An integrated EMG/biomechanical model of upper body balance and posture during human gait.

Full scale biomechanical and EMG analyses of the balance during human gait are required to understand the neural control of locomotion. The purpose of this paper was to develop an inverted pendulum model of upper body balance in both the plane of progression and the frontal plane, and a medical/lateral balance model of the total body. EMG evidence was also recorded to reinforce the conclusions from the moment of force analyses. The kinematics and kinetics for up to ten natural walking trials on each of four subjects and EMG records from walking trials on eleven subjects were investigated. The results support the following conclusions. (1) The hip extensors/flexors have an over-powering role in maintaining dynamic balance of the head, arms and trunk (HAT) in the plane of progression. Because of the lack of suitable neurological and biomechanical delays between the small head acceleration, presumably exciting vestibular afferents, and the hip moment patterns, the vestibular system appears not to be involved as a feedback sensor in the balance control during gait. (2) In the frontal plane, the hip abductors are dominant in countering the large medial-lateral (M/L) imbalance of HAT during single support but are assisted by the medial acceleration of the hip joint. (3) the total body M/L balance is achieved by the M/L placement of the foot with some opposition and some assistance by the M/L acceleration of the subtalar joint. The subtalar invertors/evertors play an insignificant role during single stance.(ABSTRACT TRUNCATED AT 250 WORDS)