There is a strong tissue that encases each muscle called fascia. It acts to contain the muscle bindles and fibers like a water balloon acts to contain the liquid. In many cases an athlete reaches a point where growth is nonexistent due to the fascia balloon being too full thus blocking further growth or expansion of the muscle. Like a water balloon fascia can be stretched. By injecting a SEO directly into a muscle belly the total volume of the muscle mass is increased resulting in a stretching effect upon the fascia. More room means a greater potential for growth.