Gaining weight is easy for many people. On the other side, building lean muscle mass can be very hard, especially for people that have a fast metabolism, often referred as hardgainers.  Like many of the people in the world that are fighting with a body fat, there are also many people that are struggling to gain weight and build muscle mass. If you are one of those from the second group, continue reading this article. I strongly believe it will help you to gain a few pounds of muscle in a couple of weeks.  There are 3 main ways to make your muscles grow: 1. Force muscles to grow with the right training 2. Feed your muscles with enough healthy calories 3. Rest, recover your muscles, let them grow Those are only three general rules for muscle gain, now continue reading to learn five principles of muscle growth. 1. Multi-Joint Movements In order to gain muscle mass faster, you need to place e...