Exercise and Diabetes. Sheri R. Colberg

diabetes 6–12 weeks postpartum (American Diabetes Association 2013a, 2013b).

      DIAGNOSIS OF DIABETES

       T1D and T2D

      Currently, the American Diabetes Association recommends the use of any of the following four criteria for diagnosing diabetes: 1) hemoglobin A1C value of 6.5% or higher; 2) fasting plasma glucose ≥126 mg/dl (7.0 mmol/l); 3) 2 h plasma glucose ≥200 mg/dl (11.1 mmol/l) during an OGTT using 75 g of glucose; or 4) classic symptoms of hyperglycemia (e.g., polyuria, polydipsia, and unexplained weight loss) or hyperglycemic crisis with a random plasma glucose of 200 mg/dl (11.1 mmol/l) or more (American Diabetes Association 2013a, 2013b) (Table 1.2). In the absence of unequivocal hyperglycemia, the first three criteria should be confirmed by repeat testing on a second occasion.

      Table 1.2 Diagnosis of Diabetes by Type

       Gestational Diabetes

      The International Association of Diabetes and Pregnancy Study Groups recently developed revised recommendations for the diagnosis of GDM (International Association of Diabetes 2010). After an overnight fast of at least 8 h, the pregnant woman ingests 75 g of glucose orally, with monitoring of fasting plasma glucose and 1 and 2 h postingestion glucose values. The diagnosis is made when any one of the following plasma glucose values is exceeded: fasting ≥92 mg/dl (5.1 mmol/l); 1 h ≥180 mg/dl (10.0 mmol/l); or 2 h ≥153 mg/dl (8.5 mmol/l) (American Diabetes Association 2013a, 2013b). It is expected that these new criteria will increase the prevalence of GDM because they require only that one abnormal value be recorded, whereas the former criteria required two to be met. Also, given that some cases diagnosed during pregnancy are actually cases of undiagnosed T2D, it is recommended that women with a history of GDM be screened for diabetes 6–12 weeks after delivery, using nonpregnant diagnostic criteria during an OGTT (American Diabetes Association 2013a).

       Prediabetes

      Individuals with prediabetes have glucose levels that do not meet the criteria for diabetes, but that are higher than normal, putting them at risk for related metabolic disorders. They can meet one or both criteria for IFG and IGT to be classified as being at high risk for developing T2D, or their overall glucose levels can exceed normal (as determined with an A1C test). Currently, prediabetes is diagnosed with fasting plasma glucose of 100–125 mg/dl (6.1–6.9 mmol/l) (i.e., IFG), 2 h OGTT plasma glucose of 140–199 mg/dl (7.8–11.0 mmol/l) (i.e., IGT), or an A1C of 5.7%–6.4%.

      PHYSICAL ACTIVITY VERSUS EXERCISE

      Before the discussion moves from what type of diabetes an individual has to which type of activity he or she should be doing, the professional needs to understand the meaning of the terms physical activity and exercise, which are used interchangeably in this book. By definition, physical activity is any bodily movement produced by the contraction of skeletal muscle that substantially increases energy expenditure (above resting), whereas exercise training is the subset of planned, structured, and repetitive bodily movements done with the intention of developing or maintaining physical fitness, which includes cardiovascular, strength, and flexibility training options (Haskell 2007, Nelson 2007).

      Although use of the broader “physical activity” in place of the narrower “exercise” has caused some confusion even among health-care and fitness professionals, the intent is simply to recognize that many types of movements can have a positive impact on health-related physical fitness without qualifying as a planned exercise. In fact, more than one type of physical activity (such as combined aerobic and resistance training programs, along with lifestyle movement) is frequently required to yield measurable improvements for each of the components in the health-related fitness category.

      Exercise training programs for individuals with diabetes typically include activities to enhance cardiovascular capacity (aerobic fitness) and muscular fitness and strength in people of all ages, as well as flexibility and balance in older individuals. Each person’s exercise program, however, should be modified according to his or her habitual physical activity, physical function, health status, exercise responses, and stated goals (Garber 2011). Adults who are unable or unwilling to meet the recommended minimal exercise targets can still benefit from engaging in amounts of exercise and other physical activities (like daily movement) that fail to meet those levels. Such strategies can be used when helping individuals with and at risk for diabetes make positive and lasting changes in their physical activity and exercise habits.

      UNDERSTANDING AND DEFINING PHYSICAL FITNESS

      It is imperative that health-care and fitness professionals use the same fitness terminology. Physical fitness has long been defined as “a set of attributes that people have or achieve relating to their ability to perform physical activity” (Caspersen 1985). What complicates physical fitness is that there are many different reasons to engage in a physically active lifestyle, including gaining positive health outcomes and optimizing sports and athletic performance. To simplify matters, the following table (Table 1.3) organizes the accepted terminology into four different categories of physical fitness: physiological fitness, health-related fitness, skill-related fitness, and sports.

      The terminology of fitness is intended to be inclusive rather than athletic in nature when considering what affects an individual’s fitness level and health outcomes. For instance, individuals with diabetes do not need to have skill-related talents, participate in sports, or work out at a fitness club to achieve physiological or health-related benefits from increased physical fitness. Thus, a primary goal of the diabetes health-care and fitness professionals should be to encourage individuals to engage in appropriate physical activities to help them achieve positive health- and fitness-related outcomes.

      Table 1.3 Fitness Categories and Related Terminology

Category	Related Terminology
Physiological	Metabolic Morphological Bone integrity Other
Health related	Cardiovascular fitness Musculoskeletal fitness (endurance and strength) Flexibility Body composition
Skill related	Agility Balance Coordination Power Speed Reaction time Other
Sports	Team Individual Lifetime Other

       Physiological Fitness

      Physiological fitness in particular relates to how an individual performs a physical activity, given that physiological fitness is most influenced by the regular inclusion of habitual physical activity (or, conversely, physical inactivity). In particular, metabolic fitness refers to the status of metabolic systems and variables predictive of the risk for diabetes and cardiovascular disease; increases in fitness lower the risk of both diabetes and heart problems (Simmons 2008, Sui 2008, Look Ahead Research Group 2010, Seeger 2011). Similarly, morphological fitness focuses on improvement in body compositional factors, such as body circumference, body fat, and regional body fat distribution, all of which can affect metabolic health and diabetes management (Jacob 2006, Iqbal 2007, Wang 2008, Lee 2009). Finally, bone integrity refers to bone strength and the status of bone mineral density, which can be positively affected by regular participation in almost any type of physical activity (Gorman 2012).

       Health-Related Physical Fitness

      Although it is closely related to the aforementioned category of physiological fitness with regard to metabolic health, the health-related physical fitness category contains terms that are recognized for their direct relationship to good health: cardiovascular fitness, musculoskeletal fitness, body composition, and flexibility. All of these components of fitness are important for patients with diabetes for optimal health and performance. For the individual engaging in a fitness