EFFECT OF REPEATED EXERCISE BOUTS ON HIGH-DENSITY LIPOPROTEIN-CHOLESTEROL AND ITS SUBFRACTIONS HDL2-C AND HDL3-C

Nine sedentary men (mean age, 22.8 yrs) were studied during and after treadmill exercise at 65 % VO2max to determine the number of repeated exercise bouts required to bring about a sustained elevation in HDL-ch olesterol and its subfraction HDL2-C and HDL3-C. A Latin square counte rbalanced design was used. Thirty minute exercise sessions were undert aken in the following patterns: (1) single bout, (2) two bouts on alte rnate days, and (3) three bouts on alternate days. The exercise bouts in patterns 2 and 3 were separated by 48 h. Patterns 1, 2 and 3 were c onducted 7 days apart. Blood samples were obtained prior to each patte rn and at 5 min, 24 and 48 h after the last session within each patter n. There were no significant differences in triglycerides and total ch olesterol between the selected blood sampling points for all patterns. Total HDL-C remained higher (p<0.05) than the pre-exercise level 5 mi n [pattern 1: 39.0 vs 41.2 mg . dl-1, pattern 2: 37.1 vs 39.2 mg . dl- 1, pattern 3: 38.8 vs 42.7 mg - dl-1] and 24 h [pattern 1: 39.0 vs 39. 4 mg . dl-1, pattern 2: 37.1 vs 39.1 mg . dl-1, pattern 3: 38.8 vs 42. 6 mg . dl-1] post-exercise. Total HDL-C declined to pre-exercise value s 48 h post-exercise in all patterns. HDL2-C was lower (p<0.05) than p re-exercise 48 h for all exercise patterns. For all patterns, HDL3-C l evels were higher (p<0.05) at the 5 min and 48 h post-exercise time po ints than at the pre-exercise. These data illustrate that exposure to repeated exercise sessions conducted on alternate days resulted in a p rolonged (i.e., 24h) elevation in HDL-C. This increase in HDL-C was pr imarily due to an increase in HDL3-C. Three repeated exercise bouts (p attern 3) brought about a prolonged (i.e., 24 h) and clinically signif icant (approximately 4.0 mg . dl-1) elevation in HDL-C.