While delivering our Certificate III and IV course in fitness, we take a look at the exercise implications and contraindications when working with clients who suffer from type 1 and type 2 diabetes, hypoglycemia or hyperglycemia.
Look around your exercise floor. Although there are no outward or telltale signs, it is likely that several of your members or clients have some form of diabetes. It is also likely that many of these people either are unaware of their condition or have difficulty managing and regulating the disorder.
While it is outside of your scope of practice as a fitness professional to dispense medical advice to diabetic clients about specific issues such as blood glucose levels or medications, you are in a unique position to help. As the number of people with diabetes (or related conditions like hyperglycemia and hypoglycemia) continues to grow, it is imperative that fitness professionals have a practical understanding of how exercise benefits and affects these clients. This article outlines the mechanisms of diabetes; risk factors; signs and symptoms; complications of the condition; exercise considerations and contraindications; and recommendations for daily care.
The Mechanisms of Diabetes
When blood glucose levels begin to rise, beta cells in the pancreas secrete insulin, a hormone that regulates blood glucose, into the bloodstream. Subsequently, insulin receptors on the cell walls allow insulin (coupled with one or more glucose molecules) to enter the cells for metabolism. This series of events lowers serum blood sugar levels.
Type 1 diabetes occurs when the body cannot manufacture its own insulin because the beta cells of the pancreas that are responsible for insulin production have been destroyed. As a result, supplemental insulin must be injected or infused into the body to normalize glucose levels. As type 1 diabetes progresses, the number of insulin receptors diminishes slightly. This, in turn, decreases the ability of insulin and the glucose molecule pair to enter cells, even when the client is getting adequate supplemental insulin. Over time, the person’s blood glucose levels become even more difficult to stabilize and manage.
Unlike type 1 diabetes, which results from an inability to produce insulin, type 2 diabetes occurs when the body’s cells are unable to utilize insulin properly; this inability is known as insulin resistance. Over decades, the pancreas gradually loses its ability to produce insulin, and the number of insulin receptors on the cell walls markedly decrease, especially in people who are inactive and overweight or obese.
Gestational diabetes mellitus (GDM) is a condition that occurs in some women during pregnancy. GDM is a form of insulin resistance; however, the exact cause is unknown. It is theorized that hormones in the placenta may block the action of the mother’s insulin (American Diabetes Association 2007). Because diet management alone does not improve glucose control in women with GDM, exercise is key to controlling blood glucose levels in women with this condition.
It is also possible for diabetes to result from causes such as surgery or illness. (Other conditions that are related to diabetes, such as exercise-induced hypoglycemia and hyperglycemia, will be discussed later.)
Considerations for Training
Fortunately, the majority of the clients you will encounter while training will not require special care for diabetes. However, some clients may have difficulties with vision and may need assistance setting up or handling fitness equipment. Similarly, clients with active retinopathy (damage to the blood vessels in the eye) should avoid strenuous activity and any exercise that involves straining, jarring or Valsalva-like maneuvers.
Clients who experience pain or impaired sensation in their fingers or feet may need you to provide alternatives to handheld weights and treadmills. Individuals with limited capacity for exercise because of obesity and severe deconditioning will require your patience and inspiration. Some clients will come to you with medical restrictions resulting from cardiac complications; if you cannot meet the needs of these people, you must use your professional discretion and refer them to other health professionals.
Most clients with diabetes are prescribed several medications to help manage their condition. The most widely prescribed medicines for diabetes are metformin, glyburide, chlorpropamide and glypizide, which decrease glucose produced by the liver and stimulate insulin production by the pancreas. Generally speaking, diabetic medications have not been shown to affect exercise tolerance, electrocardiographic data, blood pressure or heart rate. However, clients who take a class of drugs called sulfonylureas, which include glyburide, chlorpropamide and glypizide, may be less likely to achieve higher workloads than nonusers.
Exercise Benefits & Guidelines
Exercise is an established adjunctive therapy in diabetes management. Regular exercise helps control blood glucose levels in clients with type 2 diabetes and in women with GDM in the following ways:
• It increases glucose uptake by the cells.
• It improves insulin sensitivity by improving glucose metabolism.
• It reduces the risk of CVD.
Unfortunately, few studies to date have found that exercise helps control blood glucose levels in clients with type 1 diabetes. This is probably because people with type 1 diabetes have to increase their carbohydrate intake to avoid exercise-induced hypoglycemia. The effects of eating more and the resultant elevated blood glucose levels counteract the potential improvement in HbA1c. However, clients with type 1 diabetes do see improvements in insulin sensitivity, glucose metabolism and CVD risk factors after establishing a regular exercise program (ACSM 2001).
Many type 1 diabetics use an insulin pump to deliver a calculated dose of insulin at designated intervals. Each person’s pump, which is the size of a deck of cards and can be worn on a belt at the waist, is programmed to his or her individual needs. The pump delivers a continuous supply of insulin and, when necessary, a bolus to accommodate the carbohydrate load of a meal. Other type 1 diabetics use insulin syringes to inject insulin one or more times a day. A pump is more effective at controlling blood glucose levels because it can deliver very small amounts of insulin, which is not possible with a syringe. With physician approval, most users can safely disconnect their pumps for 1–2 hours. Clients need to inspect their pump insertion sites before and after exercise and must be prudent about changing sites every 2–3 days to prevent infection.
