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  • Author: Dale W. Chapman x
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Oliver R. Barley, Dale W. Chapman and Chris R. Abbiss

Context: Combat sports are typically divided into weight classes, and body-mass manipulation to reach a weight class is commonplace. Previous research suggests that weight loss practices in mixed martial arts (MMA) may be more extreme than in other combat sports. Purpose : To investigate the magnitude of weight loss and the prevalence of weight loss strategies in different combat sports. Methods: Competitors (N = 637) from Brazilian jiu-jitsu, boxing, judo, MMA, Muay Thai/kickboxing, taekwondo, and wrestling completed an online questionnaire seeking information regarding their weight loss practices. Results: Body-mass manipulation was commonly undertaken by all combat-sport athletes, with a particularly high incidence of gradual dieting, increased exercise, and fluid restriction. Skipping meals was higher in taekwondo and wrestling (84%) compared with the other combat sports (∼58%), whereas training in heated rooms and forced oral fluid loss (spitting) was higher in wrestling (83% and 47%, respectively) compared with other combat sports (∼45% and ∼19%, respectively). MMA athletes reported the highest usage of sauna (76%) and water loading (67%) while also reporting the second-highest use of training in rubber/plastic suits (63%). Conclusions: Body-mass manipulation was present in all combat sports, with the prevalence and magnitude of acute weight loss greater in MMA. The incidence of and practices reported will help support staff be fully aware of the variety of methods these athletes and coaches may use to achieve weight loss. Additionally, the results could aid regulatory bodies in the further development of policies on weight cutting.

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Kristie-Lee Taylor, Will G. Hopkins, Dale W. Chapman and John B. Cronin

The purpose of this study was to calculate the coefficients of variation in jump performance for individual participants in multiple trials over time to determine the extent to which there are real differences in the error of measurement between participants. The effect of training phase on measurement error was also investigated. Six subjects participated in a resistance-training intervention for 12 wk with mean power from a countermovement jump measured 6 d/wk. Using a mixed-model meta-analysis, differences between subjects, within-subject changes between training phases, and the mean error values during different phases of training were examined. Small, substantial factor differences of 1.11 were observed between subjects; however, the finding was unclear based on the width of the confidence limits. The mean error was clearly higher during overload training than baseline training, by a factor of ×/÷ 1.3 (confidence limits 1.0–1.6). The random factor representing the interaction between subjects and training phases revealed further substantial differences of ×/÷ 1.2 (1.1–1.3), indicating that on average, the error of measurement in some subjects changes more than in others when overload training is introduced. The results from this study provide the first indication that within-subject variability in performance is substantially different between training phases and, possibly, different between individuals. The implications of these findings for monitoring individuals and estimating sample size are discussed.

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Oliver R. Barley, Dale W. Chapman, Georgios Mavropalias and Chris R. Abbiss

Purpose: To examine the influence of fluid intake on heat acclimation and the subsequent effects on exercise performance following acute hypohydration. Methods: Participants were randomly assigned to 1 of 2 groups, either able to consume water ad libitum (n = 10; age 23 [3] y, height 1.81 [0.09] m, body mass 87 [13] kg; HAW) or not allowed fluid (n = 10; age 26 [5] y, height 1.76 [0.05] m, body mass 79 [10] kg; HANW) throughout 12 × 1.5-h passive heat-acclimation sessions. Experimental trials were completed on 2 occasions before (2 baseline trials) and 1 following the heat-acclimation sessions. These sessions involved 3 h of passive heating (45°C, 38% relative humidity) to induce hypohydration followed by 3 h of ad libitum food and fluid intake after which participants performed a repeat sled-push test to assess physical performance. Urine and blood samples were collected before, immediately, and 3 h following hypohydration to assess hydration status. Mood was also assessed at the same time points. Results: No meaningful differences in physiological or performance variables were observed between HANW and HAW at any time point. Using pooled data, mean sprint speed was significantly (P < .001) faster following heat acclimation (4.6 [0.7] s compared with 5.1 [0.8] s). Furthermore, heat acclimation appeared to improve mood following hypohydration. Conclusions: Results suggest that passive heat-acclimation protocols may be effective at improving short-duration repeat-effort performance following acute hypohydration.

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Kristie-Lee Taylor, John Cronin, Nicholas D. Gill, Dale W. Chapman and Jeremy Sheppard

Purpose:

This investigation aimed to quantify the typical variation for kinetic and kinematic variables measured during loaded jump squats.

Methods:

Thirteen professional athletes performed six maximal effort countermovement jumps on four occasions. Testing occurred over 2 d, twice per day (8 AM and 2 PM) separated by 7 d, with the same procedures replicated on each occasion. Jump height, peak power (PP), relative peak power (RPP), mean power (MP), peak velocity (PV), peak force (PF), mean force (MF), and peak rate of force development (RFD) measurements were obtained from a linear optical encoder attached to a 40 kg barbell.

