THE BIOMECHANICS OF DYNAMICALLY CONTRACTING SKELETAL MUSCLE

Abstract

History-dependent properties of skeletal muscle contraction have been observed for half a century. The origin of these properties has been the focus of intense scientific debate. One of these properties, the force enhancement following muscle stretching, has been associated with the development of sarcomere length non-uniformities. Here, we show that this long-held belief is likely not correct. We show this by rejecting three specific hypotheses that arise directly from the sarcomere length non-uniformity theory. We further found novel evidence that force enhancement is likely associated with the development of extra tension in a passive, molecular spring, such as titin or nebulin. This finding has a profound impact on the theory of force enhancement following muscle stretching, and has direct implications for muscle injuries occurring during active muscle stretching.