The muscles of the calf fuse to form the Achilles tendon which attaches to the heel. Because the tendon is very dense, strong, and has constant tension on it, the blood circulation in the tendon is limited. This makes repair from a minor tearing injury difficult.  Minor tears can lead to major tears over time due to overuse such as running sports or normal use with weak calf muscles. Specific soft tissue mobilization therapies attempt to gently move the tissue to encourage fluid exchange and release the fibrotic (scar) tissue, which the body has laid down to heal the original tears.