This will also place a big load on the heart and lungs which will increase cardiovascular
capability and efficiency, thus helping you
burn a lot
more calories and get rid of body
fat.
When you are starting to use muscles that you haven't used before, the
fat oxidative
capabilities of those muscles (using oxygen to
burn fats) is quite lower than the surrounding muscles, so your body has to rely
more on (1) sugar, and (2) particularly anaerobic use of that sugar: in order to use muscles for endurance, your body has to create a lot of infrastructure, such as capillary networks, in order to get
fat and oxygen to those muscles.