Inconsistency of Bilateral Asymmetry BetweenSprinting and Jumping Performance

Abstract

The concept of leg dominance is complicated as bilateral muscular strength/power asymmetry is linked to poor performance and/or injury risk. Bilateral asymmetry during 2-leg (2L) jumping appears to define performance, rather than limit it. During 2L jumping, the leg that developed the greatest torque/velocity is defined as dominant. PURPOSE: to investigate the relationship between apparent leg dominance in jumping and sprinting. METHODS: Men (n=18; football, basketball) and women (n=17; basketball, soccer, volleyball) athletes competing in intercollegiate sports completed repeat trials of sprint and jump testing. Sprint: three trials of a 12-m sprint with step-by-step kinematic data collected with an infrared timing system. Jump: repeat trials of 2L and single-leg (1L- left leg; 1R-right leg) squat jump without countermovement conducted on individual force plates to determine jump impulse (IMPJ). Jump height (JHt) was calculated from flight time ([INCREMENT]t). Data were averaged across trials. Asymmetry index was calculated as (L-R)/(0.5*(L+R)). Bilateral facilitation/deficit was determined from jump performance as (1L+1R)/2L. Differences were tested with ANOVA; p<0.05. RESULTS: Men (1.70±0.17 s) were faster than women (1.82±0.11 s). Horizontal acceleration (a) decreased from the first to last stride while, horizontal velocity (v) increased throughout. In contrast, step-by-step a was asymmetric while v increased linearly. a and v were always greater in men. There were no differences in 1L and 1R JHt (left & right: men: 22.0±11.7 & 21.5±11.6 cm;women: 12.4±2.7 &12.7±2.9 cm, respectively). 1L and 2L (men: 39.6 ± 3.6 cm; women: 26.4.± 4.2 cm) JHt was greater in men. Bilateral asymmetry (AI range 40 to -58%) was noted in IMPJ during 2L; both groups produced a greater jump impulse in one leg (men: 135±18 & 110±13.2 N; women: 92±18 N & 74±15 N). 2L performance was associated with a bilateral deficit (n=12) or facilitation (n=19) and was unrelated to JHt (r=-0.25). There was no relationship between the dominant leg during 2L jumping and sprinting. CONCLUSION: There is a non-linear, asymmetric acceleration pattern associated with short distance sprinting which appears to define leg dominance in sprinting. There appears to be a dominant leg during sprinting and 2L jumping, which is not consistent across performance.