Some athletes and exercisers take pain medication (aspirin or NSAIDs) because they think it may prevent muscle soreness or will help them to heal faster after a workout. However, taking pain medicines will not block pain, help you to exercise longer or to recover faster from exercise. They can increase risk for bleeding and damage to muscles, tendons or kidneys, and they can also delay muscle recovery from exercise. I believe that you should not take aspirin or NSAIDs (nonsteroidal anti-inflammatory drugs) before, during, or soon after exercising unless your doctor specifically recommends that you need to take them.
• Aspirin increases risk of bleeding into your stomach, brain, or any area that is bumped in an accident. Aspirin kills as many people by causing major bleeds as it saves by preventing heart attacks (JAMA, Jan 22, 2019;321(3):277-287). Caution about stopping daily aspirin: Do not stop taking aspirin suddenly. If you want to stop taking aspirin after taking it for a while, your doctor will tell you how to gradually taper your dose.
• NSAIDs do not block the muscle burning you feel when you exercise intensely (Med Sci in Sports and Exercise, Aug 1997;29(8):0999-1012). When you exercise intensely, you run low on oxygen which causes lactic acid to accumulate in muscles to cause muscle burning. The only way that you can stop this muscle burning during intense exercise is to slow down to allow lactic acid to be cleared.
• NSAIDs taken the next day may reduce delayed-onset muscle soreness (DOMS), but do not increase the rate of recovery from exercise (J Strength Cond Res, Feb 2003;17(1):53-9).
• NSAIDs reduce new muscle protein synthesis after intense exercise (Am J Physiol Endocrinol Metab, Mar 2002;282(3):E551-6), and reduce muscle growth after intense exercise (Sports Med, Dec 1, 2012;42(12):1017-28).
• Aspirin decreases protein synthesis after exercise (J Biol Chem, April 2007;282(14):10164-71).
• Taking NSAIDs after injuries delays healing (South African Medical Journal, Jun 6, 1995;85:517-522), and taking NSAIDs for several weeks after a fracture delays the healing of broken bones (J Orthop Trauma, May 1995;9:392-400).
• NSAIDs may increase risk of low blood sodium levels in endurance events.
• NSAIDs can constrict arteries that carry blood to the kidneys to increase risk for kidney damage.
• NSAIDs taken long term may increase tendon and muscle damage from repetitive exercise (American Journal of Sports Medicine, 1995; 23:119-123).
• NSAIDs may increase joint damage when taken during exercise by people who have osteoarthritis (J. Rheumatol, 1995;22(10):1941–1946).
Common types and brands of NSAIDs include ibuprofen (Motrin, Advil), indomethacin (Indocin), ketoprofen (Ketoprofen) and naproxen (Aleve, Anaprox, Naprelan, Naprosyn).
Also see NSAIDs Interfere with Exercise Training
NSAIDs May Block Gains in Endurance and Strength