The establishment of the World Anti-Doping Agency (WADA) and subsequent penalisation of athletes for cannabis use has prompted greater scrutiny of the effects of cannabis effects on athletic performance (Hilderbrand 2011). Docter et al. (2020) reviewed the epidemiology of cannabis use in student and elite athletes, finding that approximately one in four had used cannabis in the past year and that athletes commonly believed that cannabis would negatively affect their performance, consistent with research findings suggesting that cannabis is non-ergogenic and potentially ergolytic.
While Δ9-tetrahydrocannabinol (THC) is considered the main psychoactive constituent, cannabis contains hundreds of potentially biologically active chemicals, some of which may provide synergistic or “entourage” effects, and some revealed less potent psychotropic effects, including cannabidiol (CBD) (Russo 2011). McCartney et al. (2020) examined the potential effects and applications of cannabidiol (CBD) in sports, based on clinical trials, animal models and in vitro studies, finding that further research is needed to determine if CBD conveys analgesic, anti-inflammatory, anxiolytic and neuroprotective benefits; protection against exercise-induced gastrointestinal damage; or enhanced bone fracture healing. Huestis et al. (2011) proposed that anxiolytic, euphoric, and perceptual enhancement effects of cannabinoids may provide advantage in specific sports such as archery and shooting.
Maximal oxygen uptake (VO2Max) is a gold standard measure of cardiorespiratory fitness and a strong predictor of an athlete’s ability to maintain peak performance (Bassett and Howley 2000). Peak work capacity (PWC) or ‘peak power’ estimates the maximum power a person is capable of outputting. In modern studies, peak power is usually measured using the Wingate methodology. Kaminsky et al. (2014) suggests that PWC measures of overall exercise tolerance better, whereas VO2Max is more specific to cardiovascular conditioning. Blood pressure (BP), heart rate (HR) and lung capacity (often measured by one-second Forced Expiratory Volume; FEV1) are secondary measures of interest that detect isolated components of aerobic performance. Elevated BP decreases exercise performance (Mazic et al. 2015), HR is a key factor in cardiac output until intensity nears VO2Max (Munch et al. 2014) and lung capacity restricts oxygen intake.
To determine if scientific grounds exist for regarding cannabis as a potential doping agent, Trinh et al. (2018) performed a systematic review, finding only three studies fitting their criteria, published between 1975 and 1986 (Maksud and Baron 1980; Renaud and Cormier 1986; Steadward and Singh 1975). These studies show a small ergogenic effect on FEV1 via bronchodilation, and an opposing ergolytic effect on anaerobic performance, as measured by PWC. The bronchodilation finding is consistent with Tashkin et al. (1975), in which bronchospasm was induced in asthmatic patients via methacholine inhalation and via exercise on separate occasions. Participants were given either a 2% THC joint or placebo once bronchospasm was achieved, those receiving THC rapidly recovered in both conditions. Kennedy (2017) suggests that while THC could benefit asthmatics, common asthma medications are more effective and demonstrate fewer side effects.
Comparing older studies presents difficulties, as PWC measurement methodologies were inconsistent, using different workloads, increments and intervals. VO2 measures are more comparable, as the gas analysis is less dependent on the exertion task. Past design and reporting standards present further challenges, small samples were common and the THC content of cannabis used was typically around 2%, much lower than commonly imbibed varieties. Avakian et al. (1979) compared the exercise performance of six chronic cannabis users without cannabis, after cannabis (1.54% THC) consumption, and after smoking a placebo. No significant effects were found on VO2, or physiological measures, except heart rate, which was higher during rest, exercise and recovery phases in the cannabis condition. Renaud and Cormier (1986) compared healthy adults with and without cannabis (1.7% THC) in a crossover trial, observing slightly greater VO2 during the cannabis condition at 60–80% of maximum exertion, but no significant difference at maximum exertion. Decreased Physical Work Capacity was observed in the cannabis condition, likely the result of prematurely achieving maximum HR due to cannabis induced tachycardia.
Acute and chronic effects of cannabis consumption differ substantially. Acute use of cannabis in non-users induces tachycardia, however, as shown by Benowitz and Jones (1975), this effect rapidly fades with regular consumption of cannabis. Benowitz and Jones also observed decreases in resting HR and BP, and decreased BP elevation in response to exercise. These effects increased with dosage, and during the early maximal dosing phase were so pronounced that two of the twelve male participants were unable to complete exercise tasks due to dizziness. Hollister et al. (1968) acutely administered either THC or a synthetic analogue in men aged 21 to 44 and observed similar drops in BP, elevated HR, and impaired strength (measured on a finger ergograph). Hollister et al. found that dizziness was common, and two of the 29 participants experienced syncope when attempting to stand. In addition to tachycardia and hypotension, Goyal et al. (2017) describe an association between cannabis use and acute cardiovascular events including arrhythmias, arteritis and myocardial infarctions. Goyal et al. report an escalated risk when cannabis use is combined with regular cigarette use and/or intense exercise. Kennedy (2017) systematically reviewed past research on the relationship between cannabis and exercise, including those within patient populations, noting that in angina patients, exercise-induced angina occurs more quickly due to cannabis-induced tachycardia.
Gillman et al. (2015) comprehensively reviewed the literature on cannabis and exercise, including interactions with the endocannabinoid system, noting the absence of studies identifying the psychological impacts of cannabis on athletic performance. YorkWilliams et al. (2019) sought to resolve that lack by surveying adults in “legal” states regarding the use of cannabis with exercise. The most endorsed statements were that enjoyment of exercise and recovery from exercise were enhanced. Substantially fewer endorsements were seen for performance and motivation. Lisano et al. (2019a) also surveyed cannabis users about exercise-related use, finding the most reported reason was pain management. In contrast to YorkWilliams et al., 77% of Lisano, Phillips, et al.’s sample felt that their performance was enhanced by cannabis, with many respondents suggesting focus or “flow” effects as their reason for using before or during exercise. Zeiger et al. (2019) surveyed athletes ranging from recreational to elite and found an overwhelming majority of participants reported calming, pain reduction, and sleep aid effects from cannabis. Gillman et al. recommend exploration of the endocannabinoid (eCB) system, which is likely linked to the “runner’s high” experienced by many athletes, previously attributed to endorphins (endogenous opioids). The eCB system is proposed to affect exercise motivation through activation of dopaminergic reward pathways and may be subject to modulation by exogenous cannabinoids, however, it is unclear whether such modulation would enhance or diminish endogenous effects, or if motivational effects differ between acute and chronic use.
This systematic review aims to complement existing reviews, which primarily report on acute effects of cannabis use, by reviewing the available data on (1) the effects chronic cannabis use has on fitness measures; (2) any effects chronic cannabis use has on physical activity levels; (3) what effect chronic cannabis use has on actual sport performance.