Does Baseline HDL-C Influence the Dose and Response Relationship Between Acute Exercise and Post-Exercise HDL-C Improvement?

Does Baseline HDL-C Influence the Dose and Response Relationship Between Acute Exercise and Post-exercise HDL-C Improvement? Purpose: The purpose of this study was to determine if high density lipoprotein cholesterol (HDL-C) status (low vs. normal) affects the magnitude of post-exercise HDL-C changes over a 24 hour period and whether different caloric expenditures (300, 500 and 700 kcals) augment this relationship. Methods: Two groups of healthy untrained male volunteers participated in this study. Subjects were assigned to one of two groups based upon their resting HDL-C level. The LOW HDL-C group consisted of 13 subjects with clinically low HDL-C (< 40mg/dl) and the NORMAL HDL-C group consisted of 14 subjects with normal HDL-C (≥ 45mg/dl). Age, diet, VO2max and anthropometric data were collected prior to initiation of the experimental protocol and were similar for both groups. The characteristics of the LOW group were 21.9 ± 2.0 yrs of age, 1.8 ± 0.1 m tall, weighed 80.9 ± 7.9 kg, and had a BMI of 25.2 ± 2.2 kg/m2, a VO2max of 45.8 ± 5.1 ml/kg/min and a resting HDL-C of 35.7 ± 2.7 mg/dl. Characteristics of the NORMAL group were 23.4 ± 7.1yrs of age, 1.8 ± 0.1 m tall, weighed 78.6 ± 7.6 kg, and had a BMI of 24.3 ± 2.5 kg/m2, a VO2max of 47.5 ± 4.8 ml/kg/min and a resting HDL-C of 53.9 ± 5.8 mg/dl. Subjects randomly completed three nonconsecutive exercise trials (300, 500, and 700 kcals) on a treadmill at 65% of VO2max. Blood samples were collected pre-exercise (PRE), immediately post-exercise (IP), and 24 hours post-exercise (+24). Each sample was analyzed for HDL-C and its subfractions (HDL2-C and HDL3-C) and was corrected for plasma volume shifts. Results: There was no significant main effect of group or condition (kcal expenditure) and no interactions among variables. HDL3-C increased significantly IP regardless of group or caloric expenditure, but was not different from PRE at +24. HDL-C increased (5.6%) significantly IP regardless of group when the 500 and 700 kcal trials were combined, again the effect was transient. Individually, no caloric expenditure produced HDL-C or subfraction changes that were significantly different from one another. Conclusions: Baseline HDL-C status had no significant effect on the magnitude of post-exercise HDLC alterations. Furthermore, post-exercise improvements of HDL-C in untrained men occur via increases in HDL3-C and primarily at caloric expenditures above 300 kcal