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Module 7. Exercise for Better Health: Physical Activity Recommendations in Diabetes
The health benefits of exercise for those who have diabetes are well-documented, including potentially preventing or delaying some of the complications often associated with diabetes.1,2 Exercise plays a pivotal role in preventing type 2 diabetes mellitus (T2D) as well as managing any type of diabetes. Accordingly, health care providers often prescribe exercise for individuals with type 1 diabetes mellitus (T1D) and T2D, along with other lifestyle improvements.3 However, a greater understanding of the impact of physical activity on glycemic control, medication effects, and diabetes-related health complications is necessary for regular exercise to be undertaken safely and effectively by all individuals with any type of diabetes.
PHYSIOLOGIC BENEFITS OF EXERCISE FOR DIABETES
The good news is that exercise cannot only improve blood glucose levels and glycosylated hemoglobin (A1C) levels in most people with diabetes, but can also lead to reductions in blood pressure and cholesterol levels, decrease the risk of heart disease, promote weight loss, improve brain function, and enhance self-image. Exercise training is even associated with significant improvements in metabolic parameters irrespective of improvement in cardiorespiratory fitness, so everyone can gain health benefits from being more active.4 T2D, in particular, involves dual defects in insulin action and insulin secretion,5 which allows exercise to play a major role in its control.6 Weight loss achieved through physical activity can decrease abdominal fat, which can further improve insulin action and overall blood glucose levels. Exercise may reduce the doses of oral diabetic medications that people require to manage T2D.7
The challenge is that exercise needs to be done regularly to be effective. Once people stop being active, the physiologic benefits related to insulin action and its blood glucose-lowering effect are lost within days.8 In addition, people with T1D have to effectively balance insulin doses and food intake to achieve overall improvements in blood glucose control with exercise as an added variable.9
Regular participation in physical activity can also help prevent the onset of T2D. People who have prediabetes and a family history of diabetes should focus on both diet and exercise to promote weight loss as a way to prevent T2D. In one well-known study, the Diabetes Prevention Program, those individuals who had a high probability of developing diabetes reduced their risk by 58% as a result of lifestyle interventions that included daily exercise, changes in diet, and an average weight loss of about 12 pounds (5.4 kg).10
EXERCISE RECOMMENDATIONS FOR PATIENTS WITH DIABETES
Physical activity, which includes structured exercise, can be performed in many forms. Structured exercise programs should be tailored to a patient’s unique situation and desires. Although age and type of diabetes may support different exercise programs, the goal is the same—to improve health outcomes. For optimal health, in addition to increased lifestyle activities, a complete exercise program for patients with any type of diabetes should include aerobic activities, resistance training, and flexibility exercise, and even some balance training for individuals older than 40 years of age.
All physical activity that people do during the day counts toward daily totals, even if its intensity is mild. But until recently, vigorous exercise was believed to be required for optimal health and fitness, and while people may gain more fitness and cardiovascular benefits from engaging in harder intensity exercise, doing almost any activity (including golfing, gardening, mowing the lawn, moderate walking, etc.) for 30 to 45 minutes total per day is also beneficial to health and blood glucose control. Furthermore, lower-intensity exercises are beneficial even if done for only 10 minutes (or less) at a time. Research shows metabolic health benefits from simply breaking up sedentary time with any activity—even standing—from time to time.11 An easy recommendation is to have individuals start by standing up or walking around for 5 minutes after each hour that they spend doing something sedentary.
