Figure 5.

Speed modulation during forward and backward before and after spinal transection. A, EMG activity from nine hindlimb muscles along with stance phases (horizontal thick lines) of the left (L) and right (R) hindlimbs in one spinal cat six weeks after spinal transection during forward (FW-biped-spinal) and backward (BW-biped-spinal) bipedal locomotion at four speeds. Data are from Cat 5 with perineal stimulation in both directions. For muscle abbreviations, see Figure 1. B, Cycle, stance and swing durations in the two directions. C, Stride and step lengths in the two directions. D, Distance at contact and liftoff in the two directions. EMG burst durations (E) and phasing (F) in the two directions. B–F, Each data point or bar is the mean ± SD for the group (n = 3 cats), whereas statistical analyses were done on pooled cycles/bursts. FW-biped-spinal: n = 27, n = 35, n = 35, and n = 35 cycles/bursts at 0.1, 0.2, 0.3, and 0.4 m/s, respectively; BW-biped-spinal: n = 25, n = 38, n = 33, and n = 29 cycles/bursts at 0.1, 0.2, 0.3, and 0.4 m/s, respectively. Asterisks indicate a significant effect of direction (MLM) at *p < 0.01, **p < 0.001, ***p < 0.0001; ns, not significant.