Efficiency of aerobic exercise training in women and men with chronic heart failure

Sammanfattning: The syndrome of heart failure is one of the major public health problems in many countries. Despite advances in pharmacological therapy, patients with chronic heart failure (CHF) are characterized by exercise intolerance and a reduced health-related quality of life. Beneficial effects of physical training have been reported in men with CHF, mainly due to peripheral adaptations. Data on women is lacking, as well as studies comparing efficiency of different training modes. The aims of this thesis were to compare the phenotype of women with moderate CHF with that of men; to compare the efficiency of aerobic exercise training between the genders; and to investigate whether the quantity of muscle mass activated simultaneously affects training out comes in order to acquire the knowledge needed for planning efficient exercise-based rehabilitation for women and men with CHF. A total of 16 women and 27 men (age 41-73 years) with CHF in NYHA functional classes II-III (LVEF < 40%) participated in the trials and performed different modes of aerobic training: conventional cycle ergometer training; training of a restricted muscle mass in both knee extensors; and training of one knee-extensor muscle group at a time. Skeletal muscle biopsies and isokinetic muscle strength tests were performed. Peak work rate, peak oxygen uptake, and blood lactate and norepinephrine responses to exercise were measured. The 6-minute walking test was done and the health-related quality of life was assessed by means of several questionnaires. Contrary to men with CHF, the proportion of type I (slow-twitch) muscle fibers was normal in women, but also women, like men showed atrophy of muscle fibers. Muscle oxidative capacity was similar in both genders, while strength was lower in women. Women with CHF showed skeletal muscle trainability, as previously reported in male patients. Aerobic power was lower in women than in men, just as in a healthy population. The walking performance did not differ between the genders, nor did metabolic and hormonal responses to exercise. Both women and men reported a reduced health-related quality of life and men reported a lower psychosocial quality of life than women. Aerobic exercise training with two-leg knee extensions increased muscular oxidative capacity, peak exercise performance and strength, and decreased metabolic and hormonal responses, and improved the health-related quality of life similarly in women and men. How ever, in the group studied, aerobic power increased only in the women. When training with one-leg knee-extensions and on the cycle ergometer were compared, aerobic exercise training involving a minor muscle mass showed signs of being more efficient with regard to aerobic power, the plasma norepinephrine concentration during submaximal exercise and the health-related quality of life. Neither one of the exercise modes produced adverse effects. Since aerobic training with an intensive activation of a minor muscle mass appears to be more efficient than training involving one large muscle mass at a time, comprehensive aerobic training involving one minor muscle mass at a time is suggested as a mode in the exercise based rehabilitation of patients with CHF. Exercise training should be complemented with a physically active daily life.