The Changes in Impacts and Soft-tissue Responses of Lower Limbs between Active and Unanticipated Landings

Abstract

Muscle activity patterns can be modulated in response to soft-tissue vibrations of lower extremity induced by the magnitude of the peak impact and the high loading rate of vertical ground reaction force during landing to reduce the high injury risk. However, the sudden changed pattern of unexpected landing would potentially influence the impact force (as a input signal) and the soft-tissue vibration (as a response), which may further affact the landing performance or even cause injury. PURPOSE: To determine the biomechanical differences of impact force and soft-tissue vibration between active landing (AL) and unexpected landing (UL). METHODS: Twelve trained male basketball volunteers were requested to land from self-made elevated platform at three heights (30, 45, and 60cm) in two different landing maneuvers (AL & UL). The 3D force plates and accelerometers were used to collect the impact and soft-tissue vibration characteristics. The variables for AL & UL included: 1) impact characteristics: the peak of impact force (BW), maximum loading rate (kN/s) and impact frequency (Hz); 2) soft-tissue vibration: maximum amplitude (g) and damping coefficient (s-1) of soft-tissue vibration of quadriceps & hamstrings. A 2 × 3 (landing style × height) repeated measures analysis of variance was used to examine the differences between conditions. RESULTS: For the impact characteristics, the peak of impact force (30cm: 3.90 ± 1.16 vs. 2.17 ± 0.50 ; 45cm: 4.35 ± 1.02 vs. 2.82 ± 0.80; 60cm: 4.73 ± 0.84 vs. 3.60 ± 0.64), maximum loading rate (30cm: 240.3 ± 63.8 vs. 88.4 ± 22.5; 45cm: 273.9 ± 77.3 vs. 157.3 ± 36.0; 60cm: 301.6 ± 73.3 vs. 203.3 ± 46.0), and impact frequency (30cm: 15.6 ± 2.3 vs. 7.96 ± 2.2; 45cm: 23.1± 2.2 vs. 8.73 ± 1.7; 60cm: 26.1 ± 2.4 vs. 10.38 ± 1.5) in UL was significantly higher than those in AL (p < .05) for all three drop heights, respectively. For soft tissue vibration, UL had a significantly greater maximum amplitudes of vibration of quadriceps (except for 60 cm) and hamstrings (p < .01) and lower damping coefficients (p < .05) compared with AL. CONCLUSION: If the neuromuscular system fails to prepare properly for an unexpected landing impact, increased magnitude of impact forces and soft-tissue vibrations emerged which might be detrimental to the impact-related injury. Supported by NSFC grant (81302131).