The adoption and maintenance of physical activity are critical foci for blood glucose management and overall health in individuals with diabetes and prediabetes. Recommendations and precautions vary depending on individual characteristics and health status. In this Position Statement, we provide a clinically oriented review and evidence-based recommendations regarding physical activity and exercise in people with type 1 diabetes, type 2 diabetes, gestational diabetes mellitus, and prediabetes.
Physical activity includes all movement that increases energy use, whereas exercise is planned, structured physical activity. Exercise improves blood glucose control in type 2 diabetes, reduces cardiovascular risk factors, contributes to weight loss, and improves well-being (1,2). Regular exercise may prevent or delay type 2 diabetes development (3). Regular exercise also has considerable health benefits for people with type 1 diabetes (e.g., improved cardiovascular fitness, muscle strength, insulin sensitivity, etc.) (4). The challenges related to blood glucose management vary with diabetes type, activity type, and presence of diabetes-related complications (5,6). Physical activity and exercise recommendations, therefore, should be tailored to meet the specific needs of each individual.
TYPES AND CLASSIFICATIONS OF DIABETES AND PREDIABETES
Physical activity recommendations and precautions may vary by diabetes type. The primary types of diabetes are type 1 and type 2. Type 1 diabetes (5%–10% of cases) results from cellular-mediated autoimmune destruction of the pancreatic β-cells, producing insulin deficiency (7). Although it can occur at any age, β-cell destruction rates vary, typically occurring more rapidly in youth than in adults. Type 2 diabetes (90%–95% of cases) results from a progressive loss of insulin secretion, usually also with insulin resistance. Gestational diabetes mellitus occurs during pregnancy, with screening typically occurring at 24–28 weeks of gestation in pregnant women not previously known to have diabetes. Prediabetes is diagnosed when blood glucose levels are above the normal range but not high enough to be classified as diabetes; affected individuals have a heightened risk of developing type 2 diabetes (7) but may prevent/delay its onset with physical activity and other lifestyle changes (8).
TYPES OF EXERCISE AND PHYSICAL ACTIVITY
Aerobic exercise involves repeated and continuous movement of large muscle groups (9). Activities such as walking, cycling, jogging, and swimming rely primarily on aerobic energy-producing systems. Resistance (strength) training includes exercises with free weights, weight machines, body weight, or elastic resistance bands. Flexibility exercises improve range of motion around joints (10). Balance exercises benefit gait and prevent falls (11). Activities like tai chi and yoga combine flexibility, balance, and resistance activities.
BENEFITS OF EXERCISE AND PHYSICAL ACTIVITY
Aerobic Exercise Benefits
Aerobic training increases mitochondrial density, insulin sensitivity, oxidative enzymes, compliance and reactivity of blood vessels, lung function, immune function, and cardiac output (12). Moderate to high volumes of aerobic activity are associated with substantially lower cardiovascular and overall mortality risks in both type 1 and type 2 diabetes (13). In type 1 diabetes, aerobic training increases cardiorespiratory fitness, decreases insulin resistance, and improves lipid levels and endothelial function (14). In individuals with type 2 diabetes, regular training reduces A1C, triglycerides, blood pressure, and insulin resistance (15). Alternatively, high-intensity interval training (HIIT) promotes rapid enhancement of skeletal muscle oxidative capacity, insulin sensitivity, and glycemic control in adults with type 2 diabetes (16,17) and can be performed without deterioration in glycemic control in type 1 diabetes (18,19).
Resistance Exercise Benefits
Diabetes is an independent risk factor for low muscular strength (20) and accelerated decline in muscle strength and functional status (21). The health benefits of resistance training for all adults include improvements in muscle mass, body composition, strength, physical function, mental health, bone mineral density, insulin sensitivity, blood pressure, lipid profiles, and cardiovascular health (12). The effect of resistance exercise on glycemic control in type 1 diabetes is unclear (19). However, resistance exercise can assist in minimizing risk of exercise-induced hypoglycemia in type 1 diabetes (22). When resistance and aerobic exercise are undertaken in one exercise session, performing resistance exercise first results in less hypoglycemia than when aerobic exercise is performed first (23). Resistance training benefits for individuals with type 2 diabetes include improvements in glycemic control, insulin resistance, fat mass, blood pressure, strength, and lean body mass (24).
Benefits of Other Types of Physical Activity
Flexibility and balance exercises are likely important for older adults with diabetes. Limited joint mobility is frequently present, resulting in part from the formation of advanced glycation end products, which accumulate during normal aging and are accelerated by hyperglycemia (25). Stretching increases range of motion around joints and flexibility (10) but does not affect glycemic control. Balance training can reduce falls risk by improving balance and gait, even when peripheral neuropathy is present (11). Group exercise interventions (resistance and balance training, tai chi classes) may reduce falls by 28%−29% (26). The benefits of alternative training like yoga and tai chi are less established, although yoga may promote improvement in glycemic control, lipid levels, and body composition in adults with type 2 diabetes (27). Tai chi training may improve glycemic control, balance, neuropathic symptoms, and some dimensions of quality of life in adults with diabetes and neuropathy, although high-quality studies on this training are lacking (28).
BENEFITS OF AND RECOMMENDATIONS FOR REDUCED SEDENTARY TIME
All adults, and particularly those with type 2 diabetes, should decrease the amount of time spent in daily sedentary behavior. B
Prolonged sitting should be interrupted with bouts of light activity every 30 min for blood glucose benefits, at least in adults with type 2 diabetes. C
The above two recommendations are additional to, and not a replacement for, increased structured exercise and incidental movement. C
Sedentary behavior—waking behaviors with low energy expenditure (TV viewing, desk work, etc.)—is a ubiquitous and significant population-wide influence on cardiometabolic health (29,30). Higher amounts of sedentary time are associated with increased mortality and morbidity, mostly independent of moderate-to-vigorous physical activity participation (31–35). In people with or at risk for developing type 2 diabetes, extended sedentary time is also associated with poorer glycemic control and clustered metabolic risk (36–39). Prolonged sitting interrupted by brief (≤5 min) bouts of standing (40–42) or light-intensity ambulation (41,43,44) every 20–30 min improves glycemic control in sedentary overweight/obese populations and in women with impaired glucose regulation. In adults with type 2 diabetes, interrupting prolonged sitting with 15 min of postmeal walking (45) and with 3 min of light walking and simple body-weight resistance activities every 30 min (46) improves glycemic control. The longer-term health efficacy and durability of reducing and interrupting sitting time remain to be determined for individuals with and without diabetes.
PHYSICAL ACTIVITY AND TYPE 2 DIABETES
Daily exercise, or at least not allowing more than 2 days to elapse between exercise sessions, is recommended to enhance insulin action.
Adults with type 2 diabetes should ideally perform both aerobic and resistance exercise training for optimal glycemic and health outcomes.
Children and adolescents with type 2 diabetes should be encouraged to meet the same physical activity goals set for youth in general.
Structured lifestyle interventions that include at least 150 min/week of physical activity and dietary changes resulting in weight loss of 5%–7% are recommended to prevent or delay the onset of type 2 diabetes in populations at high risk and with pre-diabetes.