Meeting Abstract
Antagonist muscles with differences in fiber type composition, architecture and mechanical function provide useful models in comparative vertebrate muscle physiology. We have developed a framework to evaluate the physiological performance (length-tension, force-velocity-power) for different muscles within a given individual. Here, we compare active and passive stress-strain, as well as power-velocity properties for TA, a fast-twitch, and relatively pennate-fibered muscle, to SOL, a slow-twitch parallel-fibered muscle in the mouse (n = 4). We test the ideas that parallel-fibered muscle is more compliant and capable of retaining near-maximal force and power production across broader ranges of strain and speed than pennate muscle. Our results show that SOL has significantly more passive compliance than TA, a difference we expect can be explained by different titin isoforms in the two muscles. SOL also has a broader stress-strain curve (∆Ԑ = 29% ± 7%), than TA (∆Ԑ = 12% ± 2%). The differences in stress-strain are reflected in the power-velocity properties with SOL having the broadest power curve: At 2.5 Lo s-1, SOL retains 87% ± 5% peak power and TA only 56% ± 4%. Our results support the idea that parallel-fibered muscles retain force and power output over greater operating strains and speeds compared to pennate muscles. These differences likely have important implications on muscle mechanical function during movement. Going forward, similar comparisons between muscles from the same individual will allow us to determine the effects of diet and eccentric injury on muscle mechanical function.
