Identification and Selection of Studies
Through the original database search 2464 articles were identified, with six others found through other sources. Following the removal of duplicates and screening for eligibility, 27 articles remained for analysis [25, 32, 35, 36, 40,41,42, 44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63]. Figure 1 provides a schematic representation of the decision process.
Table 1 shows the characteristics of the 27 studies included in the review. Six different football codes were covered: soccer (n = 6) [40, 42, 45, 56, 57, 61], Australian Football (n = 2) [25, 47], rugby league (n = 7) [32, 36, 44, 46, 49, 50, 63], rugby sevens (n = 4) [35, 41, 51, 52], rugby union (n = 5) [48, 53,54,55, 58] and Gaelic Football (n = 3) [59, 60, 62]. Six studies reported the sex of the participants directly [42, 57, 58, 61,62,63], 19 studies reported the league/competition that the participants compete in thus the sex could be inferred, and two studies did not report the sex or competition [48, 55]. The playing standard of participants in the studies included international (n = 8; 30%), professional club (n = 12; 44%) and semi-professional/elite (n = 7; 26%). Most studies (n = 20; 77%) were carried out with only one team. Information on the microtechnology devices utilised in the study is shown in Table 2.
The scores for the assessment of methodological quality are shown in Table 3, ranging from 7 to 9, out of the 11 items assessed.
Methodology for Quantifying the Peak Match Demands
Table 4 shows the different methodologies used by the studies included in the review. Three different methods of analysis were used: segmental analysis, moving averages and the period of longest ball in play, and several different temporal durations. Two studies directly compared two methods (segmental vs. moving average) [45, 55].
Eleven studies [32, 40, 42, 44, 45, 49, 52, 55, 57, 59, 60] used segmental analysis of pre-determined time periods. This method involved authors specifying the time-period of interest, then splitting the match accordingly following the zero-minute mark. For example, for 5-min blocks a match would be split from 0–5, 5–10, 10–15 min, etc. To determine the peak demands of the match the authors then selected the period with the highest demands of their specified variable(s) of interest.
Varley et al.  were the first investigators to use the moving averages method; they directly compared it to the segmental methodology. Subsequently, 16 other studies have used this method [25, 35, 36, 41, 42, 46,47,48, 50, 51, 54,55,56, 58, 62, 63]. The moving averages method requires the analysis of the raw instantaneous data, which are sampled at a given rate dependent upon the GPS device used (i.e. a 10-Hz GPS device takes ten instantaneous speed samples per second). To determine the ‘peak’ demands using this method a moving average of a specified duration is taken from the raw data. For example, for 1-min periods a moving average of 600 data points (60 s with ten samples per second) would be calculated from the start to the end of the match, i.e. 0–600, 1–601, 2–602, 3–603, etc., for the duration of the file, and the peak 1-min identified from this.
Ball in Play
Reardon et al.  is the only study to use the ‘ball in play’ method. They defined the peak demands by identifying the longest period of time when the ball is in play, then extracted the physical demands within this period.
A range of durations were used to quantify peak demands in the studies included in the review as shown in Table 4; the most commonly used duration was 5 min, used by 78% (n = 21) of studies. Nine studies used multiple duration-specific periods [36, 46,47,48, 55, 56, 58, 62, 63], and six of these compared the derived peak demands between each duration [36, 46,47,48, 58, 62].
Variables Used for Analysing the Peak Match Demands
Table 4 shows the variables used by the studies included in the review. Two or more variables were used by 67% (n = 18) of studies. All studies used at least one locomotive variable (i.e. walking, running, sprinting).
Total Distance Covered
Total distance is the distance accumulated by a player over the specified time-period and was used by six of the studies identified in this review [35, 44, 50, 53, 57, 61]. Three different durations were used to determine the ‘peak’ total distance covered: 1 min , 5 min [44, 50, 57] and the ‘longest period of ball in play’ . Table 5 shows the distances covered in the specified durations and different methods of analysis. Although only five studies reported total distance directly, this could be extrapolated when relative distance was reported for specified time periods.
Relative Distance Covered
Relative distance (m·min−1) is a function of the distance covered relative to the time it is covered in, providing a proxy indication of the ‘intensity’ . It was used by 63% (n = 17) of the studies included in the review, with 13 out of the 17 studies using the moving average method. The peak 1-, 5- and 10-min relative distances across the football codes are shown in Fig. 2. All other duration-specific periods are shown in Electronic Supplementary Material Fig. S1. Reardon et al.  analysed relative distance within the ‘longest period of ball in play’ in rugby union.
