For patients with type 2 diabetes, exercise improves blood glucose control and reduces the risk of comorbidities including hyperlipidemia, hypertension, and ischemic heart disease.1 According to the CDC, more than 29 million Americans (about 9% of the population) have type 2 diabetes and most are not physically active.2,3
A joint position statement by the American College of Sports Medicine (ACSM) and American Diabetes Association (ADA) recommends at least 150 total minutes of moderate-intensity aerobic activity per week, with no more than 2 consecutive days without physical activity.1 The ADA Standards of Care for Diabetes in 2015 recommend reducing total sedentary time by incorporating physical activity every 90 minutes.4 In addition, the ADA recommends that patients perform resistance exercise using all eight major muscle groups two or more times per week. However, only 12% of adults with type 2 diabetes meet the ACSM/ADA resistance training recommendations and only 41% meet the aerobic recommendations.5
Following the ACSM/ADA exercise recommendations can help patients improve blood glucose control. A meta-analysis of randomized controlled clinical trials assessing the effect of structured exercise training regimens on A1C showed structured exercise for more than 150 minutes per week resulted in A1C reductions of 0.89%.6 This reduction is similar to that achieved by many oral antidiabetic medications.7 However, physical activity advice alone is not associated with A1C changes unless it is combined with dietary advice to reduce portion size and limit carbohydrates.6
The lack of physical activity among patients with type 2 diabetes is a major public health concern that physician assistants (PAs) are well suited to address. However, clinicians need adequate training to counsel patients on exercise. According to Howe and colleagues, 13.7% of medical residents and 17.3% of attending physicians self-reported adequate training in counseling patients on exercise.8 In another study, fewer than half of older adults reported ever receiving exercise suggestions from a physician.9 PAs could help fill the gap in patient education about exercise if given exercise guidelines and recommendations for patients.
The significance of structured and balanced exercise programs for patients with type 2 diabetes is emphasized throughout the literature.6 However, the role of PAs in facilitating these programs is underrepresented.
Multiple hormones and the sympathetic nervous system work at the level of the skeletal muscle and liver to maintain glucose homeostasis. During exercise, when skeletal muscles contract, blood glucose uptake increases in an insulin-independent pathway.1 This occurs through facilitated diffusion using glucose transporter 4 (GLUT4) proteins that let glucose enter skeletal muscle cells.10 Exercise increases GLUT4, which increases blood glucose uptake, even in patients with type 2 diabetes.1
At rest and after eating, glucose uptake by skeletal muscles is insulin-dependent to maintain glycogen stores. In patients with type 2 diabetes, this insulin-dependent mechanism is impaired; faulty glucose homeostasis mechanisms from the liver inadequately regulate gluconeogenesis and the balance of glucagon and insulin produced in the pancreas. However, the alternative pathway of insulin-independent uptake by skeletal muscle remains normal during exercise.1
Exercise improves insulin sensitivity in patients with type 2 diabetes in part because of the alternative mechanism for glucose metabolism and increase in transporter proteins.1 Submaximal aerobic exercise can lower blood glucose concentrations for 2 to 48 hours after exercise, and improve insulin sensitivity for up to 72 hours after exercise.1,11 Because resistance training causes muscle hypertrophy, the increased muscle mass may contribute to increased blood glucose uptake, leading to improved glucose control and insulin sensitivity.12 To maximize the physiologic benefits, patients with type 2 diabetes should participate in regular aerobic and resistance training.
Before starting exercise more intense than brisk walking, sedentary patients with type 2 diabetes should be evaluated by a medical provider.1 Stress tests are not routinely recommended by ACSM/ADA guidelines for asymptomatic patients at low risk for cardiovascular disease (CVD), and testing all patients with type 2 diabetes would create unnecessary barriers for exercising.13 This recommendation is consistent with the recommendation by the US Preventive Task Force, which concludes that stress testing should not be performed in low-risk patients because the increased risk of false-positive results outweighs the benefits of testing.14 A graded stress test should only be performed in symptomatic patients with CVD risk factors.1,13
Clinicians should assess patients for conditions such as uncontrolled hypertension, severe autonomic neuropathy, and unstable proliferative retinopathy, which may predispose patients to injury or preclude their participation in certain types of exercise.8
Use motivational interviewing techniques when prescribing exercise to patients. Consider using the Prochaska and DiClemente Stages of Change Model to assess a patient's readiness to participate in an exercise program.15 Table 1 demonstrates some examples of open-ended questions for patients in each stage.16 Using open-ended questions can help begin the discussion, set patient goals, and help clinicians and patients strategize how to implement the goals. Consider giving a sample prescription for exercise like the American College of Sports Medicine's Exercise is Medicine prescription.17
After ensuring that no further cardiac testing is required based on the patient's history and physical examination, discuss what the patient is doing for exercise. Discuss goals and interests to help patients identify exercises they will enjoy. Review the frequency, intensity, duration, and type of exercise needed to achieve maximal health benefits. A combination of aerobic and resistance training is appropriate for patients whose goals are to lose weight and optimize blood glucose levels.
