Typical plot of changes in gait cycle period measurements to perturbation.

Example of changes in the gait cycle period for two different trials (negative (A) and positive (B) offset perturbations) obtained from a subject. The horizontal axis shows time; the vertical axis shows gait cycle period. Each circle represents the measured gait cycle period per gait. The trial period consisted of the first 4 minutes of walking with no electrical stimulation followed by 4.5 or 3 minutes of walking with periodic electrical stimulation and finished with the last 1.5 minutes of walking with no stimulation. (A) For the negative offset trial, 90 second perturbation periods of electrically stimulated pulses were sent at intervals of minus 20 ms, minus 40 ms, and minus 60 ms from the initial average gait cycle period, respectively. The black lines indicate the perturbation period at the time of the trial. The black line during the last 90 seconds indicates the initial average gait cycle period, which was obtained using the last 30 strides during the first four minutes of walking. (B) For the positive offset trial, 90 second perturbation periods of electrically stimulated pulses were sent at intervals of plus 20 ms and plus 40 ms from the initial average gait cycle period. The black line during the last 90 seconds indicates the initial average gait cycle period.