJ and VJ corroborate this observation, and as such, generalisation of these results should be avoided.
Although the normative values presented in this review can offer valuable insights to practitioners, thereby enhancing the practical utility of this work, they are subject to many limitations. Careful interpretation and application of these results is therefore recommended. Additional research is required to establish specific thresholds for each playing standard. Finally, further standardisation of data analysis is required, as it was observed that some studies reported the mean value of the trials performed. Currently, it may be advised to determine club specific standards and compare players against this, thus accounting for differences in test equipment, methodology and the adopted culture and philosophy of training and testing [78].
4.3 Reliability Data
Reliability is an important concept in the overall testing process, especially in high-performance sport where success depends on marginal differences. The use of reliable tests and outcome variables can ensure that the data collected reflects an athlete’s true capacity, therefore guiding effective decision making. Nevertheless, our systematic review revealed that a relatively small number of studies reported reliability data for strength and power tests (15 and 34 studies, respectively), impairing confidence in the interpretation of test results and performance changes. This finding highlights the need to generate awareness of the utility of these metrics within the prescription and reporting of testing. It is of paramount importance for practitioners to establish their own reliability measures within their specific contexts, as the characteristics of each setting and athlete sample are unique.
Intra-day reliability was the most common type of reliability. The predominance of intra-day reliability could be attributed to the inherent complexity of conducting between-day reliability studies in elite sports. More specifically, when aiming to undertake inter-day reliability assessments, the second assessment is usually performed within 3–7 days of the first [79], which is not always feasible because of demanding training and competition schedules. Determining the between-day variability, though, can promote a more holistic and evidence-informed interpretation of performance changes, as the between-day variability is not typically the same as within-day data because biological variation is also factored in. In fact, our review revealed generally higher values for the intra-day reliability of the CMJ and SJ height compared with the inter-day reliability values reported in one study [80]. A similar observation was made in Nordic hamstring strength testing, where intra-day reliability values were considerably higher than inter-day reliability values. To address this, more ecological approaches to between-day reliability testing have been recently introduced in elite soccer [80] and rugby union [72], by integrating the reliability testing within the microcycle, where normal training is undertaken in the days prior to the re-assessment.
In terms of reliability metrics, the ICC was the most frequently reported. The ICC is a measure of relative reliability, which is the extent to which an individual maintains their ranking over the course of repeated trials. Although what is an acceptable ICC value can be debatable, it is generally embraced that the ICC ≥ 0.75 is considered as “good” reliability, with an ICC ≥ 0.90 considered as “excellent” [81]. Nonetheless, the ICC is influenced by group homogeneity and does not provide any information on the variation between efforts of an individual. Therefore, it is crucial for absolute reliability to also be established. Based on our findings, the CV and SEM were the most common metrics to evaluate absolute reliability. The CV indicates the relative dispersion of the data points around the mean by expressing the SD as a percentage of the mean, while the SEM provides an index of the precision of the measurement by estimating the range in which the population’s true score is expected to lie, within a defined level of confidence. In addition, these measures are more relevant to practice, as they are used for the assessment of sensitivity. Although the scientific community seems to broadly recognise the value of ≤ 10% as an acceptable threshold, this threshold appears to be rather arbitrary and a more nuanced and context-specific interpretation is required [82]. The paper by Mercer et al. [73] demonstrated that although certain CMJ variables produce a CV > 10%, they are still sensitive to training changes, justifying their use in practice. Readers are directed to this article to gain insights on how to determine the signal-to-noise ratio in an ecologically valid and non-disruptive to the training process manner, with their own athletes.
Regarding strength testing, the smaller number of studies reporting reliability values means that conclusions should be drawn with caution. The half-back squat seems to possess high levels of intra-day (ICC [0.94–0.97], CV [1.8–3.1], SEM [1.71]) and inter-day reliability (ICC [0.99], CV [1.8], SEM [2]). Additionally, the Nordic hamstring strength test appears to have high intra-day relative reliability levels (ICC [0.97–0.99]) in conjunction with a small CV value (1.0–3.2). In terms of inter-day reliability of the Nordic hamstring strength test, the only study performed demonstrated moderate levels of relative reliability, but with a CV value below 10%. Regarding power testing, the reported ICC ranges in CMJ (0.80–0.99), SJ (0.75–0.99) and SLCMJ (0.74–0.99) height, coupled with their CV (CMJ [1.8–15], SJ [2.1–13], SLCMJ [1.9–9.6]) and SEM (CMJ [0.6–1.4], SJ [0.6], SLCMJ [0.3–1]) values identified in this systematic review, confirm their high level of reliability. The increased availability of force plates in elite soccer will warrant the determination of reliability, particularly between days, in metrics other than jump height, representing an area where future research in elite soccer should focus. Although the current reliability data are generally robust, practitioners should still validate these measures within their specific context to ensure the accuracy and applicability of the data.
Finally, only a very limited number of studies reported the MDC. Minimal detectable change, calculated from the SEM, illustrates the minimal amount of change in performance required to be confident that the change can be considered as real at a predetermined probability level (usually 90% or 95%). This may raise the need to further determine MDC of strength and power tests in the context of elite soccer, as this will allow practitioners to identify normal variations or true changes in performance. However, it should be acknowledged that such a high confidence threshold may not be suitable for high-performance settings where a high level of physical performance has already been established and training interventions can therefore only elicit a certain degree of positive adaptations. This can lead to tiny but significant positive changes being labelled as “noise”, resulting in the discontinuation of certain training interventions that are actually working.
4.4 Limitations
Although this systematic review provided a comprehensive picture of strength and power testing in elite soccer, there are several limitations that should be acknowledged. To begin with, as Boullosa et al. [83] indicate, the conclusions of a systematic review can be influenced by the inclusion or exclusion of a few studies. In this sense, the terms “elite” and “professional” are often used interchangeably across the literature. It is likely, though, that these terms may be used differently in different geographic regions and leagues. This can be considered as a limitation, as well as a reflection of the existing soccer literature, highlighting the need for a standardised terminology for “elite” and “professional”. The large variability in equipment is another challenge in the establishment of normative standards, complicating the direct translation of these findings into practice. In addition, because of the heterogeneity of testing methods identified in the present literature review, it was not possible to carry out a meta-analysis. Last, in strength testing, a substantial lower number of studies reporting normative values was available. This discrepancy may interfere with the ability to perform reliable comparisons between men and young elite soccer players.
4.5 Directions for Future Research
This systematic review has identified several areas that require further investigation. There is a need to standardise several aspects of strength and power testing to improve the comparability and the application of the results. This includes standardising the definitions, such as the distinction between the half-back squat and the back squat, and standardising procedures for certain tests, such as the isometric adductor strength test, the Nordic hamstring test and the CMJ. Future research should focus on establishing a hybrid testing framework that incorporates standardised “core” tests for benchmarking and large-scale comparisons, while allowing practitioners to introduce additional context-specific tests tailored to the unique dynamics of their settings. A scarcity of robust reliability data is evident in elite soccer. Practitioners need to establish their own reliability measures, and subsequently the sensitivity of those, within their specific contexts, to enhance confidence in assessing performance changes and reducing reliance on published reliability thresholds. This will assist in determining any of those that do not offer any particular value in decision making, removing any redundant processes and data. A standardised data analysis process should be also adopted, as there is no consensus on the optimal approach to analyse strength and power testing results (i.e. best trial vs average of trials). Future studies should therefore examine the ramifications of each approach. Last, future studies should investigate the most effective methods of reporting the testing results to the key stakeholders to enhance the impact of testing in the training process. These studies have the potential to reshape the strength and power assessment procedures in elite soccer, enabling more robust practices and informed practices.
5 Conclusions
This systematic review, as illustrated in the infographic in Fig. 2, provides a comprehensive overview of the tests and outcome variables used to assess strength and power in elite male soccer. The wide variety of different tests employed combined with the multitude of different outcome variables indicates the lack of a consensus in strength and power testing in elite soccer. This may arise from the diverse training needs of each specific setting, as well as the different testing philosophies across cultures. In terms of frequency, isokinetic knee (extensors and flexors) strength testing and CMJ were the most administered strength and power tests, respectively. The normative values provided for these tests enhance the practicality of this review. However, the application of these normative values warrants careful consideration, as different testing protocols and instruments have been utilised. Future research should focus on the development of a hybrid testing approach to strength and power testing, combining standardised tests for benchmarking purposes, while allowing for flexible testing selection based on the unique requirements of each specific context to enable a holistic profiling of strength and power.
