Jail superintendent SP Yadav said that Janak, a software professional, was lodged in Dasna jail in February 26, 2013, in a dowry death case.
Janak's wife had died under mysterious circumstances in February 2013. A daughter was born to the couple.
Janak, who was lodged in barrack number 7-B, used to perform exercises daily with the other inmates, said Yadav.
This morning, he fell and sustained head injuries while performing an exercise using iron bars, he added.
Doctors at the jail hospital referred him to the district hospital where he died during treatment. Police have sent the body for a post-mortem, Yadav said.