Dynamic Studies On Human Body Sway By Using A Simple Model With Special Concerns On The Pelvic And Muscle Roles

Abstract

The human pelvis is such a unique structure that enables our upper body to work so perfectly with the two legs so as to control the body's balance in the complicated postures. The aim of this study is to establish a new dynamic body sway control model in the upright standing body position in coronal plane, and to reveal the possible control mechanisms underlying the body sway with special concerns on the roles that the pelvis and its muscles are performing during the sway. The plant of control model, the dynamics of human body, includes five parts, i.e. two ankles, two hips and one lumbosacral joint , which makes up a multi-link inverted pendulum system, and is driven by two pairs of muscles, the psoas major (PM) and glutaeus medius (GM). Body sway records from eight healthy young subjects showed that the angular sway scopes of the ankle on roll (lateral) plane are 0.94±0.36° (eye-open) and 1.35 ± 0.52° (eye-closed) respectively, while in lumbosacral plane, the scopes are 0.99 ± 0.41° (eye-open) and 1.27 ± 0.72° (eye-closed). The ankle and lumbosacral sways were almost in the same degree, yet their phase difference was near π, which means that the body trunk maintains perpendicular to horizon during the upright stance. Surface electromyographic (sEMG) activity from GM also showed the same evidence: the activated GM was always in the same side as the deviated center-of-pressure (COP). By assuming the corrective torque of posture is regulated by PID (proportional, integral and derivative) control, the body sway can be simulated by applying human physical parameters. Our study results demonstrated that the simulated traces are consistent with the experimental recorded, suggesting that the pelvis is an important structure for the posture maintenance and control, and the mechanism of balance keeping control during upright stance can be approximately taken as a PID control. The result also suggests a novel means for postural stability assessment in individual in the future.

A reduced order model of the spine to study pediatric scoliosis

“…As the idiopathic scoliotic patients are otherwise healthy, identifying these patients before the onset of scoliosis in order to obtain their patterns of sagittal profile is difficult [7]. Hence we turn to simulations to test the hypothesis that there is an association between the sagittal curvature and deformity patterns of the spine [3,14,17]. A reduced order model of the pediatric spine for studying scoliosis was proposed by Pasha [21].…”

Determination of Postural Control Mechanism in Overweight Adults Using The Artificial Neural Networks System and Nonlinear Autoregressive Moving Average Model

“…For normal balance ability, the postural control mechanism can be illustrated using different postural models. The single-link model is a simple approach to simulate the postural control mechanism in the anterior-posterior (AP) direction at the ankle joint [9,10]. Angular velocity and acceleration are the primary factors that maintain the body s stability [11].…”

“…In the case of postural control mechanism in the medio-lateral (ML) direction, a different method can be used to acquire the model. The relationship of contractions of two muscles, such as the gluteus medius and psoas major muscles, is an example of postural models in the ML direction and was derived by Jiang et al [9]. Although these models were acquired by different methods, the outcomes from the models such as torque of joint are the primary variables to re ect the balance control mechanism.…”

Balance-Keeping Control of Upright Standing in Biped Human Beings and its Application for Stability Assessment

“…For minimizing psychological influence, subjects were asked to numerate on mind while doing standing task. A study from eight healthy young subjects [13] shown that the body sways scope of ankle and lumbosacral were 0.94±0.36degree (eye-open), 1.35±0.52degree (eye-closed) and 0.99±0.41degree (eye-open), 1.27±0.72degree (eye-closed), respectively. No significant difference existed between the ankle and lumbosacral.…”

“…Using a force sheet to measure COP deviation, we recorded the surface EMG activities of m. tibialis anterior (TA), m. peroneus longus (PL) and Caput mediale m. gastrocnemii (MG) when asked subjects standing on one foot. The relationship between COP deviation and muscular activities was identified [13] (Fig.5).…”