Strength and power testing in elite male soccer. CMV countermovement jump, CV coefficient of variation, ICC intraclass correlation coefficient, SEM standard error of measurement, SJ squat jump, VJ vertical jump
References
Stølen T, Chamari K, Castagna C, Wisløff U. Physiology of soccer: an update. Sports Med. 2005;35:501–36.
Reilly T, Bangsbo J, Franks A. Anthropometric and physiological predispositions for elite soccer. J Sports Sci. 2000;18:669–83.
Bradley PS, Sheldon W, Wooster B, Olsen P, Boanas P, Krustrup P. High-intensity running in English FA Premier League soccer matches. J Sports Sci. 2009;27:159–68.
Carling C, Bradley P, McCall A, Dupont G. Match-to-match variability in high-speed running activity in a professional soccer team. J Sports Sci. 2016;34:2215–23.
Dolci F, Hart NH, Kilding AE, Chivers P, Piggott B, Spiteri T. Physical and energetic demand of soccer: a brief review. Strength Cond J. 2020;42:70–7.
Bloomfield J, Polman R, O’Donoghue P. Physical demands of different positions in FA Premier League soccer. J Sports Sci Med. 2007;6:63–70.
Bush M, Barnes C, Archer DT, Hogg B, Bradley PS. Evolution of match performance parameters for various playing positions in the English Premier League. Human Move Sci. 2015;39:1–11.
Allen T, Taberner M, Zhilkin M, Rhodes D. Running more than before? The evolution of running load demands in the English Premier League. Int J Sports Sci Coach. 2023;9:174795412311645.
Wisløff U, Castagna C, Helgerud J, Jones R, Hoff J. Strong correlation of maximal squat strength with sprint performance and vertical jump height in elite soccer players: figure 1. Br J Sports Med. 2004;38:285–8.
Faude O, Koch T, Meyer T. Straight sprinting is the most frequent action in goal situations in professional football. J Sports Sci. 2012;30:625–31.
Wing CE, Turner AN, Bishop CJ. Importance of strength and power on key performance indicators in elite youth soccer. J Strength Cond Res. 2020;34:2006–14.
De Hoyo M, Gonzalo-Skok O, Sañudo B, Carrascal C, Plaza-Armas JR, Camacho-Candil F, et al. Comparative effects of in-season full-back squat, resisted sprint training, and plyometric training on explosive performance in U-19 elite soccer players. J Strength Cond Res. 2016;30:368–77.
Otero-Esquina C, De Hoyo LM, Gonzalo-Skok Ó, Domínguez-Cobo S, Sánchez H. Is strength-training frequency a key factor to develop performance adaptations in young elite soccer players? Eur J Sport Sci. 2017;17:1241–51.
Stern D, Gonzalo-Skok O, Loturco I, Turner A, Bishop C. A comparison of bilateral vs. unilateral-biased strength and power training interventions on measures of physical performance in elite youth soccer players. J Strength Cond Res. 2020;34:2105–11.
Keiner M, Kadlubowski B, Sander A, Hartmann H, Wirth K. Effects of 10 months of speed, functional, and traditional strength training on strength, linear sprint, change of direction, and jump performance in trained adolescent soccer players. J Strength Cond Res. 2022;36:2236–46.
Kobal R, Loturco I, Gil S, Cal Abad CC, Cuniyochi R, Barroso R, et al. Comparison of physical performance among Brazilian elite soccer players of different age-categories. J Sports Med Phys Fitness. 2016;56:376–82.
Hoppe MW, Barnics V, Freiwald J, Baumgart C. Contrary to endurance, power associated capacities differ between different aged and starting-nonstarting elite junior soccer players. PLoS ONE. 2020;15: e0232118.
Beato M, Young D, Stiff A, Coratella G. Lower-limb muscle strength, anterior-posterior and inter-limb asymmetry in professional, Elite Academy and amateur soccer players. J Human Kinet. 2021;77:135–46.
Arnason A, Sigurdsson SB, Gudmundsson A, Holme I, Engebretsen L, Bahr R. PhysicalfFitness, injuries, and team performance in soccer. Med Sci Sports Exerc. 2004;36:278–85.
Croisier J-L, Ganteaume S, Binet J, Genty M, Ferret J-M. Strength imbalances and prevention of hamstring injury in professional soccer players: a prospective study. Am J Sports Med. 2008;36:1469–75.
Lehance C, Binet J, Bury T, Croisier JL. Muscular strength, functional performances and injury risk in professional and junior elite soccer players: muscular strength in soccer players. Scand J Med Sci Sports. 2008;19:243–51.
Beato M, Maroto-Izquierdo S, Turner AN, Bishop C. Implementing strength training strategies for injury prevention in soccer: scientific rationale and methodological recommendations. Int J Sports Physiol Perform. 2021;16:456–61.
Svensson M, Drust B. Testing soccer players. J Sports Sci. 2005;23:601–18.
Taylor JM, Madden JL, Cunningham LP, Wright M. Fitness testing in soccer revisited: developing a contemporary testing battery. Strength Cond J. 2022;44:10–21.
Pyne DB, Spencer M, Mujika I. Improving the value of fitness testing for football. Int J Sports Physiol Perform. 2014;9:511–4.
Weldon A, Duncan MJ, Turner A, Sampaio J, Noon M, Wong D, et al. Contemporary practices of strength and conditioning coaches in professional soccer. Biol Sport. 2021;38:377–90.
Turner A, Walker S, Stembridge M, Coneyworth P, Reed G, Birdsey L, et al. A testing battery for the assessment of fitness in soccer players. Strength Cond J. 2011;33:29–39.
Weakley J, Black G, McLaren S, Scantlebury S, Suchomel TJ, McMahon E, et al. Testing and profiling athletes: recommendations for test selection, implementation, and maximizing information. Strength Cond J. 2023. https://doi.org/10.1519/SSC.0000000000000784.
Paul DJ, Nassis GP. Testing strength and power in soccer players: the application of conventional and traditional methods of assessment. J Strength Cond Res. 2015;29:1748–58.
Boullosa D, Claudino JG, Fernandez-Fernandez J, Bok D, Loturco I, Stults-Kolehmainen M, et al. The fine-tuning approach for training monitoring. Int J Sports Physiol Perform. 2023;18:1374–9.
Atkinson G, Nevill AM. Statistical methods for assessing measurement error (reliability) in variables relevant to sports medicine. Sports Med. 1998;26:217–38.
Currell K, Jeukendrup AE. Validity, reliability and sensitivity of measures of sporting performance. Sports Med. 2008;38:297–316.
Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ. 2021;372: n71.
Downs SH, Black N. The feasibility of creating a checklist for the assessment of the methodological quality both of randomised and non-randomised studies of health care interventions. J Epidemiol Commun Health. 1998;52:377–84.
Owen C, Till K, Weakley J, Jones B. Testing methods and physical qualities of male age grade rugby union players: a systematic review. PLoS ONE. 2020;15: e0233796.
Morrison M, Martin DT, Talpey S, Scanlan AT, Delaney J, Halson SL, et al. A systematic review on fitness testing in adult male basketball players: tests adopted, characteristics reported and recommendations for practice. Sports Med. 2022;52:1491–532.
Jarvis P, Turner A, Read P, Bishop C. Reactive strength index and its associations with measures of physical and sports performance: a systematic review with meta-analysis. Sports Med. 2022;52:301–30.
Andrade DC, Manzo O, Beltrán AR, Álvarez C, Del Rio R, Toledo C, et al. Kinematic and neuromuscular measures of intensity during plyometric jumps. J Strength Cond Res. 2020;34:3395–402.
Weiss K, Whatman C. Biomechanics associated with patellofemoral pain and ACL injuries in sports. Sports Med. 2015;45:1325–37.
Ekstrand J, Hägglund M, Waldén M. Epidemiology of muscle injuries in professional football (soccer). Am J Sports Med. 2011;39:1226–32.
