Effect of physical activity and muscle morphology on endothelial function and arterial stiffness

Physically active persons have a reduced risk of atherosclerotic disease. Arterial stiffness and endothelial dysfunction are important risk factors for cardiovascular disease. A high proportion of type I (slow-twitch) muscle fibers in skeletal muscle is associated with a favorable cardiovascular risk profile. We tested physical activity and muscle fiber-type distribution as determinants of endothelial function and arterial stiffness in middle-aged men. Fifty-four men (median age 58) who underwent a muscle biopsy in 1984 were re-studied in 2003. Aortic pulse wave velocity (PWV) and pulse wave reflection were assessed by applanation tonometry. Endothelial function was tested by examining the effects of salbutamol and nitroglycerin on pulse wave reflection. In multiple regression analyses aortic PWV (R2=0.51) correlated positively with age (P=0.017), BMI (P=0.001), and systolic blood pressure (P=0.004). A high augmentation index (R2=0.33) was associated with smoking (P<0.001), high LDL cholesterol (P=0.02), and elevated diastolic blood pressure (P=0.03). Impaired endothelial function (R2=0.37) was associated with high age (P=0.04), high LDL cholesterol (P=0.017), high triglycerides (P=0.027), and high physical activity (P=0.005). Muscle fiber-type distribution is not a determinant of arterial stiffness or endothelial function. Impaired endothelial function was observed in physically active men, underlining the need for further research.