Children who are involved in athletics are at risk for sudden death from being hit in the chest, even with protective gear on.
This deadly blow usually happens when the child is hit directly over the heart, and can be delivered by a ball, stick, bat, puck, or human. It occurs when the blow interrupts the normal rhythm of the heart, causing it to go into an abnormal rhythm that does not allow the lower ventricles to pump properly, causing little or no blood to be pumped properly.
The answer for this is better protective equipment over the chest area, and education enough to recognize on the field when it happens and what kind of emergency treatment can be given immediately.