External Load Completed Within Speed Zones
Fifty-seven percent (n = 16) of studies used variables based on speed zones. Speed zones are categorised by specific thresholds identified by the author. Within the studies included in the review 12 different thresholds were used to categorise ‘high speed’ or ‘high intensity’ running, and four to categorise ‘sprint speed’ or ‘very high intensity’ running. Relative distance covered in specified speed zones was used by 11 studies [25, 32, 41, 42, 47, 49, 55, 56, 61, 62] and total distance covered by four [35, 45, 50, 53]. The relative and total distances covered in the specified speed zones for specified durations are shown in Tables 6 and 7. One study used percentage of distance covered at ‘high speed’ per minute of match play , and one used the number of efforts in the specified ‘sprint’ threshold .
Ten studies used an acceleration and/or deceleration metric to quantify the peak match demands, with three different variables used [35, 40, 46,47,48, 56, 57, 59,60,61]. Three studies used distance covered at acceleration to describe the peak 5-min demands [40, 59, 60]. Akenhead et al.  used distance covered at high (> 3 m·s−2) acceleration and high (< − 3 m·s−2) deceleration to describe the peak 5-min demands; however, they only reported percentage change from the mean for the peak demands for these values thus values are not reported. The two studies by Ryan et al. [59, 60] in Gaelic Football both reported acceleration distance only, and at a lower threshold of > 2 km·h−2 (0.55 m·s−2). Four studies used absolute acceleration/deceleration (AveAcc) as one combined metric [46,47,48, 56], calculated using the instantaneous acceleration and deceleration of the player (calculated as the rate of change in speed), then taken as an absolute value (i.e. all values being positive) . The studies that used this metric all utilised the moving averages approach to identify duration-specific peak AveAcc demands. The peak 1-, 5- and 10-min AveAc demands are shown in Fig. 3. All other duration-specific periods are shown in Electronic Supplementary Material Fig. S2. The final acceleration variable used was the count of high acceleration occurrences, with each of the three studies using different acceleration speed and minimum duration thresholds [35, 57, 61].
Metabolic power is based on a theoretical model that assumes accelerated running on flat terrain has the same energetic requirements as uphill running at a constant speed [64, 65]. It estimates the energetic cost of match play, using speed and acceleration derived from the microtechnology and aims to take into account the metabolically demanding movements of team sports that other variables may underestimate, i.e. accelerations and decelerations at low speeds, and high speed running . Six of the studies included in the review used metabolic power to describe peak match demands [46,47,48, 50, 51, 56]. The peak 1-, 5- and 10-min metabolic power demands across the football codes are shown in Fig. 4. All other duration-specific periods are shown in Electronic Supplementary Material Fig. S3. Kempton et al.  reported distance covered over a ‘high power’ threshold set at > 20 W·kg−1 in rugby league, reporting the peak 5-min distance to be 185 m (95% CI 181–190). Carling et al.  used a surrogate measure of metabolic power and described high metabolic load (HLMD) as the distance covered at high intensity running (> 5.5 m·s−2) plus the distance covered while accelerating above 2 m·s−2. They reported the peak 5-min HMLD during rugby union match-play to be 30.6 ± 9.0 and 19.3 ± 4.9 m for backs and forwards, respectively .
Collisions are a component of match-play in several of the football codes (e.g. rugby league, rugby union, rugby sevens, Australian Football); differences in the definition and classification of collisions exist across the codes, with some ambiguity of definitions within the codes . Only two of the studies included in the review used microtechnology to quantify collisions [32, 49], both in rugby league and using segmental analysis, shown in Table 8. In rugby league collisions are defined as any tackles or hit-ups, and decoy runs or support runs where contact is made with a player in the defensive line . Kempton et al. [44, 50] and Reardon et al.  also aimed to quantify peak collision demands, but used video analysis, thus are not considered in this review.
Repeated High-Intensity Efforts
Repeated high-intensity effort bouts (RHIE) are defined as three or more high-velocity (> 5 m·s−1), high-acceleration (≥ 2.79 m·s−2) or contact efforts with less than 21 s recovery between efforts [23, 32]. Two studies reported the peak RHIE demands, either reporting as the absolute number or relative number [32, 49]; values are shown in Table 8.
PlayerLoad™ is a manufacturer-specific parameter (Catapult Innovations, Melbourne, VIC, Australia) that provides a modified vector magnitude using accelerometer data, expressed in arbitrary units (AU) . It is expressed through the accumulation of data from all axes (anteroposterior, mediolateral and craniocaudal) and is calculated as the square root of the sum of the squared instantaneous rate of change in acceleration in each of the three vectors divided by 100 ; it attempts to indicate the ‘total load’ experienced by the athlete. PlayerLoad™ was used by two studies to describe the peak 5 min during soccer match-play, using segmental  and moving averages  analysis; values are shown in Table 8.
