Meeting Abstract

50.2  Sunday, Jan. 5 10:30  Boundaries of skeletal muscle instability at long sarcomere lengths AZIZI, E*; DUNLEVIE, MD; Univ. of California, Irvine; Univ. of California, Irvine eazizi@uci.edu

Skeletal muscles are thought to be unstable when operating at lengths beyond the plateau of the force-length curve. This instability is a result of variation in sarcomere length where sarcomeres at slightly longer lengths produce less force then their shorter counterparts. This disparity in force will tend to cause the longer and therefore weaker sarcomeres to be stretched rapidly compared to shorter and stronger sarcomeres. This mechanism will continue until the weaker sarcomere is stretched to a length where there is no overlap between actin and myosin and the sarcomere “pops”. We developed a model that explores the instability of the descending limb of the force-length curve under varying conditions. We examined the effect of sarcomere velocity as a potential mechanism to counteract sarcomere instability. We also examined how the passive properties of sarcomeres may alter the level of sarcomere length variation that may result in instability. Our results show that small degrees of sarcomere length variation may be counteracted by the effect of velocity on force. We also show that muscles with increased passive stiffness may reach instability at relatively longer sarcomere lengths. Supported by NIH AR055295.