Building Muscle. Ironically, training your muscles every day is one of the worst ways to build muscle. Muscles grow during the rest periods between sessions, says trainer and nutrition expert Damien Mase on the Muscle and Strength website. When you strength train, tiny tears form in the working muscles. It’s when you’re not working out that your body repairs this temporary damage by pumping extra blood into the affected muscles. This results in new tissue growth and therefore bigger muscles.