Be carefull what you are asking for here. As the bones get stronger what becomes the weak link? Soft tissue damage can take much longer to heal and often results in reduction in range of motion and improper alignment of joints. I would guess that there are several people in the group, myself included that would trade a grade 3 shoulder seperation for a broken collar bone any day of the week. Knee surgery vs fractured tibia/fibula? I would choose streaching over jumping for injury prevention. I wonder how they got the mice to jump in one of the studies.