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Olivier Girard, Franck Brocherie, Jean-Benoit Morin and Grégoire P. Millet

Purpose:

To determine the intrasession and intersession (ie, within- and between-days) reliability in treadmill sprinting-performance outcomes and associated running mechanics.

Methods:

After familiarization, 13 male recreational sportsmen (team- and racket-sport background) performed three 5-s sprints on an instrumented treadmill with 2 min recovery on 3 different days, 5–7 d apart. Intrasession (comparison of the 3 sprints of the first session) and intersession (comparison of the average of the 3 sprints across days) reliability of performance, kinetics, kinematics, and spring-mass variables were assessed by intraclass correlation coefficient (ICC) and coefficients of variation (CV%).

Results:

Intrasession reliability was high (ICC > .94 and CV < 8%). Intersession reliability was good for performance indices (.83 < ICC < .89 and CV < 10%, yet with larger variability for mean velocity than for distance covered or propulsive power) and kinetic parameters (ICC > .94 and CV < 5%, yet with larger variability for mean horizontal forces than for mean vertical forces) and ranged from good to high for all kinematic (.88 < ICC < .95 and CV ≤ 3.5%) and spring-mass variables (.86 < ICC < .99 and CV ≤ 6.5%). Compared with intrasession, minimal detectable differences were on average twice larger for intersession designs, except for sprint kinetics.

Conclusion:

Instrumented treadmill sprint offers a reliable method of assessing running mechanics during single sprints either within the same session or between days.

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Stef Feijen, Angela Tate, Kevin Kuppens, Thomas Struyf, Anke Claes and Filip Struyf

yet been investigated in competitive swimmers who may experience changes in physical characteristics of the muscle. Consequently, this study aims to investigate the within-session intrarater and interrater reliability of measuring shoulder flexion ROM for LDF in competitive swimmers aged 10–20 years

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Paul Comfort, Christopher Thomas, Thomas Dos’Santos, Paul A. Jones, Timothy J. Suchomel and John J. McMahon

, 31 , 32 The maximum force recorded from the force–time curve during the 5-second IMTP trial was reported as the PF. Each of the 3 trials was used to determine within-session reliability, with the mean of the best 2 trials, based on PF, used to compare between sessions, in line with previous research

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Thomas Dos’Santos, Paul A. Jones, Jonathan Kelly, John J. McMahon, Paul Comfort and Christopher Thomas

trials to assess within-session reliability for each kinetic variable across all sampling frequencies with the use of a custom spreadsheet. 30 The CV was calculated based on the mean-square-error term of logarithmically transformed data. 30 Haff et al 2 argue that although ICCs are common to report the

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Thomas Dos’Santos, Christopher Thomas, Paul A. Jones and Paul Comfort

Purpose:

To investigate the within-session reliability of bilateral- and unilateral-stance isometric midthigh-pull (IMTP) force–time characteristics including peak force (PF), relative PF, and impulse at time bands (0–100, 0–200, 0–250, and 0–300 milliseconds) and to compare isometric force–time characteristics between right and left and dominant (D) and nondominant (ND) limbs.

Methods:

Professional male rugby league and multisport male college athletes (N = 54; age, 23.4 ± 4.2 y; height, 1.80 ± 0.05 m; mass, 88.9 ± 12.9 kg) performed 3 bilateral IMTP trials and 6 unilateral-stance IMTP trials (3 per leg) on a force plate sampling at 600 Hz.

Results:

Intraclass correlation coefficients (ICCs) and coefficients of variation (CVs) demonstrated high within-session reliability for bilateral and unilateral IMTP PF (ICC = .94, CV = 4.7–5.5%). Lower reliability measures and greater variability were observed for bilateral and unilateral IMTP impulse at time bands (ICC = .81–.88, CV = 7.7–11.8%). Paired-sample t tests and Cohen d effect sizes revealed no significant differences for all isometric force–time characteristics between right and left limbs in male college athletes (P >.05, d ≤ 0.32) and professional rugby league players (P > .05, d ≤ 0.11); however, significant differences were found between D and ND limbs in male college athletes (P < .001, d = 0.43–0.91) and professional rugby league players (P < .001, d = 0.27–0.46).

