Exercise and Diabetes. Sheri R. Colberg

Duration 30–60 min daily, with minimum of 10 min/session At least 150 min/week of moderate- to vigorous-intensity activity Progression Start out on the “low” side and progress slowly over weeks to months Increase duration and frequency first, intensity last (with the possible exception of adding in faster intervals during exercise sessions)

      HRR, heart rate reserve.

      If weight loss is a major goal, a greater duration of exercise may be required to maximize caloric expenditure. The most successful weight-control programs involve combinations of exercise, diet, and behavior modification, and people who successfully maintain a large weight loss report exercising ~7 h/week (Pavlou 1989, Schoeller 1997, Weinsier 2002, Saris 2003, Donnelly 2009).

      Case in Point: Wrap-Up

      Because DG has been mostly inactive for a while, he should start with an initial exercise prescription that allows him to start “low” and progress slowly to avoid injury and to prevent his knee irritation from returning. Another important aspect of his program will be to increase his unstructured daily movement throughout the day, particularly on days that he does not plan to work out in the gym doing his structured program.

      Exercise Program Goals

      Mode of Activity: Given DG’s potential for knee issues, his recommended activities to start include stationary cycling, walking on a treadmill, and use of other conditioning machines that are lower impact (such as cross-trainers and elliptical machines).

      Intensity: DG should attempt to work up to maintaining a workout pace that feels “somewhat hard” to start, possibly “hard” when he begins to feel more conditioned. On the conditioning machines, he can choose “interval” programs that intersperse harder intervals with easier intervals to gain the most fitness with the least amount of training time. His initial target heart rate should be in the range of 104 to 130 bpm (30–59% HRR), with a later training goal of at least 131 bpm (60% of HRR) due to his limited time in the gym.

      Frequency: Because DG has stated that he can only go to the gym 3 days/week, his goal should be to schedule his structured training on 3 nonconsecutive days while increasing his unstructured activities (including golfing) on the other 4 days. In any case, he should avoid letting >2 days lapse without some sustained aerobic activities to optimize his blood glucose management.

      Duration: When beginning his exercise program, DG should engage in shorter bouts of exercise training, separated by a rest period, until he can train continuously for 30–60 min. His ultimate training goal is 150 min of physical activity spread throughout the week.

      Progression: DG should be advised to focus on increasing the duration of his structured workouts on 3 nonconsecutive days/week to attempt to achieve 150 min/week of moderate or vigorous exercise. Once he has established higher levels of physical fitness, he may choose to do combination training that includes some resistance training on at least 2 of his exercise training days.

      Daily Movement: Because of DG’s perceived time limitations and to assist with his weight loss, he should attempt to engage in more daily movement, including fidgeting (such as bouncing or swinging one’s leg repeatedly while seated), standing, and taking more steps. On days that he has no planned exercise schedule, he should attempt to maximize his unstructured activities throughout the day.

      Possible Precautions: Because DG has quite a few risk factors for cardiovascular disease (including elevated lipids, hypertension, diabetes, and obesity), he should consider having a checkup with his doctor and possibly having an exercise stress test before starting regular exercise, to determine his initial fitness level, if nothing else, although neither one is absolutely required before his participation in moderate activities like brisk walking. His medications (metformin and exenatide) should not have any effect on his blood glucose responses to exercise or increase his risk for hypoglycemia, but he should be advised to occasionally monitor his responses to bouts of activity as reductions in glucose levels resulting from exercise can be motivating for many individuals.

      People with T2D should embrace lifestyle changes that include regular physical activity to maximize their blood glucose management and lower their cardiovascular disease risk. Engaging in physical activity facilitates glucose uptake, improves insulin sensitivity, and aids in glucose homeostasis, with effects that lower blood glucose levels for 2–72 h after the last bout of activity, depending on exercise duration, intensity, and subsequent food intake. Current recommendations for adults with T2D suggest that such individuals should engage in at least 150 min a week of moderate to vigorous aerobic exercise spread out over at least 3 days during the week, with no more than 2 consecutive days between bouts of aerobic activity.

      Professional Practice Pearls

      • Participation in regular physical activity improves blood glucose control, blood lipids, blood pressure, cardiovascular risk, mortality risk, and quality of life in T2D.

      • Given that improvements in insulin action that enhance blood glucose control are short lived, aerobic exercise participation should be regular.

      • Although moderate and vigorous aerobic training improve insulin sensitivity more, a lower intensity still improves insulin action to some degree.

      • Glucose-lowering effects of moderate aerobic exercise are similar whether the physical activity is performed in a single session or in multiple bouts with the same total duration.

      • Participation in vigorous exercise may cause a transient increase in blood glucose levels that can last for several hours due to the release of glucose-raising hormones.

      • Individuals with T2D should undertake at least 150 min a week of moderate to vigorous aerobic exercise spread out over at least 3 days during the week, with no more than 2 consecutive days between bouts of aerobic activity.

      • Most people with T2D lack a sufficient aerobic capacity to work out vigorously enough to meet physical activity guidelines that allow for a lesser duration of vigorous work.

      • Each individual’s fitness level and cardiovascular risk factors should be carefully considered before prescribing low-volume, high-intensity interval training.

      • Progress by increasing physical activity gradually over time whenever more activity is necessary to meet guidelines or health goals; inactive individuals should “start low and go slow” by gradually increasing how often and how long activities are done.

      • Individuals who successfully maintain a large weight loss report exercising about 7 h/week.

      REFERENCES

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