FOOTSWITCH SYSTEM FOR MEASUREMENT OF THE TEMPORAL PARAMETERS OF GAIT

Gait analysis relies upon accurate measurement of initial and end foot contact times. These times act as a reference point for correlating a ll other gait data and as a means of distinguishing normal and patholo gic gait. We have developed a simple, inexpensive footswitch system th at provides accurate estimates of the start and end of stance phase fo r sequential steps. The estimates of the beginning and end of stance p hase do not require custom footwear, extensive calibration, or precise placement of the sensor within the shoe. The system is based on a com mercially available transducer and can be readily reproduced for use i n a laboratory setting for less than $50. We describe this system, as well as its validation. To assess the accuracy of this footswitch syst em, we compared footswitch based estimates of initial and end foot con tact times with those obtained using a force platform as 10 people too k 30 steps (10 each at slow, normal and fast walking rates) across a f orce platform. Both estimates coincided within +/- 10 ms (mean: 0 +/- 3 ms; N = 300) for the start of stance phase and within +/- 22 ms (mea n: -1 +/- 8 ms; N = 300) for the end of stance phase. For stance durat ion, the differences ranged from -24 to 28 ms (mean: 1 +/- 10 ms; N = 300). In combination, these measures can be used to estimate stance du ration to within 3% of force plate determined values for steps with st ance durations ranging from 446 to 1594 ms. Estimates of swing and str ide duration also are within 5% of force plate determined values. This system should therefore prove to be a useful tool for augmenting labo ratory based investigations of gait.