Diabetes Forecast

Exercise: Good Questions (and Answers)

It's time to get going. Here are 20 things you should know about getting fit

By Tracey Neithercott ,

You don't have to cover 26 miles on foot in order to be called an athlete. You aren't required to crest a mountain or navigate a winding road on two wheels before you're considered physically fit. And just because your doctor told you to get more exercise doesn't mean you need to plug away at the gym for hours and hours on end.

Sure, your best friend may run 6 miles a day, but you might get what you need from a brisk walk around the neighborhood. In fact, research shows that almost any physical activity is good activity when it comes to your health. Being active protects against cardiovascular disease and stroke, helps the lungs and heart work at peak performance, fights high cholesterol and high blood pressure, lessens arthritis pain, prevents falls in older adults, relieves stress, combats osteoporosis, and encourages weight loss. Exercising may also help you get a better night's sleep, revive a lagging libido, keep you healthier after a heart attack, and even improve your mood. For people with diabetes, exercise is even more of a boon, since it can lower blood glucose levels and improve insulin sensitivity.

If you've just been diagnosed and wonder how you'll get in shape—or if you've had diabetes for a long time but still want to be more active—there's no time like the present. "Don't use diabetes as an excuse not to exercise. Use it as an excuse to exercise," says Sheri R. Colberg, PhD, an exercise physiologist and professor of exercise science at Old Dominion University and author of Diabetic Athlete's Handbook. To help you launch a successful fitness plan, we grilled the experts on the basics of exercising with diabetes.

A reader tells his story of learning to manage diabetes during exercise, here.

1. Why should I exercise?

Everyone, not just people with diabetes, needs to exercise regularly. "People who are more physically fit have a lower mortality [rate]," says Ronald J. Sigal, BSc, MD, MPH, FRCPC, a professor at the University of Calgary in Canada who studies exercise as it relates to diabetes and cardiovascular disease. "They live longer over time. It does a lot of good things in terms of heart function and lowering the risk of heart attack and stroke."

2. How much aerobic exercise should I get?

According to Sigal, who was the lead author of the American Diabetes Association's exercise guidelines for type 2 diabetes, you should log 150 minutes at moderate intensity (like walking) each week. That works out to about 30 minutes a day, five days a week, or 50 minutes a day, three days a week. To cut down on the number of training sessions, you can up your intensity: Do 90 minutes of vigorous exercise (anything that leaves you short of breath) per week—or about 30 minutes a day for three days. But don't go more than two consecutive days without exercise, or its effect on insulin sensitivity will wane. And if you want to lose weight, you'll probably have to work out more. A recent study found that 50 minutes of moderate-intensity exercise five days a week was necessary for significant weight loss.

3. Do I have to exercise all at once?

Split your 30 minutes of daily exercise as you please—say, 20 minutes after lunch and 10 minutes after dinner—but keep each session at least 10 minutes long, says Sigal.

4. How does exercise affect my blood glucose?

When you work up a sweat, your body begins by using all of the glucose stored in your muscles for energy. Next, it draws glucose from your blood, lowering your levels. Exercise also helps you use the insulin circulating in your system more effectively. "Physical activity acts like a separate dose of insulin without having to take insulin," says Colberg. Depending on the type of exercise (a light walk versus a vigorous 10-mile bike ride) and how long you're active, exercise's action on insulin can last anywhere from a couple of hours to a few days.

Hypoglycemia (low blood glucose) can be a concern for people taking insulin or sulfonylureas and meglitinides. If, before exercising, you take more insulin than your body needs to maintain glucose control, or if you exercise too hard or for too long, you could go low. (Click here for details on how to prevent and treat exercise-induced hypoglycemia.)

It may seem contradictory, but exercise can also raise your blood glucose levels. During an all-out sprint that leaves you huffing for air, your body releases hormones like adrenaline and cortisol that raise blood glucose levels. If you often do intense exercises that cause blood glucose spikes, be prepared for possible dips later in the day,
says Sigal.