For insulin pump users involved with aquatic exercise, waterproof models are available; however, some health professionals recommend removing pumps before water exercise to prevent damage. Protective cases for pumps are available for those who engage in light-contact sports. Because pumps can become dislodged from their insertion sites, wearing a pump while engaged in high-contact activity is not recommended.
Clients with both types of diabetes can suffer from exercise-induced hypoglycemia, a condition that can cause undue anxiety or shakiness; changes in gait and coordination; inability to think or see clearly; excessive perspiration; dizziness; nausea; loss of consciousness; and even coma. Exercise-induced hypoglycemia is caused by a lack of glucose in the blood.
To prevent exercise-induced hypoglycemia, clients should measure their blood glucose levels before exercise, during exercise (if it lasts longer than 30 minutes) and again 15 minutes after exercise, to detect low blood glucose levels. Clients should also avoid exercise at peak time of insulin, the period in which insulin is most effective at lowering blood glucose levels. Instead, clients should be encouraged to exercise when insulin effects are low and blood glucose is on the rise (i.e., shortly after eating) (Funnell et al. 2004).
Clients with exercise-induced hypoglycemia may also benefit from eating a carbohydrate snack during their workouts. The amount and timing of the snack should depend on the intensity of the exercise, its duration, the pre-exercise blood glucose level and the individual’s response to exercise. (It is the available glucose in food rather than the amount of available carbohydrates that acutely affects blood glucose levels.) One rule of thumb is that if a client’s blood glucose level falls below 100 mg/dl, a carbohydrate snack should be eaten. (See sidebar “Carbohydrate Supplementation & Exercise Intensity,”below.) After eating the snack, the client should wait 15 minutes, then test the blood glucose level again and not return to exercising until the level is at least 100 mg/dl. Adding fat to the carbohydrate may prolong the glycemic response.
Although it is more common in type 1 diabetics, any client with diabetes can experience hypoglycemia up to 48 hours after an exercise session, so it is vital to monitor glucose levels frequently after a workout. Postexercise, late-onset hypoglycemia (PEL) is defined as a reaction more than 4 hours after exercise. Clients with diabetes should never exercise at night, because nocturnal hypoglycemia can result. Blood glucose responses to exercise in lean clients with type 2 diabetes are highly variable and less predictable than those that occur in their obese counterparts (ACSM 2007).
Hyperglycemia, defined as having blood glucose levels greater than 300 mg/dl, results when the body does not have enough glucose to meet its metabolic demands. This condition causes the body to break down proteins and fats in order to produce energy, which results in the production of compounds called ketones. The signs and symptoms of acute hyperglycemia include increased thirst; increased hunger; increased urine output; blurred vision; fatigue; and the presence of ketones in the urine as detected by a dipstick test (Wikipedia 2007). Ketoacidosis is the term used to describe an excessive formation or secretion of ketones in the body.
Fortunately, the incidence of hyperglycemia in the fitness setting is uncommon. However, ACSM recommends that clients should not exercise if their blood glucose levels exceed 250 mg/dl and ketones are detected in the urine; ACSM also recommends that clients use caution when working out if their blood glucose levels reach or exceed 300 mg/dl and no ketones are present (ACSM 2006). It is prudent to withhold exercise if ketoacidosis is detected in the dipstick test, because exercise can worsen hyperglycemia (American Diabetes Association 2007). According to ACSM guidelines, clients with blood glucose levels greater than 400 mg/dl should not participate in any form of exercise (ACSM 2001).
Developing a safe and effective exercise program for people living with diabetes can be a challenge but one that is worthwhile. As a fitness professional, you have the unique opportunity to educate, motivate and guide your clients toward a lifestyle that includes regular blood glucose monitoring, proper diet and regular physical activity.
Risk Factors for Type 2 Diabetes
history of physical inactivity
family history of diabetes
ethnicity/race (e.g., African Americans, Hispanic/Latino Americans, American Indians, some Asian Americans and some Native Hawaiians and other Pacific Islanders)
diagnosis of gestational diabetes or delivery of a baby weighing more than 9 pounds
high blood pressure (> 140/90 mm Hg)
HDL level < 35mg/dl and/or a triglyceride level > 250 mg/dl
diagnosis of prediabetes
polycystic ovarian syndrome
history of vascular disease, such as heart disease
Copy and distribute this checklist to clients who have been diagnosed with type 1 or type 2 diabetes.
Get physician clearance before starting any exercise program.
Test your blood glucose level before exercise; during exercise (if you are new to exercise or the session lasts longer than 30 minutes); and after exercise.
Follow these general guidelines for a safe exercise session: warm up and cool down, stretch, adhere to your target heart rate zone and drink plenty of water. Wear well-fitting, well-cushioned, supportive shoes, as well as polyester or blended socks, to keep your feet dry and to minimize trauma to the feet.
Avoid strenuous, high-impact or static activity unless specifically approved by your physician.
Carry a carbohydrate snack with you.
Wear identification that tells others you have diabetes.
Know and monitor the signs of exercise-induced hypoglycemia.
Do not exercise if your blood glucose level is < 70 mg/dl or
> 250 mg/dl and you have ketones in your urine. Use caution if your blood glucose level is > 300 mg/dl, whether ketones are present or not.
If you have a condition related to diabetes, such as autonomic neuropathy, peripheral neuropathy, neuropathy or retinopathy, always get approval for exercise from your physician prior to starting a fitness program; these conditions require specific guidelines and strict limitations. (Fitness professionals: Be sure to ask clients if any of these conditions apply!)