There are more myths and misconceptions about strength training than any other area of fitness. While research continues to uncover more and more reasons why working out with weights is good for you, many women continue to avoid resistance training for fear of developing muscles of Herculean proportions.

Other women have tried it and been less than thrilled with the results. “Don’t worry,” people say. “Women can’t build muscle like men. They don’t have enough testosterone.” This is, in fact, only partly true.

Many women, believing they wouldn’t build muscle, hit the gym with a vengeance and then wondered why, after several weeks of resistance training, their clothes didn’t fit and they had gained muscle weight.

The truth is, not everyone responds to training in quite the same way. While testosterone plays an important role in muscle development, the answer to why some men and women increase in muscle size and others don’t lies within our DNA.

We are predisposed to respond to exercise in a particular way, in large part because of our genetics. Our genetic makeup determines what types of muscle fibers we have and where they are distributed. It determines our ratio of testosterone to estrogen and where we store body fat. And it also determines our body type.