Piper rhythm in the activation of the gastrocnemius medialis during running

Example of real (left) and simulated (right) EMG data from subject 4. Data is centered around heelstrike (HS) with 300ms before and after. Raw signals (A and B), wavelet intensity patterns (C and D) and the summed total intensities across the wavelet bands 7–9 (E and F) are illustrated. The white lines in the wavelet intensity patterns indicate the bottom and top of wavelet bands 7–9.

Example of real (left) and simulated (right) EMG data from subject 8. The raster plots (A and B) indicate the timing of peaks (x-axis) in the total intensity traces from each trial (y-axis). The histograms (C and D) indicate the number of peaks across all trials per time bin.

Examples of histograms from real (top row) and simulated (middle row) EMG data from five subjects. Resultant autocorrelations are indicated in the bottom row (upper grey – simulated data; upper black – real data; lower grey – net autocorrelation; lower black – smoothed net autocorrelation; black circles – first 2 minima (T1 and T3) and first maxima (T2) in the filtered net autocorrelation).