Selective low-level leg muscle training alleviates dyspnea in patients with heart failure

Objectives The purpose of this study was to demonstrate in patients with moderate to severe heart failure that exertional dyspnea can be alleviated by improving muscle function. Background Dyspnea is a frequent limiting symptom in patients with chronic heart failure (CHF). This sensation may originate from activation of receptors in the musculature rather than the lung. Methods To investigate whether dyspnea could be alleviated by selective changes in leg muscle function, we performed isolated lower-limb training in 17 patients with severe CHF. Eight patients learned guided imagery relaxation techniques and served as an active control group. Exercise training consisted of three months of low-level bicycle and treadmill exercise such that minute ventilation was <25 l/min. Leg calisthenics were also performed. Maximal and submaximal exercise performance, respiratory and quadriceps muscle strength and endurance and quality-of-life and dyspnea scales were measured before and after each intervention. Metabolic stress testing (VO2), pulmonary function tests and isokinetic strength testing were also performed. Results In the active control group, no changes in leg muscle function, pulmonary function, maximal and submaximal exercise performance or quality-of-life questionnaires were observed. In the training group, peak torque of leg flexors (pre: 39 ± 15 ft-lb; post: 50 ± 13 ft-lb; p < 0.002) increased and the fatigue ratio decreased, indicating improved strength and endurance of the leg muscles. Maximal inspiratory and expiratory mouth pressures and maximum voluntary ventilation were unchanged. Peak VO2 was increased (pre:12 ± 2.2 ml/kg/min; post: 14 ± 2.6 ml/kg/min) as well as the duration of exercise at 70% peak VO2 increased (pre: 11.5 ± 3.1 min; post: 21.5 ± 5.4 min; p < 0.003). Perceived dyspnea during the submaximal testing was decreased. Minnesota Living with Heart Failure Score, Guyatt Dyspnea Scale, and the Transitional Dyspnea Index were all improved with training (all p < 0.05). Conclusions We concluded that improvement of limb muscle function alleviates dyspnea and improves exercise performance in patients with CHF.