The two sports that would be best suited to Alex would be tennis and gymnastics.
Both sports involve using the entire body and are physically demanding. Tennis uses legs, feet, hips to stand and run around the court while the arms, hands and shoulders are used to carry the racket and hit the ball back to the opponent with a significant amount of force. Physical strength is a key factor to playing Tennis. Gymnastics again uses the whole body and takes a lot of physical strength to push your body to jump, run, balance, spin, swing and so forth.