The American College of Sports Medicine (ACSM) levels of evidence (A-D) and American Diabetes Association (ADA) levels of evidence (A-C, E) are defined at the end of the "Major Recommendations" field.
Acute Effects of Exercise
Fuel Metabolism during Exercise
Physical activity (PA) causes increased glucose uptake into active muscles balanced by hepatic glucose production, with a greater reliance on carbohydrate to fuel muscular activity as intensity increases. ACSM evidence category A.
Insulin-stimulated blood glucose (BG) uptake into skeletal muscle predominates at rest and is impaired in type 2 diabetes mellitus (T2DM), while muscular contractions stimulate BG transport via a separate additive mechanism not impaired by insulin resistance or T2DM. ACSM evidence category A.
Postexercise Glycemic Control/BG Levels
Although moderate aerobic exercise improves BG and insulin action acutely, the risk of exercise-induced hypoglycemia is minimal without use of exogenous insulin or insulin secretagogues. Transient hyperglycemia can follow intense PA. ACSM evidence category C.
The acute effects of resistance exercise in T2DM have not been reported, but result in lower fasting BG levels for at least 24 h after exercise in individuals with impaired fasting glucose (IFG). ACSM evidence category C.
A combination of aerobic and resistance exercise training may be more effective in improving BG control than either alone; however, more studies are needed to determine if total caloric expenditure, exercise duration, or exercise mode is responsible. ACSM evidence category B. Milder forms of exercise (e.g., tai chi, yoga) have shown mixed results. ACSM evidence category C.
PA can result in acute improvements in systemic insulin action lasting from 2 to 72 h. ACSM evidence category A.
Chronic Effects of Exercise Training
Metabolic Control: BG Levels and Insulin Resistance
Both aerobic and resistance training improve insulin action, BG control, and fat oxidation and storage in muscle. ACSM evidence category B. Resistance exercise enhances skeletal muscle mass. ACSM evidence category A.
Lipids and Lipoproteins
Blood lipid responses to training are mixed but may result in a small reduction in low-density lipoprotein cholesterol (LDL-C) with no change in high-density lipoprotein cholesterol (HDL-C) or triglycerides. Combined weight loss and PA may be more effective than aerobic exercise training alone on lipids. ACSM evidence category C.
Aerobic training may slightly reduce systolic blood pressure (BP), but reductions in diastolic BP are less common in individuals with T2DM. ACSM evidence category C.
Mortality and Cardiovascular Risk
Observational studies suggest that greater PA and fitness are associated with a lower risk of all-cause and cardiovascular (CV) mortality. ACSM evidence category C.
Body Weight: Maintenance and Loss
Recommended levels of PA may help produce weight loss. However, up to 60 min·d-1 may be required when relying on exercise alone for weight loss. ACSM evidence category C.
Supervision of Training
Individuals with T2DM engaged in supervised training exhibit greater compliance and BG control than those undertaking exercise training without supervision. ACSM evidence category B.
Increased PA and physical fitness can reduce symptoms of depression and improve health-related quality of life (QOL) in those with T2DM. ACSM evidence category B.
PA and Prevention of T2DM
At least 2.5 h·wk-1 of moderate to vigorous PA should be undertaken as part of lifestyle changes to prevent T2DM onset in high-risk adults. ACSM evidence category A. ADA A level recommendation.
PA and Prevention and Control of Gestational Diabetes (GDM)
Epidemiologic studies suggest that higher levels of PA may reduce risk of developing GDM during pregnancy. ACSM evidence category C. Randomized controlled trials (RCTs) suggest that moderate exercise may lower maternal BG levels in GDM. ACSM evidence category B.
Before undertaking exercise more intense than brisk walking, sedentary persons with T2DM will likely benefit from an evaluation by a physician. Electrocardiogram (ECG) exercise stress testing for asymptomatic individuals at low risk of coronary artery disease (CAD) is not recommended but may be indicated for higher risk. ACSM evidence category C. ADA C level recommendation.
Recommended PA Participation for Persons with T2DM
Aerobic Exercise Training
Persons with T2DM should undertake at least 150 min·wk-1 of moderate to vigorous aerobic exercise spread out during at least 3 d during the week, with no more than two consecutive days between bouts of aerobic activity. ACSM evidence category B. ADA B level recommendation.
Resistance Exercise Training
In addition to aerobic training, persons with T2DM should undertake moderate to vigorous resistance training at least 2–3 d.wk-1. ACSM evidence category B. ADA B level recommendation.
