Fig. 1. A summary of the methods used to produce EMG activity traces from treadmill data. An accelerometer trace was used to divide each EMG trace into smaller traces that corresponded to a single locomotor cycle. This trace was then rectified, divided into 100 bins of equal duration, and the EMG activity of each bin was calculated by multiplying the number of spikes in each bin by the mean spike amplitude of each bin. EMG activity traces were then averaged on a bin-by-bin basis to produce a mean EMG activity trace for each muscle at each site.