Heel strike running is bad for the Achilles because it increases damaging compressive loads on the tendon. This happens because the further back you land on your heel when running, the more the knee-joint unbends and extends which in turn causes the upper body to shift backward. A result, there is a longer distance separation between the upper body and initial foot strike position, which causes the body to come to a crashing halt with the stance leg for a prolonged period of time, and out this, increases in compressive loading occurs on the lower leg as compared with forefoot running. Read more here!
