Age-Related Parameters of the Spinal Inhibition of Skeletal Muscles in the Regulation of Voluntary Movements in Males.

We studied the age-related features of spinal inhibition in the regulation of voluntary movements in males. It was found that presynaptic, nonreciprocal and reciprocal inhibition of the flexor of toes during voluntary movements was less intense as compared with relative muscle rest in all studied age groups. This results from the age-related features of supraspinalactivatory and inhibitory effects on la and Ib spinal interneurons, which change the mechanism of spinal inhibition of voluntary movements during the development of the organism. In boys aged 9-12 years, the presynaptic inhibition of Iaafferents is lowest, while the nonreciprocal and reciprocal inhibition of (αmotoneurons of the flexor of toes is highest among all studied age groups. In boys aged 14-15 years, the presynaptic inhibition of Iαafferents is higher, while the nonreciprocal and reciprocal inhibition of cxmotoneurons of the flexor of toes is lowest among the age groups. By the age of 17-18 years, the mechanism of nonreciprocal inhibition of αmotoneurons of the flexor of toes during voluntary movements is similar to that at the age of 14-15 years. The final level of presynaptic inhibition of Iαafferents and reciprocal inhibition of αmotoneurons. is reached at the age of 17-18 years.

[Non-Invasive Methods for the Control of Human Spinal Locomotory Systems].

We studied the interrelations between the activation of the receptors of musculoskeletal system and the spinal cord stimulation in the regulation of locomotor behavior in healthy subjects. We observed the effect of afferent stimulation on the patterns of stepping movements caused by percutaneous stimulation of spinal cord. It was found that the combination of percutaneous spinal cord stimulation and vibrostimulation increases the amplitude of leg movements. It was shown that the vibrostimulation of limb muscles at a frequency of less than 30 Hz may be used for comtrolling involuntary movements, caused by non-invasive stimulation of the spinal cord.

[Age Peculiarities of Formation of Spinal Inhibition of Skeletal Muscle in Males].

Age peculiarities of spinal inhibition in males in the relative muscular rest condition were studied. The main stages of development and formation processes of spinal inhibition in males, and set periods of weakening and increasing during ontogeny. It's shown, that the development and formation of different types of spinal inhibition in the period from 9 to 18 years there heterochronically and definitive level of their development are on a different age: presynaptic inhibition of heteronymous Ia afferent and reciprocal inhibition homonymous α-motoreurons in the age of 9-12 years, recurrent inhibition of heteronymous α-motorneurons--17-18 years, and nonreciprocal inhibition of heteronymous and homonymous α-motorneurons--14-15 years. Teenage age is a critical period in the development of presynaptic inhibition heteronymous and homonymous Ia afferents, recurrent inhibition α-motorneurons. Discusses the physiological mechanisms underlying the observed age-specific patterns.

[Muscular strength development by electromagnetic stimulation].

A new tool for muscular strength development by electromagnetic stimulation (MS) of muscular during voluntary contraction has been described. 18 healthy subjects (men) took part in the research. They were devided into two groups--control (CG) and experimental (EG). Subjects of CG and EG have equal muscular strength parameters. M. gastrocnemius of subjects in EG was exposed to MS (1.8 T, 5 Hz) during training exercises (plantar foot flection). The subjects of CG did not receive MS. The torque of plantar foot flection of EG subjects increased significantly (24%) during 10 days training. The torque of plantar foot flection of CG subjects did not change significantly. We hypothesize increasing of muscular strength of EG subjects was result of high-threshold motor units activation under MS.

[Mechanical stimulation of soles' support zones: non-invasive method of activation of generators of stepping movements in man].

The effects of mechanical stimulation of the soles' support zones in regimens of slow and fastwalking (75 and 120 steps per minute) were studied using the model of supportlessness (legs suspension). 20 healthy subjects participated in the study. EMG activity of hip and shin muscles was recorded. Kinematic of leg movements was assessed with the use of videoanalysis system. Support stimulation was followed by leg movements in 80% of cases, in 53% it was a locomotion-like movement. EMG bursts accompanied the movements. Involvement order and alteration of bursts in muscles were similar to voluntary walking. EMG activity occurred with a delay of 5.17 ± 1.08 seconds for hip muscles and 14.01 ± 2.82 seconds for shin muscles, frequency of bursts differed from stimulation frequency. Support stimulation was followed by leg movements in 80% of cases, in 53% of which they had characteristics of locomotions being accompanied by the burst-like electromyographic activities. Involvement order of the leg muscles and organization of antagonistic muscles activities were analogous to that of voluntary walking. The latencies of electromyographic activity in hip muscles composed 5.17 ± 1.083 s and 14.01 ± 2.82 s - for shin muscles, frequency of bursts differed significantly from stimulation frequency. In 31% of cases the electromyographical activity following the stimulation of the soles' support zones was not burst-like. Its amplitude rose smoothly reaching a certain level that was subsequently maintained. Results of the study showed that soles' support zones stimulation in regimen of locomotion can activate a locomotor generator and that effect evoked by this stimulation includes not only rhythmical but also non-rhythmical (probably postural) components of walking.

[Transcutaneous electrical stimulation of the spinal cord: non-invasive tool for activation of locomotor circuitry in human].

A new tool for locomotor circuitry activation in the non-injured human by transcutaneous electrical spinal cord stimulation (tSCS) has been described. We show that continuous tSCS over T11-T12 vertebrae at 5-40 Hz induced involuntary locomotor-like stepping movements in subjects with their legs in a gravity-independent position. The increase of frequency of tSCS from 5 to 30 Hz augmented the amplitude of evoked stepping movements. The duration of cycle period did not depend on frequency of tSCS. During tSCS the hip, knee and ankle joints were involved in the stepping performance. It has been suggested that tSCS activates the locomotor circuitry through the dorsal roots. It appears that tSCS can be used as a non-invasive method in rehabilitation of spinal pathology.

[Novel method for activation of the locomotor circuitry in human].

We examine the possibility for activation of the involuntary locomotion of the lower limbs by spinal electromagnetic stimulation (ES). The subject laid on the left side. The legs are supported in a gravity-neutral position by special mounting that to provide horizontal rotation in the hip, knee and ankle. ES (3 Hz and 1.56 Tesla) at the T11,-T12 vertebrae induced involuntary locomotor-like movements in the legs. The latency from the initiation of ES to the first EMG burst compoused 0.68 +/- 1.0 s and it shortened at increasing of the frequency ES from 3 Hz to 20 Hz. Thus, the spinal ES can unduce the activation of the locomotor movements in human.