Supervised and combined aerobic and resistance training may confer additional health benefits, although milder forms of PA (like yoga) have shown mixed results. Persons with T2DM are encouraged to increase their total daily unstructured PA. Flexibility training may be included but should not be undertaken in place of other recommended types of PA. ACSM evidence category B. ADA C level recommendation.
Exercise with Nonoptimal BG Control
Individuals with T2DM may engage in PA, using caution when exercising with BG levels exceeding 300 mg·dL-1 (16.7 mmol·L-1) without ketosis, provided they are feeling well and are adequately hydrated. ACSM evidence category C. ADA E level recommendation.
Persons with T2DM not using insulin or insulin secretagogues are unlikely to experience hypoglycemia related to PA. Users of insulin and insulin secretagogues are advised to supplement with carbohydrate as needed to prevent hypoglycemia during and after exercise. ACSM evidence category C. ADA C level recommendation.
Medication Effects on Exercise Responses
Medication dosage adjustments to prevent exercise-associated hypoglycemia may be required by individuals using insulin or certain insulin secretagogues. Most other medications prescribed for concomitant health problems do not affect exercise, with the exception of beta-blockers, some diuretics, and statins. ACSM evidence category C. ADA C level recommendation.
Exercise with Long-Term Complications of Diabetes
Known cardiovascular disease (CVD) is not an absolute contraindication to exercise. Individuals with angina classified as moderate or high risk should likely begin exercise in a supervised cardiac rehabilitation program. PA is advised for anyone with peripheral artery disease (PAD). ACSM evidence category C. ADA C level recommendation.
Individuals with peripheral neuropathy and without acute ulceration may participate in moderate weight-bearing exercise. Comprehensive foot care including daily inspection of feet and use of proper footwear is recommended for prevention and early detection of sores or ulcers. Moderate walking likely does not increase risk of foot ulcers or reulceration with peripheral neuropathy. ACSM evidence category B. ADA B level recommendation.
Individuals with cardiovascular autonomic neuropathy (CAN) should be screened and receive physician approval and possibly an exercise stress test before exercise initiation. Exercise intensity is best prescribed using the heart rate (HR) reserve method with direct measurement of maximal HR. ACSM evidence category C. ADA C level recommendation.
Individuals with uncontrolled proliferative retinopathy should avoid activities that greatly increase intraocular pressure and hemorrhage risk. ACSM evidence category D. ADA E level recommendation.
Exercise training increases physical function and quality of life in individuals with kidney disease and may even be undertaken during dialysis sessions. The presence of microalbuminuria per se does not necessitate exercise restrictions. ACSM evidence category C. ADA C level recommendation.
Adoption and Maintenance of Exercise by Persons with Diabetes
Efforts to promote PA should focus on developing self-efficacy and fostering social support from family, friends, and health care providers. Encouraging mild or moderate PA may be most beneficial to adoption and maintenance of regular PA participation. Lifestyle interventions may have some efficacy in promoting PA behavior. ACSM evidence category B. ADA B level recommendation.
ACSM Evidence Categories
||Source of Evidence
||Randomized, controlled trials (overwhelming data)
||Provides a consistent pattern of findings with substantial studies
||Randomized, controlled trials (limited data)
||Few randomized trials exist, which are small in size and results are inconsistent
||Nonrandomized trials, observational studies
||Outcomes are from uncontrolled, nonrandomized, and/or observational studies
||Panel consensus judgment
||Panel's expert opinion when the evidence is insufficient to place it in categories A–C
American Diabetes Association (ADA) Evidence-Grading System for Clinical Practice Recommendations
|Level of Evidence
||Clear evidence from well-conducted, generalizable, randomized controlled trials that are adequately powered, including the following:
Compelling nonexperimental evidence, i.e., the "all-or-none" rule developed by the Centre for Evidence-Based Medicine at Oxford
- Evidence from a well-conducted multicenter trial
- Evidence from a meta-analysis that incorporated quality ratings in the analysis
Supportive evidence from well-conducted randomized controlled trials that are adequately powered, including the following:
- Evidence from a well-conducted trial at one or more institutions
- Evidence from a meta-analysis that incorporated quality ratings in the analysis
||Supportive evidence from well-conducted cohort studies, including the following:
Supportive evidence from a well-conducted case–control study
- Evidence from a well-conducted prospective cohort study or registry
- Evidence from a well-conducted meta-analysis of cohort studies
||Supportive evidence from poorly controlled or uncontrolled studies, including the following:
Conflicting evidence with the weight of evidence supporting the recommendation
- Evidence from randomized clinical trials with one or more major or three or more minor methodological flaws that could invalidate the results
- Evidence from observational studies with high potential for bias (such as case series with comparison to historical controls)
- Evidence from case series or case reports
||Expert consensus or clinical experience