Forsythe B, Lavoie-Gagne OZ, Forlenza EM, Diaz CC, Mascarenhas R. Return-to-play times and player performance after ACL reconstruction in Elite UEFA professional soccer players: a matched-cohort analysis from 1999 to 2019. Orthopaed J Sports Med. 2021;9:232596712110088.
Van Dyk N, Bahr R, Burnett AF, Whiteley R, Bakken A, Mosler A, et al. A comprehensive strength testing protocol offers no clinical value in predicting risk of hamstring injury: a prospective cohort study of 413 professional football players. Br J Sports Med. 2017;51:1695–702.
Izovska J, Hank M, Cabell L, Kalata M, Bujnovsky D, Zahalka F, et al. The hamstring and ACL injury incidence during a season is not directly related to preseason knee strength ratios in elite male soccer players. Appl Sci. 2022;12:1272.
Kellis E, Sahinis C, Baltzopoulos V. Is hamstrings-to-quadriceps torque ratio useful for predicting anterior cruciate ligament and hamstring injuries? A systematic and critical review. J Sport Health Sci. 2023;12:343–58.
Timmins RG, Bourne MN, Shield AJ, Williams MD, Lorenzen C, Opar DA. Short biceps femoris fascicles and eccentric knee flexor weakness increase the risk of hamstring injury in elite football (soccer): a prospective cohort study. Br J Sports Med. 2016;50:1524–35.
Chesterton P, Draper G, Portas M, Tears C. The uptake of Nordic hamstring exercise program for injury prevention in major league soccer and its barriers to implementation in practice. J Sport Rehabil. 2022;31:1–6.
Van Dyk N, Behan FP, Whiteley R. Including the Nordic hamstring exercise in injury prevention programmes halves the rate of hamstring injuries: a systematic review and meta-analysis of 8459 athletes. Br J Sports Med. 2019;53:1362–70.
Werner J, Hagglund M, Walden M, Ekstrand J. UEFA injury study: a prospective study of hip and groin injuries in professional football over seven consecutive seasons. Br J Sports Med. 2009;43:1036–40.
Thorborg K, Serner A, Petersen J, Madsen TM, Magnusson P, Hölmich P. Hip adduction and abduction strength profiles in elite soccer players: implications for clinical evaluation of hip adductor muscle recovery after injury. Am J Sports Med. 2011;39:121–6.
Thorborg K, Branci S, Nielsen MP, Tang L, Nielsen MB, Hölmich P. Eccentric and isometric hip adduction strength in male soccer players with and without adductor-related groin pain: an assessor-blinded comparison. Orthopaed J Sports Med. 2014;2:232596711452177.
Mosler AB, Agricola R, Weir A, Hölmich P, Crossley KM. Which factors differentiate athletes with hip/groin pain from those without? A systematic review with meta-analysis. Br J Sports Med. 2015;49:810.
Padua DA, Marshall SW, Beutler AI, DeMaio M, Boden BP, Yu B, et al. Predictors of knee valgus angle during a jump-landing task. Med Sci Sports Exerc. 2005;37:S398.
Rouissi M, Chtara M, Owen A, Chaalali A, Chaouachi A, Gabbett T, et al. Effect of leg dominance on change of direction ability amongst young elite soccer players. J Sports Sci. 2016;34:542–8.
Caterisano A, Moss RF, Pellinger TK, Woodruff K, Lewis VC, Booth W, et al. The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles. J Strength Cond Res. 2002;16:428–32.
da Silva JJ, Schoenfeld BJ, Marchetti PN, Pecoraro SL, Greve JMD, Marchetti PH. Muscle activation differs between partial and full back squat exercise with external load equated. J Strength Cond Res. 2017;31:1688–93.
Drinkwater EJ, Moore NR, Bird SP. Effects of changing from full range of motion to partial range of motion on squat kinetics. J Strength Cond Res. 2012;26:890–6.
Brady CJ, Harrison AJ, Flanagan EP, Haff GG, Comyns TM. A comparison of the isometric midthigh pull and isometric squat: intraday reliability, usefulness, and the magnitude of difference between tests. Int J Sports Physiol Perform. 2018;13:844–52.
Asimakidis ND, Bishop CJ, Beato M, Mukandi IN, Kelly AL, Weldon A, et al. A survey into the current fitness testing practices of elite male soccer practitioners: from assessment to communicating results. Front Physiol. 2024;15:1376047.
Northeast J, Russell M, Shearer D, Cook CJ, Kilduff LP. Predictors of linear and multidirectional acceleration in elite soccer players. J Strength Cond Res. 2019;33:514–22.
Suchomel TJ, Sole CJ, Bellon CR, Stone MH. Dynamic strength index: relationships with common performance variables and contextualization of training recommendations. J Hum Kinet. 2020;74:59–70.
Bazyler CD, Beckham GK, Sato K. The use of the isometric squat as a measure of strength and explosiveness. J Strength Cond Res. 2015;29:1386–92.
Martinez-Santos R, Castillo D, Los AA. Sprint and jump performances do not determine the promotion to professional elite soccer in Spain, 1994–2012. J Sports Sci. 2016;34:2279–85.
Bishop C, Brashill C, Abbott W, Read P, Lake J, Turner A. Jumping asymmetries are associated withspeed, change of direction speed, and jump performance in elite academy soccer players. J Strength Cond Res. 2021;35(7):1841–7.
Bishop C, Abbott W, Brashill C, Loturco I, Beato M, Turner A. Seasonal variation of physical performance, bilateral deficit, and interlimb asymmetry in Elite Academy soccer players: which metrics are sensitive to change? J Strength Cond Res. 2023;37:358–65.
Papadakis L, Tymvios C, Patras K. The relationship between training load and fitness indices over a pre-season in professional soccer players. J Sports Med Phys Fitness. 2020;60:329–37.
Maestroni L, Turner A, Papadopoulos K, Cohen D, Sideris V, Graham-Smith P, et al. Comparison of strength and power characteristics before ACL rupture and at the end of rehabilitation before return to sport in professional soccer players. Sports Health. 2023;15:814–23.
Kozinc Ž, Pleša J. Discrepancy among different methods for vertical jump height determination and its implications for field-based testing: a narrative review. Measure Phys Educ Exerc Sci. 2023;27:248–56.
Moir GL. Three different methods of calculating vertical jump height from force platform data in men and women. Measure Phys Educ Exerc Sci. 2008;12:207–18.
Xu J, Turner A, Comfort P, Harry JR, McMahon JJ, Chavda S, et al. A systematic review of the different calculation methods for measuring jump height during the countermovement and drop jump tests. Sports Med. 2023;53:1055–72.
McMahon JJ, Jones PA, Comfort P. A correction equation for jump height measured using the just jump system. Int J Sports Physiol Perform. 2016;11:555–7.
Bishop C, Turner A, Jordan M, Harry J, Loturco I, Lake J, et al. A framework to guide practitioners for selecting metrics during the countermovement and drop jump tests. Strength Cond J. 2022;44:95–103.
Howarth DJ, Cohen DD, McLean BD, Coutts AJ. Establishing the noise: interday ecological reliability of countermovement jump variables in professional rugby union players. J Strength Cond Res. 2022;36:3159–66.
Mercer RAJ, Russell JL, McGuigan LC, Coutts AJ, Strack DS, McLean BD. Finding the signal in the noise: interday reliability and seasonal sensitivity of 84 countermovement jump variables in professional basketball players. J Strength Cond Res. 2023;37:394–402.
Sheppard JM, Doyle TLA. Increasing compliance to instructions in the squat jump. J Strength Cond Res. 2008;22:648–51.
Loturco I, Pereira LA, Kobal R, Zanetti V, Gil S, Kitamura K, et al. Half-squat or jump squat training under optimum power load conditions to counteract power and speed decrements in Brazilian elite soccer players during the preseason. J Sports Sci. 2015;33:1283–92.
Hara M, Shibayama A, Takeshita D, Hay DC, Fukashiro S. A comparison of the mechanical effect of arm swing and countermovement on the lower extremities in vertical jumping. Hum Move Sci. 2008;27:636–48.
