Exercise training has little effect on HDL levels and metabolism in men with initially low HDL cholesterol.

Low concentrations of high-density lipoprotein cholesterol (HDL-C) are a recognized risk factor for atherosclerotic cardiovascular disease. Exercise is often recommended to increase HDL-C, but the effect of exercise training on HDL levels and metabolism in subjects with low HDL concentrations is not well defined. The present study compared the HDL response to 12 months of supervised endurance exercise training without weight loss in 17 men aged 26 49 years with initially low ( < 40 mg/dl, N=7) or normal ( > 44 mg/dl, N=10) HDL-C levels. HDL-C levels and HDL apolipoprotein metabolism were assessed while the subjects consumed controlled diets before and after the year of training. Increases in total (5.1+/-2.8 versus 1.9+/-4.2 mg/dl, P=0.08) and HDL2 (3.8+/-2.9 versus 0.4+/-1.1 mg/dl, P=0.01) cholesterol were greater in men with normal initial HDL-C levels. Catabolic rates for HDL apolipoproteins decreased 7-14% and biological half-lives increased 10-15% after exercise training in subjects with normal HDL, but were unchanged in the low HDL-C group. HDL apolipoprotein synthetic rates were not consistently affected by exercise training in either group. Postheparin lipoprotein lipase activity increased 27%, the clearance rate of intravenous triglycerides increased 14%, and apolipoprotein B levels decreased 16% with training in subjects with normal HDL-C but were unchanged in the low HDL-C group. We conclude that the ability to increase HDL-C levels through endurance exercise training is limited in subjects with low initial HDL-C, possibly because exercise training in such subjects fails to alter triglyceride metabolism.

Acute effects of a single exercise session on serum lipids in untrained men.

Acute reductions in triglycerides and calculated low density lipoprotein cholesterol with little change in high density lipoprotein cholesterol have been reported in trained men after a single exercise session. To examine if a similar acute exercise effect occurs in sedentary subjects, wer measured triglycerides, total cholesterol, and high density lipoprotein cholesterol in eight sedentary men before and for 66 hours after a single 30-minute exercise session. The exercise was designed to simulate a typical exercise training session for untrained subjects. An isolated reduction in estimated low density lipoprotein cholesterol was observed 66 hours after the exercise. All other serum lipid measurements at 5 minutes and 1, 4, 18, 42, and 66 hours after exercise did not differ from pre-race concentrations. Consequently, the reductions in triglycerides and low density lipoprotein cholesterol and increase in high density lipoprotein cholesterol reported in previously sedentary subjects after exercise training are a chronic rather than an acute exercise effect.