Aerobic activities, which help improve the efficiency of the cardiovascular system, can also be beneficial for regulating blood glucose levels. Examples include walking, jogging, swimming, and biking. The current recommendations are that adults with diabetes should engage in at least 150 minutes of moderate-to-vigorous-intensity aerobic exercise per week, spread over at least 3 days per week and allowing no more than 2 days of inactivity between bouts.7 Shorter durations (minimum of 75 minutes per week) of vigorous-intensity or interval training may be sufficient for younger and more physically fit individuals. 7 Children and adolescents with type 1 or type 2 diabetes or prediabetes should engage in at least 1 hour of daily physical activity that includes some vigorous aerobic training, with vigorous muscle-strengthening activities at least 3 days per week. 7 Most recommendations note that such physical activity is important in children and adolescents in addition to limiting daily screen time (that is, sedentary activities like computer use and television viewing).12,13
For individuals who cannot engage in weight-bearing or high-impact activities, they will find that chair exercises, water aerobics, and recumbent biking can be beneficial for health and diabetes management. Including faster intervals interspersed into an aerobic-exercise session may also benefit blood glucose and improve fitness levels more effectively, and high-intensity interval training is a safe alternative to doing only more traditional continuous aerobic activities for many people with diabetes. Table 1 provides a summary of current recommendations related to physical activity from the American Diabetes Association (ADA): 7
Table 1. ADA Exercise Recommendations for People with Diabetes.
- Children and adolescents with type 1 or type 2 diabetes or prediabetes should engage in 60 min/day or more of moderate- or vigorous-intensity aerobic activity, with vigorous muscle-strengthening and bone-strengthening activities at least 3 days/week.
- Most adults with type 1 and type 2 diabetes should engage in 150 minutes or more of moderate-to-vigorous intensity aerobic activity per week, spread over at least 3 days/week, with no more than 2 consecutive days without activity. Shorter durations (minimum 75 minutes/week) of vigorous-intensity or interval training may be sufficient for younger and more physically fit individuals.
- Adults with type 1 and type 2 diabetes should engage in 2-3 sessions per week of resistance exercise on nonconsecutive days.
- All adults, and particularly those with type 2 diabetes, should decrease the amount of time spent in daily sedentary behavior. Prolonged sitting should be interrupted every 30 minutes for blood glucose benefits, particularly in adults with type 2 diabetes.
- Flexibility training and balance training are recommended 2-3 times per week for older adults with diabetes. Yoga and tai chi may be included based on individual preferences to increase flexibility, muscular strength, and balance.
Working up to daily aerobic activity has benefits for both T1D and T2D.14,15 For those with T1D, daily physical activity helps maintain the balance between insulin doses and food consumed. For those with T2D, the focus is on burning calories and weight management, but improving overall fitness levels is also important for long-term health. Keep in mind that the recommendations provided above are targets, not initial levels. If someone who is sedentary is just starting out, he or she will need to begin gradually to allow the body to adapt to the exercise. Monitoring blood glucose levels to determine exercise effects is encouraged; it may be helpful to monitor levels both prior to and within one hour following a bout of activity to determine its immediate effects on blood glucose management.
Resistance training can lower overall blood glucose control (as measured by A1C levels) and confer many other health benefits.16 Including both aerobic exercise and resistance training can also assist in optimizing the benefits related to managing blood glucose levels.6,17 Gaining muscle mass while reducing fat tissue can decrease insulin resistance and improve blood glucose control, and having stronger muscles can also improve individuals’ balance, posture, ability to move, and daily functions as well as the ability to live independently.
The goal of resistance training is to focus on exercises involving the major muscle groups, including the legs, back, chest, arms, shoulders, thighs, and abdominal area. In general, engaging in heavier resistance training will likely have greater benefits related to insulin action and muscle mass,18 although doing any type of resistance work will be beneficial in an older population with diabetes and lower fitness levels.19 Unfit and sedentary adults will have to start at a lower intensity and advance to doing harder resistance work to avoid injury and burnout.
