The Link Between Exercise and THC | Research Results

The Link Between Exercise and THC

The World Cup has just begun, hence, why the topic of this article is related to sport.

At the end of 2017, WADA (World Anti-Doping Organization) published a new list of prohibited substances and methods, which has been enforced since the beginning of 2018. The deletion of cannabidiol from this list turned out to be a novelty, so CBD is no longer a forbidden substance !!!

However, extracts obtained from cannabis may contain, in addition to CBD, also some amounts of THC, and the latter still appears as a prohibited substance during the competition. Besides, not only THC itself but also natural cannabinoids (hashish, marijuana), synthetic cannabinoids, i.e. derivatives of delta 9-tetrahydrocannabinol and cannabinomimetic.

The use of cannabinoids in sport

The main objective is to improve mood and help with relaxation. Athletes such as Michael Phelps, Usain Bolt and Ebie Smolar have used CBD for such reasons. Prohibited cannabinoids were detected in samples of test results from these athletes.

The long-term effect of hemp ingredients

The object of interest of the Australian scientists team was to determine the long-term effect of hemp ingredients, especially tetrahydrocannabinol (THC), on the human body.

THC is known to be a lipophilic compound that easily dissolves in fat.  Where is THC most in the human body? Of course in adipose tissue. Previous studies have shown that fat tissue is a good store for lipophilic compounds, including THC, which can be stored in it for at least 28 days. However, for those who regularly use cannabis and in large quantities, tetrahydrocannabinol can stay there much longer, up to six months.

Professor Iain McGregor of the Chair of Psychology at the University of Sydney has repeatedly heard about cases whereby the presence of THC and its metabolites were detected in the blood and urine, even though they have not declared the use of cannabis in recent times.

The link between exercise and THC


Professor McGregor hypothesized that as a result of intensive training, after running out of carbohydrates, the body starts to use body fat as a source of energy, which could release the stored in THC tissue back into the bloodstream. This explains the reason why THC could still be detected in the blood and urine even after 28 days of consuming marijuana.


To determine the accuracy of his hypothesis, Professor McGregor and his team of researchers decided to first conduct experiments with animals. After administration of THC to rats, they observed a decrease in the level of this compound in the blood. The animals were then given a 30-minute training. Blood tests, carried out immediately after the end of the exercise, showed that the level of tetrahydrocannabinol increased.

Human studies

The next step was to conduct research on people. For this purpose, 14 volunteers were recruited who smoked marijuana daily (an average of 3-4 grams of marijuana per week). Some people were told to have breakfast before the test and others were told to come on an empty stomach before the test. As part of the experiment, each volunteer performed a 35-minute physical exercise on a cycling exercise. Blood samples were taken before, and two hours after the end of exercise to measure the level of THC in the blood.

The researchers found that the level of tetrahydrocannabinol increased in all volunteers after exercise, and in some people were high enough to get a positive result in the drug test.

“After physical exertion, someone undergoing a drug test, i.e. in the workplace, can get a positive result despite a long period of abstinence from cannabis,” 

The researchers also found that people who are overweight or obese for whom the calculated BMI index reaches a higher value also have the highest levels of THC in the blood.

The more fat you have in the body, the larger the storage for a lipophilic compound such as THC
Professor McGregor

Wong et al

In addition to physical exercise, slimming and stress can also cause the need for the use of fat reserves by the body, which in turn may increase the level of THC in the blood. However, the results of the research conducted by Wong et al showed that 12 hours fast did not increase the concentration of tetrahydrocannabinol in the blood plasma, but, as the researchers point out, perhaps the fasting period was too short.

“Research shows that “a positive drug test does not necessarily mean that you’ve been smoking marijuana lately,” he says.

“Someone who has been tested for a drug test after a minor car accident may be wrongly accused of being under the influence because factors such as strong stress can cause the use of fatty reserves and the release of THC into the bloodstream”— emphasizes the professor.

The researchers did not say the last word and plan to repeat the study with more participants.


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