Effects of walking in a force field for varying durations on aftereffects and on next day performance.

This study investigated the effects of walking in an elastic force field (FF) for varying durations (49-1,629 strides) on: (a) the magnitude and duration of aftereffects, (b) performance in the FF on the next day. On day 1 in the FF, subjects (n = 17) showed an initial large error in peak toe velocity during swing (9-61% above baseline) that was largely reduced within the first 40 strides. After FF removal, subjects (16/17) showed aftereffects: (1) reduction in toe velocity (9-38% below baseline), (2) increase in hamstrings muscle activation. While the magnitude of aftereffects did not correlate to FF exposure duration, aftereffects duration did (p < 0.05). During FF exposure on day 2, initial toe velocity error was smaller than on day 1 (13/17 subjects, p < 0.001) regardless of day 1 exposure duration. This was associated with an earlier effective onset in hamstring activation. These results suggest that during walking, even short daily exposures to a FF (> or =49 strides) lead to significant retention of the new movement parameters.