Flexibility is also an integral part of an exercise program for those with diabetes.20 Typically, static stretching is recommended, which involves placing the body into a position that creates tension in the muscles and then holding that position for 15 to 30 seconds. However, dynamic stretching done during movement (like during yoga and tai chi exercise) can also work. Table 2 provides flexibility suggestions for adults with any type of diabetes.6
|Table 2: Flexibility-Training Recommendations for People with Diabetes6
||Adults with Type 1 or Type 2 Diabetes Mellitus
||2 – 3 days/week
||Stretch to the point of tightness (not pain)
||10 – 30 seconds per stretch (or dynamic stretching for that amount of time)
2 – 4 repetitions per stretch
||4 – 5 exercises for both the upper and lower body (can be static or dynamic exercises)
In particular, patients who are middle-aged or older have to also engage in weekly functional fitness training that includes elements of balance training.21,22 All adults start losing some natural balance with aging, but having diabetes can accelerate the loss of balance and increase the risk of falling and losing the ability to live independently well into later life.23 Another confounder can be loss of sensation in the feet as the result of diabetic neuropathy, which can alter the way people walk (gait) and increase their risk of falling; engaging in balance training can lower that risk.23 Likewise, autonomic (central) neuropathy that leads to dizziness with standing up also increases the risk of experiencing a fall, although balance training may be less effective in that regard.24
Balance training can be as simple as practicing standing on 1 leg at a time. (Sidebar 1.) Resistance training that works the lower body or the core muscles improves the ability to balance while standing and also during walking, which is when most falls actually occur. In addition, flexibility exercises that work the full range of motion around the joints can improve balance, as well as some alternative activities like tai chi and yoga. Even taking up dancing can help people stay on their feet at any age because it can improve their ability to balance effectively.
Sidebar 1: Easy Balance-Training Exercises
Balance training can be as simple as practicing standing on 1 leg at a time, but it is also possible to further increase balance with some additional exercises. Perform any and all of the following balance training exercises on a daily basis or even more than once per day.
- Side leg raises: Stand behind a sturdy chair with feet slightly apart, holding on for balance. Slowly lift 1 leg out to the side with toes facing forward. Lower that leg and repeat. Switch legs. This exercise can also be done lying on 1 side.
- Toe raises: Standing with your hand on the back of a chair or against a wall, straighten 1 leg so that the foot is off the floor and out in front. Then flex the ankle to point the toes up at the ceiling. Hold as still as you can. Relax, and repeat until fatigued. Follow this up by doing raises using the other leg.
- Calf raises: Stand with your toes on the edge of a step while holding something stable. Raise up as high as possible and lower slowly back down. Repeat 10 times, and then try with the other leg. It is also possible to work both calves at the same time. To increase the intensity, hold a weighted object in your free hand.
- Grab a towel with the toes: Place a towel on the floor, and practice grabbing it with the toes of both feet, alternately, while sitting and then while standing.
- Stand on a cushion: Use cushions or pillows of varying firmness. Put them on the floor, and stand on them with legs alternately together and farther apart.
- Stand with a changed position: Try standing with your eyes open or closed, head tilted to 1 side or straight, mouth talking or silent, and hands at your sides or out from your body.
- Sit-to-stand exercises: Practice standing up and sitting down from a stable chair without using your hands or arms for support or balance, only the legs.
- Heel-to-toe walking: Position 1 heel just in front of the toes of the opposite foot each time you take a step. Begin doing this exercise using handrails or with an adjacent wall, just in case unsteadiness results.
- Backward walking: Try walking backward along a wall or a kitchen counter without looking back, using the wall or counter to steady your body as needed.
EXERCISE-INDUCED HYPOGLYCEMIA AND HYPERGLYCEMIA
The presence of T1D, in particular, requires that blood glucose levels be fairly well-controlled before exercise.25 Keeping blood glucose between 100 mg/dL (5.6 mM) and 250 mg/dL (13.9 mM) will optimize safety by helping to avoid both exercise induced hypoglycemia and hyperglycemia.26 When blood glucose levels are controlled in a more normal range, moderate-intensity exercise usually leads to lower blood glucose levels by increasing blood flow to the muscles, which increases the rate of glucose absorbed into the cells.27 Both muscle contractions and insulin cause muscular glucose uptake from the blood, thus occurring through independent but additive mechanisms. Elevations in blood glucose levels often occur transiently after very intense exercise, such as sprinting or heavy resistance training, and are caused by the exaggerated release of glucose-raising hormones, such as adrenaline and glucagon.28
Hypoglycemia, which is usually defined as a blood glucose level lower than 70 mg/dL (3.9 mM), requires immediate treatment when symptoms occur (see Sidebar 2), and exercise must usually be stopped while symptoms are resolving in response to treatment. Typical symptoms of hypoglycemia include shakiness, hand trembling, tingling of hands or tongue, sweating, mental confusion, irritability, poor physical coordination (i.e., clumsiness), and visual changes. Symptoms can usually vary with training state, diet, environmental conditions, rate of fall in blood glucose, and more, however.
