Lower leg EMG activation during 1.0 m/s walking. Tibialis Anterior (TA), Gastrocnemius Medial Head (GASM), Gastrocnemius Lateral Head (GASL). (A) Raw EMG signals from the tibialis anterior and gastrocnemii muscles for a single stride (1.0 m/s). Data is shown for one exemplary control subject and twelve amputee subjects. EMG signals are high-pass filtered and demeaned. Vertical lines show toe-off. Median frequency is shown above each plot in gray. There was a lot of variability in EMG signal patterns across amputee subjects. Amputee subject A11 (GASM, GASL) had several EMG bursts that were approximately equally spaced and of similar amplitude across the gait cycle. A similar pattern was seen in A10 (GASL) and A05 (TA). Amputee subject A09 (GASM, GASL) had short EMG bursts of high amplitude that occurred shortly after toe-off. A similar pattern was seen in A06 (GASM) with two high-amplitude EMG bursts that occurred shortly after heel-strike and shorty before toe-off. In both A06 and A09, the amplitude of the EMG bursts exceeded those recorded during maximum activation trials. (B) Empirical cumulative density function of EMG power spectrum. Lines are shown for group means and boundaries indicate group range.