The relationship between anticipatory and compensatory components of human balance control
The central nervous system employs two principal control mechanisms, anticipatory (APAs) and compensatory (CPAs) postural adjustments, to maintain balance. While the individual roles of these two mechanisms have been extensively studied, the interplay between the two remains unattended. The purpose of this study was to determine the role of APAs in postural control, specifically, its relationship with CPAs in controlling balance. Eight healthy young adults were exposed to external predictable and unpredictable perturbations of identical magnitudes at the shoulder level while standing. EMG activity of muscles, joint angles, center of mass (COM) and center of pressure (COP) displacements were recorded. It was hypothesized that with utilization of APAs, compensatory muscle activity would be significantly reduced, resulting in smaller COM and COP displacements following a perturbation, thereby enhancing body stability. Strong APAs and significantly smaller CPAs were seen in all muscles during predictable perturbations as opposed to unpredictable perturbations which were associated with an absence of APAs and 5 times greater CPAs (p < 0.05). Consequently, with the availability of APAs, the COM displacement after the perturbation peaked to 17 ± 5.5 mm and COP displacement peaked to 28 ± 3.6 mm, while in the absence of APAs, COM peak displacement was 1.6 times larger, reaching 28 ± 9.6 mm and COP peak displacement was twice greater reaching 60 ± 14 mm, (all p < 0.01). The outcome of this study highlights the role of APAs in maintaining balance and illustrates the interplay between anticipatory and compensatory mechanisms of postural control.
Listed In: Biomechanics, Neuroscience, Physical Therapy,
Tagged In: Anticipatory Postural Adjustments, Perturbation
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