It's hard to be tactical when you're blinded by sweat and breathing like a train but boxers have to be fit enough to fight and think at the same time. In forcing durable John Ruiz to retire after a nine-round battering, and controlling Russian giant Nikolay Valuev for 12, WBA heavyweight champion David Haye is starting to prove he's a real threat to the heavyweight domination of the Klitschko brothers.

So how does he prepare for a big fight? 'The first round is the toughest because people rush you and you've got to be mentally switched on,' says Haye. Then it's a question of being fit enough to move better than your opponent and land more quality punches than he does.

'It's not enough just to have strong muscles. Boxing is an explosive sport and a boxer needs to increase the speed of contraction in his muscles to get a powerful punch.'

Rotational core strength is vital when producing punching force because knockouts come from movement as much as muscle, while rock-solid abs also soak up an opponent's body blows and pack an even bigger punch.

On the right, you'll find the workout he uses to get in knockout shape.

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