Increased Demands Of Vigorous Exercise On Your Body Are Met Primarily By What?

The human body evolved with the presence of stress. So integral is this relationship that the body may suffer harmful health consequences without stress, explains a 2009 study by researchers at the University of Missouri published in the "Journal of Physiology." Stress teaches the body to respond effectively to adversity. When you exercise vigorously, you are stressing your body, which, in turn, initiates several stress-specific responses.

Fight-or-Flight Response

To your body, exercise is stress. In these situations, the sympathetic nervous system takes over. Your nervous system consists of the central nervous system, which includes your brain and spinal cord, and the autonomic system, which controls the other parts of the body. The autonomic nervous system includes the parasympathetic system for at-rest functions, the enteric system for digestion and the sympathetic for stress situations. The sympathetic system initiates increases in blood flow and respiration to increase its efficiency during exercise. The fight-or-flight response describes the actions a body takes when in a stressful situation such as increasing adrenaline release. Its purpose is simply survival.

Cardiovascular System Response

Part of these responses involve the cardiovascular system. The harder you exercise, the greater will be the blood flow from your heart. Your blood pressure and heart rate will also increase. The cardiovascular system supports your vigorous exercise by providing oxygen and nutrients to your muscles. It will also help to cool you, which is essential during strenuous workouts to help avoid overheating and heat stroke. As your exercise intensity increases, the amount of blood pumped by the heart with each stroke increases in response to the heightened demand for fuel and oxygen.

Respiratory System Response

During vigorous exercise, your body's need for oxygen rises. The respiratory system responds by increasing your breathing rate. Oxygen supplies a raw material necessary for energy production. Your body can continue to produce energy even if your respiratory system cannot keep up. However, it can do so more efficiently using chemical reactions that involve oxygen. The body produces 18 times more energy in the presence of oxygen. The process involves breaking down sugar to produce fuel. Your increased breathing rate provides the necessary oxygen.

Energy Demands

The body uses both fat and carbohydrates for energy. During vigorous exercise, carbohydrates provide the primary energy source. It does so because it is considerably easier to break the chemical bonds of carbohydrates than fats. The body can then continue to produce energy faster to meet the demands for fuel and energy. Breaking down fats requires more energy, which the body cannot afford to lose during intense workouts. This is not to say it will not use fat. Rather, the body will use the most efficient form of energy production as long as stored reserves are available. Once the stored sugars in the muscles are depleted, fat then becomes the primary energy source.