It's a muscle endurance workout, certainly not an aerobic workout, even though your heart rate might rise during certain exercises, probably the leg and glutes ones. It will help you build strength, but maybe not much mass.
For a thin person to add muscle mass, what you really need is the Slow & Heavy series, where you take out all the momentum from the movement by adopting a slow 8 count rep. I am also an ecto, and this is the series that can add mass for me. You'll also need to commit to eating more, especially more protein to build that muscle, and to cut down on the cardio you do too, probably, no more than 3 per week. Then add on the Gym Style series with its heavier weights and slower counts. I personally plan to rotate between these two series for a while now, cutting out endurance style workouts for the upper body, but I shall still include them for the lower body.
Clare
