The influence of the intensity of treadmill walking upon changes in lipid and lipoprotein variables in healthy adults.

The purpose of the present study was to compare the acute and delayed effects of low- and moderate-intensity exercise on serum lipoprotein concentrations. Twelve healthy volunteers (five men, seven women), aged 28 (2) years [mean (SEM)], maximal oxygen uptake (VO2max) 48 (3) ml.kg-1.min-1 walked on a treadmill for 90 min, on two separate occasions, in a balanced design. On one occasion walking was at a grade which elicited 32.1 (0.8)% of VO2max, i.e. low intensity, while on the other it elicited 60.1 (1.6)% of VO2max, i.e. moderate intensity (MI). Serum concentrations of total cholesterol (TC), triacylglycerol (TAG), high density lipoprotein cholesterol (HDL-C) and the subfraction HDL2-C free fatty acids (FFA) and free glycerol were measured in venous blood samples drawn before exercise (after a 12-h fast), during walking and after 1 h and 24 h of recovery. Serum TAG concentrations decreased as a result of the exercise bout over the period of observation (P < 0.05), but this decrease was not different between the two intensities. Changes in serum TC concentrations over time differed between trials (P < 0.05). Serum free glycerol and FFA concentrations increased during exercise bouts, these increases being (P < 0.05) greater with MI. The decrease in serum TAG concentrations during and after a single episode of either prolonged low or moderate intensity exercise may be associated with an increased clearance and/or a decreased secretion of TAG-rich lipoproteins.