a half to fifteen
He had practised everything that had any bearing on the strengthening of particular muscles or general agility . He had practised cart-wheels , hand-springs , back and front flips . He had worked with his neck at the chest-weight machine . He would walk on his hands to strengthen his throat , and his collars had grown in a few weeks from thirteen and a half to fifteen , and he could no longer wear his old shirts without splitting them . He made the mats in the Kingston gymnasium almost his home . His special studies were bridging and spinning . He spent hours on his back , rising to his two feet and his head and then rolling from one shoulder to the other and spinning to his front .