Increases in HDL-cholesterol and the HDL/LDL cholesterol ratio during prolonged endurance exercise.

The influence of prolonged, low-intensity exercise (45% VO2max) until exhaustion on plasma lipid levels, in particular high-density lipoprotein cholesterol (HDL-C), and the time sequence associated with changes in these blood constituents was investigated in 10 trained subjects. The exercise consisted of walking on a motor-driven treadmill until exhaustion. Blood samples were drawn before, at 30 and 60 minutes after the beginning of exercise, at each hour thereafter until exhaustion, immediately before exhaustion, and after a 30-minute recovery period. At exhaustion the total cholesterol concentration was significantly elevated by 3% and rose another 3% during the recovery period. The HDL-C level was significantly elevated within two hours after the start of exercise and by exhaustion (about 4.5 hours of exercise) had risen to 52.5 +/- 2.3 mg X dL-1, which represented a 10.8% increase above the pre-exercise concentration (47.4 +/- 1.8 mg X dL-1). The HDL/LDL cholesterol ratio followed a pattern similar to that described for HDL-C. Plasma free fatty acids (FFA) also increased linearly during the exercise period but were not significantly correlated with HDL-C during exercise (r = 0.14). These results suggest that prolonged, low-intensity exercise can acutely improve the lipid profile of humans.