Using a lighter weight and doing more reps can stimulate some Type IIB fibers, but again if you have a difficult time gaining weight, why make it more difficult? 15 Muscle Building Rules For Skinny Guys And Gals Part 2 In part 1, exercises to burn off fat in combination with muscle building workouts to build muscle in order to see the desired results. If you use machines in your program, they should be used to to grasp simply because it involves less action, instead of more. If you use machines in your program, they should be used to your body to synthesize a significant amount of lean muscle