NEW YORK (CBSNewYork) — Some former convicts are sharing fitness secrets they learned behind bars to help people get into shape.

Behind a jail cell door on the Lower East Side, CBS2’s Alex Denis found a dimly lit gym without any equipment. Instead, there’s a prison-style boot camp taught by ex-cons.

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Coss Marte developed the ConBody program while serving time at Rikers Island for leading a multi-million dollar cocaine operation.

“This is actually the same corner we’re on, and it’s the corner where I started selling drugs,” he told Denis. “It went back to full circle.”

He shed 70 pounds in just six months inside his 9 foot by 6 foot cell.

“I took the same idea, same program from the prison yard and started taking it to the streets, local parks, and eventually here,” he said.

Class goers take off their shoes before they hit the mat for the body-weight-only class. A mixture of cardio, strength and partner work make up the 30 minute high-intensity classes.

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While getting healthy is the goal, ConBody’s mission is broader.

“Fitness is one of the binding components,” said instructor Sultan Malik. “We’re trying to break down stereotypes.”

They’re bridging the gap between formally incarcerated people and young professionals.

“I love the whole idea of it, having this whole business. You can see it in the intensity of some of the trainers,” Kristina Papilion said.

All of the instructors had a tough time getting hired after their time in jail. So the gym gave them the opportunity to move on and start over.

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If you want to try it out, classes cost $20.