You have to remember that the key in gaining muscle mass is getting adequate rest and eating foods that are high in protein. When you exercise, you have to remember that you are injuring your muscles in a controlled way. When you injure your muscles, it will repair those injuries by adding more muscle tissues. And, in order for the muscles to repair itself, you need to let it rest. Eating foods that are rich in protein, such as beef and soya milk protein will be able to make the muscle repair process faster and also make it stronger.
This is why body building exercises have intervals when it comes to exercising each muscle group. It allows each of the muscle group to have enough time to repair itself.
It is also very important to remember that you should exercise every muscle group stated. Besides, you can't expect to have a great looking biceps, triceps or chest if the back can't support it. You also need to exercise your back in order for you to develop the chest, biceps, and triceps. Also, you have to exercise the shoulders in order for you to develop your arms. Everything is connected.
These are the things that you have to remember about body building or muscle gain. Always remember that resting is very important. Allow the muscles you exercised today to rest for two days. Get enough sleep and eat foods with high protein content and you will be able to gain muscle in no time at all.