Exercise-related hypoglycemia is more likely to occur when insulin levels in the blood are elevated, especially when that elevation is related to a recent dose of injected or pumped insulin. Accordingly, monitoring blood glucose before and after exercise is critical for anyone taking insulin or other oral medications that stimulate insulin release. To catch hypoglycemia early, especially if exercise sessions are prolonged, blood glucose levels may need to be checked during the activity as well. To avoid hypoglycemia, be consistent with carbohydrate intake, meal timing, insulin use, and exercise. For example, exercise done in the early morning before breakfast (before insulin release or use) results in a minimal or no decrease in blood glucose levels — or possibly even an increase in glucose levels — compared with the same exercise undertaken later in the day, regardless of the type of diabetes someone has. Maintaining a regular time of day for an exercise routine is also helpful for predicting blood glucose responses.
Sidebar 2: Effective Treatment Options for Hypoglycemia
Any carbohydrates consumed during and after exercise to prevent or treat hypoglycemia should have a higher glycemic index (GI) for rapid absorption. Treat low blood glucose immediately with small amounts (~ 15 g) of high-GI carbohydrates, wait approximately 15 minutes for them to take effect, and then recheck glucose levels or monitor symptoms. Consume the same amount of carbohydrates again only if hypoglycemic symptoms have not begun to resolve.
The fastest treatments contain straight glucose (also called dextrose), including glucose tablets, glucose gels, and powdered glucose. Glucose tablets and gels have several benefits for treating hypoglycemia because they are the fastest forms of sugar that can be absorbed into the blood. These therapies also come in measured amounts—usually 4 g per tablet or 15 g per gel or liquid container, which makes it easy to consume a specific amount. White sugar (sucrose) in regular sodas and candies also work as a treatment because it is half-glucose (the other half is fructose, or fruit sugar). Skim milk, hard candies, bagels, bread, crackers, cornflakes, and white potatoes can also be used. Avoid fruit juice as the first choice to treat hypoglycemia because its sugar (fructose) has a relatively low GI and is absorbed more slowly. Although juice has traditionally been used in therapy, it may lead to over-treatment while the patient is waiting for the juice to take effect. Some juices have added glucose, though, and do not simply contain fructose. Never treat hypoglycemia with chocolate, doughnuts, or other high-fat sugary foods, or with low-GI carbohydrates (such as black beans) as they are not absorbed rapidly enough to treat hypoglycemia.
On the other end of the glycemic spectrum is hyperglycemia or high blood glucose. When glucose levels are poorly controlled, the liver production of glucose increases, which can result in higher blood glucose levels during exercise. In individuals with T1D, if their blood glucose levels are greater than 250 to 300 mg/dL, they may need to postpone or at least decrease the intensity of exercise, based on whether they have ketones in their blood or urine that indicate a relative state of insulin deficiency. Ketones make blood more acidic, potentially causing diabetic ketoacidosis (DKA), a condition that, if ignored, can cause coma and death. DKA is more common in T1D than in T2D. If ketones are the result of being sick, having an infection, or running a high level for too long, patients should delay exercise until they have their blood glucose under better control.
The American Diabetes Association (ADA) suggests the following general guidelines to help keep elevated pre-exercise glucose levels in check29:
- Avoid physical activity if starting blood glucose levels are greater than 250 mg/dL and moderate or higher amounts of ketones are present in blood or urine;
- Use caution during exercise with blood glucose above 300 mg/dL (16.7 mM), even if ketones are not present.
