Children tend not to limit their jumping to stay in control. The springs in the trampoline conserve energy so that a series of low-energy jumps will build up a tremendous amount of kinetic energy which must be dissipated one way or another. Acceleration of up to 6 G's is possible from the spring-loaded trampoline bed which can temporarily alter the child's balancing reflexes. Children tend to jump in groups on the trampoline which gives them the chance to collide with each other. Larger children jumping out of sync with smaller children may result in injury or ejection of the smaller child from the mat.
Trampolines can cause severe injury in children.
The most dangerous part of the trampoline is the mat itself. This is where children tend to fall and get hurt. Ejection injuries, while severe, are much less common. Parental supervision is paramount in limiting risk to children on trampolines. The best thing the parent can do is keep the jumper in control and to limit the jumpers to one at a time on the mat.