When humans run, the sympathetic division of the autonomic nervous system is activated. Activation of the sympathetic nervous system and release of hormones by the adrenal medulla increase the heart rate and force of heart contraction to ensure sufficient blood supply to the skeletal muscles. This is required for oxygen supply to muscles to sustain the running. Other effects of activated sympathetic division are increased blood glucose levels due to the breakdown of glycogen, increased breathing rate, etc.
