China's defending champion withdraws from 110m hurdles
Liu Xiang's Olympics came to a premature end after the reigning champion was forced to pull out of the 100m hurdles with an Achilles tendon injury.
Xiang, 25, became the first Chinese male athlete ever to win an Olympic gold medal in Athens and the home crowd had high expectations of a repeat performance.
However, after another athlete produced a false-start, Xiang quickly pulled-up and was visibily experiencing a great deal of pain and was unable to continue.
For runners and hurdlers in particular, Achilles tendon injuries are incredibly common. The Achilles tendon is the tissue that connects the heel to the muscles of the lower leg and hurdlers often damage this area.
Hurdlers like Liu Xiang put tremendous strain on their Achilles tendons, particularly when accelerating up to full speed and then springing over the hurdles.
Watch Liu Xiang pull-up after a false start in the video below: