By Robert Schinetsky
The humble cannabis plant is garnering the lion’s share of attention in health and fitness circles now more than ever thanks to the increasing interest in all things CBD as well as the growing popularity and legalization of marijuana.
The plant has been inextricably linked to the bodybuilding culture for decades, and there’s no more defining image than that of the great Arnold Schwarzenegger puffing on a joint following his sixth Mr. Olympia victory.
This has led many lifters to wonder if marijuana, and/or THC (tetrahydrocannabinol — the psychoactive compound in weed), is helpful or harmful to the bodybuilding goals.
Both THC and CBD (cannabidiol) affect the CB1 and CB2 receptors of the endocannabinoid system.
The endocannabinoid system is a biological system that affects appetite, immune functions, sleep, pain sensation, temperature regulation, and many other processes in the body. In fact, both fat and muscle tissues utilize these receptors to varying degrees.  
THC can help assist with increased appetite and temporary pain relief.
Now, before we get into the specific effects of THC on muscle growth, it bears mentioning that there’s not a wealth of information on the subject matter. To be quite honest, the amount of human studies investigating the effects of marijuana on muscle growth are sparse, but there is some insight to be gleaned from the available body of literature.
Let’s start by discussing marijuana’s impact on the hormone most often associated with muscle growth — testosterone.
To date, there have been several trials investigating the effects of THC on T-production in humans and the results are mixed. In persons not accustomed to smoking weed, marijuana usage does lead to a slight, temporary decrease in testosterone production levels.
However, in regular tokers, weed seems to have little-to-no impact on testosterone levels.  But, it should be noted that regardless if you do take a ride with Mary Jane your sperm quantity and quality takes quite a significant hit.
As we mentioned, the CB1 receptors of the endocannabinoid system play a role in appetite regulation. The two primary cannabinoids of marijuana (THC and CBD) interact with the cannabinoid receptors, acutely increasing appetite.
If you’re looking to pack on mass, this may be a beneficial thing as it could help you get in those all-too-important muscle-building calories if you’re someone who struggles with poor appetite. However, this is really only beneficial if the munchies you get have you eating foods that are in line with your nutrition plan.
If smoking weed has you binging on pizza, ice cream, and all sorts of other high fat, high carb, low protein foods, well then you might get more fat gain than you had initially hoped. There’s also something else to consider — while marijuana usage in the short-term acutely spikes appetite, chronic use may actually decrease appetite.
Animal studies and epidemiological research has noted that prolonged use of marijuana may cause a decrease of appetite. Researchers believe this may be due to down regulation of CB1 receptor activity over time with continued cannabis use.
At the same time, it’s important to remember that some inflammation is needed for muscle growth to take place. Therefore, if hypertrophy is your main goal, you may not want to smoke any weed immediately following your training session as the anti-inflammatory effects of ganja could conflict with the necessary immune response following resistance-training needed to drive hypertrophy.
If you’re someone looking to experiment with marijuana, the one time you really don’t want to use it is immediately prior to your training session.
The reason for this is that cannabis negatively impacts performance through a variety of mechanisms, including: 
● Reduced concentration
● Decreased reaction time
● Impaired hand-eye coordination
● Lowers exercise capacity and stamina
A recent literature review on the effects of cannabis and athletes noted the plant offers no performance benefits. So, while it may help you feel less achy in the days after your training session, it’s not advised to take it immediately prior to or immediately following exercise.
Finally, there’s hasn’t been much research done to investigate the effects of marijuana directly on muscle protein synthesis in humans, but some animal studies indicate that chronic use of marijuana may disrupt mTOR signaling. 
There’s a lot of talk regarding inflammation these days, especially with regard to chronic disease. And while we might be led to believe that any type of inflammation is bad, the truth is that inflammation is needed for muscle growth.
The times when inflammation becomes a concern is when we’re chronically inflamed and the body never has a chance to return to normal homeostasis. Since the endocannabinoid system is involved in the immune system and inflammatory response, coupled with the fact that marijuana stimulates the ECS, it may help reduce some of the aches and pains caused by inflammation induced by resistance-training.
Therefore, if you’re someone who regularly pushes the envelope and tends to experience symptoms of overtraining, marijuana may help you to recover a bit quicker.
At the end of the day, more research is needed to understand the many ways weed affects bodybuilding. It reduces performance and inflammation in the short term, which means you won’t want to use it in the hours immediately surrounding your workout.
But, if taking at other points of the day helps you relax (reduce cortisol levels) and potentially eat more “good calories” it could support the muscle growth and recovery processes.
Until more research is done, we’re mostly left to speculate and glean insight from the current body of literature.
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