Table 5 Measurement protocols for studies outcomes included in meta-analysis

Amaro et al. [121]

CMJ

Vertical jump height (cm) was obtained with the CMJ, using a contact mat connected to an electronic power time (Ergo-jump, Globus, Italy). The average of three valid attempts was taken to analysis, with a 2-min rest between maximal attempts. The ICC was > 0.95

Time trial

Participants completed two maximal 50-m front crawl attempts (with 15 min of rest between) to access their best time (s). The ICC values ranged from 0.93 to 0.98. The starts were performed in the starting block. Two experienced researchers measured time with a chronometer

Aurell-Badenas et al. [122]

CMJ

Measured (cm) using a contact platform (Optojump Next; Microgate, Bolzano, Italy). Participants were familiarized with the test. The participants were instructed to jump as high as possible whilst maintaining their hands-on hips

SJ

As above, participants were asked to perform a maximal effort vertical jump from a squat position with the knee flexed at approximately 90° (i.e. without a CMJ)

Bellver et al. [123]

Fat mass

The fat mass (gm) was assessed using dual-energy X-ray absorptiometry (Lunar DXA TM GE Medical Systems, version 12.30). Participants were measured in light clothing, barefoot, and without any jewellery or metal buttons. All subjects went to the toilet before the test. The same technician performs all measurements. Athletes were evaluated in a supine position, with their feet in slight internal rotation to have good visibility of the femoral neck

Body mass

The body mass was measured in kg

Bishop et al. [124]

Time trial

Each subject’s video footage was uploaded to Silicon Coach Pro (siliconCOACH, Ltd, Dunedin, New Zealand) and subsequently analysed to determine the time (s) to complete a distance of 5.5 m from starting stimulus. The distance was defined with visual reference points on the lane markers and poolside

Bonacci et al. [125]

Body mass

Body mass was measured to the nearest 0.01 kg. The measurements were per the International Society for the Advancement of Kinanthropometry protocols and conducted by a certified level 2 anthropometrist

Thigh girth

Girth (cm) was measured from the right thigh. The measurements were per the International Society for the Advancement of Kinanthropometry protocols and conducted by a certified level 2 anthropometrist

Born et al. [126]

Time trial

A 25-m swim sprint was performed from the starting block, and the underwater phase was allowed for a maximum of 15 m. All athletes used the kick start technique with inclined rearfoot support. After 2 familiarization trials, the best of 3 trials was used for analysis. Tests were performed in a group of 5 athletes, allowing 4 to 5 min of rest between trials. The 25-m sprint time (s) was measured from the starting signal (light trigger of the starting device visible in the video footage) until the head of the swimmer passed the 25-m mark

Breed and Young [127]

CMJ

For the CMJ, a 78 × 52 cm contact mat linked to a computer to calculate the jump height (cm). Hands were placed on the hips and the participants were instructed to maintain the same body position when landing as during the take-off (i.e. hip, knees, and ankles in an extended position)

Cañas-Jamett et al. [128]

Time trial

Swimmers completed a warm-up of 50 m using the crawl swim style in a 25-m pool, and after 5 min of rest, they performed one maximal 200 m time trial (s). They began the test by jumping from an official platform at the edge of the swimming pool. A digital watch was used to measure the race time

SJ

A SJ was used to assess maximal vertical jump height (cm) and was performed using an electronic mat system (Ergo-jump, Globus, Italy). During testing, the participants were instructed to place their hands on their hips, with their feet shoulder-width apart, and adopt a flexed ~ 90° knee position for ~ 3 s, followed by a maximal effort vertical jump. Take-off and landing were standardized to full knee and ankle extension on the same spot. Participants were instructed to maximize jump height and bend the knees after landing. 3 trials were completed with a rest period of 2 min. The highest jump was used for the subsequent analysis

Thigh girth

Thigh girth was assessed 1 cm under the gluteal skinfold and perpendicular to the thigh axis. A non-extensible metallic tape of 0.5 cm width (Lufkin, Executive-Thinline, USA) was used to measure the thigh girth (cm), while participants were standing with their feet shoulder-width apart. Three measurements were carried out for each leg, in a counterbalanced order (i.e. right, left). Since the difference between the first and second measurements was always < 0.5 cm, the mean value between them was used for the analysis

Cossor et al. [66]

