Averages of significant shifts in extensor and flexor muscle burst onset/offset cluster centers from flat to upslope (dashed lines) and flat to downslope (solid lines). Graphs show the averages (for the muscles studied) of significant changes in muscle burst onsets and offsets with slope of walking for CONTROL (top) and SELF-REINNERVATED (bottom) animals before (pre-Tx; gray lines) and after spinal transection (post-Tx; black lines). Whereas extensor activation was delayed by walking upslope in CONTROL animals postspinalization, it was advanced in SELF-REINNERVATED animals for both upslope and downslope walking both pre- and postspinalization. Extensors tended to turn off later during upslope walking prespinalization, but turned off earlier postspinalization in CONTROL animals. For SELF-REINNERVATED animals, extensors turned off earlier during downslope walking and later during upslope walking, irrespective of spinalization. Flexors tended to be active earlier for slope walking in both groups, with minimal changes in burst offsets. All changes were relatively small (∼20–60 ms). Number of subjects: 4 CONTROL at all slopes postspinalization and flat prespinalization, 3 CONTROL at ±10° slopes prespinalization, 3 SELF-REINNERVATED at all slopes postspinalization and flat prespinalization, 2 SELF-REINNERVATED at ±10° slope prespinalization. Number of muscles with significant shifts in muscle burst onset/offset cluster centers: in CONTROL animals prespinalization, for flat to upslope, n = 5 extensor and n = 3 flexor muscles, and for flat to downslope, n = 3 extensor and n = 3 flexor muscles; in CONTROL animals postspinalization, for flat to upslope, n = 2 extensor and n = 2 flexor muscles, and for flat to downslope, n = 3 extensor and n = 3 flexor muscles; in SELF-REINNERVATED animals prespinalization, for flat to upslope, n = 4 extensor and n = 2 flexor muscles, and for flat to downslope, n = 4 extensor and n = 1 flexor muscles; and in SELF-REINNERVATED animals postspinalization, for flat to upslope, n = 5 extensor and n = 1 flexor muscles, and for flat to downslope, n = 2 extensor and n = 3 flexor muscles.