A weak link in our bodies if we play a lot of sport is the Achilles tendon. The tendon attaches the very powerful calf muscles to the heel bone or calcaneus, so has too transmit a lot of force. The tendon don’t have their own blood supply that they have to rely on structures around the tendon for its nutrients and agents for healing if something goes wrong. And as people get older the tendon does degenerate. With all this going for it, no wonder we develop Achilles tendonitis when playing sport as often as we do. The achilles tendon is not only a metaphor for vulnerability, it is a factual problem.