This is a normal physiological response and also a compensatory mechanism that your body naturally undergo to meet the increasing metabolic demand when,you exercise . When, you exercise or undertake any other sternous physical activity, you cause the muscle to work harder.It obviously put the muscle to use extra energy for it`s better function.This indeed increase your basal metabolic rate. In order to meet this demand, your brain sends impulses down to the lungs through the autonomic nervous system, to breath faster and deeper.This, in turn causes the blood to get adequate amount of oxygen to feed the extra-functioning muscles during exercise.This also helps to get rid of waste products like Carbon dioxide which, results from the energy synthesis. So, it not controlled by us.It is the physiological response from the autonomic nervous system. Hope, this helps, Regards,