6.9 Wednesday, Jan. 4 Power amplification in water: modeling muscle-tendon dynamics during swimming RICHARDS, Christopher T*; SAWICKI, Gregory; Harvard University; North Carolina State University email@example.com
Models have demonstrated that the power required for some animals to jump exceeds the theoretical limits of muscle power. Such work predicted that a muscle may store elastic energy in the tendon before it is released rapidly, producing ‘power amplification’ as tendon recoil assists the muscle to accelerate the load. Can this mechanism work for hydrodynamic loads? Using a hill-type mathematical model of an in-series muscle-tendon (m-t) unit generating torque about a lever to rotate a fin submerged in water, we simulated muscle contractions against limb masses ranging from 0.3 to 3 to 30 g, fin areas from 0.005 to 0.05 to 0.5 to 5 to 50 cm2, tendon stiffness (k) values from 1250 to 1667 to 2500 to 5000 N/m and effective mechanical advantage (ema = inlever/outlever) of 0.025 to 0.05 to 0.1. Certain conditions produced power amplification where the m-t produced power ~18% greater than the limit for muscle alone. Surprisingly, k did not strongly influence m-t power output. For the heaviest limb, peak m-t power increased dramatically with ema, but was not influenced strongly by increases in fin area. For the lowest limb mass, m-t power output was highly sensitive to both ema and area, with maximum m-t power produced with fin area = 0.05 or 0.5 or 5 cm2, for ema = 0.025 , 0.05 and 0.1, respectively. These interactions suggest multiple ‘optimal’ morphological configurations for tuning m-t power which depend on interactions among limb mass, fin area and ema.