Long Range Correlations in the Stride Interval of Stair Climbing

Walking and stair climbing are tasks performed on a daily basis. The step-to-step timing during comfortable walking exhibits a consistent long-term pattern. The purpose of the current study was to determine if this step-to-step timing retains such a long-term pattern during continuous stair climbing. Ten participants were recruited for the study. Kinematic data was collected using reflective markers placed at the head of the second metatarsal of each foot and tracked with a motion capture system as participants walked on a stairmill device (StairMaster SC916, Fitness Direct, San Diego, CA). The collection began with the subjects choosing their preferred stepping rate on the stairmill. Data was then collected for three minutes at this stepping rate. Subjects were then asked to find their preferred walking rate on the treadmill and data was collected at this rate for five minutes. The mean, standard deviation, and coefficient of variation of the stride time interval, the time between two consecutive steps with the same leg, were then computed for each subject, in each condition. These values indicated that there was a larger amount of variability present during stair climbing than during treadmill walking. We speculate that this may be to due to stair climbing being a more strenuous and difficult task than treadmill walking. Detrended fluctuation analysis of the stride interval time series of each subject showed the presence of characteristic longrange correlations during treadmill walking but not during continuous stair climbing