Results:

A diurnal variation in performance was observed with afternoon values displaying an average increase of 1.5–5.6% for PP, RPP, MP, PV, PF, and MF when compared with morning values (effect sizes ranging from 0.2–0.5). Day to day reliability was estimated by comparing the morning trials (AM reliability) and the afternoon trials (PM reliability). In both AM and PM conditions, all variables except RFD demonstrated coefficients of variations ranging between 0.8–6.2%. However, for a number of variables (RPP, MP, PV and height), AM reliability was substantially better than PM. PF and MF were the only variables to exhibit a coefficient of variation less than the smallest worthwhile change in both conditions.

Discussion:

Results suggest that power output and associated variables exhibit a diurnal rhythm, with improved performance in the afternoon. Morning testing may be preferable when practitioners are seeking to conduct regular monitoring of an athlete’s performance due to smaller variability.

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Kym J. Williams, Dale W. Chapman, Elissa J. Phillips and Nick Ball

Purpose: To establish the influence of athlete-dependent characteristics on the generation and timing of system and individual joint powers during a countermovement jump (CMJ). Methods: Male national representative athletes from volleyball (n = 7), basketball (n = 6), and rugby (n = 7) performed a set of 3 CMJs at relative barbell loads of 0%, 10%, 20%, 30%, and 40% of absolute back-squat strength. Ground-reaction forces and joint kinematics were captured using a 16-camera motion-capture system integrated with 2 in-ground force plates. Limb lengths and cross-sectional areas were defined using 3-dimensional photonic scans. A repeated-measures analysis of variance determined the interaction between system and joint load–power profiles, whereas a multiregression analysis defined the explained variance of athlete-dependent characteristics on the load that maximized system power. Results: System and isolated hip, knee, and ankle peak powers were maximized across a spectrum of loads between and within sports; power values were not significantly different across loads. A positive shift in the timing of hip and ankle peak powers corresponded to a significant (P < .05) positive shift in the timing of system peak power to occur closer to toe-off. An optimal 3-input combination of athlete-dependent characteristics accounted for 68% (P < .001) of the explained variance in the load that maximized system peak power. Conclusion: The load maximizing system power is athlete-dependent, with a mixture of training and heredity-related characteristics influencing CMJ load–power profiles. The authors recommend that a combination of relative loads be individually prescribed to maximize the generation and translation of system CMJ power.

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Ina Janssen, Jeremy M. Sheppard, Andrew A. Dingley, Dale W. Chapman and Wayne Spratford

Countermovement jumps loaded with a weighted vest are often used for the training of lower body power to improve jump performance. However, it is currently unknown how this added load affects the lower extremity kinematics and kinetics, in particular whether this results in an increased injury risk. Therefore, the purpose of this investigation was to determine how lower extremity kinematics and kinetics during landing are affected by loaded jumps as demonstrated in a volleyball block jump landing. Ten elite male volleyball players performed block jump landings in an unloaded and loaded (9.89 kg) condition. Kinematic and kinetic landing data from the three highest jumps were collected and assessed. Paired samples t test was used to establish whether load condition had a significant effect on lower extremity kinematics and kinetics. Hip flexion was significantly greater in the unloaded condition compared with the loaded condition (p = .004). There was no significant difference in any other kinematic or kinetic variables measures between the unloaded and loaded conditions. These results suggest that landing from loaded volleyball block jumps does not increase injury risk compared with unloaded jumps in elite male volleyball players.

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Jessica M. Stephens, Shona L. Halson, Joanna Miller, Gary J. Slater, Dale W. Chapman and Christopher D. Askew

Purpose: To explore the influence of body composition on thermal responses to cold-water immersion (CWI) and the recovery of exercise performance. Methods: Male subjects were stratified into 2 groups: low fat (LF; n = 10) or high fat (HF; n = 10). Subjects completed a high-intensity interval test (HIIT) on a cycle ergometer followed by a 15-min recovery intervention (control [CON] or CWI). Core temperature (Tc), skin temperature, and heart rate were recorded continuously. Performance was assessed at baseline, immediately post-HIIT, and 40 min postrecovery using a 4-min cycling time trial (TT), countermovement jump (CMJ), and isometric midthigh pull (IMTP). Perceptual measures (thermal sensation [TS], total quality of recovery [TQR], soreness, and fatigue) were also assessed. Results: Tc and TS were significantly lower in LF than in HF from 10 min (Tc, LF 36.5°C ± 0.5°C, HF 37.2°C ± 0.6°C; TS, LF 2.3 ± 0.5 arbitrary units [a.u.], HF 3.0 ± 0.7 a.u.) to 40 min (Tc, LF 36.1°C ± 0.6°C, HF 36.8°C ±0.7°C; TS, LF 2.3 ± 0.6 a.u., HF 3.2 ± 0.7 a.u.) after CWI (P < .05). Recovery of TT performance was significantly enhanced after CWI in HF (10.3 ± 6.1%) compared with LF (3.1 ± 5.6%, P = .01); however, no differences were observed between HF (6.9% ±5.7%) and LF (5.4% ± 5.2%) with CON. No significant differences were observed between groups for CMJ, IMTP, TQR, soreness, or fatigue in either condition. Conclusion: Body composition influences the magnitude of Tc change during and after CWI. In addition, CWI enhanced performance recovery in the HF group only. Therefore, body composition should be considered when planning CWI protocols to avoid overcooling and maximize performance recovery.