Meeting Abstract
Elastic elements can help improve muscle function by reducing metabolic cost and amplifying power output. While increasing evidence suggests that elastic elements may only provide these benefits when tightly tuned to both muscle properties and the inertia of the system, we don’t yet know how changes in elastic systems influence their capacity to play different functional roles. For instance, are elastic systems that best improve energy conservation different from those that increase power? To explore these questions, we raised helmeted guinea fowl, a species that multi-tasks their elastic systems for both functions, in conditions that eliminated the functional demand for power production during their entire growth period. We hypothesized that elastic systems that improve energy conservation differ from those that aid power production. Thus, we predicted that birds with less demands for high power production would adapt elastic system to improve running economy. We found, instead, that there were no differences in metabolic energy costs between our restricted birds and controls at adulthood. Yet, restricted birds showed deficits in jump performance, producing lower peak forces and power during jump tests as adults. Further, these functional differences did not correspond to systematic changes in the morphology (max isometric force, optimal fiber length) of two muscles that power ankle extension (medial and lateral gastrocnemius) or of their common tendon (cross sectional area, stiffness, or slack length). From this we conclude 1) that plasticity in elastic systems during growth may be minimal and 2) differences in functional performance of elastic systems may be significantly influenced by behavioral or neurological changes.
