AUSTRALIA: Working out could give pot users an extra high — but that may not be as much a boon as users might think.
The study, published in Drug and Alcohol Dependence, found that levels of THC—marijuana’s active ingredient— were higher by an average of 15% immediately after users exercised. And that could be enough to trigger a positive blood test and suggest that users got high more recently than they actually did.
Although it’s been known for years that THC is stored in fat and can sometimes cause positive tests weeks after a person has last smoked it, the study is the first to document that exercise can lead to a rise in its levels in the blood. The data may explain cases like that of a jockey who had to lose weight for a race and tested positive for cannabis long after he’d said he had last smoked it— and instances of users testing positive in rehab when they exercise and lose weight despite being abstinent.
The study involved 15 regular marijuana users who smoked an average of a joint a day and submitted to a blood test both before and after a 35 minute bout of moderate exercise on a stationary bike. They had been abstinent for at least 24 hours when they were tested.
The researchers also measured their body fat, by recording their body mass index (BMI) and found that changes in THC levels after exercise, which ranged from zero percent to 34%, increased with body fat. “People with larger BMI showed a bigger increase [and] very thin people [had] no effect,” says the study’s lead author Iain McGregor, professor of psychopharmacology at the University of Sydney in Australia. The rise was short-lived, lasting for less than two hours.
Was it enough to cause impairment? That’s not clear because the study wasn’t designed to measure intoxication. McGregor says, however, that it’s “theoretically” possible, and is conducting more research to answer that question.