Respiratory, cardiac and learning changes in exercised muscular dystrophic children.

Abstract

A previous study (1974) on seven severe myopathic children of the Duchenne type OF luvenile Muscular Dystrophy, whose myopathies did not involve severed afferent neurons or spinal lesions showed that cardiac cost was increased and associative learning task time was decreased, as a result of 6 min. of passive exercise of myopathic muscles. N o changes were found in respiratory rate, tidal volume, and minute pulmonary ventilation. It was assumed that exercise increased blood flow through the lung allowing for greater oxygen diffusion in the brain resulting in increased efficiency in cerebral activity. The purpose was to investigate the effects of passive exercise of the lower extremities on cardiac cost, respiratory rate, tidal volume, and associative learning on the 12 students. The decision to exercise the large muscles of the lower extremities (primarily the gluteus maxirnus and medius, iliopsoas, rectus femods, quadriceps, hamstring, and gastrocnemius) stemmed from the fact that these muscle groups are usually first to be affected after the onset of the disease, and, with this type of muscular dystrophy, they are the first to lose strength and become immobilized. In addition, being transported to school in wheelchairs most muscular dystrophy students might perform some movements with their arms, but their legs remain largely inactive. The effects of passively moving silent muscles on the dependent variables was of utmost importance. All subjects ranged from 9 to 11 yr. of age. Control and exercise days were randomly selected. All exercises were performed by a registered physical therapist. After the control or exercise period, cardiac cost was assessed utilizing Brouha's ( 1959) technique. Respiratory variables were measured using a special electropneurnotachograph. Thirty minutes after control o r exercise period, an associative learning task was given utilizing high frequency AA monosyllabic words as suggested by Postman and Keppel (1969). Subjects were asked to learn 1 0 assistive pairs presented at 5-sec. intervals. Two trials without error and the time required for two correct trials without error were recorded four times, each subject being exercised on two days and not exercised on two days. The order was randomized and each score represented the mean of two trials. t tests for correlated data showed that passive exercise had a significant effect on cardiac cost ( t = 3.14, p .05) . It is clear that muscular dystrophic children are sensitive to passive exercises. It is assumed that these exercises increased blood flow through the vascular bed of the lungs, allowing for delivery of higher oxygen tensions (PO.) at the level of the cerebral cortex. This could increase efficiency of cerebral activity resulting i n higher levels of learning ability.