Bro, going to the gym can be an act of worship also. If you are doing it for the sake of Allah to stay and healthy and fit, which is also a part of Islam. 30 days rest from Gym is not a good hing to do if you go to gym regularly. If you do this then you'll lose all the muscle you had previously gained, so all those days you worked out will have gone to waste. Of course we will also do dhikr and Qur'an recitation and many other good deeds, but we'll have time for the gym also.