Bishop C, Read P, Bromley T, Brazier J, Jarvis P, Chavda S, et al. The association between interlimb asymmetry and athletic performance tasks: a season-long study in Elite Academy soccer players. J Strength Cond Res. 2022;36:787–95.
Turner AN, Jones B, Stewart P, Bishop C, Parmar N, Chavda S, et al. Total score of athleticism: holistic athlete profiling to enhance decision-making. Strength Cond J. 2019;41:91–101.
Hopkins WG. Measures of reliability in sports medicine and science. Sports Med. 2000;30:1–15.
Enright K, Morton J, Iga J, Lothian D, Roberts S, Drust B. Reliability of “in-season” fitness assessments in youth elite soccer players: a working model for practitioners and coaches. Sci Med Football. 2018;2:177–83.
Koo TK, Li MY. A guideline of selecting and reporting intraclass correlation coefficients for reliability research. J Chiropract Med. 2016;15:155–63.
Turner A, Brazier J, Bishop C, Chavda S, Cree J, Read P. Data analysis for strength and conditioning coaches: using Excel to analyze reliability, differences, and relationships. Strength Cond J. 2015;37:76–83.
Boullosa D, Behm D, Del Rosso S, Schumann M, Doma K, Foster C. The limitations of systematic reviews with meta-analyses in sport science. Int J Sports Physiol Perform. 2024;19:517–8.
Espada MC, Jardim M, Assunção R, Estaca A, Ferreira CC, Pessôa Filho DM, et al. Lower limb unilateral and bilateral strength asymmetry in high-level male senior and professional football players. Healthcare. 2023;11:1579.
Cossich VRA, Gavilão UF, Goes RA, Perini JA, Laett CT, Maffiuletti NA. Maximal vs. explosive knee extensor strength in professional soccer players: inter-limb asymmetries and relationship with knee function. Eur J Sport Sci. 2023;23:877–84.
Byrkjedal PT, Thunshelle A, Spencer M, Luteberget LS, Ivarsson A, Vårvik FT, et al. In-season autoregulation of one weekly strength training session maintains physical and external load match performance in professional male football players. J Sports Sci. 2023;41:536–46.
Wezenbeek E, Denolf S, Bourgois JG, Philippaerts RM, De Winne B, Willems TM, et al. Impact of (long) COVID on athletes’ performance: a prospective study in elite football players. Ann Med. 2023;55:2198776.
Guerra MA, Caldas LC, Souza HL, Tallis J, Duncan MJ, Guimarães-Ferreira L. The effects of physical fitness on postactivation potentiation in professional soccer athletes. J Strength Cond Res. 2022;36:1643–7.
Papadakis Z, Panoutsakopoulos V, Kollias IA. Predictive value of repeated jump testing on nomination status in professional and under 19 soccer Ppayers. IJERPH. 2022;19:13077.
Lahti J, Mendiguchia J, Edouard P, Morin J-B. A novel multifactorial hamstring screening protocol: association with hamstring muscle injuries in professional football (soccer): a prospective cohort study. Biol Sport. 2022;39:1021–31.
Bongiovanni T, Rossi A, Iaia FM, Di Baldassarre A, Pasta G, Manetti P, et al. Relationship of regional and whole-body morphology to vertical jump in elite soccer players: a data-driven approach. J Sports Med Phys Fitness. 2022;62.
Papla M, Latocha A, Grzyb W, Golas A. Relationship between lower limb power output, sprint and change of direction performance in soccer players. BJHPA. 2022;14:Article3.
Boraczyński MT, Laskin JJ, Gajewski J, Podstawski RS, Brodnicki MA, Boraczyński TW. Effects of two low-volume high-intensity interval training protocols in professional soccer: sprint interval training versus small-sided games. J Sports Med Phys Fitness. 2022;63:23–33.
Misjuk M, Rannama I. The effect of muscular strength and strength asymmetry on jumping height in soccer players. IES. 2022;30:53–60.
Cadu J-P, Goreau V, Lacourpaille L. A very low volume of Nordic hamstring exercise increases maximal eccentric strength and reduces hamstring injury rate in professional soccer players. J Sport Rehabil. 2022;31:1061–6.
Schons P, Birk Preissler AA, Oliveira R, Brito JP, Clemente FM, Droescher De Vargas G, et al. Comparisons and correlations between the anthropometric profile and physical performance of professional female and male soccer players: individualities that should be considered in training. Int J Sports Sci Coach. 2022;18:174795412211316.
Freitas TT, Pereira LA, Reis VP, Fernandes V, Alcaraz PE, Azevedo PHSM, et al. Effects of a congested fixture period on speed and power performance of elite young soccer players. Int J Sports Physiol Perform. 2021;16:1120–6.
Arregui-Martin MA, Garcia-Tabar I, Gorostiaga EM. Half soccer season induced physical conditioning adaptations in elite youth players. Int J Sports Med. 2020;41:106–12.
Leporace G, Tannure M, Zeitoune G, Metsavaht L, Marocolo M, Souto MA. Association between knee-to-hip flexion ratio during single-leg vertical landings, and strength and range of motion in professional soccer players. Sports Biomech. 2020;19:411–20.
Querido SM, Clemente FM. Analyzing the effects of combined small-sided games and strength and power training on the fitness status of under-19 elite football players. J Sports Med Phys Fitness. 2020;60:1–10.
Shalaj I, Gjaka M, Bachl N, Wessner B, Tschan H, Tishukaj F. Potential prognostic factors for hamstring muscle injury in elite male soccer players: a prospective study. PLoS ONE. 2020;15: e0241127.
Manoel LS, Xixirry MG, Soeira TP, Saad MC, Riberto M. Identification of ankle injury risk factors in professional soccer players through a preseason functional assessment. Orthopaed J Sports Med. 2020;8:232596712092843.
Krespi M, Sporiš G, Trajković N. Effects of two different tapering protocols on fitness and physical match performance in elite junior soccer players. J Strength Cond Res. 2020;34:1731–40.
Moreno-Pérez V, Méndez-Villanueva A, Soler A, Del Coso J, Courel-Ibáñez J. No relationship between the Nordic hamstring and two different isometric strength tests to assess hamstring muscle strength in professional soccer players. Phys Ther Sport. 2020;46:97–103.
Correia P, Santos P, Mil-Homens P, Gomes M, Dias A, Valamatos MJ. Rapid hamstrings to quadriceps ratio at long muscle lengths in professional football players with previous hamstring strain injury. Eur J Sport Sci. 2020;20:1405–13.
Ribeiro-Alvares JB, Dornelles MP, Fritsch CG, De Lima-e-Silva FX, Medeiros TM, Severo-Silveira L, et al. Prevalence of hamstring strain injury risk factors in professional and under-20 male football (soccer) players. J Sport Rehabil. 2020;29:339–45.
Suarez-Arrones L, Lara-Lopez P, Rodriguez-Sanchez P, Lazaro-Ramirez JL, Di Salvo V, Guitart M, et al. Dissociation between changes in sprinting performance and Nordic hamstring strength in professional male football players. PLoS ONE. 2019;14: e0213375.
Van Klij P, Langhout R, Van Beijsterveldt AMC, Stubbe JH, Weir A, Agricola R, et al. Do hip and groin muscle strength and symptoms change throughout a football season in professional male football players? A prospective cohort study with repeated measures. J Sci Med Sport. 2021;24:1123–9.
Ribeiro J, Teixeira L, Lemos R, Teixeira AS, Moreira V, Silva P, et al. Effects of plyometric versus optimum power load training on components of physical fitness in young male soccer players. Int J Sports Physiol Perform. 2020;15:222–30.
Lockie RG, Moreno MR, Orjalo AJ, Stage AA, Liu TM, Birmingham-Babauta SA, et al. Repeated-sprint ability in Division I Collegiate male soccer players: positional differences and relationships with performance tests. J Strength Cond Res. 2019;33:1362–70.
Ishøi L, Krommes K, Nielsen MF, Thornton KB, Hölmich P, Aagaard P, et al. Hamstring and quadriceps muscle strength in youth to senior elite soccer: a cross-sectional study including 125 players. Int J Sports Physiol Perform. 2021;16:1538–44.
