ALTERATIONS IN SKELETAL-MUSCLE RELATED TO IMPAIRED PHYSICAL MOBILITY - AN EMPIRICAL-MODEL

The objective of this investigation was to study impaired physical mob ility and the resulting skeletal muscle atrophy. An animal model was u sed to study morphological adaptations of the soleus and plantaris mus cles to decreased loading induced by hindlimb suspension of an adult r at for 7, 14, and 28 consecutive days. Alterations in weight, skeletal muscle growth, and changes in fiber type composition were studied in synergistic plantar flexors of the rat hindlimb. Body weight and the s oleus muscle mass to body mass ratio demonstrated significant progress ive atrophy over th 28-day experimental period with the most significa nt changes occurring in the first 7 days of hindlimb suspension. Hindl imb suspension produced atrophy of Type I and Type IIa muscle fibers a s demonstrated by significant decreases in fiber cross-sectional area (mum2). These latter changes account for the loss of contractile force production reported in the rat following hindlimb unloading. When com pared to traditional models of hindlimb suspension and immobilization, the ISC model produces a less severe atrophy while maintaining animal mobility and health. We conclude that it is the preferred animal mode l to address nursing questions of impaired physical mobility. (C) 1993 John Wiley & Sons, Inc.