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Thomas Mullen, Craig Twist, Matthew Daniels, Nicholas Dobbin, and Jamie Highton

Purpose: To identify the association between several contextual match factors, technical performance, and external movement demands on the subjective task load of elite rugby league players. Methods: Individual subjective task load, quantified using the National Aeronautics and Space Administration Task Load Index (NASA-TLX), was collected from 29 professional rugby league players from one club competing in the European Super League throughout the 2017 season. The sample consisted of 26 matches (441 individual data points). Linear mixed modeling revealed that various combinations of contextual factors, technical performance, and movement demands were associated with subjective task load. Results: Greater number of tackles (effect size correlation ± 90% confidence intervals; η 2 = .18 ± .11), errors (η 2 = .15 ± .08), decelerations (η 2 = .12 ± .08), increased sprint distance (η 2 = .13 ± .08), losing matches (η 2 = .36 ± .08), and increased perception of effort (η 2 = .27 ± .08) led to most likely–very likely increases in subjective total task load. The independent variables included in the final model for subjective mental demand (match outcome, time played, and number of accelerations) were unclear, excluding a likely small correlation with technical errors (η 2 = .10 ± .08). Conclusions: These data provide a greater understanding of the subjective task load and their association with several contextual factors, technical performance, and external movement demands during rugby league competition. Practitioners could use this detailed quantification of internal loads to inform recovery sessions and current training practices.

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Ricardo Augusto Silva de Souza, André Guedes da Silva, Magda Ferreira de Souza, Liliana Kataryne Ferreira Souza, Hamilton Roschel, Sandro Fernandes da Silva, and Bryan Saunders

CrossFit® is a high-intensity functional training method consisting of daily workouts called “workouts of the day.” No nutritional recommendations exist for CrossFit® that are supported by scientific evidence regarding the energetic demands of this type of activity or dietary and supplement interventions. This systematic review performed in accordance with PRISMA guidelines aimed to identify studies that determined (a) the physiological and metabolic demands of CrossFit® and (b) the effects of nutritional strategies on CrossFit® performance to guide nutritional recommendations for optimal recovery, adaptations, and performance for CrossFit® athletes and direct future research in this emerging area. Three databases were searched for studies that investigated physiological responses to CrossFit® and dietary or supplementation interventions on CrossFit® performance. Various physiological measures revealed the intense nature of all CrossFit® workouts of the day, reflected in substantial muscle fatigue and damage. Dietary and supplementation studies provided an unclear insight into effective strategies to improve performance and enhance adaptations and recovery due to methodological shortcomings across studies. This systematic review showed that CrossFit® is a high-intensity sport with fairly homogenous anaerobic and aerobic characteristics, resulting in substantial metabolic stress, leading to metabolite accumulation (e.g., lactate and hydrogen ions) and increased markers of muscle damage and muscle fatigue. Limited interventional data exist on dietary and supplementation strategies to optimize CrossFit® performance, and most are moderate to very low quality with some critical methodological limitations, precluding solid conclusions on their efficacy. High-quality work is needed to confirm the ideal dietary and supplemental strategies for optimal performance and recovery for CrossFit® athletes and is an exciting avenue for further research.

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Carl Foster, Daniel Boullosa, Michael McGuigan, Andrea Fusco, Cristina Cortis, Blaine E. Arney, Bo Orton, Christopher Dodge, Salvador Jaime, Kim Radtke, Teun van Erp, Jos J. de Koning, Daniel Bok, Jose A. Rodriguez-Marroyo, and John P. Porcari

The session rating of perceived exertion (sRPE) method was developed 25 years ago as a modification of the Borg concept of rating of perceived exertion (RPE), designed to estimate the intensity of an entire training session. It appears to be well accepted as a marker of the internal training load. Early studies demonstrated that sRPE correlated well with objective measures of internal training load, such as the percentage of heart rate reserve and blood lactate concentration. It has been shown to be useful in a wide variety of exercise activities ranging from aerobic to resistance to games. It has also been shown to be useful in populations ranging from patients to elite athletes. The sRPE is a reasonable measure of the average RPE acquired across an exercise session. Originally designed to be acquired ∼30 minutes after a training bout to prevent the terminal elements of an exercise session from unduly influencing the rating, sRPE has been shown to be temporally robust across periods ranging from 1 minute to 14 days following an exercise session. Within the training impulse concept, sRPE, or other indices derived from sRPE, has been shown to be able to account for both positive and negative training outcomes and has contributed to our understanding of how training is periodized to optimize training outcomes and to understand maladaptations such as overtraining syndrome. The sRPE as a method of monitoring training has the advantage of extreme simplicity. While it is not ideal for the precise recording of the details of the external training load, it has large advantages relative to evaluating the internal training load.

