Just as inactive individuals can enjoy health benefits soon after they start exercising, going without exercise for prolonged periods has physiological effects that appear as the negative images of those benefits. Neglect of exercise can lead to long-term weakness in muscles and bones, reduced ability to consume oxygen, and a host of pathological conditions due to obesity — effects that would require weeks or longer to reverse if, indeed, they could be reversed at all.
Aerobic exercise builds endurance and reduces fatigue by increasing both the number of mitochondria in the exercised muscle fibers and the number of capillaries around those fibers, according to Professor Arthur Vander, James Sherman, and Dorothy Luciano in their book “Human Physiology.” Strength training increases fiber diameter and the synthesis of the enzymes that break down glucose, providing muscles with energy. These benefits, which accrue over a period of weeks, are reversed when you stop exercising regularly, note Vander et al.
In bone, exercise induces the deposition of mineral salts and the production of collagen fibers as well as the production of calcitonin, a hormone that inhibits bone loss, notes Professor Gerard Tortora in his book “Principles of Human Anatomy.” Whereas weight-bearing activities, such as walking or moderate weight lifting, help build bone mass, the absence of the mechanical stress involved in exercise weakens bone through demineralization, or the loss of bone minerals, and decreased numbers of collagen fibers, observes Tortora. Lack of exercise can contribute to osteoporosis, a disease characterized by low bone mass and deterioration of bone tissue, state Joyce Black, Jane Hawks, and Annabelle Keene in their book “Medical-Surgical Nursing.”
The cells of your body depend on your ability to consume oxygen, an element instrumental in releasing the energy in the chemical bonds composing glucose. Endurance exercise increases maximal oxygen consumption (MOC). Normally, MOC depends on cardiac output, which, in turn, reflects how fast your heart beats and the amount of blood pumped with each contraction, according to Vander et al. Jogging for just 20 to 30 minutes three times a week at 5 to 8 miles per hour significantly increases MOC for most people, whereas the absence of exercise, as in prolonged bed rest, may decrease MOC by 15 to 25 percent, note Vander et al.
Derived from the food you eat, the sugar in your blood that is not consumed in exercise or other bodily activity is stored first as glycogen in muscle and liver cells and, eventually, as fat, note Neil Campbell, Jane Reece, and Lawrence Mitchell in their book “Biology.” Hence, prolonged failure to exercise can contribute to obesity. Obesity, in turn, increases the risk of developing coronary artery disease; diabetes; gallstones; hypertension; cardiovascular disease; breast, cervical, endometrial and liver cancer in women; and prostatic, colon and rectal cancer in men, observe Sue Huether and Kathryn McCance in their book “Understanding Pathophysiology.”
- Human Physiology: The Mechanisms of Body Function, 8th ed.; Arthur Vander, James Sherman, and Dorothy Luciano
- Principles of Human Anatomy, 9th ed.; Gerard J. Tortora
- Medical-Surgical Nursing, 6th ed.; Joyce M. Black, Jane Hokanson Hawks, and Annabelle M. Keene
- Biology, 5th ed.; Neil A. Campbell, Jane B. Reece, and Lawrence G. Mitchell
- Understanding Pathophysiology, 2nd ed.; Sue E. Huether and Kathryn L. McCance
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