Exercise And Diabetes: A Balancing Act

Exercise can provide substantial benefits to people with diabetes

The human body is a smoothly functioning food processor. It transforms the sugars, starches and other components of an individual’s diet into energy — energy needed to perform the daily tasks of life (including sitting, walking, lifting, etc.). The body’s cells need glucose (a form of sugar) to produce energy. The hormone insulin normally helps glucose enter the cells, but with diabetes that system goes awry. The precise cause of diabetes is unknown. What is known, however, is that either the cells don’t respond to insulin or the pancreas doesn’t produce enough insulin — or both. Rejected by the body’s cells, glucose accumulates in the bloodstream.

Two major forms of diabetes exist — Type I (insulin-dependent) diabetes and Type II (non-insulin-dependent) diabetes. Approximately 90 percent of the more than 14 million Americans suffering from diabetes have Type II — the more easily controlled form of the disease. Formerly referred to as “adult-onset diabetes” because it is typically diagnosed after an individual reaches age 40, Type II diabetes is usually the result of the body’s cells not responding to insulin. In some Type II diabetics, the pancreas simply does not produce enough insulin, while other individuals may suffer from both problems. Obesity and family history appear to be the two most significant risk factors for Type II diabetes.

Type I diabetes is often referred to as “juvenile-onset diabetes” because it usually occurs in children and young adults. Because individuals who suffer from Type I diabetes produce little or no insulin, they must receive insulin injections. While a family history of Type I diabetes affects an individual’s risk of developing the disease, the level of increase is not nearly as great as with Type II diabetes.

Regardless of which type diabetes an individual has, the condition can have serious consequences. For example, an extremely elevated blood-sugar level (i.e., hyperglycemia) can cause fatigue, dehydration and blurred vision. Left unchecked for a few days, particularly in individuals suffering from Type I diabetes, severe hyperglycemia can result in loss of consciousness, coma or death. Over an extended period, moderately elevated blood-sugar levels can affect the vessels feeding the brain, eyes, heart and kidneys, causing damage to those vital organs. Moderately elevated blood-sugar levels can also lead to nerve damage.

Exercise to the rescue

Fortunately, exercise can help diabetics control their condition and reduce their risk of life-threatening complications. Exercise can greatly decrease an individual’s chances of incurring the disease in the first place. In fact, research shows that exercise can reduce an individual’s likelihood of developing diabetes by more than half — including people who either are obese or are genetically predisposed to the disease. For example, in a major study conducted at the University of California, Berkeley, researchers found that for every extra 500 Calories a week an individual expends during exercise, that person’s risk of developing diabetes is reduced by 6 percent.

Exercise also can help those individuals who have developed diabetes. Among the beneficial aspects of exercise that are either directly or indirectly related to diabetes are:

Regulation of blood-sugar levels. Exercise encourages the body to use more glucose — a primary fuel source for the body. As a result, exercise has the effect of lowering elevated blood-sugar levels by helping transport glucose out of the bloodstream and into the cells where it can be used. By exercising on a regular basis, some diabetics who require medication to control their blood-sugar levels are able to reduce, or, in the case of many Type II diabetics, even discontinue their intake of medications. When individuals stop working out for as little as three days in a row, however, the beneficial effects of exercise are almost completely lost. Of the various types of conditioning regimens, aerobic exercise appears to provide the greatest benefit in terms of blood-sugar control. Strength-training workouts have also been shown to have a positive impact on blood-sugar levels.

Minimization of health risks. In diabetics, the most common causes of illness and death are coronary heart disease (CHD), stroke and various cardiovascular complications due to atherosclerosis (i.e., development of fatty deposits in the arteries). Regular exercise improves blood lipid profiles (i.e., it lowers triglycerides and low-density lipoprotein levels — the bad-type of cholesterol carrier — and raises high-density lipoprotein levels — the good type of cholesterol carrier). It also helps lower heart rate, blood pressure and blood platelet adhesiveness levels (i.e., the stickiness of the blood) which makes the blood less likely to clot. Collectively, the net effect of exercise is that it helps reduce the cardiovascular risk for diabetics.

Reduction of body weight and increased fat loss. Exercise helps individuals reduce excess weight and body fat — a major contributing factor to the development of Type II diabetes in individuals as they age. Insulin sensitivity (i.e., the responsiveness of cells to insulin) is significantly enhanced following exercise-induced reductions in weight and body-fat levels. As a result, the diabetic’s need for insulin is reduced. The lower the insulin dosage, the closer the body’s metabolic system is to its normal physiological level. As such, much less of a metabolic roller coaster occurs, allowing for better blood-sugar regulation.

