The assessment of mechanical and neuromuscular response strategies during landing.

The purpose of this study was to assess relative contributions of mechanical and neuromuscular mechanisms to control of landing. Proposed mechanical and neuromuscular response strategies were evaluated relative to lower extremity impact force attenuation. Four subjects performed three conditions of 25 landings from a 60-cm height on each of two days. Additional masses were attached at each ankle for the second and removed for the third condition. Vertical ground reaction force and integrated electromyographic (IEMG) data were used to assess responses. Fourteen of 32 total single subject comparisons were significant in a mechanically predicted direction, indicating the presence of both mechanical and neuromuscular response strategies among subjects. Responses in the mechanical direction for rearfoot impact were consistent with a model predicting mechanical force changes. The presence of mechanical responses for forefoot impact not completely accounted for by the model suggested that the definition of a neuromuscular response not be limited to responses functioning in a protective manner. Multiple regression analyses relating added mass and IEMG to impact force magnitude demonstrated the complex nature of all responses. Vastus medialis IEMG was the most common independent variable included in regression models, emphasizing the importance of knee musculature in landing control.