n International SportMed Journal - Lower extremity stiffness modulation : effect of impact load of a landing task from different drop heights : original research article
|Article Title||Lower extremity stiffness modulation : effect of impact load of a landing task from different drop heights : original research article|
|© Publisher:||International Federation of Sports Medicine|
|Journal||International SportMed Journal|
|Publication Date||Jan 2009|
|Pages||186 - 193|
|Keyword(s)||Biomechanics, Ground reaction force, Inverse dynamic, Loading rate and Spring-mass model|
Background: The characteristics of stiffness resulting from increased impact loads dropped from various heights are still uncertain. Aim: This study aimed to examine lower extremity stiffness regulation at various impact loads, and the relationship between lower extremity stiffness and the impact load. Methods: Twenty male subjects were recruited from a university's physical education department. Each subject performed a landing task from drop heights of 40, 60, and 80cm (DL40, DL60, and DL80) respectively. Leg stiffness, joint stiffness, peak vertical ground reaction force, time to peak vertical ground reaction force, loading rate, and peak proximal tibia anterior shear force were measured. Correlations of leg stiffness and joint stiffness with peak vertical ground reaction force, time to peak vertical ground reaction force, loading rate, and peak proximal tibia anterior shear force during the drop landing task were assessed. Results: The study found that increased impact load from DL40 to DL60 reduced leg stiffness, but the peak vertical ground reaction force, time to peak vertical ground reaction force, and loading rate were unchanged. When the impact load increased from DL60 to DL80, leg stiffness no longer decreased, and the knee joint stiffness increased significantly. Meanwhile, the peak vertical ground reaction force and loading rate increased significantly, and the vertical ground reaction force peaked earlier than with DL40 and DL60. Further, knee joint stiffness was significantly correlated with the peak proximal tibia anterior shear force. Conclusions: Reduced leg stiffness with increasing impact load may decrease the risk of future lower extremity injury. A significant increase in knee joint stiffness at DL80 increases the risk of knee joint injury, especially injury of the ACL.
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