According to the study, published in the journal Drug and Alcohol Dependence, the main intoxicating agent in cannabis, Tetrahydrocannabinol (THC), often tends to get stored in the fat cells and the researchers were keen to find out what happens when the fat is burned up through physical work.
The researchers asked a group of regular cannabis users, who had abstained from smoking overnight, to go through a fairly intense 35-minute workout on a stationary exercise bike. After completing the workout, the participants were tested and the researchers found a substantial increase in blood THC levels which was accompanied by a rise in free fatty acids in the blood.
"These results have potentially huge medico-legal implications. Someone subjected to workplace or roadside drug testing after a visit to the gym could end up testing positive despite an absence of recent cannabis use", lead researcher Professor Iain McGregor said.