Steroids have grown in popularity due to their potential to boost endurance, strength, and muscular mass. However, studies have shown that steroids do not increase abilities, agility, or athletic performance. They are still drugs, and like any other drug, they can be harmful to use if used incorrectly or over a long period of time. Stamina is the ability to continue working out even when you've had enough for one day. It's being able to workout even when you're tired or have other obligations. Steroids don't help with this aspect of training. In fact, using them in combination with intense exercise is likely to cause injury because your body isn't ready for it. Strength is the ability to lift heavy objects. It has nothing to do with muscle size or number, but rather how much force you can apply with each contraction of your muscles. Again, steroids aren't going to help you here either. If anything, they'll only hinder you since they promote growth in certain muscles and not others, thus reducing your overall strength. Muscular mass is the amount of muscle tissue you have. More muscle means more weight that you can lift, so they certainly seem like they would help with this aspect of stamina.