You may have noticed that the best bodybuilders take a few days off every week. The reason for this is that the muscles need a chance to rest, and it is at this time of rest that the muscle groups in the body actually, start developing. A day or two of rest is absolutely imperative in the exercise routine of any individual. The answer, therefore, lies in a careful analysis of your fitness levels, your body type, and the nature and the intensity of the exercises you perform.