Will my upper body grow bigger if I don’t train my legs is a question that resides in the head of many muscle constructors aspiring to develop a bro physique.

Surprisingly, or not, the answer is actually yes, but only to a certain extent.

The amount of muscle that your body can carry naturally is heavily dependent on your hormonal profile and frame. That’s why women look like women whereas men look like men. Ultimately, natural bodybuilders are heavily limited by their testosterone levels which regulate the construction of new muscle cells.

For the same reason, at one point, the body stops growing, and you can’t gain even 100 grams of actual muscle tissue to save your life.

Therefore, people obsessed with the upper musculature wonder:

“What If I only train my upper body and put all the muscle that I can build naturally there? Won’t my upper body grow bigger? Can I even do that?”

If you train mainly your upper body, the majority of the muscle mass that you add will be concentrated there. However, you can’t take all the leg muscle that you are not gaining on purpose and put it in your triceps for example. Only a small portion will go to the upper body.

One of the reasons behind this phenomenon is that when you focus on the upper body, all physical and mental recovery processes are concentrated on the top musculature. When you don’t train your legs, every drop of energy, time and potential goes upstairs.

Let’s say that as a natural you can build 30lbs of muscle mass during your career. If you train your body evenly, those 30lbs will be distributed in an equal ratio. If you don’t train your legs, some of that “lower body muscle” will actually be “transferred” upstairs, and your upper body will be bigger. The opposite is also true – if you train mainly your legs, you are essentially shifting the balance once again.

FAQ

But people say that my arms will get bigger if I train my legs!?

You don’t have to train your legs to build a big upper body. If you want to make a muscle bigger, you have to train that muscle specifically. You don’t expect to get better at math by learning Chinese, do you? The people in the gym who have big upper bodies and chicken legs prove that idea too.