Conclusion:

This study demonstrated high within-session reliability for unilateral-stance IMTP PF, revealing significant differences in isometric force–time characteristics between D and ND limbs in male athletes.

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Olivia R. Barber, Christopher Thomas, Paul A. Jones, John J. McMahon and Paul Comfort

Purpose:

To determine the reliability of the 505 change-of-direction (COD) test performed with both a stationary and a flying start.

Methods:

Fifty-two female netball players (age 23.9 ± 5.4 y, height 169.9 ± 3.3 cm, body mass 65.2 ± 4.6 kg) performed 6 trials of the 505 COD test, 3 with a flying start and 3 with a stationary start, once per week over a 4-wk period to determine within- and between-sessions reliability.

Results:

Testing revealed high within-session reliability for the stationary start (ICC = .96–.97) and for the flying start (ICC = .90–.97). Similarly, both the stationary start (ICC = .965) and the flying start (ICC = .951) demonstrated high reliability between sessions, although repeated-measures analysis of variance (P < .001) revealed learning effects between sessions for both tests. Performances stabilized on day 2 for the static start and on day 3 for the flying start.

Conclusions:

The 505 COD test is a reliable test in female netball players, with either a stationary or flying start. Smallest detectable differences of 3.91% and 3.97% for the stationary start and the flying start, respectively, allow practitioners to interpret whether changes in time taken to complete the 505 COD test reflect genuine improvements in performance or are measurement errors. It is suggested that 1 d of familiarization testing be performed for the stationary start and 2 d of familiarization for the flying start, to minimize learning effects.

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Thomas Dos’Santos, Paul A. Jones, Jonathan Kelly, John J. McMahon, Paul Comfort and Christopher Thomas

Purpose:

Skeletal-muscle function can be evaluated using force–times curves generated via the isometric midthigh pull (IMTP). Various sampling frequencies (500–1000 Hz) have been used for IMTP assessments; however, no research has investigated the influence of sampling frequency on IMTP kinetics. Therefore, the purpose of this study was to investigate the influence of sampling frequency on kinetic variables during the IMTP, including peak force, time-specific force values (100, 150, and 200 ms), and rate of force development (RFD) at 3 time bands (0–100, 0–150, 0–200 ms).

Methods:

Academy rugby league players (n = 30, age 17.5 ± 1.1 y, height 1.80 ± 0.06 m, mass 85.4 ± 10.3 kg) performed 3 IMTP trials on a force platform sampling at 2000 Hz, which was subsequently down-sampled to 1500, 1000, and 500 Hz for analysis.

Results:

Intraclass correlation coefficients (ICC) and coefficients of variation (CV) demonstrated high within-session reliability for all force and RFD variables across all sampling frequencies (ICC ≥ .80, CV ≤ 10.1%). Repeated-measures analysis of variance revealed no significant differences (P > .05, Cohen d ≤ 0.009) in kinetic variables between sampling frequencies. Overall, high reliability was observed across all sampling frequencies for all kinetic variables, with no significant differences (P > .05) for each kinetic variable across sampling frequencies.

Conclusions:

Practitioners and scientists may consider sampling as low as 500 Hz when measuring peak force, time-specific force values, and RFD at predetermined time bands during the IMTP for accurate and reliable data.

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John J. McMahon, Paul A. Jones and Paul Comfort

Purpose:

To determine the concurrent validity and reliability of the popular Just Jump system (JJS) for determining jump height and, if necessary, provide a correction equation for future reference.

Methods:

Eighteen male college athletes performed 3 bilateral countermovement jumps (CMJs) on 2 JJSs (alternative method) that were placed on top of a force platform (criterion method). Two JJSs were used to establish consistency between systems. Jump height was calculated from flight time obtained from the JJS and force platform.

