There are a few important factors that determine how fast and well you can add on lean muscle mass.
A good appreciation of these factors can make the difference between significant results in your bodybuilding efforts and frustration.
The first and probably the most critical is your body type.
Body types differ from person to person, and so does the rate of individuals' muscle growth and development.
The other important factor is the bodybuilding program you adopt.
A program that works just fine for one person and helps that person get great results, may not work for another person.
Before you begin bodybuilding to add on lean muscle, you would do well to determine the type of body you have.
If you find that you can easily add on weight and muscle, then you would probably have no problems finding an appropriate workout regimen.
You could just get one from a magazine or inquire from other bodybuilders at the gym.
Most of these regular programs are made for those who can build muscle easily, so they should help you too.
If however, you find it difficult to add on weight and increase muscle, then you may be a hardgainer.
You would have to pay closer attention to your workout regimen, and choose it much, more carefully.
An appropriate workout regimen for you would be one that takes cognizance of the fact that a hardgainer's body requires much longer periods for recovery and hence for growth.
A program suited for a hardgainer should make provision for adequate rest between workout sessions to allow for adequate recovery and to avoid injury.
Working out with incompletely recovered muscles would do more to hinder the growth of your muscles.
If you are a hardgainer, you should not use a program that involves more than a few hours in the gym weekly.
A good rate would be three or four one-hour sessions weekly.
With this, sufficient time is allowed between workouts for rest, and is still adequate for significant muscle growth.