Moreno-Pérez V, Beato M, Del Coso J, Hernández-Davó JL, Soler A, Peñaranda-Moraga M, et al. Intra and inter-tester reliability of a novel device to assess gluteal muscle strength in professional football players. Res Sports Med. 2022;30:156–68.
Dolci F, Kilding AE, Spiteri T, Chivers P, Piggott B, Maiorana A, et al. Modulators of change-of-direction economy after repeated sprints in elite soccer players. Int J Sports Physiol Perform. 2021;16:1649–55.
Nielsen MF, Thorborg K, Krommes K, Thornton KB, Hölmich P, Peñalver JJJ, et al. Hip adduction strength and provoked groin pain: a comparison of long-lever squeeze testing using the ForceFrame and the Copenhagen 5-Second-Squeeze test. Phys Ther Sport. 2022;55:28–36.
Silva AF, González-Fernández FT, Ceylan HI, Silva R, Younesi S, Chen Y-S, et al. Relationships between fitness status and blood biomarkers in professional soccer players. J Healthc Eng. 2022;2022:1–13.
Light N, Thorborg K, Krommes K, Nielsen MF, Thornton KB, Hölmich P, et al. Rapid spike in hip adduction strength in early adolescent footballers: a study of 125 elite male players from youth to senior. Int J Sports Physiol Perform. 2022;17:1407–14.
Saccà M, Bondi D, Balducci F, Petri C, Mazza G. Intra- and inter-seasonal fitness and training load variations of elite U20 soccer players. Res Q Exerc Sport. 2022;94:1–8.
Enes A, Oneda G, Alves DL, Palumbo DDP, Cruz R, Moiano Junior JVM, et al. Determinant factors of the match-based internal load in elite soccer players. Res Q Exerc Sport. 2021;92:63–70.
Ben Brahim M, Bougatfa R, Makni E, Gonzalez PP, Yasin H, Tarwneh R, et al. Effects of combined strength and resisted sprint training on physical performance in U-19 elite soccer players. J Strength Cond Res. 2021;35:3432–9.
Rodrigues Júnior JL, Duarte W, Falqueto H, Andrade AGP, Morandi RF, Albuquerque MR, et al. Correlation between strength and skin temperature asymmetries in the lower limbs of Brazilian elite soccer players before and after a competitive season. J Thermal Biol. 2021;99: 102919.
Capaverde VDB, Oliveira GDS, De Lima-e-Silva FX, Ribeiro-Alvares JBA, Baroni BM. Do age and body size affect the eccentric knee flexor strength measured during the Nordic hamstring exercise in male soccer players? Sports Biomechanics. 2021;9:1–11.
Ribeiro-Alvares JB, Oliveira GDS, De Lima-E-Silva FX, Baroni BM. Eccentric knee flexor strength of professional football players with and without hamstring injury in the prior season. Eur J Sport Sci. 2021;21:131–9.
Scoz RD, Alves BMO, Burigo RL, Vieira ER, Ferreira LMA, Da Silva RA, et al. Strength development according with age and position: a 10-year study of 570 soccer players. BMJ Open Sport Exerc Med. 2021;7: e000927.
Bourne MN, Williams M, Jackson J, Williams KL, Timmins RG, Pizzari T. Preseason hip/groin strength and HAGOS scores are associated with subsequent injury in professional male soccer players. J Orthop Sports Phys Ther. 2020;50:234–42.
Ocarino JM, Resende RA, Bittencourt NFN, Correa RVA, Mendonça LM, Reis GF, et al. Normative data for hip strength, flexibility and stiffness in male soccer athletes and effect of age and limb dominance. Phys Ther in Sport. 2021;47:53–8.
Read PJ, McAuliffe S, Bishop C, Oliver JL, Graham-Smith P, Farooq MA. Asymmetry thresholds for common screening tests and their effects on jump performance in professional soccer players. J Athl Train. 2021;56:46–53.
Cardoso De Araújo M, Baumgart C, Jansen CT, Freiwald J, Hoppe MW. Sex differences in physical capacities of German Bundesliga soccer players. J Strength Cond Res. 2020;34:2329–37.
Loturco I, Jeffreys I, Abad CCC, Kobal R, Zanetti V, Pereira LA, et al. Change-of-direction, speed and jump performance in soccer players: a comparison across different age-categories. J Sports Sci. 2020;38:1279–85.
Papla M, Krzysztofik M, Wojdala G, Roczniok R, Oslizlo M, Golas A. Relationships between linear sprint, lower-body power output and change of direction performance in elite soccer players. IJERPH. 2020;17:6119.
Loturco I, Pereira LA, Reis VP, Bishop C, Zanetti V, Alcaraz PE, et al. Power training in elite young soccer players: effects of using loads above or below the optimum power zone. J Sports Sci. 2020;38:1416–22.
Grazioli R, Loturco I, Baroni BM, Oliveira GS, Saciura V, Vanoni E, et al. Coronavirus disease-19 quarantine is more detrimental than traditional off-season on physical conditioning of professional soccer players. J Strength Cond Res. 2020;34:3316–20.
Śliwowski R, Marynowicz J, Grygorowicz M, Wieczorek A, Jadczak Ł. Are there differences in concentric isokinetic strength Perfor-Mance profiles between international and non-international elite soccer players? IJERPH. 2020;18:35.
Eustace SJ, Page RM, Greig M. Angle-specific isokinetic metrics highlight strength training needs of elite youth soccer players. J Strength Cond Res. 2020;34:3258–65.
Arcos AL, Aramendi JF, Emparanza JI, Castagna C, Yanci J, Lezáun A, et al. Assessing change of direction ability in a Spanish elite soccer academy. J Hum Kinet. 2020;72:229–39.
Boraczyński M, Boraczyński T, Podstawski R, Wójcik Z, Gronek P. Relationships between measures of functional and isometric lower body strength, aerobic capacity, anaerobic power, sprint and countermovement jump performance in professional soccer players. J Hum Kinet. 2020;75:161–75.
Bianchi M, Coratella G, Dello Iacono A, Beato M. Comparative effects of single vs. double weekly plyometric training sessions on jump, sprint and change of directions abilities of elite youth football players. J Sports Med Phys Fitness. 2019;59:910–5.
Michaelides MA, Parpa KM, Zacharia AI. Assessment of lower body and abdominal strength in professional soccer players. J Hum Kinet. 2019;70:15–23.
Saidi K, Zouhal H, Rhibi F, Tijani JM, Boullosa D, Chebbi A, et al. Effects of a six-week period of congested match play on plasma volume variations, hematological parameters, training workload and physical fitness in elite soccer players. PLoS ONE. 2019;14: e0219692.
Loturco I, Pereira AL, Freitas TT, Alcaraz EP, Zanetti V, Bishop C, et al. Maximum acceleration performance of professional soccer players in linear sprints: Is there a direct connection with change-of-direction ability? PLoS ONE. 2019;14: e0216806.
Van Dyk N, Wangensteen A, Vermeulen R, Whiteley R, Bahr R, Tol JL, et al. Similar isokinetic strength preinjury and at return to sport after hamstring injury. Med Sci Sports Exerc. 2019;51:1091–8.
Moreno-Pérez V, Travassos B, Calado A, Gonzalo-Skok O, Del Coso J, Mendez-Villanueva A. Adductor squeeze test and groin injuries in elite football players: a prospective study. Phys Ther Sport. 2019;37:54–9.
López-Valenciano A, Ayala F, De Ste CM, Barbado D, Vera-Garcia FJ. Different neuromuscular parameters influence dynamic balance in male and female football players. Knee Surg Sports Traumatol Arthrosc. 2019;27:962–70.
Rago V, Silva JR, Mohr M, Barreira D, Krustrup P, Rebelo AN. The inter-individual relationship between training status and activity pattern during small-sided and full-sized games in professional male football players. Sci Med Football. 2018;2:115–22.
Loturco I, Nimphius S, Kobal R, Bottino A, Zanetti V, Pereira LA, et al. Change-of direction deficit in elite young soccer players: the limited relationship between conventional speed and power measures and change-of-direction performance. Ger J Exerc Sport Res. 2018;48:228–34.
