Anticipatory locomotor adjustments of the trail limb during surface accommodation.

This paper explores anticipatory locomotor adjustments of the trail limb when stepping up to a new level. The kinematics and kinetics of the trail limb for nine subjects were compared across level gait and surface accommodation. The largest generation of new rotational energy was found at the trail ankle, during the latter part of stance (i.e. ankle 'push-off'). Accelerations of the head, arms and trunk (HAT) and foot segments during the same phase indicate that the ankle power acted to push the body and lead limb up onto the new level and drive the foot upwards at toe-off. The shank was more vertical at toe-off to ensure that the ankle energy would drive the limb upwards, rather than forward into the surface. The vertical hip translation energy increased over 300%, acting to pull upwards on the hip to increase trail limb elevation. The increased hip translational energy could be due to extension of the lead limb after it was placed on the surface and/or the piston-like drive of the increased rotational energy at the trail ankle during late stance. The findings add to the knowledge of whole body coordination strategies during anticipatory locomotor adjustments when the entire body is raised to a new level.