Mixed

Fish oil supplementation (3.85 g/day EPA+DHA) combined with resistance training significantly increases absolute and relative upper-body strength and relative lower-body strength in young adults compared to placebo, without significantly altering lean body mass.

If you are a young, healthy adult doing resistance training 3 times a week, adding 3.85 grams of combined EPA and DHA daily (from fish oil) can help you get stronger, especially in your upper body and relative strength, without necessarily making you bigger. This effect is likely due to improved muscle quality and neural factors, not just muscle growth. Ensure you are getting enough protein (at least 1.2g/kg/day) as this may be required for the fish oil to work effectively.