Mike Tyson is considered to be one of the most vicious knockout artists in the history of boxing.During his active days, 'Iron Mike' had an intimidating presence inside the squared circle. Tyson's shredded physique also added to his larger-than-life personality. View this post on Instagram A post shared by Mike Tyson (@miketyson)But unlike most people, 'Iron Mike' did not achieve his ripped muscles by lifting weights. Instead, he used to do a calisthenic routine curated by his boxing coach Cus D'Amato.The routine involves the following exercises:1,000 to 2,000 sit-ups400 to 1,000 squatsNeck Bridges for half an hour500 dips500 shoulder shrugs500 push-upsThe reason why calisthenic workouts are so effective is because of the routine's ability to combine cardio as well as strength training.Mike Tyson did not want to leave prisonMike Tyson recently made an appearance on Michael Franzese Sit Down YouTube series. On it, he talked about various aspects of his life.At one point during the conversation, the 55-year-old talked about his time in prison. he revealed that he didn't want to leave the place at the time."Listen, I'm going to tell you, I did three years there and I didn't want to leave. I was hitting my teacher. I had a lady teacher there. She'd been there for 15...and that was my level, and I said 'why do I need to be out?' I am hanging out with these guys, watching fights... Sometimes you get caught up you know? I got caught up and I didn't want to leave for a second," Mike Tyson said.You can watch the full Sit Down episode below:Mike Tyson was found guilty of rape in 1992 and was punished with a jail term of six years along with four years of probation. 'Iron Mike' eventually served only three years in prison because he was released on the grounds of good behavior.'The Baddest Man on the Planet' then returned to action in August 1995 and defeated Peter McNeeley in the first round. Tyson eventually retired from professional boxing in June 2005 with a professional record of 50-6-2.