Functional Anatomy of the Primary Downstroke Muscles in the Pallid Bat, Antrozous pallidus

Electromyographical analysis of the shoulder musculature of Antrozous pallidus indicates the existence of two patterns of activity within the primary down-stroke musculature. The first pattern, exemplified by Mm. pectoralis profundus and serratus anterior , is an adductor pattern of muscle activity responsible for powering the downstroke. A second pattern indicative of a fine control role in locomotion is exemplified by M. subscapularis in which a nearly continuous distribution of muscle activity is recorded throughout the wingbeat cycle. These findings dictate a revision of existing hypotheses about the functional division of labor in the chiropteran down-stroke musculature with respect to the temporal involvement of the three muscles during flight.