Carbohydrates (plasma glucose and muscle glycogen) and fats (plasma free fatty acids and muscle triglycerides) are the two main fuels utilized by the muscle cell to produce ATP [32]. Metabolism of amino acids may contribute a small percentage of the total energy production. Again, the selection of the specific fuel depends on the intensity and duration of the exercise. In general, at high intensities, muscle actions are mainly fuelled by muscle glycogen stores. On the other hand, lower intensity and long duration exercise utilizes the metabolism of free fatty acids for most of the energy needs. In real life, most activities activate different pathways at different points in time and use a combination of fuels to produce the ATP needed for muscle actions.