Gait analysis relies upon accurate measurement of initial and end foot contact times. These times act as a reference point for correlating all other gait data and as a means of distinguishing normal and pathologic gait. We have developed a simple, inexpensive footswitch system that provides accurate estimates of the start and end of stance phase for sequential steps. The estimates of the beginning and end of stance phase do not require custom footwear, extensive calibration, or precise placement of the sensor within the shoe. The system is based on a commercially available transducer and can be readily reproduced for use in a laboratory setting for less than $50. We describe this system, as well as its validation. To assess the accuracy of this footswitch system, we compared footswitch based estimates of initial and end foot contact times with those obtained using a force platform as 10 people took 30 steps (10 each at slow, normal and fast walking rates) across a force platform. Both estimates coincided within ± 10 ms (mean: 0 ± 3 ms; N = 300) for the start of stance phase and within ± 22 ms (mean: −1 ± 8 ms; N = 300) for the end of stance phase. For stance duration, the differences ranged from −24 to 28 ms (mean: 1 ± 10 ms; N = 300). In combination, these measures can be used to estimate stance duration to within 3% of force plate determined values for steps with stance durations ranging from 446 to 1594 ms. Estimates of swing and stride duration also are within 5% of force plate determined values. This system should therefore prove to be a useful tool for augmenting laboratory based investigations of gait.
