Im 15, 160 lbs, 5 ft 11. Recently I realized how friggin strong my legs have become... i used to only be able to leg curl 140 lbs a month ago, now im doing 3 sets of 280lb for 10 reps. big improvement in my opinion. Anyways, i was wondering that since my legs and calves are so improved, why is it that i cant run sprints very well? i dont seem to have the explosiveness of sprinting, but im great at long distance stuff, especially hiking up mountains for days on end during hunting trips. How can i improve my sprinting/explosiveness, and what workouts are associated with those?