Subjects walked at their self-determined, normal pace for eight
minutes around a 400 m running track. All subjects wore their own
shoes or sneakers. An investigator walked slightly behind each
subject during the test.
A recently developed
technique was used to measure the stride time dynamics during this relatively
long walk
on level ground (9,11,12). Two
force-sensitive switches were placed inside the subject's right shoe,
one underneath the heel of the foot and the other underneath the ball
of the foot. The output of these footswitches, which provides a
measure of the force applied to the floor, was sampled at 300 Hz and
stored in a small light-weight
(5.5x2x9 cm; .1 Kg), ankle-worn recorder.
Subsequently, the
recorded signal was automatically analyzed to determine initial
contact time (heel-strike) of each stride throughout the walk, and
hence, the stride time (the time from one heel-strike to the next
heel-strike of the same foot) time series (9). The average walking speed
was determined by measuring lap time.