Nordic hamstring curl

Kneel with your ankles held by a partner or anchored under something heavy, then lower your body toward the floor as slowly as you can, catching yourself with your hands. The hamstrings, the muscles at the back of the thigh shown in the anatomy drawing, brake the whole way down, and that lowering strength matters for skiers: the hamstrings help resist the forward shear on the shin bone that loads the ACL, though whether weak hamstrings actually predict a tear is still unproven. It is very hard at first and leaves the backs of the legs sore, so start with three to five slow reps and add a few each week.