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.

[Purpose] To investigate the effects on spinal cord excitability, as measured by evoked electromyography H waves, of a continuous stretching exercise and a repeated dynamic exercise. [Subjects and Methods] The lower limbs of 14 healthy adults with no history of neurological disorders were investigated. The H wave of the soleus muscle was measured using evoked electromyography under three conditions: at rest, continuous stretching, and repeated dynamic exercise.[Results] After continuous stretching, no significant difference was found from at rest; however, a significant decrease in H wave amplitude was found after repeated dynamic exercise. Also, after the repeated dynamic exercise, the percentage change in H wave amplitude was significantly lower than that after continuous stretching.[Conclusion] The results showed that spinal cord excitability under the repeated dynamic exercise was significantly lower than that under the continuous stretching exercise.