The exercise training effects of skeletal muscle strength and muscle volume to improve functional capacity in patients with myocardial infarction

Background No previous studies have fully investigated the exercise training effect on the skeletal muscle strength and volume to improve the exercise capacity in patients with myocardial infarction (MI). The present study was performed based on a hypothesis that the relationship between exercise capacity, skeletal muscle strength and volume might be changed by the amount of skeletal muscle volume in MI patients up to 3 months after the onset. Methods Seventy patients with MI underwent symptom-limited cardiopulmonary exercise testing using a treadmill. The lower limb muscle volume (MV) was evaluated according to electrical impedance analysis and the maximal knee extension strength (Peak torque: PT) was measured by a Biodex. All patients participated in 12-week exercise training program. The subjects were divided into 2 groups on the basis of MV: Group H, MV greater-than over equal to 22 kg; Group L, MV < 22 kg. Delta values were calculated as follows: the value at 3 months minus the value at 1 month. Results A positive and significant correlation was observed between the delta PT and delta peak VO2 (r = 0.50, p < 0.005) only in the L group. No significant correlation was observed between the delta peak VO2 and the delta lower limb MV or between the delta lower limb MV and the delta PT in the 2 groups. Conclusions Cardiac rehabilitation program combined with resistance and aerobic training improved exercise capacity and increased not the skeletal muscle volume but the skeletal muscle strength in patients with MI in their recovery phase. It was presumed that the improvement of exercise capacity was determined by the skeletal muscle strength not by the muscle volume especially in MI patients with low muscle volume.