BACKROUND: The myosin heavy chain (MHC) is altered in chronic heart failure (CHF), but the effect of exercise on MHC expression in CHF patients is not understood. The aim of the present study was to show the effect of aerobic exercise on MHC distribution in patients with CHF. METHODS: Patients (n = 17) with stable NYHA class I to III CHF were randomised into training and control groups. For a period of three months, the training group cycled on an ergometric cycle 3 times a week for 30 min, the control group continued as they did previously. Both a baseline and a final 3 month graded maximal exercise test and exercise endurance test with constant submaximal work load were performed. Muscle samples, obtained from vastus lateralis muscle at baseline and after 3 months from the 8 patients in the training group and the 9 in the control group, were analysed for MHC distribution using SDS-polyacrylamide gel electrophoresis. RESULTS: Baseline MHC distributions were similar in both groups and training did not alter the MHC distribution. Exercise duration, at constant submaximal work load, improved from 14.9 +/- 7.1 to 26.9 +/- 9.6 min (p < 0.01 for the change between the groups). Training did not improve peak oxygen consumption. CONCLUSION: No correlation between the change in exercise capacity and MHC distribution appeared despite the significant improvement of exercise duration.

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