Vastus lateralis maximum force-generating potential occurs at optimal fascicle length regardless of activation level.

Our results support the hypothesis that vastus-lateralis fascicle length for maximal force production is about constant for maximal and submaximal levels of activation, presumably taking advantage of optimal myofilament overlap at that fascicle length. This result implies that optimal vastus-lateralis lengths occur at different knee angles for different levels of activation, which is in stark contrast to findings in the literature in which submaximal force-fascicle length relationships were based on force rather than activation.