when you exercise do so in segments.\nexercise for 10-30 minutes, then take a break of 10-30 minutes. it gives your body time to completely recover.\nthen you can exercise some more, then break some more.\ntry to do a routine of different muscles worked out over time, so that you do not do all the same muscles all the time. try to find a amount of effort that you can put into your training, and then back off 18%-30 precent so that you can do training easy and well do reps. you should not be able to hurt yourself if you take it easy. it may take more time to get into great shape, but you will not have injuries to slow you down getting there. be careful.