BUNDLE, M. W.; University of Montana: Muscle efficiency during bird flight

The efficiency with which muscle converts chemical energy into mechanical energy is a basic parameter of muscle function. Yet, empirical measurements for the efficiency of vertebrate muscle exist only for isolated muscle preparations. The difficulty in measuring muscle efficiency at the whole animal level can be attributed to our inability to identify the metabolic contributions of different muscles when they act in unison to produce force. Unlike terrestrial locomotion bird flight is powered almost entirely by a single muscle, the pectoralis. This anatomy allows for easy accounting of the metabolic cost incurred by this muscle, and when combined with empirical measures of pectoralis mechanical power, muscle efficiency can be readily calculated. Three Cockatiels,Nymphicus hollandicus, were flown across a range of speeds while wearing a light-weight mask designed to capture their expired air, an aliquot of which was subsequently analyzed for oxygen and carbon dioxide fractions. Mechanical power measurements were then obtained from the same three birds over the same range of speeds using the sono-strain technique of Dial et al ’97. The ratios of the metabolic and mechanical power curves were then calculated in order to obtain the first empirical values of muscle efficiency during locomotion.