Time-of-Day Effects on Dynamic Postural Control

Abstract

[Purpose] The purpose of this study was to investigate the effect of time-of-day (early morning vs evening) on dynamic balance control using posturography and electromyography. [Participants and Methods] Nine healthy individuals participated in this study. They performed the Cross Test, moving the center of pressure (COP) laterally and longitudinally on a force plate with their eyes open and closed. The electromyograms (EMGs) from the anterior tibialis, and the medial and lateral gastrocnemius were simultaneously recorded. [Results] Compared with the evening, in the morning, the participants demonstrated decreased longitudinal COP sway when their eyes were closed, and increased EMG activity when their eyes were open. [Conclusion] In the morning, the participants showed significantly poorer performance in the dynamic balance test. Increased muscle activity in the morning might be due to compensation for reduced longitudinal sway.