Arousal is a state of physical and psychological activity that can range from deep sleep to ecstasy. Stress and anxiety can be reduced by lowering arousal levels. Arousal impairs performance owing to muscular tension and coordination issues caused by excessive arousal. In order to maintain optimal performance, it is essential that athletes learn to regulate their level of arousal throughout competition. Arousal control in sport is the ability to reduce stress and anxiety while maintaining an appropriate level of physical activity for the situation at hand. This can be done by consciously controlling the body's physiological responses. For example, an athlete may be able to slow down his or her heart rate by breathing more deeply or exercising at a lower intensity. This allows him or her to respond appropriately to the situation without being incapacitated by stress or injury. The three main systems involved in arousal are the autonomic nervous system, the endocrine system, and the neuroendocrine system. The autonomic nervous system is made up of two branches: the sympathetic branch and the parasympathetic branch. These two branches work together to regulate energy supply for active muscles, control heart rate, and balance blood pressure. The endocrine system is made up of glands such as the pituitary gland and the adrenal glands that produce hormones which affect all parts of the body through communication with the brain.