Progression of human body sway during successive walking studied by recording sole–floor reaction forces

Strain gauge transducers were firmly attached to five points of the human sole: calcaneus, 1st, 3rd, and 5th metatarsals and great toe. Forces from these five points were recorded during treadmill walking at different speeds. With this method it is possible to obtain data of several dozen steps successively. Lateral-medial force change ( x-vector) during progression was obtained from the 5th and 1st metatarsals and posterior-anterior force change ( y-vector) was obtained from the calcaneus and 3rd metatarsal. Lateral balance and medial balance were differentiated in x-vector and rearfoot phase and forefoot phase were distinguished in y-vector. The percentage of the forefoot phase among the stance period shows a linear increase with speed of progression. It was concluded that the phase of body sway forward is regulated by walking speeds.