TEMPORAL VARIABILITY IN THE PHASE DURATIONS DURING TREADMILL WALKING

In order to find speed- and step-dependencies of temporal variability in gait, treadmill walking was examined in a speed range from 2 to 6 km/h and step rate from 60 to 160 steps/min. The duration of walking phases, i.e., stride cycle, step, stance, swing and double stance, were measured by using foot switches. Intrasubject variable error (VE) and coefficient of variation (CV) in each duration was regarded as an index of stability of gait within subjects. VE and CV decreased with walking speed in every phase, thereby supporting the hypothesis that faster movement is more stable than slower movement. CV in every phase was the least at the specific step rates which were linearly dependent on walking speed. The relationship between walking speed and step rate with the least CV was invariant among the different walking phases, and was close to that found in 'free' walk. There results suggest that the stability of gait in terms of CV in the duration of the walking phases is optimal for walking with freely chosen step rate at any given speed. The relevance of these findings to the optimality of the energy expenditure in walking is discussed.