Abstract
Background Exercise is associated with a reduced risk of cardiovascular disease. Increased high-density lipoprotein cholesterol (HDL-C) levels are thought to contribute to these benefits, but much of the research in this area has been limited by lack of well-controlled subject selection and exercise interventions. We sought to study the effect of moderate and high-intensity exercise on HDL function, lipid/lipoprotein profile, and other cardiometabolic parameters in a homogeneous population where exercise, daily routine, sleep patterns, and living conditions were carefully controlled. Methods and Results Male Army recruits (n=115, age 22±0.3 years) completed a 12-week moderate-intensity exercise program. A subset of 51 subsequently completed a 15-week high-intensity exercise program. Fitness increased and body fat decreased after moderate- and high-intensity exercise (P<0.001). Moderate-intensity exercise increased HDL-C and apolipoprotein A-I levels (6.6%, 11.6% respectively), and decreased low-density lipoprotein cholesterol and apolipoprotein B levels (7.2%, 4.9% respectively) (all P<0.01). HDL-C and apolipoprotein A-I levels further increased by 8.2% (P<0.001) and 6.3% (P<0.05) after high-intensity exercise. Moderate-intensity exercise increased ABCA-1 (ATP-binding cassette transporter A1) mediated cholesterol efflux by 13.5% (P<0.001), which was sustained after high-intensity exercise. In a selected subset the ability of HDLs to inhibit ICAM-1 (intercellular adhesion molecule-1) expression decreased after the high (P<0.001) but not the moderate-intensity exercise program. Conclusions When controlling for exercise patterns, diet, and sleep, moderate-intensity exercise improved HDL function, lipid/lipoprotein profile, fitness, and body composition. A sequential moderate followed by high-intensity exercise program showed sustained or incremental benefits in these parameters. Improved HDL function may be part of the mechanism by which exercise reduces cardiovascular disease risk.