Did you know ? If you should plan to do weight-training and cardio on the same day, cardio should always be done AFTER your weight training session. The reason lies in how the body’s energy systems work. Initially, for the first twenty minutes or so, any exercise – and that applies even to low intensity cardio – , will mainly rely on the body’s “super-fuel” glycogen for energy. Later into the cardio work-out, more calories from fat will eventually contribute to fuel this aerobic- type exercise. On the other hand, weight-training can not use fat for energy, but relies primarily on the anaerobic splitting of glycogen; there is, at best, only the quite limited amount of approximately 450 g carbohydrates stored in all our muscles and the liver, which just equals 1890 cal. of carbohydrate energy. Therefore it does not make sense to start any weight-training session with already partially depleted glycogen stores, as this will definitely result in less than optimum training intensity and running out of steam before the work-out is completed.