Medial-lateral balance during stance phase of straight and circular walking of human subjects

Right and left balance during human locomotion has been estimated by the distance between locations of the sequential right and left heel-strikes, or step width. During the stance phase of human locomotion one leg maintains medial-lateral balance for the progression. We focused our attention on this point, and medial-lateral balance during straight-ahead and circular walking was investigated by recording sole-floor reaction force from five anatomically discrete points of human sole; calcaneus, 1st, 3rd, 5th metatarsals and great toe. Forces from these points were recorded during straight walking and circular walking. Medial-lateral balance was obtained by subtracting force at 5th metatarsal from force at 1st metatarsal (x-axis vector). The foot takes off the floor from medial balance in most steps, although in some steps the foot takes off from lateral balance at slower walking speed at 2 km/h or 4 km/h, showing variable patterns of x-axis vector. At faster walking speed at 6 km/h or 8 km/h body weight shifted to 1st metatarsal before taking off the floor. During circular walking body weight shift to 1st metatarsal in the outer foot, and to 5th metatarsal in the inner foot in most cases.