Both Traditional and Stair Climbing-based HIIT Cardiac Rehabilitation Induce Beneficial Muscle Adaptations.

PURPOSE There is a lack of knowledge as to how different exercise-based cardiac rehabilitation programming affects skeletal muscle adaptations in coronary artery disease (CAD) patients. We first characterized the skeletal muscle from adults with CAD compared to a group of age- and sex-matched healthy adults. We then determined the effects of a traditional moderate-intensity continuous exercise program (TRAD) or a high-intensity interval training program via stair climbing (STAIR) on skeletal muscle metabolism in CAD. METHODS Sixteen adults (n=16, 61±7 yrs), who had undergone recent treatment for CAD, were randomized to perform (3d/wk) either TRAD (n=7, 30 min at 60-80% of peak heart rate) or STAIR (n=9, 3x6 flights) for 12 wk. Muscle biopsies were collected at baseline in both CAD and healthy controls (n=9), and at 4 and 12 weeks after exercise training in CAD patients undertaking TRAD or STAIR. RESULTS We found that CAD had a lower capillary-to-fiber ratio (C/Fi, 35±25%, p=0.06), and capillary-to-fiber perimeter exchange (CFPE) index (23±29%, p=0.034) in type II fibers compared to healthy controls. However, 12wk of cardiac rehabilitation with either TRAD or STAIR increased C/Fi (type II, 23±14 %, p<0.001), and CFPE (type I, 10±23 %, p<0.01; type II, 18±22%, p=0.002). CONCLUSION Cardiac rehabilitation via TRAD or STAIR exercise training improved the compromised skeletal muscle microvascular phenotype observed in CAD patients.