Muscle fatigue prod duced with interleaved and synchronous IFM S in all six cats. The ordinate plots the number of ffatiguing episodes until the animal could no loonger rotate the trough by greater than the two-degreee criterion. The order of the bars for each animal indicates the order of the fatiguing sequences, and the color of the bar indicates whether interlleaved (light grey) or synchronous IFMS (dark greyy) was used. Cats 1–4 were implanted acutelyy, and cats 5 and 6 were implanted chronically. Fatigue experiments were conducted on cat 6 on days 24 and 71 post implant. In all animals, interleaved IFMS produced a slower rate of fatigue than did synchronous IFMS. Note that in cat 6, day 71, the fatiguing sequences were stopped at stance 100, even though the animal still produced stance exceeding the 2-degree criterion, so this value underestimates the number of stances the animal could have achieved. Overall (labeled `Group'), the median number of fatiguing episodes until the two-degree criterion could not be met was significantly greater for interleaved IFMS than for synchronous IFFMS (p < .05, *).