People that tear their hamstring are probably not keeping their front knee bent. It should have the same feeling as stepping up onto the second step in a stair case. When you step onto the second step of a stair case, your front knee is bent and all of your weight is forward over your front knee as you step up, otherwise you'd fall backwards. Same goes for getting up on one ski with one foot out.When people tear their hamstring, they are usually pushing away from the boat, so their front leg is straight, and their body is bent forward so they are basically touch their toes as they are getting up. But since they can't touch their toes while flexing their hamstring, it tears it. Same thing could happen with both feet in, btw. But if your front knee is bent, your hamstring is not getting stretched, and it will be much harder to tear it.