Here's an interesting study! (Side note: it was funded by a Japanese fishing company; so I'm sure there was no monetary incentive or motivation for a positive result *insert sarcasm*). The study was published in the Journal of the International Society of Sports Nutrition and found that those who ingested EPA (Eicosapentaenoic acid) and DHA (Docosahexaenoic acid) lost less muscle strength, had less delayed onset muscle soreness (DOMS) and experienced less muscle soreness after exercise.
16 participants (small sample size) ingested 600 mg of EPA and 260 mg of DHA or placebo daily while doing 6 sets of preacher curls
EPA and DHA omega-3 fatty acids are mainly found in fatty, oily fish such as salmon, mackerel, oysters, seabass, sardines and trout. The can also be found in plant sources such as seaweed and algae. Omega 3 FAs have been shown to improve cardiovascular health and have anti-inflammatory effects on the body.
Tsuchiya, Y, Yanagimoto, K, Ueda, H, Ochi, E. ' Supplementation of eicosapentaenoic acid-rich fish oil attenuates muscle stiffness after eccentric contractions of human elbow flexors'. Journal of the International Society of Sports Nutrition. 2019; 16: 19