5. Do I need to change my insulin dosage when I begin a fitness plan?

Maybe. Physical activity helps your body use insulin more efficiently and reduces the amount of glucose in your blood. Plus, the result of being active—bigger muscles—allows your body extra storage space for glucose. So, to avoid hypoglycemia during and after exercise, it may be necessary to scale back your insulin. For instance, if you plan to work out after lunch, you may need to reduce the insulin you take with your meal. A good place to start is by decreasing your dose by about 20 percent, says Sigal. "People who are more active tend to use less insulin," he says. "You could find a decrease in insulin requirements compared to a day when there's no physical activity." But remember, what works for one person may not work for another, so test often.

6. Do oral medications put me at risk for exercise-induced hypoglycemia?

While people who take insulin need to be cautious about low blood glucose, those with type 2 who are on oral medications have less to worry about. "We see very [little] hypoglycemia in type 2," says Sigal, who conducted a study on exercise in more than 250 people with type 2 diabetes. "It's not that it never happens, but that it happens less frequently." If you've just jumped into a new routine and fear going too low, test your blood glucose pre- and post-workout to see how your numbers change.

7. My blood glucose level is high. Can I still work out?

As long as your blood glucose levels are under 250 mg/dl, you're safe to exercise. If they rise higher, exercise with caution. People with type 1 should test for ketones once the meter reads 250. It's unwise to exercise if ketones are present in more than trace amounts.

8. When is the best time to exercise?

If you're not a morning person, you're unlikely to be successful in any fitness pursuits that involve rolling out of bed at 5 a.m., and that's fine. However, certain times of day may bolster blood glucose control better than others. In a study on exercise in people with type 2, Colberg found that working out 20 minutes after dinner led to better blood glucose control than exercising 20 minutes before the meal. Those who use insulin, however, may want to pound the pavement before eating. Doing so puts you at less risk for hypoglycemia since the only insulin in your system is the long-acting form. (If you exercise after taking insulin before a meal, your insulin may spike just as your body is using up its excess glucose.)

9. Do I really need to check with my doctor before working out?

If you conferred with your doctor every time you exercised, you (and your doctor) would go mad. Checking with the doc is key for sedentary people who want to begin an exercise routine or someone making a dramatic change. Getting a checkup and possibly a stress test might prevent a heart attack or other injuries in people over 40 who have never exercised before or in those who have neuropathy, kidney disease, retinopathy, or heart complications, says Sigal. If you're already active and looking to start a new activity—or plan on starting slow with, say, a walking program—you can do so without your doc's go-ahead.

10. Is it dangerous to exercise when the weather is hot?

Working up a sweat when it's sweltering out can lead to dehydration in anyone. But people with diabetes should take extra caution. "There's some increased risk of dehydration, and for people with diabetes that risk is accentuated because with dehydration often the glucose levels become increased," says Sigal. If you have autonomic neuropathy, which can thwart the body's ability to regulate body heat, it's particularly important to exercise in a cool place, like an air-conditioned gym.

11. I hate to go to the gym. What else can I do?

Exercise isn't synonymous with plugging away endlessly on a treadmill. "Go for a walk, hike, swim, or bike ride to get into nature and burn some calories," says Jillian Michaels, fitness coach for the TV show The Biggest Loser. Make a list of places in your town or city you'd like to explore on foot, then start checking them off. "Find something you love. Try dance classes, spinning, martial arts—whatever," she says. "Make it something you enjoy doing, and you're more likely to stick with it."

12. How can I motivate myself?

Even fitness buffs will agree: The hardest part of an exercise routine is continuing to do it. "Spend some time thinking about all the reasons you want to get in shape, all of the ways your life will improve," says Michaels. "Whatever your reasons, there isn't one too shallow or too profound. Then, write them all down and post the lists all over your house." Still lacking enthusiasm? "For many people, it's really advisable to write it into their calendars, make it part of the routine," says Sigal.

13. What should I bring on my workout?

It doesn't matter whether you're going for a short walk or an all-day hike: If you use insulin or are on an oral med that ups your risk of hypoglycemia, always have a form of fast-acting carbohydrate with you, carry a driver's license or other ID, and wear a medical alert bracelet in case you have a low. If you have type 1, stash a meter in a pocket so that you can test midway through a long workout. People with type 2 can test before and after a new activity to learn how the body reacts to exercise. Another helpful tool: your cell phone. It comes in handy, says Colberg, when you're low and need help or a ride home.

