This study investigated the effect of an eight-week dietary intervention designed to increase n-3 PUFA consumption and reduce dietary intake of n-6 PUFA on VO2peak and oxygen consumption (VO2) during submaximal exercise. Fourteen trained male cyclists were randomly assigned to two independent groups. The experimental group received n-3 PUFA supplementation (2600mg EPA and 1800mg DHA per day) and followed a dietary intervention designed to reduce n-6 PUFA intake. The placebo group received organic soy oil and a placebo dietary intervention that maintained their habitual daily n-6 PUFA intake. Venous blood samples were obtained pre supplementation, at week four and at week eight of the dietary intervention to determine erythrocyte incorporation of n-3 and n-6 PUFA. Pre and post the dietary intervention, participants completed 4 x 7 minutes of submaximal cycling on a Lode ergometer at four discontinuous incremental power outputs (100 W, 125 W, 150 W,175 W). Steady state oxygen consumption VO2 was assessed during each cycling bout. Following a 15-minute rest, participants performed an incremental ramp test to exhaustion (intensity increasing by 30 W·min-1) for the determination of VO2peak. In the fish oil supplemented group, erythrocyte incorporation of total n-3 PUFA increased (from 10.4±2.5 to 20.1±2.8 %) and total n-6 PUFA decreased (from 40.3±1.9 to 30.8±1.3 %) over the eight-week supplementation period. There were no differences in VO2peak (pre 61.7±9.0, post 61.0±7.7 ml/ kg/ min). During steady state submaximal cycling, there were no differences in oxygen consumption (VO2) at any of the four power outputs in the fish oil supplemented group (e.g. 125 W pre 2.32±0.26, post 1.98±0.11 L/min). In conclusion, despite the dietary intervention successfully increasing erythrocyte n-3 PUFA and reducing n-6 PUFA incorporation over an 8-week intervention period, this had no effect on oxygen consumption during submaximal exercise or VO2peak performance
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