Time trial

The subjects completed two hand-timed (s), push-start, maximal effort, 50-m swim

Egan-Shuttler et al. [129]

Time trial

Firstly, rowing economy was measured, following which a 30-min rest was allowed for participants to perform a maximal 500-m time trial (s) on the rowing ergometer (Model D, Concept2, VT, USA). All participants were familiar with performing maximal 500-m trials as these were performed frequently as part of their normal training and/or performance assessments, prior to enrolment in the study, but none were performed during the intervention period

Thigh girth

The thigh circumference (cm) was measured using Gulick tape. The measurements were taken by the same member of the research team for pre- and post-testing and were taken halfway up the thigh

Egan-Shuttler et al. [130]

Body mass

The participant’s body mass (kg) was measured upon arrival (to the laboratory)

Garrido et al. [131]

Time trial

All the subjects performed two maximal 25-m front crawl trials with a 15-min passive recovery period between the two trials. The evaluation process was conducted in a 25-m indoor swimming pool with in-water starts. The performance time (m/s) was determined by two trained assessors with a chronometer (Golfinho Sports MC 815, Aveiro, Portugal), and the mean value of both measurements was obtained in each trial. The ICC was 0.94

CMJ

The vertical jump height (cm) was measured using the CMJ. The protocol required the performance of three jumps, each followed by two min of rest. An average of the two best jumps was used for analysis. This test was measured on a trigonometric carpet (Ergo-jump Digitime 1000, Digest Finland). The ICC was 0.92

Jones et al. [132]

Time trial

Each subject performed three maximal effort turns, with a 3-min rest period between each turn. The swimmer swam from 20 m out towards the wall at full speed, undertook their preferred stroke turn, touch, or tumble, and swam at maximal effort back out to the 20-m mark. The time (s) to 5 m post-turn was recorded

Kramer et al. [133]

Time trial

A 2500-m time test (s) was conducted using a Concept IT-Plus Rowing Ergometer. The rowers selected their own stroke rates. However, they all rowed with the chain on the inner sprocket and the air vents closed

Martin et al. [134]

In-water jump

In-water jump was assessed using a board with a cm scale attached to it and a video camera (50-Hz sampling frequency) placed 3 m away from the board. From the floating position, the players were required to jump as high as possible. The subsequent video analysis was performed by freezing the image at the highest point of hand contact on the board. Three trials were completed with 30 s rest between each trial. The mean of the 3 trials was used for further analyses

In-water agility

Assessed using the 10-m T-agility test. Subjects were instructed to sprint from a standing starting position (upright position facing the far end of the pool) at the base of the T. The test was initiated when the examiner gave the “start” signal, and the athlete’s head crossed the photocell to initiate the timing gate (MuscleLab, version 7.18). The subjects swim 5 m to the goal and touch the crossbar with both hands, then side swim to the right post and touch it, and then side swim to the left post and touch it. After that, they swam 5 m backward until they crossed the photocell. Three trials were completed, with 5 min of rest between trials. The mean of each agility trial time (s) was used for the subsequent statistical analyses

Time trial

Maximal sprint swim times (s) were recorded for a 20-m distance in a 25-m indoor swimming pool. Subjects were positioned 1 m off the wall (upright position facing the far end of the pool), before they were signalled to start the sprint with a random sound. Infrared timing systems (MuscleLab [version 7.18]) were stationed at the sprint start and endpoints (0 and 20 m). Three trials were completed, with 5 min of rest between trials. The mean of the times achieved across the 3 trials was used for subsequent statistical analyses

CMJ

The CMJ height (cm) was calculated using an infrared timing system MuscleLab (Ergo-Jump, version 718; Ergotest Technology, Langesund, Norway). Three trials were completed with 2 min rest between each trial. The mean of the 3 trials was then used for subsequent statistical analyses

Orunchuk et al. [135]

CMJ

The athletes performed 5 CMJ with each jump separated by 5 s. The CMJ was performed with a rapid descent to a self-selected depth, immediately followed by a maximal ascent. Athletes were instructed to keep their hands on their hips. All jumps were monitored by the same researcher, and strong verbal encouragement was provided to ensure each jump was performed maximally

