A common question that bothers many people aspiring to develop the ‘bro physique*’ is:
Will my upper body be bigger, if I don’t train my legs?’.
The answer is actually: ‘Yes, to a certain point.’
The amount of muscle your body can carry is heavily dependent on your hormonal profile. That’s why women look like women and men look like men. Natural bodybuilders are heavily limited by their testosterone levels which regulate the construction of new muscle cells.
That’s why after a certain point the body refuses to grow and you can’t gain even 100 grams of actual contractible muscle tissue to save your life. This phenomenon makes people obsessed with arms wonder:
‘What If I only train my upper body and put all the muscle that I can naturally build there. Can I do that?’
If you train mainly your upper body, the majority of the muscle mass you build will be concentrated there. Let’s say that as a natural you can build 30 lbs of muscle mass over your lifetime career.
If you train your body evenly, those 30 lbs will be distributed in more equal ratio depending on your genetics – some people have easier time building legs, while others have naturally larger upper bodies.
If you don’t train your legs, some of that ‘lower body muscle’ will actually be ‘transfered’ upstairs and your arms and upper body will be bigger. The opposite is also true – if you train mainly your legs, you are essentially shifting the balance once again.
But people say my arms will get bigger, if I train my legs!
While we advise people to train their legs and have balanced training programs, you don’t need to train your legs to have big upper body. In order for a specific muscle to get stronger you need to train that muscle, not another muscle. You don’t expect to get better at math by learning Chinese, do you? There are plenty of examples of people with chicken legs proving that you don’t need to squat for big arms.
*bro physique – the bro physique consists of having large upper body and tiny legs. That’s the most common physique seen in most commercial gyms.