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Wolfgang Schobersberger, Michael Mairhofer, Simon Haslinger, Arnold Koller, Christian Raschner, Sibylle Puntscher, and Cornelia Blank

Purpose: To analyze the predictive value of parameters of submaximal and maximal cardiopulmonary exercise performance on International Ski Federation (Fédération Internationale de Ski) World Cup ranking (FIS ranking) in elite Austrian Alpine skiers. Methods: Over 7 World Cup seasons (2012–2018), exercise data (maximal oxygen uptake and maximum power output, lactate threshold 2, and ventilatory threshold 2, based on stepwise cycle spiroergometry) were analyzed to determine whether there was a correlation between world FIS ranking and exercise capacity of male and female elite Alpine skiers. Results: The data of 39 male skiers (age: 27.67 [4.20] y, body mass index: 26.03 [1.25] kg/m2) and 36 female skiers (age: 25.49 [3.18] y, body mass index: 22.97 [1.71] kg/m2) were included in this study. The maximum oxygen uptake and maximum power output ranged from 4.37 to 4.42 W/kg and 53.41 to 54.85 mL/kg/min in men and from 4.17 to 4.30 W/kg and 45.96 to 49.16 mL/kg/min in women, respectively, over the 7 seasons; the yearly mean FIS ranking ranged from 17 to 24 in men and 9 to 18 in women. In a fixed-effects model used for the subsequent panel regression analysis, no statistically significant effect on FIS ranking was found for the exercise parameters of interest. Conclusions: Neither maximal aerobic tests nor maximum power output significantly predicted competitive performance, as indexed by the FIS ranking. This reinforces the assumption that no single parameter determines competition performance in this complex sport. Therefore, identifying the optimum amount of endurance training remains a major challenge for athletes and coaches, as does identifying and improving the factors that determine performance.

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Manuel Santiago Martin, Fernando Pareja Blanco, and Eduardo Saez De Villarreal

Purpose: This study aimed to compare the effects of 5 different 18-week in-season strength training programs on strength gains and specific water polo performance. Methods: A total of 56 young male water polo players were randomly assigned to the following 5 training groups: dry-land strength training, in-water-specific strength training, combined (dry-land and in-water) strength training, ballistic training, and eccentric-overload training. Physical performance was assessed before (Pre) and after (Post) the training period using the following battery of tests: in-water boost and countermovement jump, muscle strength in bench-press and full-squat, throwing speed (ThS), in-water agility, and 20-m maximal sprint swim. Results: Significant group × time interactions were observed for countermovement jump and in-water boost. Eccentric-overload training showed significantly higher gains in ThS and bench-press and full-squat strength than the rest of the training groups. In addition, all training groups (except in-water-specific strength training) induced significant improvements (P ≤ .05) in countermovement jump, in-water boost, and bench-press and full-squat strength. All training groups significantly increased (P ≤ .001) ThS. Moreover, all training groups improved (P ≤ .05) in-water agility (except dry-land strength training) and swimming sprint performance (except in-water-specific strength training and ballistic training). Conclusion: The findings indicate that the 18-week in-season strength training programs induced improvements in strength and specific water polo skills. The eccentric-overload training resulted in greater improvements in muscle strength (in both upper and lower body) and ThS than the other training methods examined in the study.

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Simon A. Feros, Kris Hinck, and Jake Dwyer

Purpose: This study investigated the acute warm-up effects of modified-implement bowling on bowling speed, accuracy, perceived rhythm and perceived sensation with a regular ball. Methods: A total of 13 male amateur pace bowlers completed 3 sessions in a randomized, counterbalanced order. Each session comprised a warm-up of 21 progressive-effort deliveries with either a regular (156 g), 10% heavier (171.6 g), or 10% lighter (140.4 g) cricket ball followed by a 4-over pace-bowling assessment with a regular ball. Bowling speed was assessed with a radar gun, while accuracy was calculated via the radial error. Subjects rated their perceived exertion (0%–100%), rhythm (1–5 Likert scale), and sensation (1–5 Likert scale) after each delivery. Results: The linear mixed models revealed a significant effect for warm-up condition on perceived delivery sensation (F 2,916.404 = 24.137, P < .001), with a significant pairwise difference between the regular- and heavier-ball warm-up conditions of 0.20 ± 0.07 points (estimated marginal mean ± 95% confidence interval, P < .001). There were no statistically significant effects for warm-up condition on bowling speed, accuracy, and perceived delivery rhythm. Conclusions: These findings indicate that although the regular ball felt lighter to bowl with after using the heavier ball, there were no overall potentiating or detrimental effects of using this particular modified-implement warm-up on bowling speed, accuracy, and perceived rhythm in amateur pace bowlers. Future research is encouraged to trial other protocols for eliciting potentiation to ultimately enhance bowling speed in training or in shorter match formats (eg, Twenty20).

