Quantitative analysis of changes occurring in muscle vastus lateralis in patients with heart failure after low-intensity training

OBJECTIVE: To quantitate the changes occurring in muscle vastus lateralis a fter exercise training of low intensity adopted for the rehabilitation of p atients with chronic heart failure. STUDY DESIGN: Nine consecutive males with a clinical diagnosis of idiopathi c dilated and ischemic cardiomyopathy underwent an eight-week period of tra ining. The intensity of the work was calculated as 40% of peak VO2. The pro gram consisted of 30 minutes of cycling three times per week. A cardiopulmo nary exercise test, hemodynamic measurements and echocardiographic studies were carried out. Needle biopsies were taken from muscle vastus lateralis b efore starting and after completing training. Quantitative analysis was car ried out on sections stained with ATPase at pH 9.5 for measurement of the l esser diameter of type 1 and 2 fibers (by using an image analyzer) and on U EA 1-stained sections for capillary density and capillary/fiber ratio (by u sing a frame in the eyepiece of the microscope). The Wilcoxon test was appl ied to identify significant differences before and after training. Spearman 's rank correlation coefficient was also calculated to highlight any correl ation between the morphologic data and results of clinical tests. RESULTS: After completing the training program, all the patients experience d an improvement in exercise tolerance and a significant increase (P < .004 ) in the VO2 and VCO2 peak. Skeletal muscle showed a significant (P < .02) increase in the capillary/fiber ratio. The changes were not significantly c orrelated with any of the clinical findings. CONCLUSION: Low-intensity training can improve the functional capacity of p atients with heart failure while producing only mild morphologic changes in their muscles.