Muscular strength and diameter as determinants of aerobic power and aerobic power response to exercise training in CAD patients

Abstract

Objective Low exercise capacity and skeletal muscle strength are important predictors of all-cause mortality in healthy as well as diseased individuals. Compared to sedentary subjects, CAD patients have a decreased oxygen uptake (peakVO2) and show accompanying increased muscle fatiguability. Despite the known importance of oxygen extraction by peripheral muscles on improving peakVO2 and of the relationship between muscle strength and aerobic capacity, only few studies in CAD patients include measurements of muscle strength before and after cardiac rehabilitation. This study therefore aimed to evaluate how much of the variance in baseline peakVO2 and its response to exercise training can be explained by muscular parameters.Methods 260 CAD patients performed maximal incremental cycle ergometer testing and maximal knee muscle strength measurements. The rectus femoris diameter was measured using ultrasound. Zero order correlations were calculated and determinants of baseline and response in peakVO2 were analysed by multiple regression analysis.Results PeakVO2 and muscle strength and diameter increased signifi cantly after three months of cardiac rehabilitation (P < 0.0001). Zero order correlations showed signifi cant correlations between muscular parameters and baseline peakVO2 (P < 0.0001). 63% of the total variance in baseline peakVO2 could be explained by seven parameters with knee extensor muscular endurance as the strongest predictor (P < 0.0001). 32% of the variation in relative increase in peakVO2 could be explained by 5 determinants of which the increase in muscular endurance was the strongest determinant (P < 0.0001).Conclusions Knee extensor muscular endurance and its response after training are the strongest muscular predictors in explaining peakVO2 and its response in CAD patients.