Activation of interlimb interactions increases the motor output in legs of healthy subjects: Study under the conditions of arm and leg unloading

Abstract

The effect of arm movements and movements of individual arm joints on the electrophysiological and kinematic characteristics of voluntary and vibration triggered stepping like leg movements was studied under the conditions of horizontal support of the upper and lower limbs. The horizontal support of arms pro vided a significant increase in the rate of activation of locomotor automatism by noninvasive impact on tonic sensory inputs. The addition of active arm movements during involuntary stepping like leg movements led to an increase in the EMG activity of hip muscles and was accompanied by an increase in the amplitude of hip and shin movements. The movement of the shoulder joints led to an increase in the activity of hip muscles and was accompanied by an increase in the amplitude of hip and shin movements. Passive arm movements had the same effect on induced leg movements. The movement of the shoulder joints led to an increase in the activity of hip muscles and an increase in the amplitude of movements of knee and hip joints. At the same time, the movement of forearms and wrists had a similar facilitating effect on the physiological and kinematic characteristics of rhythmic stepping like movements, but influenced the distal segments of legs to a greater extent. Under the conditions of subthreshold vibration of leg muscles, voluntary arm movements led to acti vation of involuntary rhythmic stepping movements. During voluntary leg movements, the addition of arm movements had a significantly smaller impact on the parameters of rhythmic stepping than during involun tary leg movements. Thus, the simultaneous movements of the upper and lower limbs are an effective method of activation of neural networks connecting the rhythm generators of arms and legs. Under the conditions of arm and leg unloading, the interactions between the cervical and lumbosacral segments of the spinal cord seem to play the major role in the impact of arm movements on the patterns of leg movements. The described methods of activation of interlimb interactions can be used in the rehabilitation of post stroke patients and patients with spinal cord injuries, Parkinson's disease, and other neurological diseases.

Sherlock Holmes and the curious case of the human locomotor central pattern generator

“…Leg movements were accompanied by EMG activity in proximal leg muscles, which were modulated over each movement cycle and displayed similar timing as in normal locomotion (Sylos-Labini et al 2014a). In particular, movement at the shoulder increased activity of hip muscles and amplitude of hip and knee joint movements, whereas and movement of the forearms and wrists had a similar facilitating effect but with a stronger influence on distal segments (Selionov et al 2016).…”

Specific Features of the Motor Potentials of the Leg Muscles Induced by Magnetic Stimulation under the Conditions of a Five-Day “Dry” Immersion in Healthy Volunteers

“…Under terrestrial conditions, in 50-80% of healthy subjects, involuntary movements of the lower extremities can be forcibly evoked by means of vibration stimuli, percutaneous stimulation of the spinal cord, and mechanical stimulation of the supporting zones of the feet [23][24][25][26]. It was previously shown that the interneurons of the L7-S1 segments of the spinal cord, which have inputs from muscle afferents, are activated in different ways by the dorsolateral descending system, which ensures the coordinated work of antagonist muscles during the locomotor cycle [27].…”