SJ

Athletes performed a knee angle of 90°, measured with a goniometer. This position was held for 3 s before a verbal command to jump was given. An SJ was considered successful if the athlete gave a maximal effort and there was no visible countermovement. Athletes were instructed to keep their hands on their hips. All jumps were monitored by the same researcher, and strong verbal encouragement was provided to ensure each jump was performed maximally

Potdevin et al. [136]

Time trial

Assessed with a 25-m front crawl swim, with a water start without push-off. All the starts were on the initiative of the swimmer. Two independent observers recorded times, and these 2 values were averaged to calculate averaged swimming speed (m/s). The start signals for the water start without push-off the start signal consisted of the swimmer’s limbs moving

CMJ

The CMJ height (cm) was evaluated using an Ergo-jump (Junghans GMBH-Schramberg, Germany). Three trials were performed, with hands-on hips. Subjects were verbally encouraged to jump with maximal effort. The best performance was retained for statistical analysis

SJ

As above

Body mass

Measured with an impedance metric balance scale (Tanita, Tokyo, Japan)

Fat mass

Estimated with an impedance metric balance scale (Tanita, Tokyo, Japan)

Pupisova et al. [137]

CMJ

Five trials of CMJ were conducted

SJ

Five trials of SJ were conducted

Ramos-Veliz et al. [138]

Time trial

Maximal sprint swim times were recorded for a 20-m distance, in an indoor swimming pool of 25 m. The participants were positioned 1 m off the wall (upright position facing the far end of the pool) before they were signalled to start the sprint with a random sonorous sound. Infrared beams were stationed at the sprint start and endpoints (0 and 20 m) with time measured to the nearest 0.01 s using an electronic timing system (Muscle Lab.V7.18, Ergotest Technology, Langesund, Norway). Three trials were completed, with 5 min of rest between trials. The shortest time was used for analysis

1RM squat

The participants performed the full squat from a fully extended position starting with shoulders in contact with the bar. On command, the participants performed a controlled eccentric squat to a knee angle of 60°, followed without pause by a concentric leg extension (as fast as possible) returning to full extension. The trunk was kept as straight as possible and an accredited coach conducted this test and checked for correct technique. A safety belt was used by all the participants. The tests were performed in a squatting apparatus (Smith machine, Model Adan-Sport, Granada, Spain). Five to six separate single attempts were performed until the subject was unable to extend the legs to the required position. The last acceptable lift with the highest possible load was determined as 1 RM. The rest period between trials was 2 min

CMJ

Assessed with an infrared curtain system (Ergo-Jump, MuscleLabV718, Langesund, Porsgrunn, Norway) to measure flight and contact times. Five trials were completed with 1 min of rest between trials. The 2 extreme values of the 5 trials were eliminated (best and worst), and the mean of the 3 central values was used for the subsequent statistical analysis

Rebutini et al. [139]

SLJ

The horizontal jump displacement was calculated during a swimming block start performance test. Kinematic data were collected using a bi-dimensional approach. A digital video camera (Casio, model EX-FH20, Japan) operating at 210 Hz was perpendicularly positioned approximately 5 m away from the left sagittal plane of the participants. A light-emitting diode (LED) signal allowed to synchronize the kinematic and kinetic data using the instant of take-off as a reference. The markers were manually digitized using commercial software (SIMI Motion Software, version 6.1, Germany), and the coordinates were filtered using as order recursive Butterworth filter with a cut-off frequency set at 8 Hz. Thereafter, the horizontal displacement (cm) of centre of mass from the last block contact to water entrance was determined

Saez de Villareal et al. [113]

In-water jump

The authors cited a previous study to refer to the jump assessment protocol. The ICC was 0.92 (0.90–0.94)

In-water agility

Participants’ in-water agility was evaluated by using the 10-m T Swimming Agility test using a photocell timing system (Muscle Lab.V7.18). For this test, the athletes were instructed to sprint from a standing start position (from an upright floating position facing the far end of the pool) at the base of the T. Following a starting signal from the investigators, the athlete swam to the goal, touched the crossbar with both hands, then side swam to the right post, touches it before side-swimming to touch the left post. The athlete then swam 5 m backward through photocells. The test score was recorded as the best time (s) of 3 trials. A 3-min rest period was allowed between each trial. The ICC was 0.86 (0.84–0.88)

