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Thomas A. Haugen, Felix Breitschädel, Håvard Wiig and Stephen Seiler

Purpose: To quantify possible differences in countermovement jump height across sport disciplines and sex in national-team athletes. Methods: In this cross-sectional study, 588 women (23 [5] y, 66 [8] kg) and 989 men (23 [5] y, 82 [12] kg) from 44 different sport disciplines (including 299 medalists from European Championships, World Championships, and/or Olympic Games) tested a countermovement jump on a force platform at the Norwegian Olympic Training Center between 1995 and 2018. Results: Athletic sprinting showed the highest values among the men (62.7 [4.8] cm) and women (48.4 [6.0] cm), clearly ahead of the long jump/triple jump (mean difference ± 90% CL: 6.5 ± 5.0 and 4.3  ± 4.1; very likely and likely; moderate) and speed skating sprint (11.4 ± 3.1 and 7.5 ± 5.5 cm; most likely and very likely; very large and moderate). These horizontally oriented sports displayed superior results compared with more vertically oriented and powerful sports such as beach volleyball, weightlifting, and ski jumping, both in men (from 2.9 ± 4.7 to 15.6 ± 2.9 cm; small to very large; possibly to most likely) and women (5.9 ± 4.8 to 13.4 ± 3.4 cm; large to very large; very likely to most likely), while endurance sports and precision sports were at the other end of the scale. Overall, the men jumped 33% higher than the women (10.3, ±0.6 cm; most likely; large). Conclusions: This study provides practitioners and scientists with useful information regarding the variation in countermovement jump height among national-team athletes within and across sport disciplines.

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John H. Hollman, Nicholas J. Beise, Michelle L. Fischer and Taylor L. Stecklein

Context: Examining the coordinated coupling of muscle recruitment patterns may provide insight into movement variability in sport-related tasks. Objective: The purpose of this study was to examine the relationship between coupled gluteus maximus and medius recruitment patterns and hip-adduction variability during single-limb step-downs. Design: Cross-sectional. Setting: Biomechanics laboratory. Participants: Forty healthy adults, including 26 women and 14 men, mean age 23.8 (1.6) years, mean body mass index 24.2 (3.1) kg/m2, participated. Interventions: Lower-extremity kinematics were acquired during 20 single-limb step-downs from a 19-cm step height. Electromyography (EMG) signals were captured with surface electrodes. Isometric hip-extension strength was obtained. Main Outcome Measures: Hip-adduction variability, measured as the SD of peak hip adduction across 20 repetitions of the step-down task, was measured. The mean amplitudes of gluteus maximus and gluteus medius EMG recruitment were examined. Determinism and entropy of the coupled EMG signals were computed with cross-recurrence quantification analyses. Results: Hip-adduction variability correlated inversely with determinism (r = −.453, P = .018) and positively with entropy (r = .409, P = .034) in coupled gluteus maximus/medius recruitment patterns but not with hip-extensor strength nor with magnitudes of mean gluteus maximus or medius recruitment (r = −.003, .081, and .035; P = .990, .688, and .864, respectively). Conclusion: Hip-adduction variability during single-limb step-downs correlated more strongly with measures of coupled gluteus maximus and medius recruitment patterns than with hip-extensor strength or magnitudes of muscle recruitment. Examining coupled recruitment patterns may provide an alternative understanding of the extent to which hip neuromuscular control modulates lower-extremity kinematics beyond examining muscle strength or EMG recruitment magnitudes.

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Wigand Poppendieck, Melissa Wegmann, Anne Hecksteden, Alexander Darup, Jan Schimpchen, Sabrina Skorski, Alexander Ferrauti, Michael Kellmann, Mark Pfeiffer and Tim Meyer

Purpose: Cold-water immersion is increasingly used by athletes to support performance recovery. Recently, however, indications have emerged suggesting that the regular use of cold-water immersion might be detrimental to strength training adaptation. Methods: In a randomized crossover design, 11 participants performed two 8-week training periods including 3 leg training sessions per week, separated by an 8-week “wash out” period. After each session, participants performed 10 minutes of either whole-body cold-water immersion (cooling) or passive sitting (control). Leg press 1-repetition maximum and countermovement jump performance were determined before (pre), after (post) and 3 weeks after (follow-up) both training periods. Before and after training periods, leg circumference and muscle thickness (vastus medialis) were measured. Results: No significant effects were found for strength or jump performance. Comparing training adaptations (pre vs post), small and negligible negative effects of cooling were found for 1-repetition maximum (g = 0.42; 95% confidence interval [CI], −0.42 to 1.26) and countermovement jump (g = 0.02; 95% CI, −0.82 to 0.86). Comparing pre versus follow-up, moderate negative effects of cooling were found for 1-repetition maximum (g = 0.71; 95% CI, −0.30 to 1.72) and countermovement jump (g = 0.64; 95% CI, −0.36 to 1.64). A significant condition × time effect (P = .01, F = 10.00) and a large negative effect of cooling (g = 1.20; 95% CI, −0.65 to 1.20) were observed for muscle thickness. Conclusions: The present investigation suggests small negative effects of regular cooling on strength training adaptations.