Mosler AB, Agricola R, Thorborg K, Weir A, Whiteley RJ, Crossley KM, et al. Is bony hip morphology associated with range of motion and strength in asymptomatic male soccer players? J Orthop Sports Phys Ther. 2018;48:250–9.
Mosler AB, Weir A, Serner A, Agricola R, Eirale C, Farooq A, et al. Musculoskeletal screening tests and bony hip morphology cannot identify male professional soccer players at risk of groin injuries: a 2-year prospective cohort study. Am J Sports Med. 2018;46:1294–305.
Los Arcos A, Martins J. Physical fitness performance of young professional soccer players does not change during several training seasons in a Spanish elite reserve team: Club Study, 1996–2013. J Strength Cond Res. 2018;32:2577–83.
Almeida AMD, Santos Silva PR, Pedrinelli A, Hernandez AJ. Aerobic fitness in professional soccer players after anterior cruciate ligament reconstruction. PLoS ONE. 2018;13: e0194432.
Coratella G, Beato M, Schena F. Correlation between quadriceps and hamstrings inter-limb strength asymmetry with change of direction and sprint in U21 elite soccer-players. Hum Move Sci. 2018;59:81–7.
Suarez-Arrones L, Saez De Villarreal E, Núñez FJ, Di Salvo V, Petri C, Buccolini A, et al. In-season eccentric-overload training in elite soccer players: effects on body composition, strength and sprint performance. PLoS One. 2018;13:e0205332.
Gil S, Barroso R, Crivoi Do Carmo E, Loturco I, Kobal R, Tricoli V, et al. Effects of resisted sprint training on sprinting ability and change of direction speed in professional soccer players. J Sports Sci. 2018;36:1923–9.
Śliwowski R, Grygorowicz M, Wieczorek A, Jadczak Ł. The relationship between jumping performance, isokinetic strength and dynamic postural control in elite youth soccer players. J Sports Med Phys Fitness. 2018;58:1226–33.
Van Dyk N, Witvrouw E, Bahr R. Interseason variability in isokinetic strength and poor correlation with Nordic hamstring eccentric strength in football players. Scand J Med Sci Sports. 2018;28:1878–87.
Buśko K, Górski M, Nikolaidis PT, Mazur-Różycka J, Łach P, Staniak Z, et al. Leg strength and power in Polish striker soccer players. Acta Bioeng Biomech. 2018;20:109–16.
Bakken A, Targett S, Bere T, Eirale C, Farooq A, Mosler AB, et al. Muscle strength is a poor screening test for predicting lower extremity injuries in professional male soccer players: a 2-year prospective cohort study. Am J Sports Med. 2018;46:1481–91.
Lee JWY, Cai M-J, Yung PSH, Chan K-M. Reliability, validity, and sensitivity of a novel smartphone-based eccentric hamstring strength test in professional football players. Int J Sports Physiol Perform. 2018;13:620–4.
Haugen TA. Soccer seasonal variations in sprint mechanical properties and vertical jump performance. Kinesiology. 2018;50:102–8.
Murtagh CF, Vanrenterghem J, O’Boyle A, Morgans R, Drust B, Erskine RM. Unilateral jumps in different directions: a novel assessment of soccer-associated power? J Sci Med Sport. 2017;20:1018–23.
Kobal R, Loturco I, Barroso R, Gil S, Cuniyochi R, Ugrinowitsch C, et al. Effects of different combinations of strength, power, and plyometric training on the physical performance of elite young soccer players. J Strength Cond Res. 2017;31:1468–76.
Śliwowski R, Grygorowicz M, Hojszyk R, Jadczak Ł. The isokinetic strength profile of elite soccer players according to playing position. PLoS ONE. 2017;12: e0182177.
Abade E, Sampaio J, Gonçalves B, Baptista J, Alves A, Viana J. Effects of different re-warm up activities in football players’ performance. PLoS ONE. 2017;12: e0180152.
Requena B, García I, Suárez-Arrones L, Sáez De Villarreal E, Naranjo Orellana J, Santalla A. Off-season effects on functional performance, body composition, and blood parameters in top-level professional soccer players. J Strength Cond Res. 2017;31:939–46.
Light N, Thorborg K. The precision and torque production of common hip adductor squeeze tests used in elite football. J Sci Med Sport. 2016;19:888–92.
Loturco I, Pereira LA, Kobal R, Maldonado T, Piazzi AF, Bottino A, et al. Improving sprint performance in soccer: effectiveness of jump squat and Olympic push press exercises. PLoS ONE. 2016;11: e0153958.
Mosler AB, Crossley KM, Thorborg K, Whiteley RJ, Weir A, Serner A, et al. Hip strength and range of motion: normal values from a professional football league. J Sci Med Sport. 2017;20:339–43.
Pareja-Blanco F, Sánchez-Medina L, Suárez-Arrones L, González-Badillo JJ. Effects of velocity loss during resistance training on performance in professional soccer players. Int J Sports Physiol Perform. 2017;12:512–9.
Krommes K, Petersen J, Nielsen MB, Aagaard P, Hölmich P, Thorborg K. Sprint and jump performance in elite male soccer players following a 10-week Nordic hamstring exercise protocol: a randomised pilot study. BMC Res Notes. 2017;10:669.
Yanci J, Los AA. Monitoring perceived respiratory and muscular exertions and physical fitness in young professional soccer players during a 32-week period. Kinesiology. 2017;49:153–60.
Belhaj K, Meftah S, Mahir L, Lmidmani F, Elfatimi A. Isokinetic imbalance of adductor–abductor hip muscles in professional soccer players with chronic adductor-related groin pain. Eur J Sport Sci. 2016;16:1226–31.
Van Dyk N, Bahr R, Whiteley R, Tol JL, Kumar BD, Hamilton B, et al. Hamstring and quadriceps isokinetic strength deficits are weak risk factors for hamstring strain injuries: a 4-year cohort study. Am J Sports Med. 2016;44:1789–95.
Fessi MS, Zarrouk N, Filetti C, Rebai H, Elloumi M, Moalla W. Physical and anthropometric changes during pre and in-season in professional soccer players. J Sports Med Phys Fitness. 2016;56:1163–70.
Spineti J, Figueiredo T, Bastos DE, Oliveira V, Assis M, Fernandes DE, Oliveira L, Miranda H, et al. Comparison between traditional strength training and complex contrast training on repeated sprint ability and muscle architecture in elite soccer players. J Sports Med Phys Fitness. 2016;56:1269–78.
Carvalho A, Brown S, Abade E. Evaluating injury risk in first and second league professional Portuguese soccer: muscular strength and asymmetry. J Hum Kinet. 2016;51:19–26.
Rey E, Padrón-Cabo A, Barcala-Furelos R, Mecías-Calvo M. Effect of high and low flexibility levels on physical fitness and neuromuscular properties in professional soccer players. Int J Sports Med. 2016;37:878–83.
Loturco I, Pereira LA, Kobal R, Kitamura K, Ramírez-Campillo R, Zanetti V, et al. Muscle contraction velocity: a suitable approach to analyze the functional adaptations in elite soccer players. J Sports Sci Med. 2016;15:483–91.
Noon MR, James RS, Clarke ND, Akubat I, Thake CD. Perceptions of well-being and physical performance in English elite youth footballers across a season. J Sports Sci. 2015;33:2106–15.
Enright K, Morton J, Iga J, Drust B. The effect of concurrent training organisation in youth elite soccer players. Eur J Appl Physiol. 2015;115:2367–81.
Ruas CV, Pinto MD, Brown LE, Minozzo F, Mil-Homens P, Pinto RS. The association between conventional and dynamic control knee strength ratios in elite soccer players. IES. 2015;23:1–12.
Tsiokanos A, Paschalis V, Valasotiris K. Knee extension strength profile of elite Greek soccer players. IES. 2016;24:79–82.
Pareja-Blanco F, Suarez-Arrones L, Rodríguez-Rosell D, López-Segovia M, Jiménez-Reyes P, Bachero-Mena B, et al. Evolution of determinant factors of repeated sprint ability. J Hum Kinet. 2016;54:115–26.
Bogdanis G, Kalapotharakos V. Knee extension strength and hamstrings-to-quadriceps imbalances in elite soccer players. Int J Sports Med. 2015;37:119–24.
