Cannabis does not appear to make you weaker in terms of raw muscle strength. Studies measuring grip strength and maximal force output after smoking weed found no reduction compared to sober performance. The picture gets more complicated, though, when you look at endurance, heart rate, and the indirect ways cannabis could affect your workouts over time.
What Happens to Strength When You’re High
The most direct test of whether weed makes you weaker is simple: measure how hard someone can squeeze or push after smoking, then compare it to their sober baseline. When researchers did exactly this, having participants smoke a moderate dose of THC (about 18 mg), they found no effect on handgrip strength. A separate study measuring knee extension force actually found a slight increase in force output after smoking cannabis, though the result wasn’t statistically significant at higher THC doses.
At the nerve and muscle level, this makes some sense. THC appears to amplify excitatory signals to motor neurons, the nerve cells that tell your muscles to contract, while dampening inhibitory signals. In animal studies, THC nearly doubled the strength of excitatory inputs to motor neurons (a 188% increase) and reduced inhibitory signals by about 65%. The net effect is that THC may actually make it easier for your nervous system to recruit muscle fibers, not harder. This doesn’t mean weed is a performance enhancer for lifting, but it does mean the drug isn’t directly weakening your muscles’ ability to produce force.
Where Performance Does Suffer
The real issue isn’t strength. It’s endurance and sustained effort. Cannabis reliably raises your resting and submaximal heart rate, a response called tachycardia. Your heart beats faster even when you’re not working that hard, which creates a problem: your body reaches what feels like a high-effort heart rate zone sooner than it normally would. In one well-designed study, participants who smoked cannabis before cycling reached exhaustion significantly faster than they did under placebo conditions.
Here’s the nuance, though. That gap between cannabis and placebo performance shrank as intensity increased. At workloads above 80% of maximal effort, there was no measurable difference between the two groups. Oxygen consumption, breathing rate, and heart rate at peak effort were all identical. So if you’re doing short, heavy sets in the gym, cannabis likely won’t hurt your output. If you’re running, cycling, or doing anything that requires sustained moderate effort, the artificially elevated heart rate can cut your session short.
Cannabis and Testosterone
An early and widely cited study from the 1970s reported that heavy cannabis users had lower testosterone levels, and that the drop was dose-dependent. This finding fueled decades of concern that weed could impair muscle growth by suppressing the hormone most responsible for building it. But larger, more recent studies haven’t confirmed this.
A study of over 1,200 men found that testosterone levels were actually higher in cannabis users than non-users. Another involving more than 1,500 men found no difference between users and non-users, though men who had used cannabis more recently tended to have slightly higher levels. The largest cohort study to date, examining thousands of men at a single urology center, found that average testosterone was modestly higher in cannabis users (13.4 nmol/L versus 12.6 nmol/L), but this association disappeared entirely after adjusting for age, weight, and other factors. The conclusion: cannabis does not appear to negatively impact testosterone levels in any meaningful way.
Body Composition Over Time
If weed made people weaker and hormonally compromised, you’d expect chronic users to carry less muscle and more fat. The opposite pattern has shown up repeatedly. Research from UC Irvine found that animals exposed to THC during adolescence, then taken off the drug, had reduced fat mass and increased lean mass compared to controls. They were also partially resistant to obesity and blood sugar spikes. Several of these same features, lower body fat and leaner builds despite higher calorie intake from “the munchies,” have been observed in human cannabis users as well. The mechanisms aren’t fully understood, but the data doesn’t support the idea that long-term use erodes your physique.
Recovery and Inflammation
CBD, the non-psychoactive compound in cannabis, has shown modest benefits for exercise recovery. One study found that 60 mg of CBD supplementation reduced two key markers of muscle damage, creatine kinase and myoglobin, within 72 hours after exercise. These are proteins that leak into your blood when muscle fibers are damaged during hard training, so lower levels suggest less damage or faster repair. This doesn’t mean smoking a joint helps recovery (smoked cannabis delivers mostly THC, not meaningful amounts of CBD), but isolated CBD products may offer a small edge in bouncing back from tough workouts.
The Practical Tradeoffs
Cannabis won’t reduce your one-rep max or make your muscles physically weaker. It won’t tank your testosterone. It may even support leaner body composition over time, though the reasons for that aren’t clear yet. What it will do is raise your heart rate, which can make cardio feel harder and end sooner. It can also impair coordination, reaction time, and focus, none of which show up in a grip strength test but all of which matter when you’re under a loaded barbell.
The World Anti-Doping Agency prohibits cannabinoids during competition, but not because they enhance strength or power. The ban is based on cannabis meeting criteria related to health risk, potential to enhance performance through reduced anxiety or pain perception, and violation of the “spirit of sport.” CBD was exempted from the prohibited list in 2019. The distinction matters: the global authority on athletic doping doesn’t consider cannabis a strength-boosting drug.
If your concern is whether regular use is silently eating away at your gains, the available evidence says it isn’t. If your concern is whether getting high before training is a good idea, the answer depends on what you’re doing. Heavy, short-duration lifting is unlikely to be affected. Anything requiring sustained effort, balance, or sharp focus will take a hit.