Fourteen male university rugby union players with a resistance training history of over 2 years were recruited to take part in the study (Table 1). All participants had at least 6 months uninterrupted resistance training, performing at least three resistance training sessions each week. Participants were screened prior to the study for any contraindication to physical activity. Throughout the study participants refrained from dietary supplements, and the only medication used by one participant was for the treatment of mild asthma. All protocols were explained and informed consent was obtained from all individual participants included in the study prior to the beginning of the study. Ethics approval was granted by the university ethics committee.
This study was a randomised-crossover design that took place over 4 weeks at the beginning of the university rugby union pre-season (i.e., July–August). All participants had followed an off-season resistance training programme and initiated the study with a comparable training base. The study consisted of a familiarisation assessment, followed by three resistance training protocols (i.e., TRAD, SS, TRI) in a randomised order. Twenty-four hours after the resistance training protocol participants were required to return to the exercise laboratory for follow-up measures. Figure 1 further outlines the protocols and timepoints. In the 48 h before all testing, participants were asked to refrain from vigorous exercise, maintain normal dietary patterns, sleep well (i.e., >7 h), consume a meal 2 h before testing, and maintain normal hydration levels. After each testing session, participants were asked to consume their regular post-exercise meal and to not partake in any further exercise for 24 h.
Resistance training protocols
Each protocol contained the same six exercises (i.e., back squat, bench press, Romanian deadlift, dumbbell shoulder press, bent-over row, and upright row), although grouped into a TRAD, SS, or TRI configuration (refer to Fig. 1). TRAD resistance training referred to the completion of a single exercise set followed by a rest period. All exercise sets were then completed prior to completing any other exercises. In the SS protocol, however, two different exercise sets were completed consecutively followed by a rest period. These two different exercises were then repeated until the required number of sets was completed. TRI involved an additional exercise and set (i.e., three consecutive sets of different exercises) followed by a rest period. All three exercise sets were then completed prior to completing the final three exercises. Sixty-five percent of each movement’s three repetition maximum (3RM) was calculated and used as the prescribed intensity for each exercise across the three training protocols. This intensity was selected due to previous research by Sabido et al. (2016) indicating that when completing supersets, intensities above this cause notable losses in repetition completion (i.e., 12.5%). All participants participated in the three resistance training sessions with exactly 7 days between protocols.
On testing days, participants were informed of the protocol that would be completed, and provided a salivary and finger-tip blood sample on arrival for the analysis of testosterone and cortisol concentration, and [Lac] and creatine kinase concentration [CK], respectively. Upon the completion of a standardised warm up, which included dynamic exercise and exercise specific stretches [i.e., walking lunges, squats, heel flicks, high knees, skipping, three submaximal CMJ, and plyometric push ups (Roe et al. 2016b)], a CMJ was completed upon a force platform (NMP Technologies Ltd., ForceDecks Model FD4000a, London, UK). After the CMJ, an exercise specific warm up utilising the first exercise/grouping of exercises (i.e., squat in the TRAD; squat and bench press in the SS; squat, bench press, and Romanian deadlift in the TRI) was completed. This consisted of eight repetitions with an empty bar, followed by two sets of five repetitions and then three repetitions at submaximal self-selected loads. This has previously been completed in resistance training literature (Darrall-Jones et al. 2015; Weakley et al. 2017a, b). After the completion of the exercise specific warm up, the exercises were organised with 65% of the participants 3RM and a 2-min rest prior to the commencement of exercise was provided.
