Effects of submaximal exercise on high-density lipoprotein-cholesterol subfractions

Acute high-density lipoprotein-cholesterol (HDL) changes were determined in 18 healthy college aged-men completing two-counterbalanced running trials at different exercise intensities: trial 1 at 70 % lactate threshold (LT) (372.5 +/- 28.9 kcal); trial 2 at LT intensity (365.9 +/- 75.9 kcal). For each trial, blood samples were collected at pre-exercise (baseline), 15 min post-exercise (15 m PE) and 24 hours post-exercise (24 h). Serum samples were analyzed for HDL/HDL 2 /HDL 3 subfraction, low density lipoprotein (LDL), very low density lipoprotein (VLDL), total cholesterol (TC), free cholesterol (FC), cholesterol ester, and triglycerides (TG). In addition, capillary blood samples were collected for analysis of blood lactate concentrations during incremental test to determine LT. All samples were corrected for plasma volume changes and compared to pre-exercise (baseline). In assessing the lipid and lipoprotein variables, the significant increase in HDL (p < 0.05) at the 24 h was due to the increase in both HDL 2 and HDL 3. The increase in 15 m PE TC at the LT intensity occurred while the decreases in 24 h TG and VLDL concentrations at the LT intensity occurred at different time periods, respectively. These decreases in the concentrations of TG and VLDL were significantly different, contributing to change in 24 h HDL concentration. No significant difference was determined in changes of HDL over time ratios of FC/CE and HDL 2 /HDL 3. Therefore, the significant increase in 24 h HDL at LT intensity was potentially due to increases in both HDL 2 and HDL 3 subfractions even though 24 h FC was increased significantly. Exercise at LT intensity might favourably alter the lipid profile as demonstrated in 24 h HDL concentration in combination with decreases in TG and VLDL at 24 h post-exercise. Consequently, the LT intensity might appear to be the threshold intensity of acute aerobic exercise (expending 350 kcal) necessary to promote a significant increase in HDL.