EFFECTS OF EXERCISE INTENSITY AND TRAINING ON LIPID-METABOLISM IN YOUNG-WOMEN

We examined the effects of exercise intensity and training [12 wk, 5 d ays/wk, 1 h, 75% peak oxygen consumption ((V) over dot O-2peak)] On li polysis and plasma free fatty acid (FFA) flux in women(n = 8; 24.3 +/- 1.6 yr). Two pretraining trials (45 and 65% of (V) over dot O-2peak) and two posttraining trials [same absolute workload (65% of old (V) ov er dot O-2peak; ABT) and same relative workload (65% of new (V) over d ot O-2peak; RLT)] were performed using infusions of [1,1,2,3,3-H-2]gly cerol and [1-C-13]palmitate. Pretraining rates of FFA appearance (R-a) , disappearance (R-d), and oxidation (R-oxp) were similar between the 65% (6.8 +/- 0.6, 6.2 +/- 0.7, 3.1 +/- 0.3 mu mol . kg(-1). min(-1), r espectively) and the 45% of (V) over dot O-2peak trials. At ABT and RL T training increased FFA R-a to 8.4 +/- 1.0 and 9.7 +/- 1.1 mu mol . k g(-1). min(-1), R-d to 8.3 +/- 1.0 and 9.5 +/- 1.1 mu mol . kg(-1). mi n(-2), and R-oxp to 4.8 +/- 0.4 and 6.7 +/- 0.7 mu mol . kg(-1). min(- 1), respectively (P less than or equal to 0.05). Total FFA oxidation f rom respiratory exchange ratio was also elevated after training at ABT and RLT, with all of the increase attributed to plasma FFA sources. P retraining, glycerol R-a was higher during exercise at 65 than 45% of (V) O-2peak (6.9 +/- 0.9 VS. 4.7 +/- 0.6 mu mol . kg(-1). min(-1)) but was not changed by training. In young women 1) plasma FFA kinetics an d oxidation are not linearly related to exercise intensity before trai ning, 2) training increases FFA R-a, R-d, and R-oxp whether measured a t given absolute or relative exercise intensities, 3) whole body lipol ysis (glycerol R-a) during exercise is not significantly impacted by t raining, and 4) training-induced increases in plasma FFA oxidation are the main contributor to elevated total FFA oxidation during exercise exertion after training.