High intensity knee extensor training, in patients with chronic heart failure: Major skeletal muscle improvement

Skeletal muscle adaptations to high intensity knee extensor strength and/or endurance training in patients with chronic heart failure were investigated. Eleven patients with chronic heart failure were randomized into two groups and exercised the m. quadriceps femoris 3 days/week for 8 weeks. After training, the maximal exercise intensity tolerated on the ergometer cycle was raised from 99 (32) to 114 (40) watts (W, P < 0.05) for all 11 patients. Peak dynamic knee extensor work rate showed the greatest increase after endurance training (40%, P < 0.01). Maximal dynamic and isometric strength were elevated by 40-45% (P < 0.05) after strength training. The cross-sectional area of m. quadriceps femoris was increased in the strength-trained legs (9%, P < 0.05), and the capillary per fibre ratio of m. vastus lateralis was raised by 47 and 58% in the endurance-trained legs (P < 0.05). The oxidative enzyme activity in m. vastus lateralis was significantly raised above 50% after endurance training, whereas glycolytic enzyme activity was unaltered. The peripheral skeletal musculature in patients with chronic heart failure adapts fairly quickly to high intensity knee extensor training. This results in a marked rise in local, and a small rise in total work capacity, indicating maintained plasticity of skeletal muscle in chronic heart failure patients.