Effects of high- and low-intensity exercise training on aerobic capacity and blood lipids

Sixteen non-obese, non-smoking males, ages 20-30 yr, were assigned to one of two training groups, exercising on a cycle ergometer 3 d/wk for 18 wk: high-intensity (H; N=7; 80-85% VO_2max 25 min/session) or low-intensity (L; N=9; 45% VO_2max body weight, percent body fat, and 12-h fasting blood levels of cholesterol (CHOL), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C). The average post-training increase in VO_2max for group H (0.56 1·min^-1 8.5 ml·min^-1·kg^-1) was not significantly (P>0.05) greater than for group L (0.45 1·min^-1 6.5 ml·min^-1·kg^-1). Significant reductions in percent body fat occurred in both groups, amounting to an average fat loss of approximately 1.35 kg. No statistically significant changes in CHOL, TG, HDL-C, LDL-C, CHOL/HDL-C, or HDL-C/LDL-C occurred in either group. However, changes in HDL-C after 18 wk of training were inversely correlated (r=-0.57, P<0.05) with pre-training levels. We conclude that 1) the minimum exercise training-intensity threshold for improving aerobic capacity is at least 45% VO_2max; 2) 18 wk of high- or low-intensity exercise training is ineffective in significantly altering CHOL, TG, HDL-C, LDL-C, CHOL/HDL-C, and HDL-C/LDL-C in young male subjects with low blood lipid levels, and 3) exercise training-induced changes in HDL-C are dependent upon initial pre-training levels.