Effects of exercise intensity and training on lipid metabolism in young women

We examined the effects of exercise intensity and training [12 wk, 5 days/wk, 1 h, 75% peak oxygen consumption ((V) over dot O-2peak)] On lipolysis 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) over dot O-2peak; ABT) and same relative workload (65% of new (V) over dot O-2peak; RLT)] were performed using infusions of [1,1,2,3,3-H-2]glycerol 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), respectively) and the 45% of (V) over dot O-2peak trials. At ABT and RLT training increased FFA R-a to 8.4 +/- 1.0 and 9.7 +/- 1.1 mu mol . kg(-1). min(-1), R-d to 8.3 +/- 1.0 and 9.5 +/- 1.1 mu mol . kg(-1). min(-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 from respiratory exchange ratio was also elevated after training at ABT and RLT, with all of the increase attributed to plasma FFA sources. Pretraining, 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 and oxidation are not linearly related to exercise intensity before training, 2) training increases FFA R-a, R-d, and R-oxp whether measured at given absolute or relative exercise intensities, 3) whole body lipolysis (glycerol R-a) during exercise is not significantly impacted by training, and 4) training-induced increases in plasma FFA oxidation are the main contributor to elevated total FFA oxidation during exercise exertion after training.