Meeting Abstract
Muscle, the biological motor of movement in animals, is used to perform a diverse range of tasks. For instance, muscles can be employed to produce the mechanical energy used to power a movement, or can act as a sink to dissipate that energy. Some muscle contractile properties, such as shortening speed and twitch time, vary among muscles, and it is reasonable to expect that such properties are matched to the demands of the task. Sprinting, for example, is a rapid, cyclical movement that may be limited by the twitch time of muscles. Biting, on the other hand, is a more episodic movement that may not be as dependent on cycling rate. We examined the contractile physiology of a locomotor and a feeding muscle in Anolis lizards to test the hypothesis that the mechanical properties of these muscles vary according to their functional demands. We found that twitch times were on average 1.7 times faster in locomotor muscles than feeding muscles. Further, we found that passive tension tended to develop at lower normalized muscle lengths in locomotor muscles than in feeding muscles. These findings suggest that locomotor muscles are tuned to allow for the very rapid force generating events during sprinting. The observation that feeding muscles develop passive tension at longer lengths compared with locomotor muscles may be related to a reduced risk of active lengthening in jaw muscles, if passive forces serve as mechanical protection against potential muscle damage during active lengthening. These results show that the mechanical properties of muscles may be closely linked to their different functional demands. This research was supported by NSF grant IOS 1354620.