Results:

Intraclass correlation coefficients (ICCs) demonstrated excellent within-session reliability of the CMJ height measurement derived from both the JJS (ICC = .96, P < .001) and the force platform (ICC = .96, P < .001). Dependent t tests revealed that the JJS yielded a significantly greater CMJ jump height (0.46 ± 0.09 m vs 0.33 ± 0.08 m) than the force platform (P < .001, Cohen d = 1.39, power = 1.00). There was, however, an excellent relationship between CMJ heights derived from the JJS and force platform (r = .998, P < .001, power = 1.00), with a coefficient of determination (R 2) of .995. Therefore, the following correction equation was produced: Criterion jump height = (0.8747 × alternative jump height) – 0.0666.

Conclusions:

The JJS provides a reliable but overestimated measure of jump height. It is suggested, therefore, that practitioners who use the JJS as part of future work apply the correction equation presented in this study to resultant jump-height values.

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Maurizio Fanchini, Roberto Ghielmetti, Aaron J. Coutts, Federico Schena and Franco M. Impellizzeri

Purpose:

To examine the effect of different exercise-intensity distributions within a training session on the session rating of perceived exertion (RPE) and to examine the timing of measure on the rating.

Methods:

Nineteen junior players (age 16 ± 1 y, height 173 ± 5 cm, body mass 64 ± 6 kg) from a Swiss soccer team were involved in the study. Percentage of heart rate maximum (%HR) and RPE (Borg CR100®) were collected in 4 standardized training sessions (conditions). The Total Quality of Recovery scale (TQR) and a visual analogue scale (VAS) for pain of the lower limbs were used to control for the effect of pretraining fatigue. Every session consisted of three 20-min blocks of different intensities (ie, low-moderate-high) performed in a random order. RPE was collected after every block (RPE5), immediately after the session (RPE-end), and 30 min after the session (RPE30).

Results:

RPE5s of each block were different depending on the distribution sequence (P < .0001). RPE-end, TQR, and VAS values were not different between conditions (P = .57, P = .55, and P = .96, respectively). The %HR was significantly different between conditions (P = .008), with condition 3 higher than condition 2 (74.1 vs 70.2%, P = .02). Edwards training loads were not significantly different between conditions (P = .09). RPE30 was not different from RPE-end (P > .05).

Conclusions:

The current results show that coaches can design training sessions without concern about the influence of the within-session distribution of exercise intensity on session-RPE and that RPE can be collected at the end of the session or 30 min later.

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Paul Comfort, Paul. A. Jones, John J. McMahon and Robert Newton

The isometric midthigh pull (IMTP) has been used to monitor changes in force, maximum rate of force development (mRFD), and impulse, with performance in this task being associated with performance in athletic tasks. Numerous postures have been adopted in the literature, which may affect the kinetic variables during the task; therefore, the aim of this investigation was to determine whether different knee-joint angles (120°, 130°, 140°, and 150°) and hip-joint angles (125° and 145°), including the subjects preferred posture, affect force, mRFD, and impulse during the IMTP. Intraclass correlation coefficients demonstrated high within-session reliability (r ≥ .870, P < .001) for all kinetic variables determined in all postures, excluding impulse measures during the 130° knee-flexion, 125° hip-flexion posture, which showed a low to moderate reliability (r = .666–.739, P < .001), while between-sessions testing demonstrated high reliability (r > .819, P < .001) for all kinetic variables. There were no significant differences in peak force (P > .05, Cohen d = 0.037, power = .408), mRFD (P > .05, Cohen d = 0.037, power = .409), or impulse at 100 ms (P > .05, Cohen d = 0.056, power = .609), 200 ms (P > .05, Cohen d = 0.057, power = .624), or 300 ms (P > .05, Cohen d = 0.061, power = .656) across postures. Smallest detectable differences demonstrated that changes in performance of >1.3% in peak isometric force, >10.3% in mRFD, >5.3% in impulse at 100 ms, >4.4% in impulse at 200 ms, and >7.1% in impulse at 300 ms should be considered meaningful, irrespective of posture.