Stair walking transitions are an anticipation of the next stride

According to the CDC, the majority of fall-related accidents occur during stair walking. It is likely that the required increases in range of motion and muscle activity during stair walking contribute to increased fall risk. In addition, compared to level walking, the transition strides before and after stair walking demonstrate increased fall risk. We hypothesized that the transition strides would have joint angle trajectories and muscle activity patterns that are most similar to a theoretical transition stride, calculated as the mean between the before stride and the after stride. Twelve healthy men completed the protocol of level and stair walking. We analyzed three sagittal plane joint angles and six leg muscle activity patterns of the left leg for transitions from level to stairs and from stairs to level, both up and down. We compared each time point of the transition strides to the corresponding time points of the before stride, the after stride, and a theoretical mean stride with a series of 2-sample t-tests. Contrary to our hypothesis, all transition strides exhibited the least number of significantly different time points with the after stride (34%), not the mean stride (51%). This result suggests that the mechanics of a transition stride are not simply an intermediate between a before stride and an after stride, neither are they a continuation of the before stride, but rather they are a unique anticipation of the upcoming surface.