Ten weeks of aerobic training does not result in persistent changes in VLDL triglyceride turnover or oxidation in healthy men

Objective: Very low density lipoprotein triglyceride (VLDL-TG) and free fatty acids (FFA) constitute a substantial proportion of human energy supply both at rest and during exercise. Exercise acutely decreases VLDL-TG concentration, and VLDL-TG clearance is increased after an exercise bout. However, the effects of long-term training are not clear. 

Design: The aim was to investigate long-term effects of training by direct assessments of VLDL-TG and palmitate kinetics and oxidation in healthy lean men (n=9) at rest, before and after a 10-week training program, compared with a non-training control group (n=9). 

Methods: VLDL-TG kinetics were assessed by a primed constant infusion of [1-¹⁴C]VLDL-TG, and VLDL-TG oxidation by specific activity (¹⁴CO₂) in expired air. The metabolic study days were placed 60-72 h after the last exercise bout. 

Results: Palmitate kinetics and oxidation were assessed by a 2 h constant infusion of [9,10-³H]palmitate. In the training group (n=9), maximal oxygen uptake increased significantly by ≈20% (P<0.05), and the insulin sensitivity (assessed by the hyperinsulinemic-euglycemic clamp) improved significantly (P<0.05). Despite these metabolic improvements, no changes were observed in VLDL-TG secretion, clearance, or oxidation or in palmitate kinetics. 

Conclusion: We conclude that 10 weeks of exercise training did not induce changes in VLDL-TG and palmitate kinetics in healthy lean men.