The Hypertrophy Accelerator can't be picked when you level up. It can be bought from Doctor Usanagi in the New Vegas medical clinic for 4000 caps, designed to enhance the muscle mass of the person it's installed in by acting as an automatic version of steroids, forcing the body to make a large amount of muscle mass.
Behind the scenesEdit
Hypertrophy is the condition where the volume of tissue increases as a result of a growth in the size of the component cells. In this case, the growth of musculature by enlarging the muscle cells is referred to as 'muscular hypertrophy'.