Exercises were grouped, so that similar muscle groups were not completed consecutively (Sabido et al. 2016), and so that large muscle groups were exercised prior to smaller muscle groups (e.g., back squat followed by bench press) (Haff and Triplett 2015). The specific exercise routine was undertaken with 2-min rest between every exercise set/grouping of exercises. While all repetitions maintained a two second eccentric phase (monitored by the lead researcher) followed by an explosive concentric phase. In total, six exercises each consisting of three sets and ten repetitions were completed. Finger-tip blood samples were taken after the 6th and 12th sets for the assessment of [Lac]. At the completion of the 18th and final set, finger-tip samples were taken again (for [Lac]), along with CMJ and salivary sample (for testosterone and cortisol concentration). 15 min after the completion of each resistance training protocol participants provided an RPE utilising a modified-Borg scale (Singh et al. 2007). At 24-h post-protocol, participants returned and provided a 5 ml salivary sample and a finger-tip blood sample was taken for [CK]. Following these measures, participants completed the same standardised warm up as the previous day and completed CMJ testing upon the same force plate. Figure 1 outlines the protocols and timepoints of testing.
Strength measures and anthropometric assessment
During a familiarisation session 3RM strength, body mass, and height were measured. Body mass and height were measured to the nearest 0.1 kg and 0.1 cm, respectively, using calibrated Seca Alpha (model 220, Germany) scales and Seca Alpha (model 213, Germany) stadiometer. Strength was measured with the back squat, bench press, Romanian deadlift, dumbbell shoulder press, bent-over row, and upright row being tested. These movements were chosen as they have previously been used in similar studies (Harries et al. 2016; Smart and Gill 2013; Till et al. 2015), while all participants were familiar with the movements as they had been in previous resistance training programmes.
3RM strength was assessed using the following exercise protocols, previously outlined (Haff and Triplett 2015; Smart and Gill 2013; Uribe et al. 2010; Weakley et al. 2017b). The back squat was completed with the bar resting on the upper trapezium with participants required to lower themselves, so that the top of the thigh was parallel with the floor. The bench press was completed with hand position at a self-selected width with the bar lowered to the chest and returned to a locked-out position. Romanian deadlift maintained a slight bend in the knee and the lowering of the bar until immediately below the patellar. Dumbbell shoulder press begun with the arms holding the dumbbells, so that the elbow was at a 90° angle with the dumbbells in line with the cranium. The arms were extended and lowered, so that the arms returned to the 90° elbow angle. The bent-over row was completed with an overhand grip which raised the bar to the lower sternum, while the torso was maintained parallel to the ground. The upright row required the participant to hold the barbell with a shoulder width grip; the bar was then raised to the nipple line and returned to the hang position without any additional leg drive.
Saliva samples were taken at three timepoints (i.e., at arrival, immediately post the completion of each protocol, and at the 24-h post-protocol follow-up) across the 24-h period. To standardise collection of all salivary samples, participants were asked not to eat or brush their teeth within 60 min of providing a sample. Furthermore, 15 min before initiating a passive drool, participants were provided 200 ml of water. This was used to ensure minimal sample dilution and to remove food residue within the mouth. The first and last saliva samples were taken at the same time each day to assist in the control for circadian rhythm. Saliva was used due to its previous use in rugby union players, ease of compliance, low invasiveness, and ability to measure biologically active hormones (e.g., testosterone and cortisol) (Crewther and Cook 2010; Gaviglio et al. 2014).
A 5 ml volume of saliva was deposited from the mouth into a 10 ml cryovial and centrifuged within 60 min of provision. Centrifugation was at 3000 RPM for 15 min with the supernatant then being transferred by pipette to commercially available storage equipment (Salimetrics Cryovials, Salimetrics, CA, USA). This was then stored immediately at −80 °C prior to analysis at a private commercial laboratory (Psychology Laboratory, Anglia Ruskin University, UK). The interassay coefficient of variation (CV) for the hormone responses was reported to be 4.3% for testosterone and 7.2% for cortisol.
