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Ian M. Wilcock, John B. Cronin and Wayne A. Hing

Purpose:

To assess the effect that post exercise immersion in water has on subsequent exercise performance.

Methods:

A literary search and review of water-immersion and performance studies was conducted.

Results:

Seven articles were examined. In 2, significant benefits to performance were observed. Those 2 articles revealed a small to large effect on jump performance and isometric strength.

Practical Application and Conclusions:

It is possible that water immersion might improve recovery from plyometric or muscle-damaging exercise. Such a statement needs to be verified, however, because of the scarcity of research on water immersion as a recovery strategy.

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Alex Ross, Nicholas D. Gill and John B. Cronin

Anthropometrical and physical characteristics have been used to distinguish players of different competition levels and position groups; however, there is no literature on rugby sevens.

Purpose:

To compare the anthropometrical and physical characteristics of international and provincial rugby sevens players and between forwards and backs.

Methods:

To assess whether differences exist, 65 rugby sevens players including 22 international players and 43 provincial-level players were assessed for height, mass, body composition, speed, repeated-sprint ability, lower-body power, upper-body strength, and maximal aerobic endurance during in-season preparation for tournaments.

Results:

Clear differences (2.8−32%; small to very large effect sizes) were observed in all anthropometrical and physical measures between international and provincial players, with the largest differences observed in repeated-sprint ability (5.7%; very large effect size), 40-m-sprint time (4.4%; large effect size), 50-kg squat-jump peak power (32%; large effect size), and multistage fitness-test performance (19%; large effect size). Fewer and smaller differences (0.7−14%; trivial to large effect sizes) were found when comparing forwards and backs, with body height being the most discriminant characteristic (3.5%; large effect size).

Conclusions:

Lower-level rugby sevens players should seek to improve their overall physical profile, particularly their repeated-sprint ability, to reach higher levels in rugby sevens. Furthermore, positional status may have little importance when preparing for rugby sevens.

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Alex Ross, Nicholas D. Gill and John B. Cronin

Purpose:

To compare the running demands and match activity profiles of international and provincial rugby sevens players.

Participants:

84 rugby sevens players, consisting of 16 international players from 1 team and 68 provincial players from 8 teams.

Methods:

Global positioning system analysis was completed during international and provincial tournament matches. Video analysis was also used to quantify the individual match activities during tournament matches.

Results:

Trivial to moderate differences were found in the running demands of international and provincial players, with internationals covering a greater distance at very high speed (ES = 0.30) and performing a greater number of sprints (ES = 0.80). Small differences were found between the 2 levels in all but total tackles (ES = 0.07) and defensive ruck effectiveness (ES = 0.64). International matches incurred a greater overall ball-in-play time than provincial matches (proportion ratio = 1.32).

Conclusions:

These findings demonstrate that both physical and technical factors distinguish international and provincial rugby sevens, although overall match demands are similar.

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Keir T. Hansen, John B. Cronin and Michael J. Newton

Purpose:

The purpose of this study was to investigate the effect of set structure, in terms of repetition workrest ratios on force, velocity, and power during jump squat training.

Methods:

Twenty professional and semiprofessional rugby players performed training sessions comprising four sets of 6 repetitions of a jump squat using four different set configurations. The first involved a traditional configuration (TR) of 4 × 6 repetitions with 3 min of rest between sets, the second (C1) 4 × 6 × singles (1 repetition) with 12 s of rest between repetitions, the third (C2) 4x3 × doubles (2 repetitions) with 30 s of rest between pairs, and the third (C3) 4 × 2 × triples (3 repetitions) with 60 s of rest between triples. A spreadsheet for the analysis of controlled trials that calculated the P-value, and percent difference and Cohen’s effect size from log-transformed data was used to investigate differences in repetition force, velocity, and power profiles among configurations.

Results:

Peak power was significantly lower (P < .05) for the TR condition when compared with C1 and C3 for repetition 4, and all cluster configurations for repetitions 5 and 6. Peak velocity was significantly lower (P < .05) for the TR condition compared with C3 at repetition 4, significantly lower compared with C2 and C3 at repetition 5, and significantly lower compared with all cluster conditions for repetition 6.

Conclusions:

Providing inter-repetition rest during a traditional set of six repetitions can attenuate decreases in power and velocity of movement through the set.

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Trent W. Lawton, John B. Cronin and Michael R. McGuigan

Purpose:

There is no common theory on criteria to appropriately select crew rowers in pursuit of small performance gains. The purpose of this study was to establish whether anthropometry, rowing ergometry, or lower body strength were suitable criteria to identify differences between selected and nonselected sculling crews.

Method:

Twelve elite women performed a 2000-m ergometer time trial and a 5-repetition leg-press dynamometer test, were anthropometrically profiled, and participated in on-water national crew seat-racing trials. Log-transformed data were analyzed to compare percent (± SD) and standardized differences in group means (ES; ±90% confidence interval [CI]) between selected and nonselected oarswomen, with adjustments for body mass where appropriate.

Results:

Selected crew boats were 4.60% ± 0.02% faster and won by an average margin of 13.5 ± 0.7 s over 1500 m. There were no differences between crews on average in height, arm span, seated height, body mass, or 8-site skinfold sum (body fat). Difference in 2000-m ergometer times were also trivial (ES = 0.2, 90%CI = −0.6 to 1.1, P = .63); however, selected crews had moderately greater leg-press strength (ES = 1.1, 90%CI = 0.3−1.9, P = .03).

