The term “high” in the context of physical activity refers primarily to the psychoactive effects of delta-9-tetrahydrocannabinol (THC), the main intoxicating compound in cannabis. The increasing social acceptance and legalization of cannabis have led to a rise in people combining its use with exercise. This trend raises important questions about the impact of THC on the body under exertion. This article examines the specific scientific effects and immediate safety implications of exercising while under the influence of cannabis.
How Cannabis Affects Physical Systems During Exercise
The acute introduction of THC stimulates the sympathetic nervous system, causing a measurable increase in cardiac activity even at rest. This effect is dose-dependent, typically elevating the resting heart rate by 20 to 50 beats per minute for up to three hours following consumption. When physical activity is added, the heart’s workload is compounded, creating greater strain on the cardiovascular system.
Exercise naturally increases heart rate and blood pressure, but THC exacerbates this physiological response. Studies indicate that THC can increase the heart’s output by 4% to 9%, leading to a higher rate pressure product, an indicator of myocardial oxygen demand. This means the heart requires more oxygen to perform its work under increased stress. THC-dominant cannabis has also been shown to alter cardiac function, such as reducing the septal isovolumic contraction time after exertion.
The respiratory system is also affected, though the impact depends heavily on the method of consumption. THC can act as a bronchodilator, which might make breathing easier in some individuals. However, smoking cannabis introduces irritants and carbon monoxide, which binds to hemoglobin and forms carboxyhemoglobin. This decreases the blood’s capacity to deliver oxygen to working muscles, counteracting any potential bronchodilation benefit during exercise.
Changes in Motor Skills and Athletic Output
The psychoactive properties of THC interfere directly with central nervous system functions that govern movement and balance. Research consistently shows that cannabis impairs psycho-motor skills, including coordination, stability, and fine motor control. This impairment stems from THC’s effect on brain regions responsible for motor planning and execution.
This disruption translates to a measurable delay in reaction time, making it harder to respond quickly to unforeseen events or adjust body position during complex movements. For activities that require precision, such as heavy resistance training or technical sports, this deficit increases the likelihood of error. Some data suggests that training under the influence can reduce work capacity output by as much as 25%.
Despite the objective decline in measurable metrics, many users report a subjective feeling that their workout is easier or more enjoyable. This is attributed to the way THC alters the perception of effort, seemingly lowering the intensity of the physical strain. Additionally, cannabis possesses analgesic properties that can dampen the sensation of pain, allowing a user to push past discomfort. Actual physiological metrics like maximal oxygen uptake and muscular strength are typically not improved and may even be negatively impacted.
Assessing the Immediate Safety Risks
Synthesizing the physiological and motor skill effects reveals clear and immediate safety hazards when combining cannabis use with physical activity. The most significant concern is the heightened risk of an acute cardiovascular event. Since THC significantly increases heart rate and blood pressure, adding the strain of exercise can overwhelm the circulatory system, especially in individuals with undiagnosed or pre-existing cardiac conditions.
The combination of an elevated heart rate from THC and the further increase from exertion places the myocardium under substantial stress, raising the risk of cardiac arrhythmias or myocardial infarction. Even in young, otherwise healthy individuals, the simultaneous use of cannabis and intense exercise may act as a trigger for a coronary event.
A second major safety risk is the increased potential for musculoskeletal injury due to impaired motor function. The reduced coordination, balance, and slowed reaction time make activities requiring precision, like operating heavy machinery or lifting weights, particularly hazardous. Furthermore, the altered pain perception can mask the early signs of an injury, leading a person to continue an activity that causes further tissue damage. The risk level is directly related to the complexity and physical danger inherent in the chosen exercise.