What are some good ways to build more muscle?
My dad is disappointed in me for not having enough muscle. Although the doctor says that I am on the slim side of normal and have more muscle than most girls my age, my dad thinks that I am not fit enough. I play tennis every day, go for runs, and play outside every night. I am looking for some ways to build more muscle to make my dad happy. However, I would prefer not to go to a gym.