A poster stated gluts. It starts further up.
* Work on your abs. Sprinters and all explosive movement athletes know. Explosive movement athletes do not only risk sore Achilles. Explosive movement athletes worry about complete Achilles rupture. You need to work on your abs as if you're a sprinter.
* Gluts. Your abs and glutes if muscular are your shock absorbers. If abs and glutes are not strong, a chain reaction will occur.
* If your abs and glutes are not strong and if your quads are too strong in relation to your hamstrings, risk of pulls & tears to hamstrings. Chain reaction continues.
* If hamstrings are not strong enough, your lower legs will have to over work. Chain reaction continues.
* Calf strain to Achilles rupture is not uncommon.
Build up to 250 sit ups a day like the sprinters.