A comparison of knee extensor strength curves obtained theoretically and experimentally.

Strength curves relate a measure of maximal voluntary force of a group of synergistic muscles, typically a resultant knee joint moment, to a measure of muscular length, typically a joint angle. In this study, it was hypothesized that the shape of strength curves is primarily determined by the force-length properties of the individual muscles within a synergistic group. This hypothesis was tested for knee extensor strength curves by comparing theoretically determined strength curves based on the force-length relations of the individual muscles with those obtained experimentally. The agreement between theoretical and experimental curves was good, suggesting that the initial hypothesis was correct. Accepting this result, it is possible to determine the contribution of individual muscles to the total force of the synergistic group. This information, in turn, may be utilized for practical applications in sports or for evaluating strength curves of patients with injuries or diseases of the musculoskeletal system.