One mistake people make when trying to build muscle is following a traditional bodybuilding program training each muscle once a week.
To accelerate growth in non assisted people you must train frequently enough with the correct level of volume. Research suggests 50-100 reps per muscle group per week is optimal
How you reach them reps is important. If you do all them reps in one workout you will make very slow gains than if your broke them up into two sessions.
Doing this will allow you to hit each muscle more frequently which produces better results
Contact me if you need a program putting together for maximum muscle growth.