Meeting Abstract
Muscles are multifunctional. During concentric contractions, they shorten quickly to produce motion. During eccentric contractions, they slowly lengthen while activated to dissipate energy and absorb forces. These contractions not only differ in function, but also in the impact they have on the muscles themselves. Whereas concentric contractions do not typically induce much damage, eccentric contractions can injure the sarcomere and tear surrounding connective tissue. Eccentric contractions also induce more damage in large, fast-twitch type II muscle fibres than in small, slow-twitch type I muscle fibres due to ultrastructural differences. Because most animals’ muscles regularly perform both types of contractions, studies have primarily focused on short-term muscle damage. However, toads differ: hindlimbs almost exclusively perform concentric contractions for hopping and forelimbs perform eccentric contractions to decelerate into a safe landing. This separation of function provides us with a unique opportunity to determine if long term morphological and compositional strategies have evolved to enhance specialized muscle functions. Preliminary histological results demonstrate that anconeus muscle fibres are significantly smaller and more densely arranged (1815±495.6 µm2, 262±87.9 cells/mm2) than plantaris muscle fibres (3959±792.6 µm2, 190±42.8 cells/mm2; p<0.01 and n=3 for both). This indicates that muscle fibre type may be a critical adaptation for both performing the sustained eccentric contractions and protecting the muscles from repeated damage. We are also investigating if differences in amount and type of connective tissue exist to further enhance specialized muscle function.
