A new study in Acta Physiologica compared active folks' muscle mass after eight weeks of strength training while taking a daily aspirin, ibuprofen, naproxen, or other non-steroidal anti-inflammatory drug (NSAID). Researchers found that participants who took a high dose only developed half as much muscle mass and significantly less strength as compared to those who took a low dose.
While eight weeks is a long time to be consuming daily ibuprofen, athletes might still be giving up the real gains they’ve earned if taken in high doses for just a few days of discomfort: “NSAIDs inhibit the cyclooxygenase (COX) enzymes, which we believe are important regulators of muscle protein turnover,” explains lead study author Tommy Lundberg, Ph.D., lecturer of physiology at Karolinska Institute in Stockholm. Less active COX enzymes means less muscle protein synthesis (so less muscle is built). Even though his team hasn’t tested short-term use of NSAIDs on muscle development, Lundberg says the drug acts on the COX enzymes within an hour, so “there’s no reason to believe the negative effect of high-dose NSAIDs would not kick in immediately.”
But dose is really the key here: Lundberg's study showed less muscle gains among the people taking 1200 mg of ibuprofen, which is a normal 24-hour dose, but not among those taking just 75 mg, which is far below the recommended dose of 200 mg every four to six hours as needed. What’s more, a previous Canadian study found taking 400 mg of an NSAID on training days (five per week) didn’t affect the participants’ muscle gains after six weeks.
If you’re in such pain that you need high doses of painkillers regularly, talk to your doctor first. As for the occasional low-dose ibuprofen to help treat a headache or avoid delayed-onset muscle soreness, you’re probably fine: “Taking an NSAID just a few times per week will most likely not have a significant impact on muscle growth or strength,” Lundberg concludes.