EFFECT OF A NORMAL AND ABOVE NORMAL BOUT OF AEROBIC EXERCISE ON ACUTE HDL-C CHANGES 529

Abstract

An acute increase in high density lipoprotein-cholesterol (HDL-C) has been observed following a single bout of aerobic exercise. Prior research has observed significant increases in HDL-C with as low as an 800 kcal expenditure in moderately trained individuals, whereas in more highly trained subjects, no change was observed at a similar caloric expenditure. It was hypothesized that one's training level may play an important role in acute HDL-C changes. Therefore, the purpose of this study was to evaluate a normal and above normal bout of aerobic exercise on acute HDL-C changes. It was speculated that a normal bout of exercise would have no effect, whereas an above normal bout of exercise would acutely increase HDL-C. Based on previous month exercise diaries, twelve trained cyclists (29.4 ± 8yr) completed a normal bout of exercise (1006 ± 288 kcal) and 1.5× normal (1546 ± 476 kcals) at 70% of VO2max, while cycling. Blood samples were collected at 24h pre-exercise (24h Pre) and 24, 48 and 72h post-exercise (PE). Blood samples were measured for total cholesterol (T-C), triglycerides (TG), HDL-C, HDL2-C, and HDL3-C. All values were corrected for plasma volume changes. A significant decrease (p<.05) in TG was observed between 24h Pre and 24h PE (101.6± 46.2 and 81.0 ± 35.3 mg·dl-1; respectively), across trials. No significant difference was observed for T-C, HDL-C, and HDL-C subfractions. In conclusion, it appears that when an individual completes a normal and 1.5× normal bout of exercise, no additional increase in HDL-C is observed. The lack of change in HDL-C following an above normal bout of exercise is not clearly understood.