Intramyocellular lipid changes in men and women during aerobic exercise: a (1)H-magnetic resonance spectroscopy study

This study was designed to compare intramyocellular lipid (IMCL) changes during 60 min of submaximal exercise in men and women. Eighteen moderately active (18-38 yr) men (n = 9) and women (n = 9) were recruited. Maximum oxygen consumption (O(2)max) and body composition were used to match subjects for aerobic fitness and body composition. Subjects performed cycle ergometry for 1 h at 65% of O(2)max. Expired gases were collected throughout exercise to determine caloric expenditure and substrate use. Blood samples were collected before and after exercise to evaluate markers of lipid metabolism. Pre- and postexercise proton spectra were acquired from the vastus lateralis using a 3-T whole-body imaging system. Spectra were acquired from an 18-mm(3) region of interest (echo time = 45 msec; repetition time = 2000 msec) for IMCL evaluation. IMCL decreased significantly with exercise (11.5-28.5% for men and 17.1-21.7% for women) (P < 0.05); however, there were no significant differences between men and women. Although changes were found for many plasma variables [free fatty acids, glycerol, and norepinephrine (P < 0.05)], group differences were only evident for norepinephrine. In conclusion, a significant decrease in IMCL was observed during 60 min of cycling in matched men and women.