Patients doing aerobic or resistance exercises should start with a warm-up period of at least 5 minutes.15 After aerobic or resistance exercise, patients should perform a cool-down phase at a lower intensity. Patients who are deconditioned can benefit from multiple short bouts of exercise throughout the day, rather than one long exercise bout.18 The minimum weekly goal is 150 minutes of cumulative moderate-intensity aerobic exercise. The Borg Rate of Perceived Exertion can be helpful for patients to quantify the intensity of cardiovascular and strength training exercises (Table 2).19 Multiply the Borg rating by 10 to get an estimated heart rate.
Patients interested in heart rate training can use one of the many fitness tracking devices that calculate heart rates, including heart rate monitors and smartphone applications. A patient's theoretical heart rate maximum is 220 minus the patient's age; moderate-intensity exercise is defined as 50% to 70% of the heart rate maximum, and vigorous intensity exercise is 70% to 85% of the heart rate maximum.20 Patients with known cardiac disease, cardiac autonomic neuropathy, and those on beta-blockers should use caution with heart rate training.
Resistance training should occur two to three times per week, on nonconsecutive days, focusing on all eight major muscle groups.1 Patients should perform 5 to 10 exercises; any modifications to squats, push-ups, crunches, calf raises work most all the major muscle groups. ACSM recommends performing eight to 10 repetitions per set and two to three sets total, at a sufficiently challenging weight (defined as 75% to 80% of the one repetition maximum).1
Flexibility exercises such as yoga, tai chi, and Pilates may confer additional benefits to patients with diabetes but should not replace other exercises for increasing fitness.1 More research is needed to determine the effect of these exercises on glycemic control. Because these exercises may help improve balance and coordination (especially important for reducing fall risk in older adults with diabetes and those with peripheral neuropathy), consider recommending them on an individual basis.21
BLOOD GLUCOSE AND EXERCISE
Patients with type 2 diabetes who exercise must take into account blood glucose fluctuations so they can avoid hyper- and hypoglycemia. Tell patients to have carbohydrate-dense, easily digestible foods readily available when they are exercising. Glucose tablets are a convenient option because they do not melt and are quantity controlled. Remind patients that one tablet typically equals 5 g of carbohydrates, so they must take three to four tablets to raise blood glucose sufficiently. Other options include hard candy, 2 tablespoons of raisins, or 4 oz of juice or nondiet soda.1
For patients with diabetes, hypoglycemia is a major barrier to exercise.22 For patients not on insulin secretagogues (that is, sulfonylureas such as glipizide, glimepiride, and glyburide) or insulin, exercise-induced hypoglycemia is rare.1 However, patients taking oral insulin secretagogues and insulin regimens should check their blood glucose before exercising. Although the risk of hypoglycemia for patients on sodium-glucose cotransporter 2 inhibitors is low, it may increase with exercise. This class of drugs lowers systolic BP and hypovolemia is an adverse reaction. Caution patients about the drugs' effects and to stay well hydrated during exercise. For patients taking these medications, ACSM/ADA recommends consuming at least 15 g of carbohydrates before exercise if the patient's blood glucose level is less than 100 mg/dL.1 Also encourage patients to monitor their glucose after exercising to determine if food consumption or medication changes need to be made. For prolonged endurance exercise, such as aerobic exercise lasting more than 60 minutes, patients should monitor their glucose during activity.
Patients taking insulin or insulin secretagogues can reduce their dosages before exercise if they experience hypoglycemia with exercise.23 ACSM/ADA also recommends patients supplement carbohydrates before, during, and after prolonged exercise.1 Patients who take longer-acting insulins typically do not experience exercise-induced hypoglycemia.24 Rapid-acting insulins tend to cause hypoglycemia during and after exercise; patients may need to reduce their dosages before exercising.1 Continuous glucose monitoring systems may be ideal for patients who are at risk for hypoglycemia during exercise.25
Patients should exercise cautiously if their glucose levels are greater than 300 mg/dL without ketosis.1 Because very hyperglycemic patients are at risk for dehydration and electrolyte imbalances, ACSM/ADA recommends proper hydration and that patients only exercise if they feel well enough at this glucose level.1 Intense exercise can initially worsen hyperglycemia because a release of catecholamines (epinephrine and norepinephrine) causes the liver to increase gluconeogenesis, raising blood glucose levels.
