Spend any time around serious meatheads and you’ll no doubt hear that too much cardio is counterproductive for muscle growth. In other words, doing excessive cardio robs you of potential gains.
While this notion has permeated throughout the fitness industry, particularly bodybuilding culture, for decades, is it actually rooted in science or is it yet another myth that continues to infest physical culture.
Cardio & Muscle Growth
Pros of Cardio for Muscle Growth
Cardio is beneficial for a few reasons.
For starters, it increases your daily energy expenditure, which means you’re burning more calories during the day. Typically, in order to gain muscle, individuals often embrace the “see food, eat food” mentality. And, while eating a surplus of calories is necessary for building muscle, there’s only so much new muscle tissue the body can synthesize over a given period of time. Consuming calories beyond that amount (typically 250-500 extra calories per day) just results in added fat gain. Doing cardio helps you “lean gain” whereby you can eat more calories, build more muscle, and gain less fat.
Secondly, cardio (as well as other forms of physical activity) improves insulin sensitivity, which can help your body more effectively utilize and store carbohydrates. This is particularly useful during mass-gaining phases to help keep blood sugar levels more favorable and make you look less “puffy” and bloated.
Thirdly, cardio is beneficial for cardiovascular health…hence its name of “cardio.”
Given these facts, why is it commonly thought that cardio can “rob” you of muscle gains.
Cons of Cardio & Muscle Growth
Well, there are a couple of potential reasons.
The first is that performing cardio increases your energy expenditure. For those with a big appetite, performing cardio is helpful. However, if you’re someone who struggles to eat a lot of food, every calorie matters, and doing extra movement during the day/week, means you have to eat that much more food in order to put your body in a calorie surplus and therefore gain weight and build muscle.
Second, performing too much cardio can actually hamper your ability to recover in between workouts. Remember, in order to effectively stimulate muscle growth, you need to create overload in your training. If you’re performing so much cardio that you’re chronically sore and fatigued and can’t create overload in your workouts (e.g. more reps, more weight, etc.), then you won’t grow.
What About Testosterone?
There’s been a long held belief that excessive exercise (namely cardio) can impair muscle growth because it lowers testosterone levels. This is primarily due to the fact that exercise is a stressor and stress exposure causes an increase in cortisol (a catabolic hormone).
Chronically elevated cortisol levels adversely impact testosterone levels (the body’s primary anabolic hormone). Therefore, it’s believed that performing too much cardio can elevate cortisol levels, reduce testosterone levels, and ultimately hamper hypertrophy.
But, how real is this?
Research notes that “men chronically exposed to training for endurance sports exhibit persistently reduced basal free and total testosterone concentrations.”
However…research to date shows that this exercise-induced low testosterone is “limited to men who have been persistently involved in chronic endurance exercise training for an extended period of time, and thus is not a highly prevalent occurrence.”
In other words, if you’re just doing a few short cardio sessions per week, in addition to your regimented resistance-training workouts, you really don’t have much to worry about. So long as you’re crushing your workouts, eating enough protein & calories, and getting ample sleep, you’ll still build muscle.
If you’re really concerned about the potential adversarial effects of cardio on your muscle gains, they limit your cardio to simply walking. Aim to hit a certain amount of steps per day (in addition to your weight lifting workouts), and that will be more than enough to build muscle and support cardiovascular health.
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