Fig. 7. Summary diagram showing the onset and duration of lateral hypaxial muscle EMG activity relative to maximum body bending in two Ambystoma tigrinum during swimming. Values are means ± S.D. for -burst (filled bars) and ß-burst (open bars) onset and duration times, which are calculated from values normalized to locomotor cycle duration. -bursts occur during every swimming cycle (obligate), whereas ß-bursts are more variable and do not necessarily occur in every swimming cycle (facultative). The S.D. of the normalized time of maximum opposite bending is plotted on a point in the center of the body. Sample sizes (N): individual A, TA=52, TA_ß=20, OI=52, OI_ß=40, OEP=52, OEP_ß=26, OES=52, OES_ß=3; individual B, TA=21, TA_ß=21, OI=20, OEP=21, OEP_ß=4, OES=21, OES_ß=8. OES, m. obliquus externus superficialis; OEP, m. obliquus externus profundus; OI, m. obliquus internus; TA, m. transversus abdominis. *Denotes the side of the body on which the electrodes were implanted.