Recent studies in the UK have found that the number of head injuries of riders with helmets has gone down but the rate of neck injuries is up. Believe it or not, your reflexes are quite sharp and genetic. Most instances are for the body to protect the important parts. The hands, shoulders and knees get the damage while protecting the head and neck. Tuck and roll is almost instinctive. The real worries and damage is from the resulting trajectory of the bicycle. Like ski's, snow boards, skate boards and water ski's, bicycles always find their way back to the rider after departure to inflict even more damage.