Stored elastic energy amplifies muscle power to reduce performance loss at low temperatures

 

 

Western fence lizards maintain nearly the same maximum running speed and acceleration at 25° as at 35° C, despite a 50% drop in muscle velocity and power. This has important implications for survival, since a cool lizard basking in the morning is at risk for predation. Previous work has shown that lizards have just enough muscle to power acceleration, but the in vitro muscle experiments used to measure power were conducted at 39° C, which suggests that performance should drop significantly at lower temperatures. There is currently no explanation for the mismatch between the muscle contractile properties and the lizards’ locomotor abilities. I am testing the hypothesis that lizards use elastic energy stored in tendons to amplify muscle power and maintain acceleration performance over a wide range of temperatures.

 

I am testing this using two techniques. First, I am using in vitro muscle preparations to measure the potential for elastic energy storage in lizard locomotor muscles at multiple temperatures. Second, I am using inverse dynamics to measure the power output of the locomotor muscles during acceleration at multiple temperatures. If calculated muscle power is higher than the capabilities of the muscle, then the lizards may be amplifying power using stored elastic energy.