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Alexandru Nicolae Ungureanu, Paolo Riccardo Brustio, Gennaro Boccia, Alberto Rainoldi, and Corrado Lupo

Purpose: To evaluate if the internal training load (ITL; Edwards heart rate [HR]-based and session-rating of perceived exertion [RPE] methods) is affected by the presession well-being perception, age, and position in elite (ie, Serie A2) female volleyball training. Methods: Twelve female elite volleyball players (age: 22 [4] y, height: 1.80 [0.06] m, body mass: 74.1 [4.3] kg) were monitored using an HR monitor during 32 team training sessions (duration: 1:36:12 [0:22:24], in h:min:s). Linear mixed-effects models were applied to evaluate if well-being perception (ie, perceived sleep quality/disorders, stress level, fatigue, and delayed-onset muscle soreness) may affect ITL depending on age and tactical position. Results: Presession perceived fatigue influenced ITL according to the session-RPE (P = .032) but not according to the Edwards method. Age was inversely correlated to the Edwards method (P < .001) and directly correlated to the session-RPE (P = .027). Finally, central blockers experienced a higher training load than hitters (P < .001) and liberos (P < .001) for the Edwards method, as well as higher than hitters (P < .001), liberos (P = .003), and setters (P = .008) for  session-RPE. Conclusions: Findings indicated that female volleyball players’ perceived ITL is influenced by presession well-being status, age, and position. Therefore, coaches can benefit from this information to specifically predict players’ ITL in relation to their individual characteristics.

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Simon J. de Waal, Josu Gomez-Ezeiza, Rachel E. Venter, and Robert P. Lamberts

Purpose: To provide a systematic overview of physiological parameters used to determine the training status of a trail runner and how well these parameters correlate with real-world trail running performance. Method: An electronic literature search of the PubMed and Scopus digital databases was performed. Combinations of the terms “trail run” or “trail runner” or “trail running” and “performance” were used as search terms. Seven studies met the inclusion criteria. Results: Trail running performance most commonly correlated (mean [SD]) with maximal aerobic capacity (71%; r = −.50 [.32]), lactate threshold (57%; r = −.48 [.28]), velocity at maximal aerobic capacity (43%; r = −.68 [.08]), running economy (43%; r = −.31 [.22]), body fat percentage (43%; r = .55 [.21]), and age (43%; r = .52 [.14]). Regression analyses in 2 studies were based on a single variable predicting 48% to 60% of performance variation, whereas 5 studies included multiple variable regression analyses predicting 48% to 99% of performance variation. Conclusions: Trail running performance is multifaceted. The classic endurance model shows a weaker association with performance in trail running than in road running. Certain variables associated with trail running research (such as testing procedures, race profiles, and study participants) hinder the execution of comparative studies. Future research should employ trail-specific testing protocols and clear, objective descriptions of both the race profile and participants’ training status.

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Dale R. Wagner and James D. Cotter

Ultrasound is an appealing tool to assess body composition, combining the portability of a field method with the accuracy of a laboratory method. However, unlike other body composition methods, the effect of hydration status on validity is unknown. This study evaluated the impact of acute hydration changes on ultrasound measurements of subcutaneous fat thickness and estimates of body fat percentage. In a crossover design, 11 adults (27.1 ± 10.5 years) completed dehydration and hyperhydration trials to alter body mass by approximately ±2%. Dehydration was achieved via humid heat (40 °C, 60% relative humidity) with exercise, whereas hyperhydration was via ingestion of lightly salted water. Ultrasound measurements were taken at 11 body sites before and after each treatment. Participants lost 1.56 ± 0.58 kg (−2.0 ± 0.6%) during the dehydration trial and gained 0.90 ± 0.21 kg (1.2 ± 0.2%) during the hyperhydration trial even after urination. The sum of fat thicknesses as measured by ultrasound differed by <0.90 mm across trials (p = .588), and ultrasound estimates of body fat percentage differed by <0.5% body fat. Ultrasound measures of subcutaneous adipose tissue were unaffected by acute changes in hydration status by extents beyond which are rare and overtly self-correcting, suggesting that this method provides reliable and robust body composition results even when subjects are not euhydrated.

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Marco Beato, Sergio Maroto-Izquierdo, Anthony N. Turner, and Chris Bishop

Due to the negative effects that injuries have on performance, club finances, and long-term player health (permanent disability after a severe injury), prevention strategies are an essential part of both sports medicine and performance. Purpose: To summarize the current evidence regarding strength training for injury prevention in soccer and to inform its evidence-based implementation in research and applied settings. Conclusions: The contemporary literature suggests that strength training, proposed as traditional resistance, eccentric, and flywheel training, may be a valid method to reduce injury risk in soccer players. Training strategies involving multiple components (eg, a combination of strength, balance, plyometrics) that include strength exercises are effective at reducing noncontact injuries in female soccer players. In addition, the body of research currently published supports the use of eccentric training in sports, which offers unique physiological responses compared with other resistance exercise modalities. It seems that the Nordic hamstring exercise, in particular, is a viable option for the reduction of hamstring injuries in soccer players. Moreover, flywheel training has specific training peculiarities and advantages that are related to the combination of both concentric and eccentric contraction, which may play an important role in injury prevention. It is the authors’ opinion that strength and conditioning coaches should integrate the strength training methods proposed here in their weekly training routine to reduce the likelihood of injuries in their players; however, further research is needed to verify the advantages and disadvantages of these training methods to injury prevention using specific cohorts of soccer players.