As long as someone feels well, is adequately hydrated, and has no significant ketones in their urine or blood, it is unnecessary to postpone exercise based on hyperglycemia alone. In such cases, mild- or moderate-intensity exercise may actually be helpful in lowering blood glucose levels, especially if the high glucose level develops after a meal when insulin is released by the pancreas or taken to cover the food.30 If ketones are present, however, it is prudent to postpone exercise until blood glucose levels return to a safer range. Often, treatment includes the administration of insulin to regain normal glucose levels, along with adequate hydration.31
INSULIN NEEDS AND DIETARY ADJUSTMENTS WITH EXERCISE
Being active significantly improves insulin action, and it typically lowers the amount of insulin needed for the body to lower blood glucose levels for 2 to 72 hours after exercise.32 Even in insulin users with any type of diabetes, improved insulin action can lead to decreases in the amount of insulin needed.25
The most usual response to being physically active is that blood glucose will decrease during exercise. This decline occurs since contracting muscles are able to take up glucose from the blood-stream without insulin; although at rest, insulin is necessary to keep blood glucose in check. The glycemic response is not always as predicted, though, and many factors can affect it, such as exercise intensity and duration. Moreover, intensive activities may actually raise blood glucose levels instead of lowering them.
If people are controlling their diabetes with diet and exercise alone, their risk of developing low blood glucose during exercise is minimal. Although mild or brisk walking generally allows the body to use more fat as a fuel, it is still possible to use a significant amount of blood glucose when walking longer than 2 to 3 hours. Longer-duration activities cause the muscles to use more stored carbohydrates (muscle glycogen). When these carbohydrates become depleted, the risk of developing low blood glucose is increased, although the chances are still minimal unless someone takes supplemental insulin.
Depending on the duration and intensity of an exercise session, people may have to ingest additional carbohydrates and other food before, during, and after exercise to prevent hypoglycemia.26,33 If blood glucose levels are low before an exercise bout (less than 90-100 mg/dL), some individuals may need some carbohydrate to avoid hypoglycemia during exercise, especially if they use insulin. But that really depends on how they manage their insulin doses and timing and the types of activity in which they engage.28 They can start with 10 to 15 g of higher GI carbohydrates without any insulin coverage, especially if their blood glucose levels typically start to drop during the first 30 minutes of activity. Additional carbohydrates may be needed at regular intervals during exercise as well to maintain euglycemia.
For those with T2D, extra carbohydrates are not typically needed before exercise because hypoglycemia is not common, unless people are using insulin or insulin-stimulating medications. Other oral diabetes medications (e.g., metformin, thiazolidinediones, and alpha-glucosidase inhibitors) generally do not cause hypoglycemia or require consumption of extra carbohydrate to prevent hypoglycemia. Eating when it is not absolutely necessary for glycemic balance may also hinder weight loss while being active, if that is a goal.
Individuals can also lower insulin doses for exercise or use a combination of insulin reductions and carbohydrate intake to prevent hypoglycemia. Being able to adjust insulin doses takes a higher level of knowledge about how insulins work, experience adjusting doses, and quite a bit of trial-and-error, no matter how much someone knows about his or her own body’s responses. If patients are unsure about how to adjust their insulin doses, urge them to consult with their health care provider, particularly if they begin to experience hypoglycemia related to their training and are relatively new to being active. Alternatively, many people may be able to gauge how to lower pre-exercise insulin doses or increase carbohydrate intake themselves by determining the glycemic effects of the activity using frequent monitoring of blood glucose levels. To keep blood sugars stable during exercise, patients may have to decrease their insulin doses before meals that occur within hours prior to physical activity. The general recommendations for insulin adjustments that follow apply mostly to rapid- or short-acting insulin given within 2 to 3 hours of exercise, not basal insulin changes. The 2 can be done, however, depending on the exercise intensity, duration, and timing.34
Impact of Medications on Blood Glucose Control During Exercise
Diabetes can be controlled with the appropriate use of medications, including oral and non-insulin injectable agents (mostly used in T2D) and insulin. A general understanding of how these medications work can help prevent hypoglycemia. The pair of classes of oral diabetes medications for T2D to watch closely are the sulfonylureas and the meglitinides, both of which can cause hypoglycemia35 (Table 3). Insulin use will also greatly increase the risk of hypoglycemia, both during and following exercise.
