Usain Bolt has bet with coaches on when he'll get retirement 'belly'

Usain Bolt tells BBC Sport's Steve Cram why he will not go back on his decision once he retires after the London 2017 World Championships and how long his managers think it will be before he develops a 'belly'.

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Watch Usain Bolt: The Final Chapter on BBC One, Saturday at 13:15 BST (UK only)