Fig. 4. (A,B) Representative fascicle strain and EMG recordings obtained at the four sampled regions of the pectoralis muscle, together with strain recordings of the aponeurosis and overall muscle force obtained from the DPC strain gauge. Recordings are for two wingbeats obtained from pigeons 1 and 3 during slow (4-5 m s^-1) level flight. EMG signals were bandpass filtered from 40 to 1500 Hz, and sonomicrometer and strain gauge recordings were low-pass (40 Hz) filtered, using a 4th order zero-lag digital Butterworth filter. In-series proximal and distal segment strain measurements obtained at the Ant and Mid SB sites were averaged to yield the overall patterns of fascicle strain depicted here for those muscle sites. (C) Mean fascicle and aponeurosis strains during a single wingbeat cycle based on data recorded from all individuals for which recordings were made at each site. Data were normalized to a full wingbeat cycle before being averaged, to maintain temporal consistency across individual animals.