Time trial

Maximal 20-m sprint swim times were recorded to the nearest 0.01 s using an electronic timing system (Muscle Lab.V7.18), in an indoor swimming pool of 25 m. Participants were positioned 1 m off the wall (from an upright floating position facing the far end of the pool) before they were signalled to start the sprint with a random start signal. Three trials were completed, with 5 min of rest between trials. The shortest time was used for analysis. The ICC was 0.91 (0.90–0.93)

CMJ

The countermovement jump (CMJ) test was performed using an infrared curtain system (Ergo-Jump; Muscle Lab.V7.18, Langesund, Norway). Five trials were completed with 1 min of rest allocated between each trial. The 2 extreme values of the 5 trials were eliminated (best and worst), and the mean of the 3 central values was used for the subsequent statistical analysis. The ICC was 0.93 (0.91–0.95)

1RM squat

Participants performed the full squat from a fully extended position starting with shoulders in contact with the bar. On command, the participants performed a controlled eccentric squat to an internal knee angle of 60°, followed without pause by a concentric leg extension (as fast as possible) returning to full extension. The trunk was kept as straight as possible and an accredited coach conducted this test and checked for correct technique. A safety belt was used by all participants. The tests were performed in a squatting apparatus (Smith machine; Model Adan-Sport, Granada, Spain). Five to six separate single attempts were performed until the subject was unable to extend the legs to the required position. The last acceptable lift with highest possible load was determined as 1 RM. The rest period between trials was 2 min

Saez de Villarreal et al. [112]

In-water jump

The authors cited a previous study to refer to the jump assessment protocol

In-water agility

Assessed using the 10-m T-agility test. The subjects were instructed to sprint from a standing starting position (upright position facing the far end of the pool) at the base of the T. The test was initiated when the examiner gave the signal to initiate the test and the athlete’s head crossed the photocell to initiate the timing apparatus (Muscle Lab.V7.18, Langesund, Norway). In this test, the subjects were instructed to swim to the goal and touch the crossbar with 2 hands, then side swim to the right post and touch it and then side swim to the left post and touch it. After that, the subject was required to swim 5-m backward until they crossed the photocell and timing was ceased. A 2-min rest period was allowed between each trial. The mean of each agility trial time (s) was used for the subsequent statistical analyses

Time trial

Maximal sprint swim times were recorded for a 20 m distance in a 25-m indoor swimming pool. Subjects were positioned 1 m off the wall (upright position facing the far end of the pool) before they were signalled to start the sprint with a random sonorous sound. Infrared beams were stationed at the sprint start and endpoints (0 and 20 m) with time measured to the nearest 0.01 s using an electronic timing system (Muscle Lab. V7.18). Three trials were completed, with 2 min of rest between trials. The mean of the times achieved across the 3 trials was used for subsequent statistical analyses

1RM squat

Participants performed the full squat from an extended position with the bar held across the shoulders with a standardized front squat grip. On command, the subjects performed a controlled eccentric squat to a depth that allowed for the attainment of a 60° (using a goniometer) knee angle. Once this knee angle was achieved, a squat depth that allowed for this knee angle the subjects performed a concentric knee extension motion as fast as possible to return to a fully extended position. All subjects wore a standard lifting belt during each trial. The tests were performed in a Smith machine (Model AdanSport, Granada, Spain). Four to six separate single attempts were performed until the subject was unable to perform each lift with appropriate technique or unable to complete a repetition with the tested load. The last acceptable lift with used to quantify 1 RM. The rest period between trials was 2 min

CMJ

Assessed with an infrared curtain system (MuscleLab.V718; Ergo-Jump, Langesund, Norway). Three trials were completed with 2 min of rest between each trial. The mean of the 3 trials was then used for subsequent statistical analyses

Sammoud et al. [141]

Time trial

Swimmers performed the 50-m front crawl swimming trials with a diving start. All starts were voluntarily initiated by the swimmers. Two independent observers recorded performance times using stop-watches. The average of the two recorded values was used. The start signal for the observer was the moment as the swimmer’s feet left the block. The distance was standardized using markers at the bottom of the pool. The final signal for the observer was the moment when the swimmer’s hand touched the wall. The ICC ranged between 0.89 and 0.91 and the TEM ranged between 1.2 and 2.5%

CMJ

CMJ techniques were visually controlled by the first author of this study. Jump height was recorded using an Optojump photoelectric system (Microgate, SRL, Bolzano, Italy). The ICC was 0.98 and the TEM was 2.9%

