How exactly does lifting weights build muscle?

How does weight lifting help muscles get bigger? When muscles are asked to do something more than they are accustomed to, they suffer minor ruptures. This occurs during weight training. The reason for soreness after or during a workout is due to micro-tears in your muscles. These mini-injuries are repaired while the body is resting. The repaired muscle is slightly bigger than before, and better able to handle the stress that caused the initial tears. This is why doing the same routine over weeks or longer gets easier and easier. You should not do exercises that use the same muscles two days in a row because they need about 48 hours or so to repair. It is fine to workout different muscle groups two days in a row, but you would not want to do the same muscles two days in a row. This is because when you lift you tear the muscle fibers and they need time to repair. If you workout the same muscles the following day you can tear them even more which can lead to injury. Some experts also say that it is alright to train your abdominals daily, others disagree. If you feel that you can complete the quality of abdominal exercises daily, slowly begin increasing the intensity and repetitions.