ABSTRACT

　Standing posture, which is fundamental to various movements and essential for daily life, can be destabilized by various factors, ultimately increasing the risk of falling. One of the factors that increases the risk of falling is the fear of falling. Besides, the activity of the lower limb muscles is crucial for maintaining postural balance, and this muscle activity is generated by the excitation of spinal motor neurons （spinal MNs）．Therefore, the purpose of this study was to investigate how fear of falling during standing posture influences the excitability of spinal MNs in the lower limb muscles. Eleven adult males participated in the experiment, performing a static standing task for 90 seconds while wearing a head-mounted display. The task was conducted under three conditions with different levels of induced fear of falling（Low-threat, Mediumthreat, and High-threat conditions）．During each condition, transcutaneous spinal cord stimulation（tSCS） was applied to a lumber region 15 times. The motor-evoked responses from the vastus lateralis, biceps femoris, tibialis anterior, soleus, medial gastrocnemius, and lateral gastrocnemius muscles were recorded as spinal reflexes. The results showed that the spinal reflex amplitude of the tibialis anterior muscle was significantly increased in the High-threat condition compared to the Low-threat condition. In contrast, no significant differences in the spinal reflex amplitudes were observed in the other muscles among conditions. Our findings indicate that the fear of falling facilitates the excitability of spinal MNs in the tibialis anterior muscle during standing posture.

DECENTE SPORTS SCIENCE Vol.46/The DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE