Does acetaminophen improve endurance performance?

Acetaminophen (brand name Tylenol) is a popular choice for pain relief for many runners before and after runs and hard workouts. For years researchers have debated whether or not the pain reliever had an ergogenic effect, but a recent meta-analysis has confirmed that when taken 45 minutes to an hour before a big effort, acetaminophen can, in fact, improve performance. Here’s how.

RELATED: UTMB bans painkillers at all events

How does acetaminophen work?

Although Acetaminophen (also known as paracetamol) often gets lumped together with other painkillers like ibuprofen (Advil) and aspirin, it is not a non-steroidal anti-inflammatory drug (NSAID). According to the researchers, it works “primarily by inhibiting prostaglandin synthesis, which reduces transduction of the sensory nerves, resulting in decreased nociceptive impulse transmission.” In other words, it helps cool the body and changes the way you feel pain, elevating your pain threshold so more pain needs to develop before you actually feel it.

The study

The researchers analyzed data from 10 studies to understand the relationship between acetaminophen and endurance performance. In the main meta-analysis, they found no significant difference between acetaminophen and a placebo, but when they looked only at studies that administered the drug 45-60 minutes before exercise, the story was very different. When given within that shorter window of time, acetaminophen appeared to have an ergogenic effect in time-to-exhaustion tests. Interestingly, there was no significant effect between the drug and a placebo in studies that focused on time trial tests.

What does this mean for runners?

This analysis suggests that taking acetaminophen 45-60 minutes before a hard workout or race may have a positive effect on performance by increasing your endurance capacity, but it doesn’t actually directly improve your speed. The researchers admit that these effects are generally small, but more research needs to be done to fully understand the impact of acetaminophen on performance.

RELATED: NSAIDs and endurance running: what are the risks?

Outside of UTMB, acetaminophen is not a banned substance under World Anti-Doping Agency (WADA) regulations, but that doesn’t mean runners should start using the drug regularly. All painkillers, including over-the-counter drugs like Tylenol, carry potential health risks, particularly when taken chronically or in conjunction with long bouts of high-intensity exercise. Runners should be cautious when taking any drug to avoid any potentially dangerous side effects.