Enhanced psychological well-being. Although the physiological effects of exercise are most frequently examined, exercise also can have a significant psychological impact on diabetics. For example, regular exercise may effectively reduce emotional stress, increase feelings of well-being and improve the overall quality of life for clients with diabetes. While these psychological effects are difficult to precisely quantify, they are well supported anecdotally and represent important benefits for individuals with diabetes.

Choosing the right kind of exercise

Regular exercise — particularly aerobic exercise — has proven to be effective in helping control diabetes. In general, exercise is safest and most beneficial for individuals with Type II diabetes. Any exercise program for a diabetic, however, should be designed in accordance with the type of diabetes and its level of severity. Although some disagreement exists regarding how exercise can best be incorporated into the “total” treatment program for diabetes, specific guidelines have been identified that will help ensure the potential hazards of exercise are minimized and the benefits are maximized. Among those guidelines are the following:

* Diabetic individuals should undergo a complete medical evaluation before starting an exercise program. Exercise is contraindicated for individuals with poor blood-sugar control (i.e., their fasting blood-sugar level exceeds 250 mg/dl). If the diabetic is over age 35, the evaluation should include an exercise stress test to check for the presence of “silent” coronary heart disease.

* Diabetics should keep a diary of their blood-glucose levels and record how they change under different conditions. They should be encouraged to monitor their blood-sugar levels before, during and after exercise. This step will allow individuals, along with their physicians, to assess the effects of exercise on blood-sugar levels and make any needed adjustments in food intake or the dosage or timing of medication. Available clinical data suggest that it is safe to exercise if a diabetic’s blood-sugar level is between 100 and 250 mg/dl.

* Unless limited by some resulting complications of the disease, diabetics can engage in the same types of aerobic activities as non-diabetics. Obese diabetics (common for Type II) or those with eye or nerve damage (typically seen in Type I) should avoid high-impact exercise and should select non-weight-bearing or low-impact alternatives such as cycling, walking or machine-based stair climbing.

* The intensity of exercise for diabetics should be slightly lower than (50 to 70 percent of maximal heart rate) that which is typically prescribed for healthy adults. The exercise prescription for individuals without medical problems often involves workouts that are either too long or too frequent for those with diabetes.

* Diabetics with autonomic neuropathy may not be able to use heart rate to accurately determine exercise intensity. Instead, such individuals should use ratings of perceived exertion and/or MET equivalents for monitoring exercise intensity.

* Type I diabetics should be advised to exercise 20 to 40 minutes per session. Exercise performed for longer than 40 minutes increases the risk of hypoglycemia for Type I diabetics. In contrast, Type II diabetics should be encouraged to exercise for a longer duration (40 to 60 minutes per session) to further enhance weight loss.

* Both types of diabetics should be encouraged to exercise daily — preferably at the same time each day. A consistent exercise pattern helps diabetics to more effectively balance their training with their diets and medications and, thus, maintain better control of their blood-sugar levels.

* Diabetics should be encouraged to exercise within one to three hours after a meal or snack, when blood-sugar levels are still relatively high. Because of the insulin-like effect of exercise, diabetics who engage in physical activity without adequate food ingestion (especially carbohydrate) are at high risk for experiencing hypoglycemia (low-blood sugar).

* Type I diabetics should be instructed to 1) avoid exercising during periods of peak insulin activity or take special precautions (e.g., consume a light meal or carbohydrate snack) and 2) alter the insulin injection site to an area of the body which is not primarily involved in the exercise activity (the abdomen tends to be an effective location) to prevent exercise-induced hypoglycemia.

* Diabetics should be instructed to always carry a form of fast-acting carbohydrate (e.g., juice, soft drinks, candy, glucose tablets, etc.) in case of a hypoglycemic emergency.

* Diabetics should be encouraged to exercise with a partner. Diabetics and their partners should be aware of the signs of hypoglycemia (e.g., confusion, weakness, unconsciousness, convulsions) and should know how to effectively treat hypoglycemia (see Table 1). If diabetic individuals choose to exercise alone, they should be instructed to wear a diabetic identification tag — a step which should help to ensure that they receive proper treatment in the event they become ill while exercising.

* Diabetics (especially Type I) should be advised to avoid exercising in extreme heat due to their increased susceptibility for anhydrosis (failure of the sweating mechanism). As a general rule, diabetics should curtail exercise when the temperature is above 90 degrees Fahrenheit and, concurrently, when the relative humidity is above 60 percent.