In individuals using insulin and/or oral medications that increase the body’s insulin secretion, physical activity can cause hypoglycemia if the medication dose or carbohydrate consumption is not altered. Individuals on these therapies may need to ingest some added carbohydrates if pre-exercise glucose levels are less than 90-100 mg/dL, depending on whether they can lower insulin levels during the workout (such as with an insulin pump or reduced pre-exercise insulin dosage), the time of day the exercise is done, and the intensity and duration of the activity.
|Table 3: Diabetes Medications and Risk of Exercise-Induced Hypoglycemia
|Class of Drug
||Risk of Exercise-Induced Hypoglycemia
||micronized glyburide (Glynase), tolbutamide (Orinase), chlorpropamide (Diabinese)
glyburide (DiaBeta, Micronase)
glimepiride (Amaryl), glipizide (Glucotrol)
|High (lasts > 24 hours) Medium-High (24 hours)
Medium (12-16 hours)
||metformin (Glucophage), oral metformin (Riomet), metformin ER (Glucophage XR, Glumetza, Fortamet)
||rosiglitazone (Avandia), pioglitazone (Actos)
||sitagliptin (Januvia), saxagliptin (Onglyza), alogliptin (Nesina), linagliptin (Tradjenta)
||repaglinide (Prandin), nateglinide (Starlix)
(during exercise shortly after meals)
||acarbose (Precose), miglitol (Glyset)
||canagliﬂozin (Invokana), dapagliﬂozin (Farxiga), empagliflozin (Jardiance), ertugliflozin (Steglatro)
||lispro (Humalog, Admelog), aspart (NovoLog, Fiasp), glulisine (Apidra), regular (Humulin R, Novolin R), inhaled (Afrezza)
(injected, pumped, or inhaled)
(given within 2-3 hours of last bolus)
||glargine (Lantus, Basaglar, Toujeo), detemir (Levemir), degludec (Tresiba), isophane (Humulin N, Novolin N)
(but lower overall doses may be needed when active)
(can make hypoglycemia harder to treat effectively)
|GLP-1 Receptor Agonists
||exenatide (Byetta), liraglutide (Victoza), exenatide ER (Bydureon), dulaglutide (Trulicity), semaglutide (Ozempic)
|Abbreviations: DPP-4, dipeptidyl peptidase-4; SGLT2, sodium-glucose co-transporter 2; GLP-1, glucagon-like peptide-1.
Insulin must be injected; it cannot be consumed orally, although an inhaled insulin called Afrezza is commercially available for use in people with T1D and T2D. Most individuals with T1D follow a basal/bolus insulin regimen, although more adults with T2D use basal insulins only.
An alternate delivery option for insulin is with an insulin pump programmed to deliver basal and bolus doses to mimic the natural release of insulin from the pancreas. Insulin levels can be adjusted up (for food) or down (for activity) to provide more flexibility and more physiologic levels of insulin. For physically active people, the ability to more precisely administer insulin and reduce levels during and following exercise can make hypoglycemia easier to avoid.36
A number of different insulins that differ based on onset of action, time of peak activity, and duration of activity are used to treat diabetes. In general, rapid-acting and short-acting insulins have a relatively quick onset and time of peak action. These types of insulin are given before meals and must often be adjusted before exercise. The extent to which insulin should be decreased depends on the intensity of exercise. If activity occurs within 2 hours of eating, pre-meal insulin should be decreased 5% to 30% (5% for low-intensity exercise and 30% for high-intensity and long-duration exercise).36 Intermediate-acting insulin has a longer onset of action as well as a longer duration. Unless someone is engaging in prolonged exercise, intermediate-acting insulin often does not need to be adjusted. Long-acting basal insulin does not have much of a peak; rather, it provides a low but constant level of insulin for approximately 24 hours or longer (depending on the type). Like intermediate-acting insulin, long-acting insulin may or may not need adjustment for exercise (before or afterward).
Exercise is not recommended during peak insulin times, unless doses are lowered before exercise or extra carbohydrates are eaten to compensate.26,36 The combination of the high levels of insulin and the glucose-lowering effect of exercise can lead to hypoglycemia without appropriate adjustments. Frequent monitoring of blood glucose levels (pre-, during, and post-exercise) allows for additional modifications to food intake and insulin doses.
Please refer to the module on insulin therapy for additional information and details about insulin products and treatment approaches.
