Influence Of Anticipatory Postural Adjustments For Postural Response To Standing Postural Perturbations

Purpose: Standing postural will be disturbed by many factors from either inward or outward the body. When postural perturbation happens, the body needs proper adjustments to make the body’s center of mass within the surface of support. Otherwise, falls will happen. The central nervous system will use two mechanisms to adjust the posture of body to maintain the body balance, anticipatory postural adjustments(APAs) and compensatory postural adjustments(CPAs). The purpose of the study was to investigate the effects of anticipatory postural adjustment for postural response to standing postural perturbations. We examined the kinematics performance and myoelectric activity when response to backward platform perturbations in the state of “Anticipation” and “Without Anticipation”.Methods: Three-dimensional video graphic and surface electromyography(EMG) data were collected from 13 male young people. Horizontal Co M displacement, muscle activations during APAs(from 100 ms before perturbation to 50 ms after perturbation) and CPAs(from 50 ms after perturbation to 200 ms after perturbation) and angular changes were measured.Results: 1) The peak of Co M displacement: smaller Co M displacement in the state of Anticipation, and it has significant difference between these two states; 2) It was faster to reach the peak Co M displacement position in the state of Anticipation, and it has significant difference between these two states; 3) Smaller angular changes were found in ankle, knee and hip joint in the state of Anticipation and it had better control for trunk movement, and it has significant difference between these two states; 4) In the balance disturbance phase, smaller angular changes were found in ankle, knee, hip and trunk movements in the state of Anticipation, but it has no significant difference; 5) In the balance reaction phase, smaller angular changes were found in ankle, knee, hip and trunk movements in the state of Anticipation, but it has significant difference; 6) The state of Anticipation increased activation magnitudes of tibialis anterior, rectus femoris and rectus abdominis before perturbation, decrease activation magnitudes of erector spinae, biceps femoris muscle and musculus gastrocnemius after perturbation.Conclusions: The anticipation postural adjustments could effectively promote body stability after perturbations, it will decrease the segments’ movement amplitude instead of change the movement patterns. By means of mobilize relevant muscles in advance, it will timely control the trunk forward and reduce the oscillation amplitude of the body.