No, they don't. They just have a high coefficient of restitution. If it had a lot of energy then the ball wouldn't bounce. There would be a collision, the ball would slow down, but it would not bounce if it carried a considerable amount of energy like, say, a car.
Normally I would agree, but I can assure you that no one got injured on any way of those balls. They make you fly violently, but the inpact does not hurt since it's somewhat just trasfering the energy from the ball to your body pretty smooth and bunchy, instead of, with a normal ball would just smack your head in.
Ofc, it might hurt a little, but what do you expect when you hit the ball with full force right into the wall and back into your face?