Age-related parameters of spinal inhibition of skeletal muscles in regulation of voluntary movements in men

Age-related features of spinal inhibition in the regulation of voluntary movements in men were studied. It was found that presynaptic and nonreciprocal and reciprocal inhibitions of the flexor of toes during voluntary movements were less intense than inhibition during relative muscle rest in subjects of all age groups. This results from the age-related features of supraspinal excitatory and inhibitory effects on Ia and Ib spinal interneurons, which change the mechanism of spinal inhibition of voluntary movements as the organism develops. In boys 9–12 years of age, execution of voluntary movements is accompanied by the lowest presynaptic inhibition of Ia afferents and the most pronounced increase in nonreciprocal and reciprocal inhibition of α-motoneurons in the flexor of toes, compared to the other age groups. Execution of voluntary movements by boys 14–15 years of age leads to an increase in presynaptic inhibition of Ia afferents and the most pronounced decrease in reciprocal and nonreciprocal inhibition of spinal α-motoneurons of the flexor of toes. By the age of 17–18 years, the mechanism of nonreciprocal inhibition of α-motoneurons of the flexor of toes during voluntary movements is similar to that in adolescents aged 14–15 years. The definitive level of presynaptic inhibition of Ia afferents and reciprocal inhibition of α-motoneurons of the flexor of toes during voluntary movements is reached by 17–18 years.