Meeting Abstract
P2.133 Monday, Jan. 5 The Effects of Long Tendons on the Energetic Cost of Muscle Contraction MOON, Brad R.*; HAMPTON, Paul M.; Univ. Louisiana, Lafayette BradMoon@louisiana.edu
Muscles that have long tendons often shorten less than muscles with short tendons, which suggests that muscles with long tendons have a lower cost of contraction. However, in most muscles it is difficult to separate the effects of fiber type and tendon length on contractile cost. The shaker muscles in the tails of rattlesnakes are good models for studying how tendon length affects contractile energetics because they vary along the tail in tendon length but have a single dominant fiber type, which provides a natural control that is lacking in typical muscles. Shaker muscle segments with long tendons were found previously to shorten significantly less than segments lacking tendons. We are now testing the hypothesis that muscles with long tendons have a lower contractile cost than segments without tendons. We are using denervation and selective paralysis to block the contraction of muscles segments while measuring oxygen consumption in western diamond-backed rattlesnakes (Crotalus atrox). By carefully measuring and subtracting the metabolic rates under different conditions (resting, all shaker muscles active, only muscles with long tendons active, and all muscles blocked), we can partition the cost of contraction between muscles that have long tendons and no tendons. Our early results indicate that (1) shaker muscles have metabolic rates that are high enough to allow selective paralysis without loss of metabolic signal strength, (2) denervation of the distal-most muscles segments does not alter the activation or contractile strains of more proximal, intact segments, and (3) the cost of contraction in segments with long tendons is lower than in segments without tendons. The results on a larger sample are likely to be representative of other fast muscles, which appear to be relatively common in diverse lineages of animals.
