The purpose of this study was to investigate the effects of maximal exercise on the composition of plasma fatty acid in trained and untrained subjects. Five trained distance runners and five untrained subjects performed maximal treadmill running. Lactate, glycerol, free fatty acid, fatty acid composition in plasma, and acetone, ethane, pentane and butane in the expired air were measured at rest, during and after the maximal exercise. The blood glycerol, following the maximal exercise, was significantly higher in the trained subjects when compared to the untrained subjects (P< 0.01).
　There was no significant effect of acute maximal exercise on the fatty acid composition of plasma in the trained or untrained subjects. The palmitic acid of the trained subjects was higher than that of the untrained subjects at rest and during recovery (P< 0.01). The stearic acid and oleic acid in the trained subjects were lower than that in untrained subjects at rest and after the exercise. The acetone in expired air during exercise correlated significantly with the exercise intensity (% of Vo₂) in the trained subjects (r=0.611, P< 0.01), and all the subjects (r= 0.401, P< 0.05). There was significant relationship between linoleic acid in plasma and ethane in expired air at rest, and after exercise, in all subjects.
　These results suggest that, 1) aerobic training caused changes in the composition of plasma fatty acid, but acute maximal exercise did not cause such changes, 2) the acetone in expired air increased with an increase in exercise intensity, 3) the ethan in expired air might be caused by linoleic acid in the plasma.

DESCENTE SPORTS SCIENCE Vol.13/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE