Mechanism of the Fast Neurogenic Component of the Ventilatory Response to the Initiation of Locomotor Activity

Experimental and clinical material allowed a quantitative assessment of the contribution of the central (cortical) and reflex (proprioceptive) components to the origin of the initial phase of exercise-associated hyperpnea and modulation of this ventilatory response depending on the excitability of central and peripheral chemoreceptors. It was established that, in healthy subjects, the pattern of involuntary stepping movements induced by vibration ("stepping in the air") significantly changes its characteristics during hypercapnic stimulation of the respiratory center. In spinal patients, voluntarily increased ventilation of the lungs induces rhythmic EMG activity in the musculus rectus femoris according to the respiratory rhythm. This phenomenon was explained by the stretch reflexes from the expiratory abdominal muscles, impulses from which might affect the lumbar motoneurons, bypassing the site of lesion. These data clearly demonstrate the real mechanisms of interactions between the regulations of the locomotor and autonomic functions of the body and provide a theoretical basis for the principal possibility of controlling locomotor activity by regulating respiratory movements, which can be used in clinical practice for the rehabilitation of spinal patients.