MIKE TYSON grew a 20-INCH neck by the age of 18 through a gruelling training technique.

Boxers train the neck to increase their ability to take a punch.

And Tyson, the youngest heavyweight of all time aged 20, was no different in the gym.

He used a technique called neck bridges, which involve a rocking back and forth motion.

Even current boxing stars like 33-year-old Anthony Joshua, who is preparing for his rematch with Dillian Whyte next month, have used the old school technique.

Tyson, now 57, remains one of the most celebrated fighters of all time, retiring in 2005.

He did make a shock comeback in 2020 and drew with fellow legend Roy Jones Jr, 54, in an exhibition bout.

Tyson, who looks unlikely to fight again, used to consume anywhere from 3,000-4,000 calories a day.

He started his day early with a three to five-mile jog around 4am.

After two hours he would come back, shower and go to sleep again until about 10am, when it was time for breakfast.

By midday he would be in the gym for his first boxing session, which was normally ten straight rounds of sparring.

Tyson then did three sets of Calisthenics, including squats, tricep extensions, pushups, shrugs with 30 kilos and neck crunches.

Afterwards, at 2pm the heavyweight would then have lunch before returning back to the gym for more boxing.

This consisted of sparring, bag work, pads with his trainer, and an hour on the stationary bike as well as more Calisthenics.

At 5pm, Tyson would do four more sets of the same calisthenics routine and then slow shadow boxing, focusing on just ONE technique.

Two hours later he would have dinner, before his final session of the day at 8pm, which was a light 30 minutes on the exercise bike for recovery.

Tyson was in bed at 9pm, watching TV or studying fight films before hitting the hay.