Influence of gender and muscle architecture asymmetry on jump and sprint performance.

Muscle architecture is a determinant for sprinting speed and jumping power, which may be related to anaerobic sports performance. In the present investigation, the relationships between peak (PVJP) and mean (MVJP) vertical jump power, 30m maximal sprinting speed (30M), and muscle architecture were examined in 28 college-aged, recreationally-active men (n = 14; 24.3 ± 2.2y; 89.1 ± 9.3kg; 1.80 ± 0.07 m) and women (n = 14; 21.5 ± 1.7y; 65.2 ± 12.4kg; 1.63 ± 0.08 m). Ultrasound measures of muscle thickness (MT), pennation angle (PNG), cross-sectional area (CSA), and echo intensity (ECHO) were collected from the rectus femoris (RF) and vastus lateralis (VL) of both legs; fascicle length (FL) was estimated from MT and PNG. Men possessed lower ECHO, greater muscle size (MT & CSA), were faster, and were more powerful (PVJP & MVJP) than women. Stepwise regression indicated that muscle size and quality influenced speed and power in men. In women, vastus lateralis asymmetry negatively affected PVJP (MT: r = -0.73; FL: r = -0.60) and MVJP (MT: r = -0.76; FL: r = -0.64), while asymmetrical ECHO (VL) and FL (RF) positively influenced MVJP (r = 0.55) and 30M (r = 0.57), respectively. Thigh muscle architecture appears to influence jumping power and sprinting speed, though the effect may vary by gender in recreationally-active adults. Appropriate assessment of these ultrasound variables in men and women prior to training may provide a more specific exercise prescription. Key pointsThe manner in which thigh muscle architecture affects jumping power and sprinting speed varies by gender.In men, performance is influenced by the magnitude of muscle size and architecture.In women, asymmetrical muscle size and architectural asymmetry significantly influence performance.To develop effective and precise exercise prescription for the improvement of jumping power and/or sprinting speed, muscle architecture assessment prior to the onset of a training program is advised.

Body composition assessment in athletes: Comparison of a novel ultrasound technique to traditional skinfold measures and criterion DXA measure.

OBJECTIVES: This investigation compared ultrasound and skinfolds as measures of body fat for athletes, relative to dual-energy X-ray absorptiometry. DESIGN: Fifty-six well-trained athletes from various sports participated in a cross-sectional study. METHODS: The participants attended one testing session, where total body fat mass was measured using dual-energy X-ray absorptiometry, and subcutaneous adipose tissue was measured using brightness-mode ultrasound and skinfolds with callipers. The ultrasound and skinfold measures were correlated independently against standardised fat mass from dual-energy X-ray absorptiometry. RESULTS: The correlation between standardised fat mass and sum-of-eight (Σ8) sites ultrasound (r=0.959, p<0.001), and with sum-of-seven (Σ7) sites skinfolds (r=0.911, p<0.001), were both high positive correlations. In the lowest quartile by fat proportion, the correlation between standardised fat mass and Σ8 ultrasound (r=0.811, p<0.001) was a high positive correlation, whilst the correlation with Σ7 skinfolds (r=0.652, p=0.011) was a moderate positive correlation. In the highest quartile by fat proportion, the correlation between standardised fat mass and Σ8 ultrasound (r=0.847, p<0.001) was a high positive correlation, whilst the correlation with Σ7 skinfolds (r=0.591, p=0.026) was a moderate positive correlation. CONCLUSIONS: Ultrasound and skinfolds are both very good methods to accurately assess body composition in athletes, relative to dual-energy X-ray absorptiometry. However, ultrasound delivered consistently more accurate results, throughout a broad athletic spectrum.

State Population Influences Athletic Performance Combine Test Scores in High School-Aged American Football Players.

This study compared athletic performance differences among high school American football combine participants originating from states of different population sizes. High school-aged American football players (n=7,214) who had participated in athletic performance combines between March 2015 and January 2016 were included in this analysis. Data included combine date and location, school state of origin, football position, class, height, weight, 10-, 20-, and 40-yd dash times, pro-agility, L-cone drill, vertical jump, broad jump, and power push-up. Participants were separated into high- (state population>10,000,000; HIGH; n=2,804), mid- (state population=5,000,000-9,999,999; MID; n=2,911), or low-population (state population<5,000,000; LOW; n=1,499) state of origin. Data were allometrically scaled to account for differences in body mass across high school grade levels and American football positions. All statistical analyses were performed on the allometrically scaled data. LOW athletes performed better than HIGH athletes in the 20-yd dash (p≤0.01). LOW athletes performed better than HIGH and MID in the 40-yd dash, pro-agility, broad jump, and power push-up (p<0.01). LOW and HIGH athletes performed better than MID in the L-cone and vertical jump (p<0.01). When considering population size, athletes originating from LOW states may demonstrate higher levels of athletic performance in football combine events hypothetically due to more opportunities for sports participation and playing time, leading to greater athletic development. Youth and high school coaches in MID and HIGH states might consider providing more opportunities for playing and individualized coaching to encourage long-term athletic development.

Consensus on measurement properties and feasibility of performance tests for the exercise and sport sciences: a Delphi study.

BACKGROUND: Performance tests are used for multiple purposes in exercise and sport science. Ensuring that a test displays an appropriate level of measurement properties for use within a population is important to ensure confidence in test findings. The aim of this study was to obtain subject matter expert consensus on the measurement and feasibility properties that should be considered for performance tests used in the exercise and sport sciences and how these should be defined. This information was used to develop a checklist for broader dissemination. METHODS: A two-round Delphi study was undertaken including 33 exercise scientists, academics and sport scientists. Participants were asked to rate the importance of a range of measurement properties relevant to performance tests in exercise and sport science. Responses were obtained in binary and Likert-scale formats, with consensus defined as achieving 67% agreement on each question. RESULTS: Consensus was reached on definitions and terminology for all items. Ten level 1 items (those that achieved consensus on all four questions) and nine level 2 items (those achieving consensus on ≥2 questions) were included. Both levels were included in the final checklist. CONCLUSIONS: The checklist developed from this study can be used to inform decision-making and test selection for practitioners and researchers in the exercise and sport sciences. This can facilitate knowledge sharing and performance comparisons across sub-disciplines, thereby improving existing field practice and research methodological quality.