Gil S, Loturco I, Tricoli V, Ugrinowitsch C, Kobal R, Cal Abad CC, et al. Tensiomyography parameters and jumping and sprinting performance in Brazilian elite soccer players. Sports Biomechanics. 2015;14:340–50.
Loturco I, Nakamura FY, Kobal R, Gil S, Cal Abad CC, Cuniyochi R, et al. Training for power and speed: effects of increasing or decreasing jump squat velocity in elite young soccer players. J Strength Cond Res. 2015;29:2771–9.
Ardern CL, Pizzari T, Wollin MR, Webster KE. Hamstrings strength imbalance in professional football (soccer) players in Australia. J Strength Cond Res. 2015;29:997–1002.
Loturco I, Pereira LA, Kobal R, Zanetti V, Kitamura K, Abad CCC, et al. Transference effect of vertical and horizontal plyometrics on sprint performance of high-level U-20 soccer players. J Sports Sci. 2015;33:2182–91.
Ruas CV, Minozzo F, Pinto MD, Brown LE, Pinto RS. Lower-extremity strength ratios of professional soccer players according to field position. J Strength Cond Res. 2015;29:1220–6.
Arcos AL, Martínez-Santos R, Yanci J, Mendiguchia J, Méndez-Villanueva A. Negative associations between perceived training load, volume and changes in physical fitness in professional soccer players. J Sports Sci Med. 2015;14:394–401.
Booysen MJ, Gradidge PJ-L, Watson E. The relationships of eccentric strength and power with dynamic balance in male footballers. J Sports Sci. 2015;33:2157–65.
Owen A, Dunlop G, Rouissi M, Chtara M, Paul D, Zouhal H, et al. The relationship between lower-limb strength and match-related muscle damage in elite level professional European soccer players. J Sports Sci. 2015;33:2100–5.
Tol JL, Hamilton B, Eirale C, Muxart P, Jacobsen P, Whiteley R. At return to play following hamstring injury the majority of professional football players have residual isokinetic deficits. Br J Sports Med. 2014;48:1364–9.
Edholm P, Krustrup P, Randers MB. Half-time re-warm up increases performance capacity in male elite soccer players: Half-time re-warm up and soccer performance. Scand J Med Sci Sports. 2014;25:e40–9.
Brocherie F, Girard O, Forchino F, Al Haddad H, Dos Santos GA, Millet GP. Relationships between anthropometric measures and athletic performance, with special reference to repeated-sprint ability, in the Qatar national soccer team. J Sports Sci. 2014;32:1243–54.
Haddad M, Dridi A, Chtara M, Chaouachi A, Wong DP, Behm D, et al. Static stretching can impair explosive performance for at least 24 hours. J Strength Cond Res. 2014;28:140–6.
Arcos AL, Yanci J, Mendiguchia J, Salinero JJ, Brughelli M, Castagna C. Short-term training effects of vertically and horizontally oriented exercises on neuromuscular performance in professional soccer players. Int J Sports Physiol Perform. 2014;9:480–8.
Koundourakis NE, Androulakis N, Spyridaki EC, Castanas E, Malliaraki N, Tsatsanis C, et al. Effect of different seasonal strength training protocols on circulating androgen levels and performance parameters in professional soccer players. Hormones. 2014;13:104–18.
Koundourakis NE, Androulakis NE, Malliaraki N, Tsatsanis C, Venihaki M, Margioris AN. Discrepancy between exercise performance, body composition, and sex steroid response after a six-week detraining period in professional soccer players. PLoS ONE. 2014;9: e87803.
Portella DL, Cossio-Bolaños MA, Hespanhol JE, De Arruda M. Fat-free mass and bone mineral content positively affect peak torque production in Brazilian soccer players. IES. 2014;22:273–8.
Requena B, Garcia I, Requena F, Bressel E, Saez-Saez De Villarreal E, Cronin J. Association between traditional standing vertical jumps and a soccer-specific vertical jump. Eur J Sport Sci. 2014;14:S398-405.
Haugen TA, Tønnessen E, Seiler S. Anaerobic performance testing of professional soccer players 1995–2010. Int J Sports Physiol Perform. 2013;8:148–56.
Rebelo A, Brito J, Maia J, Coelho-e-Silva M, Figueiredo A, Bangsbo J, et al. Anthropometric characteristics, physical fitness and technical performance of under-19 soccer players by competitive level and field position. Int J Sports Med. 2012;34:312–7.
Menzel H-J, Chagas MH, Szmuchrowski LA, Araujo SRS, De Andrade AGP, De Jesus-Moraleida FR. Analysis of lower limb asymmetries by isokinetic and vertical jump tests in soccer players. J Strength Cond Res. 2013;27:1370–7.
Silva JR, Magalhães J, Ascensão A, Seabra AF, Rebelo AN. Training status and match activity of professional soccer players throughout a season. J Strength Cond Res. 2013;27:20–30.
Loturco I, Ugrinowitsch C, Tricoli V, Pivetti B, Roschel H. Different loading schemes in power training during the preseason promote similar performance improvements in Brazilian elite soccer players. J Strength Cond Res. 2013;27:1791–7.
Castagna C, Castellini E. Vertical jump performance in Italian male and female national team soccer players. J Strength Cond Res. 2013;27:1156–61.
Lago Peñas C, Rey E, Lago Ballesteros J, Dominguez E, Casais L. Seasonal variations in body composition and fitness parameters according to individual percentage of training completion in professional soccer players. Int SportMed J. 2013;14:205–15.
Daneshjoo A, Mokhtar AH, Rahnama N, Yusof A. Effects of the 11+ and Harmoknee warm-up programs on physical performance measures in professional soccer players. J Sports Sci Med. 2013;12:489–96.
Boone J, Vaeyens R, Steyaert A, Bossche LV, Bourgois J. Physical fitness of elite Belgian soccer players by player position. J Strength Cond Res. 2012;26:2051–7.
Chaouachi A, Manzi V, Chaalali A, Wong DP, Chamari K, Castagna C. Determinants analysis of change-of-direction ability in elite soccer players. J Strength Cond Res. 2012;26:2667–76.
Daneshjoo A, Mokhtar AH, Rahnama N, Yusof A. The effects of injury preventive warm-up programs on knee strength ratio in young male professional soccer players. PLoS ONE. 2012;7: e50979.
Whiteley R, Jacobsen P, Prior S, Skazalski C, Otten R, Johnson A. Correlation of isokinetic and novel hand-held dynamometry measures of knee flexion and extension strength testing. J Sci Med Sport. 2012;15:444–50.
Greco CC, Da Silva WL, Camarda SRA, Denadai BS. Rapid hamstrings/quadriceps strength capacity in professional soccer players with different conventional isokinetic muscle strength ratios. J Sports Sci Med. 2012;11:418–22.
Requena B, Sáez-Sáez De Villarreal E, Gapeyeva H, Ereline J, García I, Pääsuke M. Relationship between postactivation potentiation of knee extensor muscles, sprinting and vertical jumping performance in professional soccer players. J Strength Cond Res. 2011;25:367–73.
Silva JR, Magalhães JF, Ascensão AA, Oliveira EM, Seabra AF, Rebelo AN. Individual match playing time during the season affects fitness-related parameters of male professional soccer players. J Strength Cond Res. 2011;25:2729–39.
Jovanovic M, Sporis G, Omrcen D, Fiorentini F. Effects of speed, agility, quickness training method on power performance in elite soccer players. J Strength Cond Res. 2011;25:1285–92.
Helgerud J, Rodas G, Kemi OJ, Hoff J. Strength and endurance in elite football players. Int J Sports Med. 2011;32:677–82.
Rønnestad BR, Nymark BS, Raastad T. Effects of in-season strength maintenance training frequency in professional soccer players. J Strength Cond Res. 2011;25:2653–60.
Bogdanis GC, Papaspyrou A, Souglis AG, Theos A, Sotiropoulos A, Maridaki M. Effects of two different half-squat training programs on fatigue during repeated cycling sprints in soccer players. J Strength Cond Res. 2011;25:1849–56.
Faude O, Kellmann M, Ammann T, Schnittker R, Meyer T. Seasonal changes in stress indicators in high level football. Int J Sports Med. 2011;32:259–65.
