A new sledge jump system that allows almost natural reactive jumps

JOURNAL OF BIOMECHANICS

卷:43

Article

Kramer, A.¹  Ritzmann, R.¹  Gollhofer, A.¹  Gehring, D.¹  Gruber, M.² 

[1] Univ Freiburg, Dept Sport & Sport Sci, D-79117 Freiburg, Germany

[2] Univ Potsdam, Dept Training & Movement Sci, Potsdam, Germany

关键词: Sledge;    SSC;    Motion analysis;    Hopping;    Electromyography;   

DOI  :  10.1016/j.jbiomech.2010.06.027

来源: Elsevier

【 摘 要 】

Aim: Sledge jump systems (SJS) are often employed to examine the underlying mechanical and neuromuscular mechanisms of the stretch-shortening cycle (SSC) as they allow the systematic variation of impact velocity and energy. However, in existing SJS the jumps are not very comparable to natural jumps because of the long contact times (similar to 200%), which prevent the storage of kinetic energy. The aim of the present study was to evaluate if an ultra-light sledge, built in a way that joint movement is barely restricted, allows jumps that are comparable to natural jumps. Methods: Ground reaction forces, kinematic and electromyographic (EMG) data of 21 healthy subjects were compared between normal hoppings (NH) on the ground and hoppings in a custom-built SJS (sledge hoppings, SH). Results: Normalized to NH, the ground contact times for the SH were prolonged (+22%), while the peak forces (-21%) and the preactivity of the soleus and gastrocnemius medialis muscles were reduced (-20% and -22%, respectively). No significant changes were observed for the iEMG of the short latency response of those muscles (+1% and +8%) and the ranges of motion in the ankle, knee and hip joint (differences of 1, 1 and 2 degrees). The reduced peak forces were associated with a reduced leg stiffness (-21%). Conclusion: The new system allows reactive jumps that are rather comparable to natural jumps. Therefore, the new SJS seems to be an adequate system in order to examine the SSC under controlled and almost natural conditions. (C) 2010 Elsevier Ltd. All rights reserved.

【 授权许可】

Free