Exercise and Diabetes. Sheri R. Colberg

2008). Subjective intensity can be estimated using a scale of 0 to 10, where resting is 0, maximal effort is 10, moderate-intensity activity is 5 to 6, and vigorous-intensity activity is 7 to 8 on that scale (Physical Activity Guidelines Advisory Committee 2008).

       Frequency

      Adults with T1D should perform aerobic exercise at least 3–5 days/week, depending on exercise intensity and duration, but greater regularity may facilitate diabetes management in these individuals. Increased insulin sensitivity resulting from the last bout of exercise is relatively short lived, and more frequent participation in physical activity confers greater benefits in this regard (King 1995, Kirwan 2000, Clevenger 2002, Houmard 2004, Evans 2005, Hawley 2008, Bajpeyi 2009).

      Children and adolescents should engage in daily physical activity, including aerobic, muscle-strengthening, and bone-strengthening activities (Physical Activity Guidelines Advisory Committee 2008). Not all three of these activities necessarily need to be done every day, although some overlap between categories exists.

       Duration

      Adults with T1D should engage in a minimum of 60–75 min/week of vigorous activity (>6 metabolic equivalents [METs]) or 150 min/week of moderate-intensity exercise (3–6 METs), performed for at least 20–30 min/session (minimum of 10-min bouts). As with all adults, around 150 min/week of moderate-intensity exercise is associated with reduced morbidity and mortality, but more health benefits may result from longer participation (Physical Activity Guidelines Advisory Committee 2008).

      Children and adolescents should engage in 60 min (1 h) or more of physical activity daily, or minimally 420 min a week (Physical Activity Guidelines Advisory Committee 2008). This recommended duration, however, includes aerobic activities, usual play, and muscle- and bone-strengthening activities.

       Progression

      If an adult is already normally active or has a reasonable fitness level, he or she can skip the initial training phase and start directly with the improvement phase. Sedentary or deconditioned adults with T1D are advised to begin with low-intensity workouts (<40% HRR), gradually progressing in both exercise intensity and volume to minimize the risk of injury or noncompliance, particularly if he or she has any health complications (Physical Activity Guidelines Advisory Committee 2008). The initial focus should be on increasing frequency and duration of the exercise rather than intensity, although faster training intervals may be used to promote greater fitness and blood glucose management (Guelfi 2005a, 2005b; Guelfi 2007; Iscoe 2011). If weight loss is a major goal, then an exercise duration of ~7 h/week may be necessary (Pavlou 1989, Schoeller 1997, Weinsier 2002, Saris 2003, Donnelly 2009).

      Youth should not solely do moderate-intensity activity, but rather they should include vigorous-intensity activities to elicit greater improvements in cardiorespiratory fitness; their activities, therefore, should progress to include ones of a higher intensity. If starting out deconditioned, they should slowly increase their activity in small steps and in ways that they enjoy. Once conditioned or if beginning at that level, they should maintain or increase their activity level beyond 60 min/day and vary the kinds of activities they do to reduce the risk of overtraining or injury. Adolescents and children with T1D may meet recommended levels of physical activity by doing free play, structured programs, or both (Physical Activity Guidelines Advisory Committee 2008). Structured exercise programs can include aerobic activities, such as playing a sport, and muscle-strengthening activities like lifting weights, using resistance bands, or using body weight for resistance (e.g., push-ups, pull-ups, and sit-ups). Muscle-strengthening activities count if they involve a moderate to high level of effort and work the major muscle groups of the body (i.e., legs, hips, back, abdomen, chest, shoulders, and arms). All of these recommendations are summarized for both adults and youth in Table 6.1.

      Table 6.1 Recommended Aerobic Exercise Rx for Adults and Youth with Type 1 Diabetes

Mode	Adults: Walking, jogging/running, cycling, swimming, rowing, aquatic activities, team sports, dancing, conditioning machines, seated exercise, and more
Youth: Running, hopping, skipping, jumping rope, swimming, dancing, bicycling, basketball, tennis, skateboarding, rollerblading, and team sports
Intensity	Adults: 40–89% HRR (initial intensity may need to be lower for sedentary, deconditioned, and overweight individuals) Perceived exertion of “somewhat hard” (5–6 on 10-point scale) to “hard” (7–8)
Youth: moderate or vigorous intensity (40–89% HRR), but vigorous-intensity physical activity (60–89% HRR) at least 3 days a week Perceived exertion of “somewhat hard” (5–6) to “hard” (7–8)
Frequency	Adults: 3–7 days/week (including structured and lifestyle activity) 3 days of vigorous or 5 days of moderate intensity (greater regularity may facilitate diabetes management)
Youth: 7 days/week of physical activity (including aerobic, muscle-strengthening, and bone-strengthening activities)
Duration	Adults: At least 20–30 min/session (minimum 10-min bouts) Minimum of 150 min/week of moderate-intensity (3–6 METs) or 60–75 min/week of vigorous-intensity (>6 METs) physical activity
Youth: At least 60 min (1 h) of daily physical activity (420 min a week), including aerobic activities, usual play, and muscle- and bone-strengthening activities
Progression	Adults: Start out on the “low” side if deconditioned, and progress slowly over weeks to months; start with the “improvement” phase if fitness levels adequate Increase duration and frequency first, intensity last (with the possible exception of adding in faster intervals during exercise sessions)
Youth: Start out slowly with small increases in activity if deconditioned, but all should progress to engaging in vigorous activity at least three times weekly; once conditioned, maintain or increase activity level and vary activities to reduce the risk of overtraining or injury Possible to meet recommended levels of physical activity by doing free play, structured programs, or both

      HRR, heart rate reserve; MET, metabolic equivalent.

      Case in Point: Wrap-Up

      Because MF desires to focus on both weight and diabetes management through her exercise program and her schedule is somewhat flexible in college, she decides to start regularly working out at her university’s student recreation center, where she has access to fitness equipment, classes, and other activities.

      Exercise Program Goals

      Mode of Activity: MF desires to undertake multiple training activities—she likes the idea of cross-training to get more fit and avoid injuries—so she can include conditioning machines (like cross-trainers and elliptical machines), lap swimming, and spinning (cycling) classes as some of her choices.

      Intensity: Because MF is starting out somewhat deconditioned (except for walking around campus), she should start with more moderate activities (that feel “somewhat hard” or 5–6 on a 10-point scale) to start and work up to “hard” ones (7–8 using that scale). She should choose interval or hill workouts on the conditioning machines. Her initial target heart rate should start in a moderate-intensity range (130–152 bpm, or 40–59% HRR), with a target goal of 60–89% HRR (153–187 bpm), with a maximal target of 187 bpm (89% HRR). Her intensity during each training session can vary, however, and she may choose to do harder (vigorous) and easier (moderate) workout days to prevent overtraining.

      Frequency: Depending on how MF alternates her training intensity, she should do 3–5 days of planned training a week (3 days if vigorous, 5 days if moderate, or a combination of the two intensities and frequencies), keeping in mind that being more regular with her training may make it easier for her to make regimen changes to manage her blood glucose levels. Her insulin action may stay