THE EFFECT OF AEROBIC EXERCISE ON MUSCLE TISSUE IN PATIENTS WITH SEVERE HEART FAILURE AND NORMAL BODY WEIGHT
Aim. To assess the response of skeletal muscle and myocardium to original aerobic exercise (AE) program in patients with heart failure (HF) with reduced ejection fraction (HFrEF); to assess morphometric changes in skeletal muscle fiber after AE. Material and methods. The study included 100 patients with class III HFrEF (age - 52±5,2 years; body mass index (BMI) - 23,5±2,8 kg/m<sup>2</sup>). At baseline and after 6 months of AE, an echocardiogram, peak oxygen uptake (VO<sub>2peak</sub>), exercise tolerance and quality of life (QOL) were evaluated. Lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) activity were evaluated in biopsy material of lower leg muscles. Results. After 6 months of AE, the left ventricular ejection fraction (LVEF) increased by 10,5±2,3%, QOL - by 24,8±3,5 points, exercise tolerance - by 9,7±0,5 points, VO<sub>2peak</sub> - by 5,2±0,5 ml/min/kg (p<sub>1,2,3,4</sub><0,05). In 6 patients, the diameter of muscle fiber decreased slightly. The activity of ALP (initially - 0,33±0,09 D) increased by 24,2% (p<0,05); LDH in glycolytic fibers was initially 0,213±0,08 D, in oxidative fibers - 0,083±0,04, and after 6 months of AE, decreased by 24,4% and 6,0%, respectively (p<sub>1</sub><0,05, p<sub>2</sub>>0,05). A positive relationship was found between the dynamics of HF class and fiber diameter (r=0,4, p=0,05); an increase in сardiopulmonary exercise test was associated with ALP activity (r=0,5, p=0,05). Conclusion. 1. Dosed aerobic exercise in patients with stable class III HFrEF, normal BMI, based on reaching the lactate threshold, had a positive effect on LVEF, QOL, exercise tolerance and VO<sub>2peak</sub>. 2. With exercise training, a decrease in fiber diameter and LDH activity in both oxidative and glycolytic fibers, an increase in ALP activity were revealed. 3. The functional relationship between the increase in exercise tolerance and ALP content in muscle tissue was revealed.