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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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Bethany Barone Gibbs, Melissa A. Jones, John M. Jakicic, Arun Jeyabalan, Kara M. Whitaker, and Janet M. Catov

Background: Though moderate- to vigorous-intensity physical activity is recommended, limited research exists on sedentary behavior (SED) during pregnancy. Methods: The authors conducted a prospective cohort study to describe objectively measured patterns of SED and activity during each trimester of pregnancy. Women wore thigh- (activPAL3) and waist-mounted (ActiGraph GT3X) activity monitors. SED and activity were compared across trimesters using likelihood ratio tests and described using group-based trajectories. Exploratory analyses associated SED and activity trajectories with adverse pregnancy outcomes and excessive gestational weight gain. Results: Pregnant women (n = 105; mean [SD] age = 31 [5] y; prepregnancy body mass index = 26.2 [6.6] kg/m2) had mean SED of 9.7, 9.5, and 9.5 hours per day (P = .062) across trimesters, respectively. Some activities differed across trimesters: standing (increased, P = .01), stepping (highest in second trimester, P = .04), steps per day (highest in second trimester, P = .008), and moderate- to vigorous-intensity physical activity (decreased, P < .001). Prolonged SED (bouts ≥ 30 min) and bouted moderate- to vigorous-intensity physical activity (≥10 min) were stable (P > .05). In exploratory analyses, higher SED and lower standing, stepping, and steps per day trajectories were associated with increased odds of adverse pregnancy outcomes (P < .05). No trajectories were associated with excessive gestational weight gain. Conclusions: Pregnant women exhibited stable SED of nearly 10 hours per day across pregnancy. Future research evaluating SED across pregnancy and adverse pregnancy outcome risk is warranted.

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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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Shikha Prashad, Yue Du, and Jane E. Clark

Current methods to understand implicit motor sequence learning inadequately assess motor skill acquisition in daily life. Using fixed sequences in the serial reaction time task is not ideal as participants may become aware of the sequence, thereby changing the learning from implicit to explicit. Probabilistic sequences, in which stimuli are linked by statistical, rather than deterministic, associations can ensure that learning remains implicit. Additionally, the processes underlying the learning of motor sequences may differ based on sequence structure. Here, the authors compared the learning of fixed and probabilistic sequences to randomly ordered stimuli using a modified serial reaction time task. Both the fixed and probabilistic sequence groups exhibited learning as indicated by decreased response time and variability. In the initial stage of learning, fixed sequences exhibited both online and offline gains in response time; however, only the offline gain was observed during the learning of probabilistic sequences. These results indicated that probabilistic structures may be learned differently from fixed structures and have important implications for our current understanding of motor learning. Probabilistic sequences more accurately reflect motor skill acquisition in daily life, offer ecological validity to the serial reaction time framework, and advance our understanding of motor learning.

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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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Manuel J. Escalona, Daniel Bourbonnais, Michel Goyette, Damien Le Flem, Cyril Duclos, and Dany H. Gagnon

The effects of walking speeds on lower-extremity muscle synergies (MSs) were investigated among 20 adults who walked 20 m at SLOW (0.6 ± 0.2 m/s), natural (NAT; 1.4 ± 0.1 m/s), and FAST (1.9 ± 0.1 m/s) speeds. Surface electromyography of eight lower-extremity muscles was recorded before extracting MSs using a nonnegative matrix factorization algorithm. Increasing walking speed tended to merge MSs associated with weight acceptance and limb deceleration, whereas reducing walking speed does not change the number and composition of MSs. Varying gait speed, particularly decreasing speed, may represent a gait training strategy needing additional attention given its effects on MSs.

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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.

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Catherine E. Draper, Karen Milton, and Jasper Schipperijn