Like thoroughbred horses. I remember kids working out with our s/c coach and they would never last. The secret was kids and youngmen have to work out doing whole body movements. Bearcrawls, squatthrusts, there are a lot more that have come out. Oh by the way our strength coach was a body builder with little football background. These kind of stories are 20- 40 years old. Anaroebic training has gone by the wayside, even though it still has its place. You can be over or undertrained and still have injuries. But I will say that there are better, best , and below average S/c programs.Watch sprints in olympic trials and you will always see hammy pulls.???