Watch: World heavyweight champion Anthony Joshua lifts weights with his teeth

A close up of Joshua's face shows the strain he is putting in while lifting the weights. Photo / Instagram

Anthony Joshua may not have been seriously tested in the ring during his professional career but he is certainly putting the hard work in outside it.

With just over four days to go before Joshua's second defence of his IBF world heavyweight title against Eric Molina - the British boxing star has released training footage of him lifting weights with his TEETH.

Joshua released the footage on social media on Monday and it shows him tying two kettlebells to a towel and then sitting on the edge of the ring and putting the towel in his mouth and lifting the weights.

Joshua posted the clip - which is sure to strengthen his neck muscles - with the caption: 'Old school tekkers'.

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Joshua has a perfect professional record of 17 wins from 17 fights - all by knock out - and he will be looking to continue that record against American Molina at the Manchester Arena on Saturday.

Joshua has only been past the third round twice in his career, once against Dillian Whyte and again in his last fight against Dominic Breazeale, which both went into the seventh round - but AJ says he has trained and is fully prepared to go the distance if needed.

Speaking on Sky Sports' The Gloves Are Off, Joshua said: 'I can predict it going 12 rounds, and not getting hit. That should be the mindset I'm in.'

Molina, who has 25 wins from 28 fights, put up in impressive yet ultimately unsuccessful fight against WBC champion Deontay Wilder in June last year and Joshua is looking forward to seeing how he compares against the only opponent that both fighters will have fought.

He added: 'I don't want to make this fight about Deontay Wilder.

'[Molina] put up a hell of a fight because Wilder is supposed to be this one-punch knockout artist who's been in the game for eight years.

'It will be a good comparison in the back of my mind, God willing I get the job done. But that doesn't make me a better fighter than Wilder, or him a better fighter. Everyone has their own attributes.'