Here’s Why You Should Never Take OTC Painkillers Before a Workout

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Your Body on Ibuprofen
When you’re hurtin’, a group of lipid compounds called prostaglandins are being produced by the tissues in your body. These travel through your blood to the brain, and act as signals that cause swelling in the tissue (a.k.a. inflammation) and fever. These prostaglandins are regulated by something called COX enzymes. 

“Tylenol is great for headaches and fever, but not so great for muscle soreness and injury.”

When you take a non-steroidal anti-inflammatory (NSAID) like Advil/ibuprofen or Aleve/naproxen, you’re blocking the two types of COX enzymes required for prostaglandin production, and essentially reducing the inflammation and fever, says Speaker. The issue, though, is that COX enzymes also play a critical role in protecting your stomach and intestinal lining. So when you block those enzymes, you’re putting your tummy at risk. A 2012 study found that ibuprofen can aggravate exercise-induced injury in the small intestine and cause gut barrier dysfunction in otherwise healthy athletes. Not fun. 

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Plus, a recent study tested the impact of ibuprofen on performance that was impaired by muscle soreness. Researchers had 20 healthy distance runners brought into a lab 48 hours before and 48 hours after a bout of exercise that caused muscle soreness in their legs. While in the midst of maximal soreness, half of the subjects were given 1.2 grams of ibuprofen an hour before exercising, while the other half received a placebo pill. The scientists discovered that the ibuprofen did not reduce the effect of muscle pain on performance—meaning participants weren’t able to work out any better due to their pain pills, and the meds didn’t help alleviate the negative effects we often associate with muscle soreness (slower times, less reps, etc). So while the ibuprofen can help relieve the inflammation itself, it’s better to just take the pill after your workout, not before.

Why Acetominophen Isn’t Any Better
Taking a pain reliever like acetaminophen—a.k.a. Tylenol—before you exercise can also mess with your body’s ability to regulate temperature, says Speaker. As you work out, your body naturally expends more energy and raises your body’s temperature. That’s perfectly normal. But “through its inhibitory effects on the temperature regulation system in the brain, Tylenol may interfere with your body’s ability to properly regulate temperature,” says Speaker. When that happens, it can also lead to thyroid issues. 

“Taking ibuprofen a few hours before exercise to help mitigate menstrual cramps could be very beneficial.”

Not to mention that acetaminophen isn’t going to do you any good when it comes to easing inflammation-induced muscle soreness. “What makes Tylenol unique is that it isn’t really able to block COX enzymes in the body; instead it works more in the central nervous system,” says Speaker. “That’s why it’s best for reducing a fever. It does not possess strong anti-inflammatory properties, so Tylenol is great for headaches and fever, but not so great for muscle soreness and injury.”

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The Bottom Line
Lastly, there’s the matter of your workout itself. If you’re in enough pain that you’re considering a pill in the first place, Speaker says it’s important to ask yourself if you should be exercising at all. “Oftentimes the pain associated with a fever or soreness is purposeful and not meant to be dampened,” says Speaker. “Fevers help kill pathogens and soreness is intended to remind you to rest and recover versus train. Ignoring those can be potentially harmful to your health.”

Really, the only time Speaker says it could be kosher to take something: When you have your period. “Taking ibuprofen a few hours before exercise to help mitigate menstrual cramps could be very beneficial,” she says. Just be sure to take that pain reliever a few hours before going to the gym, rather than right before. “It takes that much time for it to really start working anyway, depending on the dose, the type, and whether or not you took them with food,” she says. “Once they start working, they only last four to six hours.”

Otherwise, if you’re feeling enough pain that you can’t imagine not taking a pill, schedule a rest day instead—your body deserves it.