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Christopher Michael Brogden, Lewis Gough and Adam Kelly

Context: Physiological fitness testing, such as the Yo-Yo Intermittent Recovery Test (YYIR) is a key requirement of the Elite Player Performance Plan, introduced by the English Premier League. Eccentric hamstring strength has been identified as a risk factor for hamstring injuries in soccer players, with fatigue highlighted to further exasperate this issue. Objective: The aim of the current study was to examine the effect of the YYIR level 1 (YYIR1) on eccentric knee flexor strength assessed using the NordBord in youth soccer players. Design: Experimental design. Setting: Soccer club academy. Participants: A total of 67 male academy soccer players (age = 16.58 [0.57] y; height = 175.45 [5.85] cm; mass = 66.30 [8.21] kg) volunteered to participate in the current study during the English competitive soccer season. Main Outcome Measures: Participants conducted eccentric hamstring strength assessments using the NordBord prior to and immediately postcompletion of the YYIR1, with outcome measures of peak force and peak force relative to body mass recorded. Results: Paired t tests highlighted increased absolute eccentric knee flexor strength values (P < .001) immediately post-YYIR1 for both the dominant and nondominant limbs, with the same trend (P < .001) observed for eccentric strength relative to body mass. Conclusions: The results of this study indicate that the YYIR1 does not induce eccentric knee flexor fatigue and as such is not a valid assessment method to assess the effects of fatigue on hamstring function. However, results do suggest that the NordBord may be considered a viable and more accessible alternative to detect pre–post fitness test/fatigue protocol differences in eccentric knee flexor peak strength while working in the field.

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Michelle Ogrodnik, Jillian Halladay, Barbara Fenesi, Jennifer Heisz and Katholiki Georgiades

Background: Participation in physical activity (PA) is a modifiable factor that contributes to academic success, yet the optimal dose (ie, frequency) and mechanisms underlying the effect require further exploration. Methods: Using data from 19,886 elementary and 11,238 secondary school students across Ontario, Canada, this study examined associations between PA participation frequency, academic achievement, and inattention and hyperactivity. Results: Among elementary students, there was a positive association between PA frequency and academic achievement. Participating in 1 to 2 days per week of PA related to higher academic achievement compared with no days, whereas 7 days per week had the largest associations. For secondary students, a minimum of 3 to 4 days per week was associated with higher academic achievement with no significant benefit of additional days. Indirect effects of inattention and hyperactivity were found for both groups, suggesting that the benefits of PA on academic achievement may be partly explained by reductions in inattention and hyperactivity, especially for secondary school students. Conclusion: Students may experience academic benefits from PA even if they are not meeting the guidelines of exercising daily. These benefits may occur, in part, through reductions in inattention and hyperactivity. Further work is needed to determine the temporality and mechanism of these associations.

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Nikolaos Zaras, Angeliki-Nikoletta Stasinaki, Polyxeni Spiliopoulou, Giannis Arnaoutis, Marios Hadjicharalambous and Gerasimos Terzis

Purpose: The purpose of the present study was to investigate the relationship between weightlifting performance and the rate of force development (RFD), muscle architecture, and body composition in elite Olympic weightlifters. Methods: Six male Olympic weightlifters (age 23.3 [3.4] y, body mass 88.7 [10.2] kg, body height 1.76 [0.07] m, snatch 146.7 [15.4] kg, clean and jerk 179.4 [22.1] kg), all members of the national team, participated in the study. Athletes completed a 16-week periodized training program aiming to maximize their performance at the national competition event. Measurements, including maximal strength (1-repetition maximum) in snatch, clean and jerk, back and front squat, isometric leg press RFD and peak force, countermovement jump, vastus lateralis muscle architecture, and body composition, were performed before and after the training period. Results: Weightlifting performance increased significantly after training (P < .05). Leg press RFD increased only in time windows of 0 to 200 and 0 to 250 milliseconds after training (8.9% [8.5%] and 9.4% [7.7%], respectively, P < .05) while peak force remained unaltered (P < .05). Front squat strength increased significantly (P < .05), while countermovement jump power increased 2.3% (2.1%) (P < .05). No changes were observed for muscle architecture and lean body mass (P > .05). Significant correlations were observed between performance in snatch and clean and jerk with isometric leg press RFD, at all time windows, as well as with lean body mass and squat 1-repetition maximum. Conclusions: These results suggest that regular examination of RFD, lean body mass, and lower extremities’ 1-repetition maximum may be useful performance predictors in elite Olympic weightlifters.

