Trenebol is a pro-hormone. Most formulations were banned about a year ago. It is a very potent anabolic but with a major cost. It is very kidney toxic. It also causes acne, baldness, major gynecomastia (man boobs), testicular atrophy and high blood pressure. Most juicers who I have spoken with also claim that this is one of the anabolics with the most psychiatric effects. Mood swings and irritability are very common. In order to put on muscle mass you will need to eat, weight train and reduce your running. The downside, as you say is the potential for losses in speed and agility. Again, I would avoid this stuff. The short term gain is not woth the long term cost.