Invariant characteristics of gait initiation.

Studies were undertaken first to describe the invariant characteristics of gait initiation and second to better understand the function of each limb in the process of gait initiation. Analysis of variance indicated significant main effects for speed for time to onset of EMG activity and force plate recordings, time to swing toe-off and heel-strike and stance toe-off. However, when the dependent variables were expressed as a percentage of the initiation cycle, no significant main effects were noted. For the second study, two force plates were utilized, and reflective markers were placed on the sacrum and anterior superior iliac spines. The timing of heel-strike of the swing limb and toe-off of the stance limb showed a high degree of coordination in both experiments (r = 0.95 and 0.98). It was concluded that the relative invariance of selected parameters indicates that gait initiation is centrally programmed. It also appears that the swing limb, although forces were very small, is responsible for the initial weight shift to the stance limb and that the stance limb is then primarily responsible for the generation of momentum.