Posterior-anterior body weight shift during stance period studied by measuring sole-floor reaction forces during healthy and hemiplegic human walking.

Posterior-anterior body weight shift during stance phase of human overground locomotion was investigated by recording sole-floor reaction force from five anatomically discrete points with strain gauge transducers of 14 mm diameter attached firmly to the sole of bare foot. At first the subject was asked to walk straight on the laboratory floor at his/her preferred velocity. Then the subject was asked to walk curved path of about 1m radius. For kicking off the body at the end of stance phase, sole-floor reaction force from 3rd metatarsal was stronger than 1st metatarsal or 5th metatarsal during the straight walking, thus body weight shift is represented from heel to 3rd metatarsal line. When walking along a curved path, two types of strategies were recognized; a group of subjects walked leaning to inner leading foot during stance period as judged by stronger forces recorded from 5th metatarsal combined with stronger force from 1st metatarsal of outer trailing foot. Another group of subjects showed almost the same patterns either in the straight and curved walking, suggesting the subjects changed direction of the foot during the immediately previous swing phase to the tangent direction of the curve and placed the foot without leaning the body weight to either direction. Hemiplegic patients showed strikingly different distribution of sole-floor reaction forces from the five points; strongest forces were recorded from 3rd and 5th metatarsals combined with reduced reaction force from heel, therefore characteristic y-vector patterns were observed.