SLJ

Participants executed the SLJ with their legs and arms for maximal horizontal distance. Participants had to land with both feet simultaneously, avoiding falling forward or backward. Distance was measured to the nearest cm, between the starting line and the heel of the rear foot, recorded via tape measure. ICC = 0.96; TEM = was 0.5%

Body mass

The body mass was recorded by a trained anthropometrist assisted by a recorder. Standardized procedures were applied per the International Society for the Advancement of Kinanthropometry

Sammoud et al. [140]

Time trial

Swimmers performed 50-m front crawl trials with a diving start. All starts were voluntarily initiated by the swimmers. Two independent observers recorded performance times using stop-watches. During the diving start tests, participants were not allowed to drift forward or backward before initiating the start. The average of the two recorded values was used for statistical analyses. The start signal for the observer was the moment as the swimmer’s feet left the block. The distance was standardized using markers at the bottom of the pool. The final signal for the observer was the moment when the swimmer’s hands touched the wall. The ICC ranged between 0.89 and 0.91

CMJ

CMJ techniques were visually controlled by the first author of this study. Jump height was recorded using an Optojump photoelectric system (Microgate, SRL, Bolzano, Italy). The ICC was 0.98

SLJ

The starting position of the SLJ required subjects to stand with their feet behind a starting line. Participants executed a countermovement with their legs and arms and jumped at maximal effort in horizontal direction. Participants had to land with both feet simultaneously and were not allowed to fall forward or backward. The horizontal distance (cm) between the starting line and the heel of the rear foot was recorded via tape measure to the nearest 1 cm. The ICC for was 0.96

Body mass

The body mass was assessed by a trained anthropometrist who was assisted by a co-worker. Standardized procedures were applied which were per the International Society for the Advancement of Kinanthropometry

Veliz et al. [142]

In-water jump

The in-water jump was assessed using a board with a cm scale attached to it and a video camera (50-Hz sampling frequency) placed 3 m away from the board. From the floating position the players were required to jump the highest that they could reach. The subsequent video analysis was performed by freezing the image at the highest point of hand contact on the board by the players. Three trials were completed with 2 min of rest between trials. The mean of the 3 values was used for the subsequent statistical analyses

Time trial

The time trial was recorded for 20-m maximal sprint swim, in an indoor swimming pool of 25 m. The participants were positioned 1 m off the wall (upright position facing the far end of the pool), before they were signalled to start the sprint with a random sonorous sound. Infrared beams were stationed at the sprint start and endpoints (0 and 20 m) with time measured to the nearest 0.01 s using an electronic timing system (Muscle LabV718). The head of the athletes triggered the infrared timing beams. Three trials were completed, with 5 min of rest between trials, and the shortest time was used for the subsequent statistical analysis

1RM squat

The participants performed the full squat from a fully extended position starting with shoulders in contact with the bar. On command, the participants performed a controlled eccentric squat to a knee angle of 60°, followed without pause by a concentric leg extension (as fast as possible) returning to full extension. The trunk was kept as straight as possible and an accredited coach conducted this test and checked for correct technique. All the participants used a safety belt. The tests were performed in a squatting apparatus (Smith machine, Model Adan-Sport, Granada, Spain). Four to six separate single attempts were performed until the subject was unable to perform each lift with appropriate technique or unable to complete a repetition with the tested load. The last acceptable lift with the highest possible load was determined as 1 RM. The rest period between trials was 2 min

CMJ

The CMJ test was performed using an infrared curtain system (Ergo-Jump, MuscleLabV718, Langesund, Porsgrunn, Norway). Three trials were completed with 2 min of rest between trials. The mean of the 3 values was used for the subsequent statistical analyses

Vlachopoulos et al. [56]

CMJ

Assessed on a jump mat (Probotics Inc., AL, USA). Three maximal jumps were performed, using the best score

SLJ

For the SLJ, participants were advised to jump as far as possible to land with both feet and the distance (cm) measured between the starting line and the participant’s heels was recorded. For SLJ, three maximal jumps were performed and the best score was used

Fat mass

A Lunar Prodigy DXA scanner (GE Healthcare Inc., WI, USA) was used to measure the fat mass (g). All scans were undertaken by the same fully trained operator. The DXA percentage coefficient of variation has been reported between 1.0 and 2.9%