You shouldn't put yourself through torture in order to get results. If you're hurting while working out, it could be due to overexertion or even a bad diet. Intense exercise can sometimes bring on the process of lactic acidosis in the body, which throws off your chemical equilibrium and increases the amount of lactic acid in your bloodstream. This in turn causes a burning sensation, nausea-related symptoms, muscle ache and/or rapid breathing. Buffer the situation by eating lots of fruits and vegetables at every meal to help reduce excess acid. And if you're just starting a challenging, new exercise routine, ease into it slowly so your body has time to adapt.