Increasing obstacle height and decreasing toe-obstacle distance affect thejoint moments of the stance limb differently when stepping over an obstacle

Foot placement during gait is important in regulating the dynamics of the j oints of the supporting limb and in maintaining balance of the whole body. We hypothesized that increasing obstacle height and decreasing toe-obstacle distance (distance between the trailing foot and the obstacle during stanc e of the trailing foot just prior to stepping over the obstacle) would affe ct the joint moments of the stance limb differently when stepping over an o bstacle. A total of 14 healthy young adults stepped over an obstacle 51, 10 2, 153, and 204 mm in height in a self-selected manner (i.e, toe-obstacle d istance was not controlled) and for toe-obstacle distance targets of 10, 20 , 30, and 40% of their step lengths measured during unobstructed gait. The adduction and internal rotation moments at the ankle joint increased as toe -obstacle distance decreased. The adduction and internal rotation moments a t the hip joint during early stance, the internal rotation moment at the kn ee joint during late stance, and the dorsiflexion moment at the ankle joint during late stance increased with obstacle height. Reductions in toe-obsta cle distance had greater effects on the moments of the ankle joint, and inc reases in obstacle height had greater effects on the moments of the hip joi nt. These greater demands on joint moments may affect the abilities of thos e elderly having decreased muscle strengths to safety step over obstacles. (C) 1998 Elsevier Science B.V. All rights reserved.