HEALTH LIMITATIONS TO EXERCISE AND SAFETY PRECAUTIONS
In general, medical clearance prior to starting a new exercise regimen is recommended for people who have any signs or symptoms of complications, if they have not been regularly active, or if they desire to increase their current exercise program from moderate- to vigorous-intensity activity.6,7,37 In any of these cases, it is recommended that they abstain from starting a vigorous exercise program without being evaluated by a health care professional first,6,7 although engaging in mild or moderate activities is allowed. (See Sidebar 3.)
Sidebar 3: Who Needs to See a Doctor Before Starting Exercise?
Health care professionals may advise a physical examination or a cardiac stress test (i.e., tread-mill test during which heart rhythm is monitored) before exercising, particularly if a patient:6
- Is planning on participating in vigorous activities, not just easy or moderate ones, and he or she is unaccustomed to doing vigorous workouts;
- Is over 40 years old (or over 30, with any of the criteria below);
- Has had diabetes for more than 10 years;
- Has heart disease, a strong family history of heart disease, and/or high cholesterol;
- Has poor circulation in feet or legs (or lower leg pain while walking);
- Has diabetic eye disease, kidney disease, numbness, burning, tingling, or loss of sensation in the feet, and/or dizziness when moving from sitting to standing;
- Has not consistently controlled blood glucose levels well;
- Has any other concerns about exercising, including joint pain, arthritis, or other chronic health problems?
If people with diabetes have preexisting microvascular or macrovascular disease, additional precautions may be necessary to implement a safe and effective exercise training program. The presence of diabetic retinopathy, peripheral neuropathy, and nephropathy may affect exercise choices.
Diabetic retinopathy: Annual dilated eye examinations done by an ophthalmologist can detect eye problems and should be considered before starting a vigorous exercise program.7,38 Diabetic retinopathy is a disease affecting the retina of the eye. If this malady is present, certain activities should be avoided to prevent further damage.6 Mild background retinopathy will not affect exercise choices, but those with moderate nonproliferative diabetic retinopathy will need to avoid exercises that unduly affect blood pressure (e.g., heavy resistance training).3 Anyone with severe nonproliferative retinopathy should avoid contact sports and heavy lifting. Straining while lifting weights can lead to an increased risk of intraocular bleeding and retinal detachment for those with proliferative and severe nonproliferative eye disease. Unstable proliferative diabetic retinopathy requires the most precautions: people should focus on low-impact cardiorespiratory exercises, such as walking, swimming, and stationary cycling and never do any exercise while having a retinal hemorrhage. (See Sidebar 4.)
Peripheral neuropathy: Another potential concern is peripheral neuropathy, which is nerve damage that can alter the sensation of the hands and feet as well as your balance.24 Peripheral nerve damage causes people to be more susceptible to foot ulcers and bone damage because of the lack of sensation and weakening of the muscles and ligaments in the foot. Falls are also more common with this condition. Proper footwear is a must to prevent blisters or ulcers, along with daily foot inspections. Lower-impact activities such as swimming and stationary biking are preferred in these cases to limit complications, although aquatic activities are not an option with unhealed ulcers.24 While considering safety is important in people with peripheral neuropathy, studies have shown that moderate-intensity walking may not lead to an increased risk of ulceration if proper footwear is used.39 Additionally, 150 minutes/week of moderate exercise was reported to improve outcomes in people with prediabetic neuropathy in one study.40 In summary, all people with peripheral neuropathy should wear proper footwear and be educated on daily foot inspection. Anyone with a foot injury or open sore should be restricted to non-weight bearing activities until such issues have resolved.7
Diabetic Kidney Disease (DKD): Physical activity can result in increases in urinary albumin excretion. Despite this finding, there is no evidence that vigorous exercise increased the rate of progression of DKD.41 The ADA states that based on current evidence there appears to be no need for specific exercise restrictions for people with DKD in general.7
Sidebar 4: Precautions for Exercising with Diabetes and/or Its Complications
Having diabetes and engaging in physical activity require some precautions to ensure exercise is safe and effective. Follow these guidelines to get the most out of being active with diabetes:
- Have a blood glucose meter accessible to check glucose levels before, possibly during, and/or after exercise, or if any symptoms of low blood glucose occur;
- Immediately treat any hypoglycemia during or following exercise with quickly absorbed carbohydrates, such as glucose tablets, dextrose-based candy, or regular soft drinks;
- Inform exercise partners about diabetes, and show them how to give glucose or another carbohydrate should the patient need assistance;
- Stay properly hydrated with frequent intake of small amounts of cool water, and take in adequate fluids before exercising, particularly if blood glucose levels are elevated;
- Consult with a physician prior to exercising with any of the following conditions:
- Proliferative retinopathy or active retinal hemorrhage (eye disease),
- Neuropathy (nerve damage), either peripheral or autonomic,
- Foot injuries (including ulcers),
- High blood pressure,
- Serious illness or infection.
