Comparisons of the inter-joint coordination between leading and trailing limbs when crossing obstacles of different heights.

Fifteen normal adults walked and crossed obstacles of different heights (10%, 20% and 30% of leg length) with each limb while kinematic data were measured to obtain joint angles in the sagittal plane. Phase angles of each joint were calculated from the angular velocities (x') and displacements (x) as phi=tan(-1)(x'/x). Relative phase angles were then calculated by subtracting phase angles of a distal joint from the proximal joint (phi(hip-knee), phi(knee-ankle)). The standard deviations of the relative phase curve points for the stance and swing phase for each obstacle height were averaged to obtain the respective deviation phase (DP) values. The calculated DP variables were tested using a two-factor repeated ANOVA. The leading and trailing limbs were found to have similar patterns of inter-joint coordination, but different levels of stability, the leading being more stable than the trailing during swing (p<0.05), while only leading knee-ankle coordination was less stable than that of the trailing during stance (p<0.05). Only the stability of the knee-ankle coordination for both limbs decreased with increasing obstacle height during stance (p<0.05). It is suggested that clinical obstacle-crossing training programs for patients with unilateral pathology should include the training of the affected limb, not only as leading but also as trailing limb. An increase of the stability of the ankle joint may be helpful for the stability of the knee-ankle coordination and thus for the general performance of obstacle-crossing.