Zebis MK, Andersen LL, Ellingsgaard H, Aagaard P. Rapid hamstring/quadriceps force capacity in male vs. female elite soccer players. J Strength Cond Res. 2011;25:1989–93.
Cotte T, Chatard J-C. Isokinetic strength and sprint times in English Premier League football players. Biol Sport. 2011;28:89–94.
Henderson G, Barnes CA, Portas MD. Factors associated with increased propensity for hamstring injury in English Premier League soccer players. J Sci Med Sport. 2010;13:397–402.
Wong P, Chaouachi A, Chamari K, Dellal A, Wisloff U. Effect of preseason concurrent muscular strength and high-intensity interval training in professional soccer players. J Strength Cond Res. 2010;24:653–60.
López-Segovia M, Palao Andrés JM, González-Badillo JJ. Effect of 4 months of training on aerobic power, strength, and acceleration in two under-19 soccer teams. J Strength Cond Res. 2010;24:2705–14.
Till KA, Cooke C. The effects of postactivation potentiation on sprint and jump performance of male academy soccer players. J Strength Cond Res. 2009;23:1960–7.
Mujika I, Santisteban J, Castagna C. In-season effect of short-term sprint and power training programs on elite junior soccer players. J Strength Cond Res. 2009;23:2581–7.
Mujika I, Santisteban J, Impellizzeri FM, Castagna C. Fitness determinants of success in men’s and women’s football. J Sports Sci. 2009;27:107–14.
Sporis G, Jukic I, Ostojic SM, Milanovic D. Fitness profiling in soccer: physical and physiologic characteristics of elite players. J Strength Cond Res. 2009;23:1947–53.
Bravo D, Impellizzeri F, Rampinini E, Castagna C, Bishop D, Wisloff U. Sprint vs. Interval training in football. Int J Sports Med. 2008;29:668–74.
Hoshikawa Y, Iida T, Muramatsu M, Nakajima Y, Fukunaga T, Kanehisa H. Differences in thigh muscularity and dynamic torque between junior and senior soccer players. J Sports Sci. 2009;27:129–38.
Clark NA, Edwards AM, Morton RH, Butterly RJ. Season-to-season variations of physiological fitness within a squad of professional male soccer players. J Sports Sci Med. 2008;7:157–65.
Ronnestad BR, Kvamme NH, Sunde A, Raastad T. Short-term effects of strength and plyometric training on sprint and jump performance in professional soccer players. J Strength Cond Res. 2008;22:773–80.
Chamari K, Chaouachi A, Hambli M, Kaouech F, Wisløff U, Castagna C. The five-jump test for distance as a field test to assess lower limb explosive power in soccer players. J Strength Cond Res. 2008;22:944–50.
Cressey EM, West CA, Tiberio DP, Kraemer WJ, Maresh CM. The effects of ten weeks of lower-body unstable surface training on markers of athletic performance. J Strength Cond Res. 2007;21:561.
Rampinini E, Bishop D, Marcora S, Ferrari Bravo D, Sassi R, Impellizzeri F. Validity of simple field tests as indicators of match-related physical performance in top-level professional soccer players. Int J Sports Med. 2007;28:228–35.
Voutselas V, Papanikolaou Z, Soulas D, Famisis K. Years of training and hamstring-quadriceps ratio of soccer players. Psychol Rep. 2007;101:899–906.
Kalapotharakos VI, Strimpakos N, Vithoulka I, Karvounidis C, Diamantopoulos K, Kapreli E. Physiological characteristics of elite professional soccer teams of different ranking. J Sports Med Phys Fitness. 2006;46:515–9.
Ostojic SM. Elite and nonelite soccer players: preseasonal physical and physiological characteristics. Res Sports Med. 2004;12:143–50.
Kraemer WJ, French DN, Paxton NJ, Häkkinen K, Volek JS, Sebastianelli WJ, et al. Changes in exercise performance and hormonal concentrations over a big ten soccer season in starters and nonstarters. J Strength Cond Res. 2004;18:121–8.
Chamari K, Hachana Y, Ahmed YB, Galy O, Sghaïer F, Chatard J-C, et al. Field and laboratory testing in young elite soccer players. Br J Sports Med. 2004;38:191–6.
Askling C, Karlsson J, Thorstensson A. Hamstring injury occurrence in elite soccer players after preseason strength training with eccentric overload: hamstring training in soccer players. Scand J Med Sci Sports. 2003;13:244–50.
Ozcakar L. Comprehensive isokinetic knee measurements and quadriceps tendon evaluations in footballers for assessing functional performance. Br J Sports Med. 2003;37:507–10.
Helgerud J, Engen LC, Wisloff U, Hoff J. Aerobic endurance training improves soccer performance. Med Sci Sports Exerc. 2001;33:1925–31.
Casajús JA. Seasonal variation in fitness variables in professional soccer players. J Sports Med Phys Fitness. 2001;41:463–9.
Cometti G, Maffiuletti NA, Pousson M, Chatard J-C, Maffulli N. Isokinetic strength and anaerobic power of elite, subelite and amateur French soccer players. Int J Sports Med. 2001;22:45–51.
Al-Hazzaa HM, Almuzaini KS, Al-Refaee SA, Sulaiman MA, Dafterdar MY, Al-Ghamedi A, et al. Aerobic and anaerobic power characteristics of Saudi elite soccer players. J Sports Med Phys Fitness. 2001;41:54–61.
Gür H, Akova B, Pündük Z, Küçükoǧlu S. Effects of age on the reciprocal peak torque ratios during knee muscle contractions in elite soccer players. Scand J Med Sci Sports. 2007;9:81–7.
Wisløff U, Helgerud J, Hoff J. Strength and endurance of elite soccer players. Med Sci Sports Exerc. 1998;30:462–7.
Aagaard P, Simonsen EB, Trolle M, Bangsbo J, Klausen K. Specificity of training velocity and training load on gains in isokinetic knee joint strength. Acta Physiol Scand. 1996;156:123–9.
Chin MK, Lo YS, Li CT, So CH. Physiological profiles of Hong Kong elite soccer players. Br J Sports Med. 1992;26:262–6.
Mangine RE, Noyes FR, Mullen MP, Barber SD. A physiological profile of the elite soccer athlete. J Orthop Sports Phys Ther. 1990;12:147–52.
Poulmedis P. Isokinetic maximal torque power of Greek elite soccer players. J Orthop Sports Phys Ther. 1985;6:293–5.
Rhodes EC, Mosher RE, McKenzie DC, Franks IM, Potts JE, Wenger HA. Physiological profiles of the Canadian Olympic Soccer Team. Can J Appl Sport Sci. 1986;11:31–6.
Bishop C, Manuel J, Drury B, Beato M, Turner A. Assessing eccentric hamstring strength using the NordBord: between-session reliability and interlimb asymmetries in professional soccer players. J Strength Cond Res. 2022;36:2552–7.
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NA, CB and AT conceived the idea for this review. All authors contributed to the establishment of the search criteria and the refinement of final methodology. NA, CB and AT conducted the literature search. All authors collectively interpreted the results of the systematic review. NA wrote the first draft of the manuscript. CB, MB and AT revised the manuscript. All authors read and approved the final version.
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Nikolaos D. Asimakidis, Irvin N. Mukandi, Marco Beato, Chris Bishop and Anthony N. Turner have no conflicts of interest that are directly relevant to the content of this review.
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The dataset generated and analysed during the current study are available from the corresponding author on reasonable request.
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Author Contributions
NA, CB and AT conceived the idea for this review. All authors contributed to the establishment of the search criteria and the refinement of final methodology. NA, CB and AT conducted the literature search. All authors collectively interpreted the results of the systematic review. NA wrote the first draft of the manuscript. CB, MB and AT revised the manuscript. All authors read and approved the final version.
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Asimakidis, N.D., Mukandi, I.N., Beato, M. et al. Assessment of Strength and Power Capacities in Elite Male Soccer: A Systematic Review of Test Protocols Used in Practice and Research. Sports Med (2024). https://doi.org/10.1007/s40279-024-02071-8
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DOI: https://doi.org/10.1007/s40279-024-02071-8