- Seek immediate medical attention for chest pain or any pain that radiates down the arm, jaw, or neck and for serious indigestion, any of which may indicate a lack of blood to the heart and a possible heart attack;
- If someone has high blood pressure, he or she should avoid activities that cause that pressure to go up dramatically, such as heavy weight training, head-down exercises, and anything requiring breath holding;
- Wear proper footwear, and check feet daily for signs of trauma, such as blisters, redness, or other irritation;
- Immediately stop exercising if experiencing bleeding into the eyes caused by active, unstable proliferative retinopathy;
- Wear a diabetes Medical Alert bracelet or necklace with your physician’s name and contact information on it;
- Carry a cell phone to call for assistance, if needed
Regular exercise is a cornerstone in the management of diabetes. Given an exercise program’s many health benefits, it should include more lifestyle activity, regular aerobic exercise, resistance training, flexibility training, and balance training, assuming no contraindications exist. Exercise can be undertaken without worsening or causing health-related complications. In most cases, exercise results in enhanced overall blood glucose control. It is critical for people to understand how exercise can lead to both hypoglycemia and hyperglycemia and how to maintain normal blood glucose levels during physical activity. Use of certain oral and injectable medications increases the risk of developing exercise-induced hypoglycemia, without appropriate adjustment of medication doses or food intake. In addition, the presence of certain diabetic complications may require adjustments to ensure that exercise is done safely and effectively.
|Benefits of Exercise
- The health benefits of exercise for those who have diabetes include potentially preventing or delaying some of the complications associated with diabetes.
- Exercise can improve blood glucose levels and glycated hemoglobin (A1C) levels in most people with diabetes, and can also lead to reductions in blood pressure and cholesterol levels, decrease the risk of heart disease, promote weight loss, improve brain function, and enhance self-image.
- Exercise may reduce the doses of oral glucose-lowering medications that people require.
- Exercise needs to be done regularly to be effective; once people stop being active, the benefits related to insulin action and its blood glucose-lowering effect are lost within days.
- Regular participation in physical activity can also help prevent the onset of type 2 diabetes mellitus (T2D).
- A complete exercise program for patients with any type of diabetes should include aerobic activities, resistance training, and flexibility exercise, and even some balance training for older individuals.
- Even breaking up sedentary time helps. An easy recommendation is to start by standing up or walking around for 5 minutes after each 30minutes – 1 hour that you spend doing something sedentary.
- Gaining muscle mass while reducing fat tissue can decrease insulin resistance and improve blood glucose control, and having stronger muscles can also improve your balance, posture, ability to move, and daily functions as well as the ability to live independently.
- Typically, static stretching is recommended, which involves placing the body into a position that creates tension in the muscles and then holding that position for 15 to 30 seconds.
- Balance training can be as simple as practicing standing on 1 leg at a time.
- To avoid hypoglycemia, be consistent with carbohydrate intake, meal timing, insulin use, and exercise.
- In general, medical clearance prior to starting a new exercise regimen is recommended if you have any signs or symptoms of complications, if you have not been regularly active, or if you desire to increase your current exercise program from moderate- to vigorous-intensity activity.
- Chimen M, Kennedy A, Nirantharakumar K, et al. What are the health benefits of physical activity in type 1 diabetes mellitus? A literature review. 2012;55:542-551.
- Williamson DA, Rejeski J, Lang W, et al. Impact of a weight management program on health-related quality of life in overweight adults with type 2 diabetes. Arch Intern Med. 2009;169:163-171.
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