WATCH: Ajax manager tries to get involved in training, promptly snaps Achilles tendon

There's a reason that there aren't many 45-year-old professional footballers.

Once the big 4-0 is reached, bodies just don't move in quite the same way that they did when players were spry, flexible twenty-somethings. Frank de Boer was a terrific player in his time, becoming a club legend at Ajax and Barcelona, but he's not finding it easy to do what he once did. The current Ajax manager decided to get involved with a spot of foot volley at training this week and it did not end well. When stretching for a ball, de Boer snapped his Achilles tendon and had to be stretchered off the training pitch, only to be replaced by assistant manager Dennis Bergkamp. Let this be a cautionary tale to all managers out there. Stick to the tactics board.