Force enhancement and mechanisms of contraction in skeletal muscle

This paper presents a study on force enhancement and mechanisms of contraction in skeletal muscle. Force enhancement was evaluated in four conceptually different experimental preparations: in vivo human muscles activated through voluntary contractions; isolated, in situ muscle preparations (typically the cat soleus), isolated single fibres (typically from the lumbrical muscles of the frog), and isolated single myofibrils (from the rabbit psoas). Results show that force enhancement is caused by an active and passive component. The passive component appears to be associated with sarcomere length and have been speculated to originate within the structural protein, titin. The active component of force enhancement appears to be related to the molecular interaction of actin and myosin, and therefore, seems to be intricately linked to the basic mechanism of contraction