COMORBIDITIES AND SPECIAL CONSIDERATIONS
Type 2 diabetes is associated with peripheral and autonomic neuropathy (reduced RR variability on ECG, poor or blunted exercise BP and heart rate responses), coronary artery disease, retinopathy, peripheral arterial disease (PAD), peripheral vascular disease, and chronic kidney disease (CKD).1 Because of these multiple comorbidities, patients should be counseled on additional risks associated with exercise. Encourage patients to wear a medical identification bracelet or necklace.
Clinicians should examine patients' feet at every office visit and recommend that patients with diabetes inspect their feet daily. Remind patients that weight-bearing exercise can rub the foot, leading to callus formation, ulcerations, and blistering. Because patients with diabetes are at risk for peripheral neuropathy, proper footwear and checking feet before and after exercise is important. Patients who have foot lesions or active Charcot foot should avoid weight-bearing exercises, and instead perform nonweight-bearing resistance training or use an arm crank for an upper extremity cardiovascular exercise.1 Tell patients with peripheral neuropathy that walking does not increase the risk of foot ulcers or recurrent ulceration.1 However, patients with an active Charcot foot should be completely nonweight-bearing and consult with a podiatrist or foot surgeon.
Even patients with severe PAD should exercise.1 Consider potential limitations and that patients with PAD may be unable to perform moderate-intensity weight-bearing activities because of claudication symptoms. Aerobic and resistance training has been shown to improve endothelial function in patients with PAD.26 Encourage patients to rest if claudication symptoms become too severe and to perform a different activity, possibly a nonweight-bearing activity that does not cause discomfort.
All patients with type 2 diabetes should undergo annual ophthalmologic examinations.4 Patients with glaucoma, proliferative or preproliferative retinopathy, or macular degeneration should avoid activities that increase intraocular pressure, such as high-intensity aerobics such as running, yoga poses that place the head below heart level, plyometrics or jumping type movements, contact sports, and high-intensity resistance training.1,4 These exercises can increase patients' risk of retinal hemorrhage as well as raise systemic and ocular BP. Instead, patients can use elliptical machines, indoor cycles, and swim laps. Patients with mild nonproliferative diabetic retinopathy have no exercise restrictions.1
Patients who have type 2 diabetes and CKD should be encouraged to participate in regular exercise because it improves quality of life.27 However, patients with late-stage CKD should avoid Valsalva or high-intensity exercise that significantly raises BP.1,28 Weight-bearing exercises may be helpful for patients with CKD, given their increased risk of bone fracture because of secondary hyperparathyroidism associated with CKD.27 Patients on dialysis may continue to exercise as long as their hematocrit, calcium, potassium, and magnesium remain balanced.1 Many patients with CKD suffer concurrent chronic anemia and require erythropoietin to reduce anemia-related fatigue so that they can exercise.29
In addition to the multiple comorbidities discussed, patients with type 2 diabetes often take medications that can reduce their exercise capacity and recovery, including beta-blockers, diuretics, and statins. In patients who do not have CAD, beta-blockers can reduce exercise capacity.1 However, in patients with CAD, beta-blockers can improve exercise capacity through improved left systolic function.30 Diuretics can lower blood and fluid volume resulting in dehydration, which increases heat- and dehydration-related exercise injuries.1,31 Finally, statins can increase myopathies, which could impair exercise performance.
Patients with diabetes also are more prone to overuse injuries such as adhesive capsulitis, carpal tunnel syndrome, metatarsal fractures, plantar fasciitis, and trigger finger.32 Diabetes can damage joints through an inflammatory response related to the excessive waste products formed from glucose metabolism.32 The formation of glucose waste products binding to collagen can lead to joint pain and stiffness, which can limit exercise ability. Because warm-up can decrease injury risk, patients should be instructed on safe warm-ups to avoid joint problems.15
Despite multiple chronic comorbidities associated with type 2 diabetes, patients can safely exercise regardless of their physical capacity if they are given appropriate recommendations for the type, frequency, intensity, and duration of exercise.
Exercise advice should be a routine part of office visits for patients with diabetes, similar to foot care and nutrition. As with any medical advice, schedule follow-up visits to discuss exercise progress, barriers, and adherence. Modify the exercise prescription as appropriate using the “SMART” goal mnemonic (Specific, Measurable, Achievable, Realistic, and Time-oriented).33
Although the ACSM/ADA recommendations should be applied to all patients with type 2 diabetes, recognize that any form of physical activity is beneficial and should be encouraged. By increasing counseling efforts in patients with type 2 diabetes, PAs can help their patients meet the minimum fitness recommendations by ACSM/ADA to improve glucose control, increase cardiorespiratory fitness, decrease the risk of diabetes-related comorbidities, and improve quality of life. As the population of patients with type 2 diabetes grows, so will the need for PAs to prescribe exercise. Continuing education will help fill the gap in formal education on this topic for PAs.
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Keywords:Copyright © 2016 American Academy of Physician Assistants
type 2 diabetes; exercise; patient education; resistance training; American College of Sports Medicine; guidelines