Rationale: Recent changes to cannabis laws have contributed to increased use, including among athletes. Athletes report using marijuana to enhance athletic performance, although some research shows negative impacts of cannabis on athletic performance. (Peretti Patel et. al 2003). This study asks whether there are any effects of THC on athletic performance.

Method: There were 15 participants in this study, all 19 years old, regular cannabis users, and on cycling or rowing teams. They did not use other recreational drugs. Subjects participated in 4 experimental sessions that took place at least 3 days apart, and were abstinent from cannabis use for at least 2 days before each session, confirmed by urinalysis. Participants were cannabis-free for the first session, and then were tested following intake of: THC predominant cannabis smoked from a pipe; THC predominant cannabis from a vaporizer; and CBD prominent cannabis from a vaporizer. At each session, researchers measured heart rate and power output during low and high-intensity cycling.

Results: Either smoked or vaporized THC exposure prior to exercise decreased power output, while CBD had no effect on power output. The study also showed increased heart rate during low intensity exercise following THC.

Meaning: These data suggest that THC use decreases exercise efficiency, and may compromise athletic performance.