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Tanya Tripathi, Stacey C. Dusing, Peter E. Pidcoe, Yaoying Xu, Mary S. Shall and Daniel L. Riddle

Aims: The American Academy of Pediatrics recommends “parents to incorporate supervised, awake ‘prone play’ in their infant’s routine to support motor development and minimize the risk of plagiocephaly”. The purpose of this feasibility study was to compare usual care to a reward contingency–based intervention, developed to increase prone tolerance and improve motor skills. Methods: Ten full-term infants, 3–6- months old, with poor prone tolerance were randomized to either the Education group or Reward contingency group. Each group participated in three parent education sessions and 15 intervention sessions, over the period of three weeks. Infants in the Reward contingency group used the Prone Play Activity Center, a technology developed to reinforce motor behavior of infants in prone position. Intervention frequency and parent feedback data determined the feasibility of the interventions. Results: Infants in the Reward contingency group practiced a median of 12 of the 15 anticipated intervention sessions in the Prone Play Activity Center. These infants used the device for a mean of 18 minutes per day. Parents of infants in the Education group practiced a median of 10 sessions of the 15 anticipated intervention sessions. Conclusion: The reward contingency–based intervention is feasible for use in a future clinical trial with some modifications.

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Kendall J. Sharp, Charles C. South, Cherise Chin Fatt, Madhukar H. Trivedi and Chad D. Rethorst

Exercise reduces depressive symptoms and improves physical health in persons with depression. However, the interventions implemented in research studies require significant resources, limiting adoption into clinical practice and suggesting the need for more efficient interventions. In two nonrandomized pilot studies, the authors evaluated the feasibility of a multicomponent intervention (group educational sessions, Fitbit, and access to exercise facility) in adult persons with depression and breast cancer survivors with depression. The participants in both pilot studies completed 12 weeks of group educational sessions to increase physical activity levels, were provided with self-monitoring devices, and were provided access to on-site exercise facilities. Depressive symptoms significantly decreased postintervention, and over 90% of the participants reported that they had benefited from the intervention. These results indicate that implementing a multicomponent intervention is feasible and may reduce depressive symptoms and improve other psychosocial outcomes.

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Audrey G. Evers, Jessica A Somogie, Ian L. Wong, Jennifer D. Allen and Adolfo G. Cuevas

The objective of this study was to examine the effectiveness of a pilot mindfulness program for student athletes by assessing mental health, mindfulness ability, and perceived stress before and after the intervention. The mindfulness program was adapted from a program developed at the University of Southern California. The four-session intervention taught the basics of mindfulness, self-care skills, and guided meditations. Participants completed surveys before and after the intervention. Mindfulness ability was assessed with the Cognitive and Affective Mindfulness Scale, mental health was assessed with a modified Short Form Health Survey, and stress was assessed with the Perceived Stress Scale. After the intervention, participants reported improvement in mindfulness ability, t(28) = −2.61, p =  .014, mental health, t(28)  =  −2.87, p =  .008, and a trending improvement in perceived stress, t(28)  =  1.86, p =  .073. A short mindfulness program may be effective for improving mental health and mindfulness ability in collegiate student athletes.

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Noora J. Ronkainen, Michael McDougall, Olli Tikkanen, Niels Feddersen and Richard Tahtinen

Meaning in movement is an enduring topic in sport social sciences, but few studies have explored how sport is meaningful and for whom. The authors examined the relationships between demographic variables, meaningfulness of sport, and craftsmanship. Athletes (N = 258, 61.6% male, age ≥18) from the United Kingdom completed a demographic questionnaire, the Work and Meaning Inventory modified for sport, and the Craftsmanship Scale. Older age and individual sport significantly correlated with higher craftsmanship. Craftsmanship and religion were two independent predictors of meaningfulness, but emphasized somewhat different meaning dimensions. Meaningfulness in sport seems to be related to how athletes approach their craft, as well as their overall framework of life meaning.