Training affects muscle phospholipid fatty acid composition in humans

Training improves insulin sensitivity, which in turn may affect performance by modulation of fuel availability. Insulin action, in turn, has been link ed to specific patterns of muscle structural lipids in skeletal muscle. Thi s study investigated whether regular exercise training exerts an effect on the muscle membrane phospholipid fatty acid composition in humans. Seven ma le subjects performed endurance training of the knee extensors of one leg f or 4 wk. The other leg served as a control. Before, after 4 days, and after 4 wk, muscle biopsies were obtained from the vastus lateralis. After 4 wk, the phospholipid fatty acid contents of oleic acid 18:1(n-9) and docosahex aenoic acid 22:6(n-3) were significantly higher in the trained (10.9 +/- 0. 5% and 3.2 +/- 0.4% of total fatty acids, respectively) than the untrained leg (8.8 +/- 0.5% and 2.6 +/- 0.4%, P < 0.05). The ratio between n-6 and n- 3 fatty acids was significantly lower in the trained (11.1 +/- 0.9) than th e untrained leg (13.1 +/- 1.2, P < 0.05). In contrast, training did not aff ect muscle triacylglycerol fatty acid composition. Citrate synthase activit y was increased by 17% in the trained compared with the untrained leg (P < 0.05). In this model, diet plays a minimal role, as the influence of dietar y intake is similar on both legs. Regular exercise training per se influenc es the phospholipid fatty acid composition of muscle membranes but has no e ffect on the composition of fatty acids stored in triacylglycerols within t he muscle.