Myosin heavy chain isoform and ubiquitin protease mRNA expression after passive leg cycling in persons with spinal cord injury

Objective: To determine the effects of passive leg cycling exercise on myos in heavy chain (MHC) isoform and ubiquitin (UBI) protease mRNA expression i n patients with spinal cord injury (SCI). Study Design: Case series. Intervention: Eight SCI subjects (5 men, 3 women) participated in a 12-week exercise program involving the Psycle ergometer. Training occurred 2 days a week at 75% of each subject's maximum heart rate. Anthropometric measures (body weight, thigh girth, and body mass index) and muscle biopsy specimen s were obtained before and after training. Analyses were performed to deter mine the mRNA expression of types I, IIa, and IIx MHC, as well as UBI, a UB I-conjugating enzyme (E2), and 20S proteasome (20S). Results: Despite small increases, paired t tests (p < .05) to assess change s from pretraining to posttraining failed to locate significant differences for the three anthropometric measures. For mRNA expression, there were sig nificant increases in expression of MHC types IIa and IIx and significant d ecreases in expression for UBI, E2, and 20S. Conclusion: Exercise using passive leg cycling increases the expression of fast MHC isoforms while concomitantly decreasing proteolytic activity assoc iated with muscle degradation, thus helping to possibly ameliorate muscle a trophy in patients with SCI.