Conclusion:

Selected oarswomen with comparable anthropometry and 2000-m ergometer ability had greater lower body strength. Coaches of elite oarswomen might consider leg strength as part of crew-selection criteria, given acceptable on-water boatmanship and attainment of 2000-m ergometer benchmarks.

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Emanuele D’Artibale, Maheswaran Rohan and John B. Cronin

Purpose: The technological advancements in motorcycle road racing have ensured the evolution of motorcycle performance; however, it is unknown whether these advancements have resulted in increased speed and therefore risk. To better understand the top level of this sport and inform future regulations, performance-related strategies, and safety procedures, this study aimed to (1) analyze and describe how the performance characteristics of the top class of the Fédération Internationale de Motocyclisme Grand Prix motorcycle world championship (GPWC) have changed with time and (2) quantify potential interactions between performance data (ie, crashes, speed, and environmental conditions). Methods: Variables such as top 10 riders’ speed of racing, crashes, starting position of winner, participants, and environmental conditions were collected from official race reports from 1997 to 2016. Data standardization was also ensured by including only dry competitions in the analysis. Results: The mean racing speed ranged from a minimum of 155 (7.27) km·h−1 (year 2000) to a maximum of 165 (6.48) km·h−1 (year 2015). Linear mixed-model analysis revealed that the variables year and class significantly influenced changes in mean speed (faster racing). Per race, 12–14% of starters (95% confidence interval) suffered a crash. No significant associations were found between crashes and mean speed, ground temperature, air temperature, or air humidity. Conclusions: The speed of dry racing of the top class of the GPWC has increased over a 20-y span. Motorcycle circuit racing riders should consider the importance of being prepared to cope with crashing events to minimize chances of injury.

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Dustin J. Oranchuk, André R. Nelson, Adam G. Storey and John B. Cronin

Purpose: Regional muscle-architecture measures are reported widely; however, little is known about the variability of these measurements in the rectus femoris, vastus lateralis, and anterior and lateral vastus intermedius. The aim of this study was to quantify this variability. Methods: Regional muscle thickness, pennation angle (PA), and calculated and extended-field-of-view–derived fascicle length (FL) were quantified in 26 participants using ultrasonography across 51 limbs on 3 occasions. To quantify variability, the typical error of measurement (TEM) was multiplied by 2, and thresholds of 0.2–0.6 (small), 0.6–1.2 (moderate), 1.2–2.0 (large), 2.0–4.0 (very large), and >4.0 (extremely large) were applied. In addition, variability was deemed large when the intraclass correlation coefficient (ICC) was <.67 and coefficient of variation (CV) >10%, moderate when ICC > .67 or CV < 10% (but not both), and small when both ICC > .67 and CV < 10%. Results: Muscle thickness of all muscles and regions had low to moderate variability (ICC = .88–.98, CV = 2.4–9.3%, TEM = 0.15–0.47). PA of the proximal and distal vastus lateralis had low variability (ICC = .85–.96, CV = 3.8–8%) and moderate to large TEM (TEM = 0.42–0.83). PA of the rectus femoris was found to have moderate to very large variability (ICC = .38–.74, CV = 11.4–18.5%, TEM = 0.61–1.29) regardless of region. Extended-field-of-view–derived FL (ICC = .57–.94, CV = 4.1–11.5%, TEM = 0.26–0.88) was superior to calculated FL (ICC = .37–.84, CV = 7.4–17.9%, TEM = 0.44–1.33). Conclusions: Variability of muscle thickness was low in all quadriceps muscles and regions. Only rectus femoris PA and FL measurements were highly variable. The extended-field-of-view technique should be used to assess FL where possible. Inferences based on rectus femoris architecture should be interpreted with caution.

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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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Eric R. Helms, Caryn Zinn, David S. Rowlands, Ruth Naidoo and John Cronin

Purpose:

Athletes risk performance and muscle loss when dieting. Strategies to prevent losses are unclear. This study examined the effects of two diets on anthropometrics, strength, and stress in athletes.

Methods:

This double-blind crossover pilot study began with 14 resistance-trained males (20-43 yr) and incurred one dropout. Participants followed carbohydrate-matched, high-protein low-fat (HPLF) or moderate-protein moderate-fat (MPMF) diets of 60% habitual calories for 2 weeks. Protein intakes were 2.8g/kg and 1.6g/kg and mean fat intakes were 15.4% and 36.5% of calories, respectively. Isometric midthigh pull (IMTP) and anthropometrics were measured at baseline and completion. The Daily Analysis of Life Demands of Athletes (DALdA) and Profile of Mood States (POMS) were completed daily. Outcomes were presented statistically as probability of clinical benefit, triviality, or harm with effect sizes (ES) and qualitative assessments.

Results:

Differences of effect between diets on IMTP and anthropometrics were likely or almost certainly trivial, respectively. Worse than normal scores on DALDA part A, part B and the part A “diet” item were likely more harmful (ES 0.32, 0.4 and 0.65, respectively) during MPMF than HPLF. The POMS fatigue score was likely more harmful (ES 0.37) and the POMS total mood disturbance score (TMDS) was possibly more harmful (ES 0.29) during MPMF than HPLF.

Conclusions:

For the 2 weeks observed, strength and anthropometric differences were minimal while stress, fatigue, and diet-dissatisfaction were higher during MPMF. A HPLF diet during short-term weight loss may be more effective at mitigating mood disturbance, fatigue, diet dissatisfaction, and stress than a MPMF diet.

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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.