A handful of amateur and professional athletes admit to using marijuana to boost endurance or ease pain. But doctors caution combining cannabis and exercise.

Does getting high help you go the distance?

Marijuana and exercise don’t seem like an obvious combination — the resulting high can have a sedative effect or sap motivation. It also can induce appetite, which may be counterproductive if you’re trying to get fit.

When it comes to smoking marijuana, you’re much more likely to picture two dudes eating chips on a couch than a marathon runner.

But some fitness buffs are trying to change that.

Roger Boyd, a long-distance cyclist in the U.K., posts pictures of his travels — some 19,000 miles in the past two years — most of which he’s done while vaping. Among other places, the 37 year old has biked across Europe, India, Nepal, Australia, and New Zealand.

“I’ve always loved getting out on my bike and doing exercise while stoned,” Boyd told the Daily Star. “There is a negative perception about people who use cannabis compared to those who use alcohol, but alcohol is more harmful — there’s an imbalance there.”

High-profile athletes including Olympic gold medal swimmer Michael Phelps and NBA legend Kareem Abdul-Jabbar have also admitted to using marijuana.

But scientifically, does marijuana actually help or hinder when it comes to exercise?

The answer is hazy.

Anecdotally, some users report that using marijuana prior to exercise makes it more enjoyable or that they find they can push through the pain — pounding out a few extra reps for example — because of the high.

Some have pointed out that using marijuana before highly-repetitive exercises, such as running on a treadmill, can make it more enjoyable and motivate you to run for longer.

However, you won’t find any scientific studies to back up those claims — yet. Marijuana is still a Schedule I controlled substance, meaning that it requires significant money and dealing with a lot of red tape to seek approval for clinical studies.

For now, there’s little information available that directly examines marijuana and exercise together, but there are well-established physiological impacts of marijuana that can shed some light on the discussion.

While smoking, and for about an hour afterward, marijuana is known to increase heart rate, blood pressure, and subsequently heart attack risk. These effects are also dose dependent — meaning the more marijuana used, the greater the effects on the cardiovascular system.

But that in and of itself is unlikely to affect your workout — if you’re healthy.

“The consensus of the available data at this time indicates that cannabis use alone fails to present a significant health risk to otherwise healthy subjects,” Paul Armentano, the deputy director of NORML, told Healthline.

That position was also supported by Dr. Kenneth Mukamal, an associate professor of medicine at Harvard University who has previously authored studies on marijuana use and heart health.

“These effects could be dangerous during exercise, but the evidence mostly comes from people with existing heart disease,” he said.

So, depending on your current health, fitness level, and exercise goals, the risks of using marijuana are likely to change significantly.

“Our best guess is that marijuana smoking is particularly risky for people at high risk for heart disease. The higher one’s underlying risk due to age, blood pressure, diabetes, etc., the higher the potential risk from marijuana,” said Mukamal.

But even for healthy individuals, changes in blood pressure during intense workouts has the potential to cause dizziness and falling.

Beyond cardiovascular interactions, there are other health considerations to navigate when combining exercise and marijuana.

The euphoric and sedative-like effects of marijuana can also potentially have a detrimental, even dangerous effect on a workout.

“Marijuana could reduce coordination, which could make trauma more likely during exercise — but those issues haven’t been well-studied. For young people, however, those are likely to be more important issues than cardiovascular disease,” said Mukamal.

On the other hand, anecdotal evidence of marijuana allowing users to push through perceived physical pain during a workout does have some scientific merit. Cannabinoid compounds found within marijuana are known to affect perception of pain and discomfort.

Still, there’s little beyond anecdote to support the notion that marijuana use will actually give you a better workout.

“I’m not aware of evidence particularly supportive of such claims that either compound can be ‘performance enhancing’ in a conventional sense, though certainly there are athletes who report using cannabis in lieu of conventional painkillers or in lieu of alcohol or sleep aids,” said Armentano.