The Pain of Growing Ki Hearts

The process of growing Ki Hearts was just as hard as Howard thought, but a lot more painful. A Horned's biology was different from a normal human's biology in that there were 60 meridians instead of the basic 12 main meridians. 

10 of these main meridians were located in both arms, 20 in the heart region, 20 in the leg region and 10 in head. However, most people only ever created roughly 5 Ki Hearts in one of their arms before they would give up. It was simply too difficult to endure the pain of supplying Ki to your Ki Hearts.