Reardon and colleagues  were the only investigators to use maximum velocity to describe the peak demands. They reported the maximum velocity obtained within the identified longest period of ball in play in rugby union; 4.9 (4.70–5.12) m·s−1 for tight five forwards, 5.72 (5.48–5.97) m·s−1 for back row forwards, 6.02 (5.79–6.25) m·s−1 for inside backs and 6.84 (6.57–7.12) m·s−1 for outside backs.
Peak Demands in Football Codes
The peak match demands of rugby league were analysed by 26% (n = 7) of the studies included in the review, making it the most commonly investigated football code. Duration-specific peak relative distance values are shown in Fig. 2; peak 1-min relative distance ranged from ~ 154 to 179 m·min−1 across positional groups [36, 46, 63], and peak 5-min values ranged from ~ 92 to 126 m·min−1 [32, 36, 46, 49, 63]. The two studies that investigated position-specific running intensities reported peak relative distances for 1, 5 and 10 min to be the greatest for fullbacks (~ 172–179, ~ 118–122 and ~ 105–109 m·min−1 respectively), and lowest for the middle forwards (~ 154–163, ~ 102–111 and ~ 90–98 m·min−1, respectively) [36, 46]. Total or relative high speed running distance reported by the studies included in the review in rugby league are shown in Tables 6 and 7. Two studies [32, 49] used > 5 m·s−1 as the specified threshold for ‘high-speed running’; their data showed greater ranges in relative high-speed running distance for the professional clubs across the ‘high’ and ‘low’ success clubs match-play (~ 8–22 m·min−1)  than at the semi-professional level (~ 10–15 m·min−1) . The highest relative high-speed running was reported for ‘low success’ professional outside backs (22 ± 2 m·min−1), and lowest for the professional ‘high-success’ adjustables (8 ± 5 m·min−1) [32, 49]. Other variables used to describe the peak demands in rugby league included AveAcc (Fig. 3 and Electronic Supplementary Material Fig. S2), metabolic power (Fig. 4 and Electronic Supplementary Material Fig. S3), collisions and RHIE (Table 8). Peak 1- and 5-min AveAcc ranged from ~ 1.22 to 1.28 and ~ 0.80 to 0.91 m·s−2, respectively, across positions, and was greatest for hookers at most duration-specific periods . Peak 1- and 5-min metabolic power ranged from ~ 16.4 to 18.1 and ~ 10.7 to 11.7 W·kg−1, respectively, across positions .
Peak 1-min total and high-speed distance covered in international level rugby sevens match play was reported by Murray and Varley  to be 183 ± 30 and 86 ± 30 m, respectively. Granatelli et al.  reported 31.2% of distance covered in 1 min to be the peak high-speed running (> 3.9 m·s−1) demands of professional level match-play. Electronic Supplementary Material Fig. S3 shows peak metabolic power for a 2-min duration . Murray and Varley  used a moving average approach to identify peak acceleration count (≥ 2.87 m·s−2), reporting values of 3.8 ± 1.6 for a 1-min period.
AveAcc (Fig. 3 and Electronic Supplementary Material Fig. S2) and metabolic power (Fig. 4 and Electronic Supplementary Material Fig. S3) were analysed by Delaney and colleagues  for different positional groups: outside backs, half backs, tight five and loose forwards. For 1-min durations peak AveAcc ranged from ~ 0.87 to 1.01 m·s−2 and metabolic power ranged from ~ 14.0 to 17.3 W·kg−1 across positional groups. Duration-specific peak relative distances were reported for different positional groups by three studies [48, 55, 58], shown in Fig. 2. For the peak relative distance values ranged from ~ 139 to 185 m·min−1 for the 1-min periods and from ~ 86 to 116 m·min−1 for the peak 5-min periods [48, 55, 58], with the highest demands reported for Academy level scrum halves at both durations . Reardon et al.  identified the average longest period of ball in play for positional groups; tight five forwards (161 s), back row forwards (152 s), inside backs (154 s) and outside backs (155 s). The relative distances covered in these periods were: 109 (104–114) m·min−1 for tight five forwards, 111 (105–117) m·min−1 for back row forwards, 123 (117–129) m·min−1 for inside backs, and 124 (117–131) m·min−1 for outside backs. Total distances covered during the longest period of ball in play are shown in Table 5. Two studies reported relative high-speed running distance during rugby union match play (shown in Table 7), both of which reported greater distances for backs compared to forwards [53, 55]. Reardon et al.  also reported the number of ‘sprint’ efforts during the peak period: 0.02 (− 0.04 to 0.07) for tight five forwards, 0.02 (− 0.04 to 0.08) for back row forwards, 0.06 (0.00 to 0.11) for inside backs and 0.11 (0.04 to 0.16) for outside backs in the longest period of ball in play.
