The Increase in Intramyocellular Lipid Content Is a Very Early Response to Training

The present study investigated the influences of a 2-wk training program on intramyocellular lipid (IMCL) content, IMCL decrease during exercise, fat oxidation, and insulin sensitivity. Nine untrained men (age, 23.3 3.2 yr; body mass index, 22.6 2.6 kg/m2; maximal power output, 3.8 0.6 W/kg body weight) trained for 2 wk. Before and after training, subjects cycled for 3 h while substrate oxidation was measured. IMCL content in the vastus lateralis muscle was determined before and after cycling by proton magnetic resonance spectroscopy. Before and after training, insulin sensitivity was assessed by an insulin tolerance test. The training period resulted in a significant increase in IMCL content by 42 14%. IMCL content decreased signifi-cantly during cycling. However, 2 wk of training were no