Adaptability in frequency and amplitude of leg movements during human locomotion at different speeds

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Abstract
In this study of human locomotion we investigate to what extent the normal frequency and amplitude of leg movements can be modified voluntarily at different constant velocities, and how these modifications are accomplished in terms of changes in duration and length of the support and swing phases of the stride cycle. Eight healthy male subjects performed walking and running on a motor‐driven treadmill at speeds ranging from 1.0 to 3.0 m s‐1 (walking) and 1.5 to 8.0 m s‐1 (running), respectively. At each speed the subjects walked and ran with: (i) normal stride frequency; (2) the highest possible stride frequency, and (3) the lowest possible stride frequency. Time for foot contact was measured with a special pressure transducer system under the sole of each shoe. At all speeds of walking and running it was possible to either increase or decrease the frequency of leg movements; that is, to decrease or increase stride cycle duration. The range of variation decreased with increasing speed. The mean overall stride frequency range was 0.41 (low frequency walk 1.0 m s‐1)‐3.57 Hz (high‐frequency run 1.5ms‐1). Stride length ranged 0.40 (high frequency walk 1.0 ms‐1)‐5.00 m (low frequency run 6.0 m s‐1). At normal frequency the overall ranges of stride frequency and length were 0.83–1.95 Hz and 1.16–4.101m, respectively. The stride frequency increased with speed in low frequency walking and running (as in normal frequency) and decreased in high frequency, despite the effort to maintain extreme frequencies. Only in high frequency walking could the stride frequency be kept approximately constant. Stride length increased with speed in all situations, except for low frequency running, where a levelling off occurred at approximately 6 m s‐1. A decrease was observed in support duration with speed, except in high frequency running where it was kept approximately constant (0.12–0.145). Support length showed a total range of 0.19–1.62 m. The longest support length was observed in low frequency walking (all speeds). In normal and high frequency support length increased with speed (in normal frequency up to 1. 10–1.20 m in both walk and run). Thus, locomotion over a wide range of constant velocities can be achieved by different combinations of durations and amplitudes of the stride cycle and its different phases. The normal combination represents a compromise allowing for functional adjustments.

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