Fitness trainer Rakesh Udiyar, who had worked with superstar Aamir Khan in "Dangal" and Bollywood star Salman Khan in "Sultan", is currently working with actor Ram Charan for the upcoming Telugu action-thriller "Dhruva", said a source."For the introduction song 'Dhruva Dhruva', which will be shot uniquely in the coming week, he (Ram Charan) was required to attain a certain physique. Hence, Rakesh was brought on board and he is overseeing the extensive workout of Ram Charan," a source from the film's unit.Over the last few days, Ram Charan has been closely working with Udiyar."He has been working very hard. Ram has never looked so fit and muscular in his career so far. His transformation will stun audiences," he said.On Monday, Ram's wife Upasana posted on her Twitter page a video of her husband working out, and it has already gone viral.Directed by Surender Reddy, "Dhruva" is gearing up for December 2 release. A remake of Tamil blockbuster "Thani Oruvan", it also stars Rakul Preet Singh and Arvind Swami.Produced by Geetha Arts, the film has music by hip-hop Tamizha.