THE EFFECTS OF GROWTH AND ATROPHY UPON THE STRENGTH OF SKELETAL MUSCLE

Abstract

The method of expressing tension developed by a muscle in terms of unit cross-section of muscle-cell phase (chloride free material) is used in the belief that it gives the best comparative measure of the instant physiologic state of the contractile mechanism. In the normal rat the full strength of the contractile mechanism per unit size was realized at about 90 days of age. Wt. loss in denervation atrophy was found to proceed to about 20% without loss of strength per unit muscle-cell phase. Following this a progressive and severe loss in the strength of the remaining muscle-cell phase occurred. Fasting atrophy was accompanied by no loss of strength in the remaining muscle-cell phase. Atrophy following tenotomy was accompanied by a severe impairment of the contractile strength of the muscles. This change was found to be reversible following spontaneous tendon repair. A major factor in developing and maintaining the contractile strength of the muscle is probably the physiologic stretch produced by the attachment of the muscle to the bony skeleton, this being enhanced by the postural and gross-movement reflexes.