Does Smoking Weed Affect Muscle Growth? What Research Says

There's no solid evidence that smoking weed directly stops you from building muscle, but research does show that being high hurts athletic performance: it lowers endurance, raises your heart rate and messes with balance and coordination, so lifting or training while stoned works against you. The use of cannabis in sports is a hot-button topic that keeps evolving. Some athletes swear by it for pain relief and anxiety, while sports bodies and public health agencies warn about the potential risks and side effects.

Over the last few years, as more countries legalize and accept cannabis, the debate over weed in sports has only gotten louder.

How weed helps and hurts athletic performance and health

The World Anti-Doping Agency (WADA) considers marijuana a performance-enhancing drug and a health risk. According to a 2011 paper published in the journal Sports Medicine, cannabis induces euphoria, boosts self-confidence, promotes relaxation and steadiness, and relieves the stress of competition.

The same report warns that athletes who smoke cannabis during competition put themselves and others at risk, because of more risk-taking, slower reaction times and poorer decision-making.

How does weed affect your body? What the experts say

WADA's position is “untenable and outdated,” according to Jordan Tishler, a physician and cannabis specialist at Inhale MD in Boston, Massachusetts. If anything, he argues, marijuana is a performance-degrading drug: peak performance (max strength, top speed, VO2 max) just isn't likely to happen while you're using cannabis.

That makes sense, considering the effects of cannabis can include altered body movements, trouble thinking and problem-solving, breathing issues and a higher heart rate, none of which help you perform at your best.

So... does smoking weed affect muscle growth?

The thing is, the effects of cannabis that could influence performance really only matter while you're under the influence, Tishler says. If you inhale it, the effects last three to four hours; if you take it orally, they last eight to 12 hours, he explains.

Of course, that also depends on the person and their tolerance, says Ryan Vandrey, a professor of psychiatry and behavioral sciences at Johns Hopkins School of Medicine and a member of Realm of Caring, a nonprofit focused on cannabis research, education and advocacy.

If you use cannabis at night to help you sleep, there may be some leftover cognitive impairment the next morning, Vandrey notes, and researchers still haven't pinned down the window after which cannabis impairment is no longer a concern.

Vandrey makes a good point: there isn't much data on how marijuana affects athletic performance, for better or worse. People claim there's a benefit, and you can make a theoretical case that weed could be debilitating, but nobody has done the in-depth research to settle it. Without the data, he says, all anyone can do is guess and speculate.

What does research say about weed and muscle growth?

A scientific review published in April 2021 in The Journal of Sports Medicine and Physical Fitness concluded that marijuana use does not act as a performance-enhancing agent, contrary to popular belief.

The researchers found that cannabis use before exercise should be avoided if you want to maximize performance, because it reduces athletes' ability to sustain effort, raises heart rate and breathing rate as well as the heart muscle's oxygen demand, and worsens balance problems.

In short, instead of giving you an edge, cannabis makes athletes more likely to underperform.

Weed and running: what about amateur runners?

If you're not actively under the influence of cannabis, it probably won't affect your performance at all, according to Dr. Jordan Tishler. That's relevant to the Sha'Carri Richardson case: under anti-doping rules, cannabinoids aren't banned outright, they're only prohibited in competition, from 11:59 p.m. the day before an event until the event ends.

The catch is that THC can show up in urine anywhere from one to 21 days after use, which can lead to a suspension even if the athlete no longer feels any effects.

Weed's pros and cons: what recreational runners should consider

For recreational runners who are also social cannabis users, it's important to think about how often you use, how much and how it hits you, says Professor Ryan Vandrey. Using cannabis occasionally but in big doses is a very different risk profile from an occasional small dose, he explains.

Using several times a day, he adds, could put you at risk of developing a substance use disorder. Vandrey also points out that smoking is harder on the lungs than vaping, and that edibles are easier on the lungs than either one.

Weed before a race: performance and cannabis use

Don't expect a PR if you decide to take cannabis before a big race. There are still plenty of unknowns about how weed affects athletic performance, but the evidence we have suggests you won't hit your full potential while you're high. So if you're trying to perform at your best, skipping cannabis before competing is the smart call.

Does weed make you lose muscle mass?

Smoking joints can make it harder to talk, swallow food and breathe. Why does that happen? Does weed weaken your muscles? And why does cannabis make you more uncoordinated?

Researchers at the University of Cádiz (UCA) in Spain have studied how cannabinoids act on the nervous system, and they've come up with some answers.

How cannabinoids affect motor neurons

Until recently, no studies had described the direct impact of cannabinoids on the neurons that control muscles, known as motor neurons. Scientists already knew about the effect on the higher central nervous system, but not on motor neurons.

Professor Bernardo Moreno and his team set out to investigate by looking at how cannabinoids affect the muscles of the tongue. That choice wasn't random: the tongue is a key muscle for breathing, speaking and swallowing food or saliva, and those functions seem to be altered in cannabis users.

Therapeutic upsides: why lower motor neuron activity can help

This dampening of neuron activity also has therapeutic potential. In people with conditions like multiple sclerosis, which involves muscle overactivity, the drop in motor neuron activity caused by cannabis may ease symptoms.

According to Professor Moreno, in these conditions, lower neuron activity can lead to an improvement in symptoms.