EFFECTS OF ENDURANCE TRAINING ON TOTAL FAT OXIDATION IN ELDERLY PERSONS

We examined the influence of 8 wk of endurance training on basal level s of fat oxidation and its association with changes in norepinephrine (NE) kinetics, resting metabolic rate (RMR), and body composition in 1 8 healthy elderly persons (66.1 +/- 1.4 yr; 10 men, 8 women). Fatty ac id appearance rate and total body fat oxidation were determined from [ C-14]palmitate infusion and indirect calorimetry, NE kinetics were det ermined from infusions of [H-3]NE, RMR was determined from the ventila ted hood technique, and body composition was determined from underwate r weighing. Endurance training increased peak oxygen consumption by 11 % (1.9 +/- 0.1 to 2.1 +/- 0.1 l/min; P < 0.01) and increased RMR by 7% (1.20 +/- 0.02 to 1.28 +/- 0.02 kcal/min; P < 0.01). Endurance traini ng increased NE appearance rate by 35% (0.51 +/- 0.04 to 0.69 +/- 0.04 mu g/min; P < 0.01), whereas no change in NE clearance was noted. End urance training increased fat oxidation by 22% (201.0 +/- 11.2 vs. 244 .0 +/- 15.2 mu mol/min; P < 0.01) but did not after fatty acid appeara nce rate. Approximately two-thirds of the variation (r(2) = 0.65) for the increase in fat oxidation was explained by increased NE appearance rate (r(2) = 0.51; P < 0.01) and changes in fat-free weight (r(2) = 0 .14; P < 0.01). We conclude that 1) endurance training shifts in vivo basal substrate utilization toward greater fat oxidation in elderly in dividuals and 2) enhanced fat oxidation is associated with increased a ctivity of the sympathetic nervous system and alterations in fat-free mass.