Elucidation of Strain Mechanism Focusing on Spinal Reciprocal Inhibition
【Supercategory:7. DESCENTE SPORTS SCIENCE Subcategory:7.41 Vol.41】
ABSTRACT
Excessive co-contraction interferes with smooth joint movement via mechanisms including failed spinal reciprocal inhibition against antagonists. However, the function of spinal reciprocal inhibition during co-contraction remains unclear. To investigate the influence of changes in contraction intensity during co-contraction on spinal reciprocal inhibition, 20 healthy adults were subjected to four stimulation conditions: a conditioning stimulus test stimulation interval (CTI) of -2, 2, or 20 ms or a test stimulus without a conditioning stimulus (single).Co-contraction (change in soleus muscle [Sol] vs. tibialis anterior [TA] activity) was examined at task A 0% vs. 0% maximal voluntary contraction (MVC), task B 5% vs. 5% MVC, task C 15% vs. 15% MVC, task D 5% vs. 15% MVC, and task E 15% vs. 5% MVC. C,and D than in the single condition. Among the tasks, the H-reflex amplitude values were lower for A, B, C, and D than for E. At CTI of 20ms, the H-reflex amplitude was significantly lower in tasks A,B,C,D, and E. Among the tasks, the H-reflex amplitude was significantly lower from task and B to task E. For co-contraction <15% MVC, reciprocal Ia inhibition may be modulated depending on the Sol vs. TA muscle activity ratio. D1 inhibition was equivalent when the Sol/TA ratio was equal or TA muscle activity was high. During co-contraction with high Sol muscle activity, D1 inhibition decreased from rest but D1 inhibition remained.
DECENTE SPORTS SCIENCE Vol.41/The DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE
Excessive co-contraction interferes with smooth joint movement via mechanisms including failed spinal reciprocal inhibition against antagonists. However, the function of spinal reciprocal inhibition during co-contraction remains unclear. To investigate the influence of changes in contraction intensity during co-contraction on spinal reciprocal inhibition, 20 healthy adults were subjected to four stimulation conditions: a conditioning stimulus test stimulation interval (CTI) of -2, 2, or 20 ms or a test stimulus without a conditioning stimulus (single).Co-contraction (change in soleus muscle [Sol] vs. tibialis anterior [TA] activity) was examined at task A 0% vs. 0% maximal voluntary contraction (MVC), task B 5% vs. 5% MVC, task C 15% vs. 15% MVC, task D 5% vs. 15% MVC, and task E 15% vs. 5% MVC. C,and D than in the single condition. Among the tasks, the H-reflex amplitude values were lower for A, B, C, and D than for E. At CTI of 20ms, the H-reflex amplitude was significantly lower in tasks A,B,C,D, and E. Among the tasks, the H-reflex amplitude was significantly lower from task and B to task E. For co-contraction <15% MVC, reciprocal Ia inhibition may be modulated depending on the Sol vs. TA muscle activity ratio. D1 inhibition was equivalent when the Sol/TA ratio was equal or TA muscle activity was high. During co-contraction with high Sol muscle activity, D1 inhibition decreased from rest but D1 inhibition remained.
DECENTE SPORTS SCIENCE Vol.41/The DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE
Researcher | Ryo Hirabayashi, Mutsuaki Edama, Hideaki Onishi |
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University or institution | Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare |
Keywords
Spinal function, Electromyogram, H-reflex, Co-contraction, Electrical stimulation