Ultra-marathoner Avery Collins is one of the many athletes who have been coming out in support of cannabis use in sports. He claims to smoke before each of his own races saying it helps increase his concentration.

"It allowed me to be very present and not to worry as much about overall times and what’s going on with the run,” Collins told The New York Times.

“You have two different reasons potentially for using cannabinoids,” said Marcel Bonn-Miller, an adjunct assistant professor of psychology in psychiatry at the University of Pennsylvania Perelman School of Medicine who also works with pharmaceutical companies and nonprofit groups doing cannabinoid research. “One is to enhance your ability to train. The other is recovery oriented.”

Many runners have been using cannabis to achieve both ends. So it's not surprising that the American Journal on Addictions says cannabis is now the second most widely used drug among athletes after alcohol. Even the World Anti-Doing Agency (WADA)—whose strict code is used by the International Olympic Committee and International Paralympic Committee—allows for recreational cannabis use now. In fact they raised the amount of THC that can be found in athlete's drug tests before dismissal significantly higher than numinous other sports organizations such as the NBA and MLB.

But, Bonn-Miller says research on athletics and cannabis is sparse.

“Most of the work is, at the moment, observational, looking at people who use and don’t use and comparing them,” said Dr. Bonn-Miller, who is conducting studies on the use of cannabinoids among former professional football players. “There hasn’t been a whole lot of funding for this.”

But not everyone is convinced that cannabis aids the recovery process or improves concentration. 

“It is generally considered that THC won’t improve aerobic performance and strength, and my review confirms that impression,” says Dr. Michael C. Kennedy - a cardiologist, clinical pharmacologist and associate professor at the University of New South Wales. 

“It will not make you faster, it may slow you down and certainly should not be used if there is any possibility of heart disease," Kennedy added in reference to studies that suggest cannabis use is linked to heart disease.

Cannabis-derived CBD is also commonly used as a post-exercise treatment as it has been shown to have anti-inflammatory properties.

“It lowers the amount of many, many pro-inflammatory cytokines—things that our body makes naturally in response to any inflammation response,” said Dr. Orrin Devinsky, director of the Comprehensive Epilepsy Center at NYU Langone Health, who is studying the use of CBD to treat epilepsy.

If nothing else runners like Scott Dunlap sees cannabis use as a nice way to unwind after a big race. He doesn't understand why that's any different that having a beer at the end of the day, except a lot of races provide the beer.