Objective: The aim of this study was to test the hypothesis that 8-week eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplementation improves peripheral muscle performance by concentric contractions (CONs) of elbow flexors in humans.
Methods: Sixteen healthy men were randomly administered with EPA and DHA supplement (EPA, n = 8) or placebo (PL, n = 8) by a double-blind method. The EPA group was administered EPA-rich fish oil, containing 600 mg EPA and 260 mg DHA per day for 8 weeks. The subjects performed 5 sets of 6 maximal CONs of elbow flexors. The work output and peak torque were assessed during exercise. Changes in the maximal voluntary isometric contraction torque, range of motion (ROM), upper arm circumference, muscle fatigue by rating of perceived exertion, transverse relaxation time, cross-sectional area (CSA), and lactate in blood were also assessed before, immediately after, and 1 day after exercise.
Results: The work output during CONs in the EPA group was greater than that in the placebo group at the fifth set (EPA group; 94.0 ± 11.7%, placebo group; 82.5 ± 11.7%, p < 0.05). In addition, ROM in the EPA group was significantly greater than that in the placebo group immediately after exercise (p < 0.05). The increase of CSA in the EPA group was significantly smaller than that in the placebo group immediately after exercise (p < 0.05).
Conclusions: The present study suggests that the reduction of muscle work output caused by 30 CONs can be attenuated by an 8-week EPA and DHA supplementation. In addition, EPA and DHA supplementation can cause inhibition for reduction of ROM and increase of CSA after CONs.
Keywords: Eicosapentaenoic acid; docosahexaenoic acid; endurance performance; muscle fatigue; shortening contractions.