* Diabetics should be instructed to check their feet carefully before and after exercise because they have an increased susceptibility to infection. They should watch for skin lesions, blisters, discoloration or swelling and consult their physician if any of these appear.

* Strength training at a low/moderate intensity (a range of 12 to 20 repetitions per set) level can be incorporated into the total fitness program for the diabetic. Strength training, like aerobic training, can improve glucose uptake by exercising the skeletal muscles.

* Since exercise has a lingering effect, diabetics may need to eat more than usual after they finish working out. Otherwise, they may become hypoglycemic that night or even possibly the next day.

A delicate balance

The role of exercise in treating diabetes involves a carefully considered balance. When properly combined with a sensible diet and appropriate medications, exercise can have a positive impact on the lives of diabetics. The challenge is to strike the proper balance between the three critical elements of an effective treatment program for diabetics — diet, medication and exercise.

It is important to understand that a change in one of the three primary treatment factors usually requires a concurrent adjustment in the other two elements as well. For example, an increase in the level of physical activity by a diabetic often necessitates an increase in food intake and/or an alteration in the dosage or timing of medication for that individual.

Statistics indicate the number of diabetics is growing rapidly. In fact, approximately 650,000 new cases of diabetes are diagnosed each year. During that same period, an estimated 650,000 new cases of diabetes will go undiagnosed. It would seem logical to assume, therefore, that over time, the number of Type II diabetics joining health/fitness facilities would also rise. Accordingly, the more fully health/fitness professionals comprehend the nature of the delicate balance that exercise has in treating diabetes, the more prepared they will be to meet the unique needs of this group of individuals. Without question, exercise is sound medicine. Consequently, exercise must be an integral ingredient in a diabetic’s recipe for a well-balanced, healthy life.

REFERENCES

American College of Sports Medicine. Guidelines for Exercise Testing and Prescription (5th ed). Baltimore, MD: Williams & Wilkins, 1995.

American College of Sports Medicine. Resource Manual Guidelines for Graded Exercise Testing and Exercise Prescription (2nd ed). Philadelphia, PA: Lea & Febiger, 1993.

Goldberg, L., & D. L. Elliot. Exercise for Prevention and Treatment of Illness. Philadelphia, PA: F.A. Davis Co., 1994.

Horton, E.S. Role and management of exercise diabetes mellitus. Diabetes Care 11(2):201-211, 1988.

Peterson, J.A., & C. X. Bryant (eds.). The StairMaster Fitness Handbook (2nd ed). Champaign, IL: Sagamore Publishing Co. Inc., 1995.

Prevention Magazine Editors. Training the Body to Cure Itself: How to Use Exercise to Heal. Emmaus, PA: Rodale Press, 1992.

Skinner, J.S. Exercise Testing and Exercise Prescription for Special Cases: Theoretical Basis and Clinical Application (2nd ed). Philadelphia, PA: Lee & Febiger, 1993.

Taunton, J.E., & L. McCarger. Managing activity in patients who have diabetes. The Physician and Sportsmedicine 23(3) 41-52, 1995.

Zinman, B., & M. Vranic. Diabetes and exercise. Medical Clinics of North America 69(1) 145-157, 1985.

Cedric X. Bryant, Ph.D., is director of sports medicine for StairMaster Sports/Medical Products, L.P. , and James A. Peterson, Ph.D., is a sports medicine specialist residing in Mesa, Ariz. Both Bryant and Peterson are fellows of the American College of Sports Medicine.

Table 1. How to treat hypoglycemia

The following steps should be taken at the first hint of a hypoglycemic reaction:

* The individual should stop what he/she is doing and immediately consume any form of quick-acting sugar. If no quick-acting sugar can be found, the individual should consume any food that is available, preferably foodstuffs that are primarily carbohydrate or protein.

* The individual should sit down. If the hypoglycemic symptoms persist after 10 minutes, repeat the first step. If the symptoms do not subside within 10 minutes of the second
treatment, seek appropriate medical attention.

* Before resuming activity, the individual should eat a snack containing protein and a longer-acting carbohydrate (e.g., milk and crackers). The individual should also eat all scheduled meals that day — including a bedtime snack.

James Peterson, Ph.D., FACSM, is a sports medicine consultant, fellow of the American College of Sports Medicine, a former faculty member at the United States Military Academy and a former director of sports medicine for StairMaster Sports/Medical Products Inc.

Regulate diabetes and your blood sugar levels with exercise.