A double-blind placebo controlled study included 24 young health men who consumed either a fish oil supplement (600 mg EPA and 260 mg DHA) or a placebo for eight weeks prior to the exercise. After 8 weeks of supplementation, the men performed 5 sets of 6 maximal eccentric elbow flexion exercises (described in the paper’s study methods), followed by an additional 5 days of supplementation.

Following maximal eccentric elbow flexion exercises, men supplementing with EPA and DHA omega-3s experienced significant increases to maximal voluntary contraction (MVC) and range of motion (ROM) compared to a placebo group.

At 2–5 days after exercise, MVC was found to be significantly higher in the omega-3 group than the placebo group, and at 1–5 days after exercise, ROM was also significantly higher in the omega-3 group than the placebo group. Muscle soreness of the brachialis was also found to be significantly greater in the placebo group than the EPA group at 3 days after exercise only, suggesting the EPA and DHA diminished the level of muscle soreness.

This study showed that 8 weeks of fish oil supplementation reduced the level of muscle soreness and strength loss, and improved range of motion after exercise.

Tsuchiya Y, Yanagimoto K, Nakazato K, Hayamizu K, Ochi E. Eicosapentaenoic and docosahexaenoic acids-rich fish oil supplementation attenuates strength loss and limited joint range of motion after eccentric contractions: a randomized, double-blind, placebo-controlled, parallel-group trial. Eur J Appl Physiol. 2016;116(6):1179-88.