Analysis of CMJ was completed using a force platform (NMP Technologies Ltd., ForceDecks Model FD4000a, London, UK) which sampled at a rate of 1000 Hz. All participants performed three CMJs with feet placed approximately shoulder width apart and with hands placed on hips. Participants lowered themselves to a self-selected depth and jumped as high as possible. Between each maximal exertion, 60 s rest was provided (Weakley et al. 2017b). The outcome variables which were included in the analysis were: CMJ height (jump height), flight time:contraction time (FT:CT), and peak power per kg of body mass (PP/BM). Jump height was used due to its common use as a measure of lower body power (Roe et al. 2016b; Till et al. 2016; Weakley et al. 2017b). FT:CT was assessed as it provides the practitioner insight into movement strategies and has been suggested to be a valuable measure of fatigue due to it being derived from time-related variables (Gathercole et al. 2015; McGuigan 2017). PP/BM was analysed due to its very large relationship (r = 0.81) with ballistic capabilities (Hori et al. 2008). The best of the three scores at each timepoint was used in analysis (Haddad et al. 2015). Participant CV of these variables was reported to be 4.6% (jump height), 7.8% (FT:CT), and PP/BM (1.3%).
Whole blood samples were collected to assess [CK] upon arrival at the testing facility and at the same corresponding timepoint 24 h later. Samples were collected via finger-tip puncture which was made with a spring-loaded single use disposable lancet. Approximately 30 µl of whole capillary blood was collected using a plastic capillary tube (MICROSAFE©, Safe-tec, Numbrecht, Ivyland, USA) and immediately analysed using reflectance photometry (Reflotron® Plus, Boehringer, Manheim, Germany). 20 min before each testing session, the machine was calibrated using a standardised [CK] strip. Participant reliability of this machine has previously been reported (CV = 5.3%) (Roe et al. 2016a).
Blood [Lac] was analysed before, during, and after the exercise protocols using a lactate analyser (Lactate Plus, Nova Biomedical, MA, USA). After sterilising the finger, a puncture was made with a spring-loaded single use disposable lancet. The first drop of blood was wiped away, with the second drop being applied to an assay strip and inserted into the [LAC] analysing device. This device has previously been reported to demonstrate high levels of reliability (intraclass correlation coefficient = 0.99) at a range of [Lac] values (Baldari et al. 2009).
RPE and session perceived load measures
Participants were asked to provide an RPE 15 min after each resistance training protocol after being asked the question “How was your workout?” Participants were presented with a modified-Borg ratio-10 scale and verbally indicated an answer which was recorded (Singh et al. 2007). Training time was recorded to the nearest minute of duration by the lead researcher, with this time being recorded and then multiplied with the corresponding RPE value to provide session perceived load (Foster et al. 2001).
Calculation of volume load and efficiency
Volume load (kg) [i.e., the multiplication of all sets, repetitions, and weight (kg)] has previously been used as a means of calculating resistance training loads (Peterson et al. 2011). The volume load for each participant was standardised across each protocol, with all sets, repetitions, and external weight being used in the calculation. The volume load value was then divided by training duration in minutes (previously used in the calculation of session perceived load) to calculate training efficiency (kg min−1). This method of calculating resistance training efficiency has previously been used (Robbins et al. 2010a, c).
Data are presented as mean ± standard deviation (SD) or standardised effect size (ES) ± 90% confidence intervals (90% CI). Prior to analysis, all data were log transformed to reduce bias arising from non-uniformity error, and then analysed for practical significance using magnitude-based inferences (Batterham and Hopkins 2006). The threshold for a change to be considered to meet the smallest worthwhile change/difference (SWC/D) was set at 0.2 × the between participant SD and was calculated using an online spreadsheet (Hopkins 2006b). For between group comparisons (e.g., TRAD vs. SS), the standardised ES of the variables being analysed were compared to assess the magnitude of difference between the two protocols (Hopkins 2006a). The probability that the magnitude of change or difference was greater than the SWC/D was rated as <0.5%, almost certainly not; 0.5–5%, very unlikely; 5–25%, unlikely; 25–75%, possibly; 75–95%, likely; 95–99.5%, very likely; >99.5%, almost certainly (Hopkins et al. 2009). Where the 90% confidence interval (CI) crossed both the upper and lower boundaries of the SWC/D (ES ± 0.2), the magnitude of change was described as unclear (Hopkins et al. 2009). ES thresholds were set at <0.2 (trivial), 0.2–0.6 (small), 0.6–1.2 (large), and 1.2–2.0 (very large) (Hopkins et al. 2009).