Muscle Building and Genetics
People often ask if it is easier for some people to put on muscle than others, and the simple answer is yes. Some people are genetically blessed with the ability to develop muscle and strength. Two individuals of the same sex and similar body type, could do the same workout and get very different results. It may seem unfair that someone seems to get more results for putting the same effort in, but unfortunately this is what scientists refer to as the 'Individual response'. Everyone one will respond differently to exercise than everyone else.
So when training it is a good idea not to look at what other people are doing in the gym, and instead focus on yourself. Look at where you started and where you are now in terms of your fitness.
The more you train, the more you will understand how your own body works. If you are looking to build muscle and are finding results are slow, then try and change your routine. Maybe look at your diet and increase the calories if needed. I often train clients who are looking to put on muscle mass, and they train very hard. Then I will get them to do a food diary for a week, and more often than not they are eating the wrong stuff, or not eating enough calories. In my personal experience too many weight lifters do not focus enough attention on their diet. Arnold Scwarzenegger once said that diet made up over 70 % of his success. And this is completely true. Arnold Scwarzenegger had a very strict diet regime that consisted of a lot of calories, but not just any calories but the right calories.