Soccer is the only football code in the studies included in this review to report peak demands for female players during match play [57, 61]. Peak relative distance has been reported for different positional groups in male and female soccer over a number of duration specific periods (Fig. 2 and Electronic Supplementary Material Fig. S1). The 5-min duration values reported ranged from ~ 129 to 148 m·min−1 for male soccer  and from ~ 132 to 146 m·min−1 for female soccer  using the moving averages method of analysis, with the greatest values reported for the central midfielders and midfielders, respectively. Conversely, Ramos et al.  reported female ‘midfielders’ to cover the least total distance during the peak 5 min using segmental analysis, and fullbacks to cover the most (595 ± 51 vs. 653 ± 41 m, respectively) (Table 5). Five out of the six studies on soccer reported relative or total high-speed running, all of which used different thresholds, shown in Tables 6 and 7, respectively. Varley et al.  revealed greater high intensity running (> 4.17 m·s−1) distance covered using moving averages compared to segmental analysis (177 ± 91 vs. 142 ± 24 m) for peak 5-min periods of match play for male players. For female soccer players both studies reported fullbacks to cover the greatest high-speed running distance (~ 100–153 m), and centre backs the least (~ 67–101 m), over a 5-min epoch [57, 61]. Ramos et al.  also reported the peak 5-min ‘sprint’ distance (> 5.6 m·s−1) during female soccer match play: 37.1 ± 15.3 m for centre backs, 57.4 ± 16.9 m for fullbacks, 36.4 ± 13.6 m for midfielders and 60.7 ± 14.6 m for forwards. Metabolic power (Fig. 4 and Electronic Supplementary Material Fig. S3) and AveAcc (Fig. 3 and Electronic Supplementary Material Fig. S2) were reported over a range of duration-specific periods for male players during match play . For 1-min durations peak AveAcc ranged from ~ 0.81 to 0.89 m·s−2 and ~ 16.7 to 19.0 W·kg−1 across positional groups . Peak 5-min acceleration count of female match play was reported by two studies [57, 61], and deceleration count by one . Ramos et al.  reported the lowest acceleration count for centre backs (2.11 ± 0.60 m·s−2), and highest for forwards (3.44 ± 1.13 m·s−2), whereas Trewin et al.  reported the highest count to be for both centre backs (3.44 ± 0.59 m·s−2) and forwards (3.44 ± 0.74 m·s−2). PlayerLoad™ was reported by two studies for peak 5-min periods (values are shown in Table 8). Using segmental analysis across positional groups, peak 5-min PlayerLoad™ values of ~ 68–75 AU were reported , compared to ~ 70–87 AU when moving averages analysis was used .
Figure 2 and Table 6 show duration-specific peak relative distance and relative high-speed running distance, respectively, for durations from 1 to 10 min. Relative distance ranged from ~ 199 to 215 m·min−1 for peak 1-min durations, and from ~ 131 to 141 m·min−1 for 10 min across positional groups, with higher intensities for midfielders and mobile forwards than tall backs . The highest relative high-speed running distance was reported for mobile forwards, and lowest for rucks, across all durations investigated . Duration-specific peak AveAcc and metabolic power for 1-, 5- and 10-min durations are shown in Figs. 3 and 4, respectively, with peak 1-min values ranging from ~ 0.94 to 1.05 m·s−2 for AveAcc and ~ 17.8 to 20.8 W·kg−1 for metabolic power, across positional groups. At durations of 1, 5 and 10 min mobile backs were reported to have the greatest AveAcc (1.05 ± 0.17, 0.81 ± 0.13 and 0.72 ± 0.05 m·s−2, respectively), and mobile forwards the greatest metabolic power (20.8 ± 3.6, 14.6 ± 1.3 and 12.8 ± 1.3 W·kg−1, respectively) .
Relative total, high-speed running and sprint distances were reported by Malone et al.  for 1–10 min across different positions: full-back, half-back, midfield, half-forward and full-forward. For the 1-min duration peak relative distance ranged from ~ 194 to 255 m·min−1 and relative high-speed running distance ranged from ~ 36 to 50 m·min−1 across positions, with midfielders reported to cover the greatest and full-backs and full-forwards the least for both variables (Fig. 2). The peak acceleration distance covered over 5 min was reported by two studies [59, 60]. A whole squad average peak acceleration distance of 296 ± 10 m was reported in one study , but position-specific values have also been reported : 372 ± 107 m for full-backs, 458 ± 79 m for half-backs, 538 ± 58 m for midfielders and 455 ± 95 m for half-forwards, 349 ± 98 m for full-forwards.