The Effects of Exercise on Oxygen Extraction

Although strength exercises do not require much oxygen, endurance exercises involve muscle fibers that depend on oxidative phosphorylation, which devours oxygen. Habitually performing endurance exercises renders individual muscle fibers more able to use the oxygen in the bloodstream. It also raises the capacity of your heart and vascular system to deliver oxygen. Exercise also activates sympathetic nerves, which increases the flow of oxygen-laden blood to exercising muscles.

  1. Anaerobic Exercise

    • Strength exercises, such as weight lifting, pullups and pushups, demand relatively little oxygen. Such exercises activate muscle fibers, known as glycolytic fibers, that contain large stores of energy in the form of glycogen and high concentrations of enzymes that can break down glycogen without oxygen. Glycolytic muscle fibers use energy derived through glycolysis, a metabolic pathway open even in the absence of oxygen, according to Arthur Vander, James Sherman and Dorothy Luciano in their book “Human Physiology.”

    Aerobic Exercise

    • Endurance exercises, such as running, dancing, biking and swimming, demand lots of oxygen. Such exercises activate muscle fibers, known as oxidative fibers, that extract energy from glucose through oxidative phosphorylation. Oxidative phosphorylation enables the extraction of far more energy from glucose than can be derived through glycolysis, but unlike glycolysis, which can occur with or without oxygen, oxidative phosphorylation requires oxygen, according to Neil Campbell, Jane Reece, and Lawrence Mitchell in their book “Biology.”

    Cellular Changes

    • The performance of endurance exercise, if habitual, changes the oxidative fibers themselves. First, it increases the number of mitochondria inside each fiber, according to Vander et al. Mitochondria are the structures within the cell, inside which oxidative phosphorylation occurs, according to Campbell et al. By increasing oxidative phosphorylation, multiplying mitochondria makes more energy available to working muscles. In addition, regular endurance exercise stimulates growth in the capillaries, the tiny blood vessels around the muscle fibers, which increases the flow of oxygen-rich blood to the fibers, according to Vander et al.

    Oxygen Consumption

    • Up to a point, you can raise your heart’s capacity to pump blood and thereby deliver oxygen to your muscles. For most people, attaining this depends on two possible effects of endurance exercise: thicker heart muscle and increased contractility of heart ventricles, according to Vander et al. It may also reflect two other effects endurance exercise can have: increased blood volume and increases in the number of blood vessels in skeletal muscles, both of which would increase blood flow through the muscles and the return of blood to the heart, according to Vander et al.

    Sympathetic Nerves

    • Your heart never rests, continually moving blood and delivering oxygen to cells for energy, according to Joyce Black, Jane Hokanson Hawks and Annabelle Keene in their book “Medical-Surgical Nursing.” Exercise, however, can alter circulation by activating the sympathetic division of the autonomic nervous system, observes Gerard Tortora in his book “Principles of Human Anatomy.” Sympathetic nerves raise heart rate and strengthen heart contractions, dilate blood vessels supplying muscles, and constrict blood vessels supplying organs unessential to exercise, notes Tortora. These effects accelerate and redirect blood flow to working muscles, increasing oxygen extraction where oxygen is most needed.