Exercise Improves Blood Sugar Regulation
"He is one of my best success stories! I started working with him when his doctor told him his blood sugar was high. His blood pressure was also elevated, and he has a family history of heart disease. He walks on his own several days a week, and works out at the fitness center three days a week. At his last checkup, his doctor said his blood sugar and blood pressure were within the normal range."
Diabetes, insulin and blood sugar
Diabetes mellitus refers to a group of disorders characterized by high blood sugar and problems with blood sugar regulation. These problems are caused by defects in the production of and/or the body's response to an important hormone called insulin. In healthy people, insulin is produced by the pancreas in response to a rise in blood glucose (sugar) levels. Insulin is released into the bloodstream, where it binds with special sites (receptors) on the body's cell membranes. Insulin signals the cells to take up glucose from the blood, and use it for energy or store it as glycogen (in muscles and liver) or fat (in muscles and adipose tissue, for example). As the cells take glucose from the blood, the blood sugar level falls, and the pancreas stops releasing insulin.
The most common type of diabetes, and one of the most common chronic health problems, is called type 2 diabetes mellitus (T2DM). Approximately 90 to 95 percent of people with diabetes have the type 2 variety. T2DM often develops gradually as people consume more calories than they expend, and accumulate excess fat, especially around the abdominal organs (viscera). Some population groups, including African Americans, Hispanic/Latino Americans and Native Americans have especially high rates of T2DM.
T2DM usually begins as a condition known as insulin resistance, in which enough (or what should be enough) insulin is produced, but the response of the cell membrane receptors is sluggish, and the cells do not take up glucose as fast as they should. This may lead to a diagnosis of "prediabetes," where blood sugar levels are somewhat elevated, although not high enough to qualify for an "official" diabetes diagnosis. Prediabetes is often reversible with increased physical activity, dietary changes and weight loss (for people who are overweight). People with prediabetes are never really "cured," because they remain at risk for developing diabetes at a later point in their lives, especially if they stop exercising.
If prediabetes is not reversed, continuing high blood sugar levels may progress to T2DM. Prediabetes and T2DM are often associated with high blood pressure and a risky blood lipid profile, a cluster of symptoms known as metabolic syndrome. Diabetes alone increases risk for a number of complications, including cardiovascular disease, retinopathy (damage to the eye's retina), kidney disease and neuropathy (nerve damage).
Type 2 diabetes: Issues for fitness professionals
Exercise, both cardiovascular and resistance exercise, improves receptor sensitivity to insulin, and enhances the uptake of glucose by muscles and the liver. Exercise can also help reduce excess abdominal fat. Thus, regular physical activity is an important part of diabetes treatment programs. All clients with diabetes should have a physician's consent to exercise, since diabetes-related complications can make exercise dangerous.
Treat clients in the early stages of T2DM with no complications as you would any client, developing exercise programs suitable for current fitness level, health concerns and personal preferences. Clients with more severe T2DM, and especially those using medications to help control blood glucose, should work closely with their diabetic care team to monitor blood glucose before and after exercise, and adjust medications as necessary. Be sure to refer clients with poor glucose control back to their providers to improve their diabetes management.
T2DM is associated with a sedentary lifestyle, so many clients coming to you with this disorder may have little and mostly negative experiences with physical activity. Make adherence a priority, and do everything you can to make exercise a positive contribution to the lives of your clients with diabetes.
By Barbara A. Brehm
- American College of Sports Medicine. Diabetes mellitus, pp 207-211 in ACSM's Guidelines for Exercise Testing and Prescription. Lippincott, Williams and Wilkins: Philadelphia, Pa., 2006.
- Centers for Disease Control. National Diabetes Fact Sheet. United States, 2005. www.cdc.gov/diabetes/pubs/pdf/ndfs_2005.pdf
- Verity, L.S. Overview of type 2 diabetes. ACSM's Certified News 17 (3): 3-4, July-Sep. 2007.
- Barbara A. Brehm, Ed.D., is professor of exercise and sport studies at Smith College, Northampton, Mass.
Copyright 2007, Fitness Management magazine, Madison, Wis., www.fitnessmanagement.com.