Smoking, physical activity, and other predictors of endurance and heart rate response to exercise in asymptomatic hypercholesterolemic men: the Lipid Research Clinics Coronary Primary Prevention Trial

The association of known coronary risk factors with progressive submaximal treadmill exercise tolerance test performance was studied in 6,238 asymptomatic white 34-60-year-old hypercholesterolemic men screened between 1973 and 1976 for the Lipid Research Clinics Coronary Primary Prevention Trial. Cigarette smoking and habitual physical inactivity were each associated with a doubling of the rate of symptom-related discontinuation of the exercise test; the tests of sedentary smokers were discontinued at four times the rate observed for active nonsmokers. Smaller increases in heart rate were observed during exercise testing in physically active men and in smokers than in their sedentary and nonsmoking counterparts. Thus, smoking, like habitual physical activity, reduced the heart rate required to sustain a given external workload. However, the heart rates of smokers tended to remain elevated after exercise, while those of physically active men returned more rapidly toward resting levels. Age, Quetelet index, and low plasma levels of high density lipoprotein cholesterol were also strong predictors of decreased endurance, while resting heart rate and blood pressure levels were significant predictors of heart rate response. Comparison of these results with those previously reported for ischemic electrocardiographic changes in this cohort suggests that coronary risk factors may selectively influence specific aspects of exercise tolerance test performance.