Improvement in Walking Distance after Rehabilitation in Patients with Peripheral Arterial Disease is Associated with Changes in Skeletal Muscle Myosin Heavy Chains

Intermittent claudication in peripheral arterial disease limits exercise capacity. Rehabilitation can produce an improvement in absolute walking distance. Very often changes in skeletal muscle, rather than changes in blood flow, are responsible for the improved exercise capacity. We studied 8 patients with intermittent claudication (Fontaine 2 class) that underwent a 4week treadmill mild-moderate aerobic endurance training. We analyzed the Myosin Heavy Chain (MHC) composition of the gastrocnemius muscle before and after rehabilitation by taking needle microbiopsies. The absolute walking distance increased from 394 ± 188 m to 580 ± 215 (p<0.05). No changes in peak VO2 were found. This improvement was accompanied by a significant increase in the percent expression of the slow aerobic MHC1 isoform, which was paralleled by a decrease of the anaerobic, fast twitch MHC2b. This finding suggests that the increased exercise capacity obtained with this specific rehabilitation protocol may be related to favorable changes in skeletal muscle composition.