Landing from different heights: Biomechanical and neuromuscular strategies in trained gymnasts and untrained prepubescent girls.

The purpose of this study was to examine the biomechanics of the lower limb, during landing in female prepubertal gymnasts and prepubertal untrained girls, aged 9-12years. Ten healthy participants were included in each group and performed five landings from 20, 40, and 60cm. Kinematics, ground reaction forces (GRF) and electromyogram (EMG) from the lateral gastrocnemius, tibialis anterior, and vastus lateralis are presented. Gymnasts had higher vertical GRF and shorter braking phase during landing. Compared to untrained girls, gymnasts exhibited for all examined drop heights more knee flexion before and at ground contact, but less knee flexion at maximum knee flexion position. Especially when increasing drop heights the gymnasts activated their examined muscles earlier, and generally they had higher pre- and post landing EMG amplitudes normalized to the peak EMG at 60cm drop height. Furthermore, gymnasts had lower antagonist EMG for the tibialis anterior compared to untrained girls, especially when landing from higher heights. It is concluded that the landing strategy preferred by gymnasts is influenced by long-term and specialized training and induces a stiffer landing pattern. This could have implications in injury prevention, which requires further investigation.

Validity and reliability of the single-trial line drill test of anaerobic power in basketball players.

AIM: This study evaluated the validity, reliability, and sensitivity of the single-trial line drill test (SLDT) for anaerobic power assessment. METHODS: Twenty-four volunteers were assigned to either a control (C, N.=12) or an experimental (BP, N.=12 basketball players) group. SLDT's (time-to-complete) concurrent validity was evaluated against the Wingate testing (WAnT: mean [MP] and peak power [PP]) and a 30-sec vertical jump testing test (VJT: mean height and MP). Blood lactate concentration was measured at rest and immediately post-test. SLDT's reliability [test-retest intraclass correlation coefficients (ICC), coefficient of variation (CV), Bland-Altman plots] and sensitivity were determined (one-way ANOVA). RESULTS: Kendall's tau correlation analysis revealed correlations (P<0.05) between SLDT time and WAnT's PP (=0.78) and MP (=0.56) and VJT's MP (=0.85) and height (=0.90). SLDT lactate concentration was moderately (P<0.05) correlated with the respective lactate values of WAnT (=0.40) and VJT (=0.66). SLDT time in BP correlated (P<0.05) with VJT's MP (=0.80) and height (=0.90) but not with WAnT performance variables. SLDT lactate responses in BP were moderately (P<0.05) correlated with WAnT's PP (=0.54) and VJT MP (=0.68), height (=0.65), and lactate concentration (=0.65). ICCs for time and lactate were 0.92 and 0.93, respectively (P<0.05) although Bland-Altman plots and CV indicate that SLDT time demonstrated greater reliability than lactate responses. In all tests, BP demonstrated higher (P<0.05) performance levels compared to C indicating an adequate sensitivity for SLDT. CONCLUSION: Results suggest that the SLDT appears to be a valid, reliable, and sensitive field test of anaerobic capacity for basketball players.