Fatty acid profile of skeletal muscle phospholipids in trained and untrained young men

Endurance trained (n = 14) and untrained young men (n = 15) were compared r egarding the fatty acid profile of the vastus lateralis muscle after 8 wk o n diets with a similar fatty acid composition. The skeletal muscle phosphol ipids in the trained group contained lower proportions of palmitic acid (16 :0) (-12.4%, P < 0.001) and di-homo-gamma-linolenic acid [20:3( n-6)] (-15. 3%, P = 0.018), a lower n-6-to-n-3 ratio (-42.0%, P = 0.015), higher propor tions of stearic acid (18:0) (19.8%, P = 0.004) and sum of n-3 polyunsatura ted fatty acids (133.8%, P = 0.009), and a higher ratio between 20:4(n-6) t o 20:3(n-6) (+18.4%, P = 0.006) compared with those in the untrained group. The group differences in 16:0, 20:3(n-6), 18:0/16:0, and 20:4(n-6)/20:3(n- 6) were independent of fiber-type distribution. The trained group also show ed a lower proportion of 16:0 (-7.9%, P < 0.001) in skeletal muscle triglyc erides irrespective of fiber type. In conclusion, the fatty acid profile of the skeletal muscle differed between trained and untrained individuals, al though the dietary fatty acid composition was similar. This difference was not explained by different fiber-type distribution alone but appears to be a direct consequence of changes in fatty acid metabolism due to the higher level of physical activity.