14. Do I have to warm up and cool down?

Yes. You should add five minutes of light aerobic activity to the start of your workout and close with five minutes of stretching. "The warm-up is meant to literally heat your body up, to help you avoid injury by creating more elasticity in your muscles and tendons," says Michaels. "The cooldown is to help your heart recover and to stretch out tight muscles."

15. Should I lift weights?

Either aerobic exercise (jogging, biking, or swimming) or resistance training (like weight lifting) can improve your glycemic control. But Sigal found in a study on exercise in people with type 2 diabetes that doing both will generate better results. In the study, published in the September 2007 issue of the Annals of Internal Medicine, participants who followed an aerobic and strength-training program reduced their A1Cs more than those who did either exercise alone. You should strength train three times a week, skipping a day between each session. The reason? Weight lifting causes minor damage to the muscles, and you'll need a full day of recovery.

16. How often—and how heavy a weight—should I lift?

Sigal recommends about six or eight exercises per session. You should aim to complete eight to 10 repetitions per exercise, working your way up to three sets for each exercise. Pick a weight that you can't lift more than 12 times in a row with good form, says Michaels. If you hit rep No. 12 and your muscles aren't fatigued, switch to a heavier weight.

17. Should I do cardio or lift weights first?

After your five-minute warm-up, Michaels suggests circuit training, a combination of cardio and strength training. "This means you do your weight training in an aerobic way by not resting in between sets," she says. "So, for example, you would do a set of push-ups immediately followed by a set of squats, then a quick 30-second cardio interval of jumping jacks." Repeat the circuit three times with no rest, and you'll work your cardiovascular system and tire your muscles. And if you're exercising outside, you can do the same thing by interrupting a walk with a set of lunges, push-ups, or squats.

18. What is interval training, and should I do it?

To get your heart really pumping, combine moderate-intensity cardio with spurts of vigorous activity. If you work out on a stationary bike, for example, punctuate a steady cruising speed with a minute or two of extra-fast pedaling every five minutes. You can also interval train outside: "Every few minutes, try to walk faster from one driveway to the next driveway," says Colberg.

19. Which exercises should I do, and which muscles should I target?

Find an activity you enjoy and you'll be more likely to stick with it. That said, if you simply want to get fit and get it over with, Michaels suggests incline walking on a treadmill. "It burns tons of calories but has very minimal impact [on your joints]," she says. To build strength, focus on your major muscle groups and watch smaller muscles form in the process. "Train your back and you will hit the biceps automatically. Train the chest and you will hit the shoulders and triceps as well," says Michaels. "Train [your buttocks, thighs, and hamstrings], and you will hit the calves, too. Then don't forget a little abs work."

20. Do I need to start slow if I'm new to exercising?

"Always err on the side of being too easy when you start a [new] exercise," says Colberg. In other words: Begin with a stationary bike before you hit the trails, or go for a nightly stroll before you try a hike. "Give your body two weeks to acclimate to the exercise regimen to avoid injury," says Michaels. "Then you can start stepping
things up."

Once you get going, you may be surprised at how much you enjoy being active, challenging your body, and reaping rewards like better mobility. You may even look forward to a brisk bike ride after a long workday or a cool swim on a sweltering summer afternoon. "It's very rewarding to see that if you do an activity, it made your blood sugar go down," says Colberg. In fact, even if you've been recently diagnosed with diabetes, you may find you're healthier (and happier!) after your diagnosis than you were before.

Don't Go Low

A recent study revealed what most people with type 1 diabetes already know: Many don't exercise for fear of low blood glucose. If you use insulin, you have an increased risk for hypoglycemia during exercise, and it's important to take precautions. "When you inject insulin, you can't turn it off. And exercise increases absorption," says Sheri R. Colberg, PhD, an exercise physiologist and professor of exercise science at Old Dominion University and author of Diabetic Athlete's Handbook. "You really have to do a little planning."

If, for instance, you take insulin and intend to exercise in the afternoon, you'll need to determine whether the short-acting insulin you took with lunch will be active—or peaking—at that time. "The most flexible way to deal with [the chance of a low] is by taking more carbohydrates," says University of Calgary professor Ronald J. Sigal, BSc, MD, MPH, FRCPC, who studies exercise as it relates to diabetes and cardiovascular disease. "Glucose tablets are probably the best because they are fast acting, you're not getting [too many] calories, and they're quite portable." Another option is to reduce your rapid-acting insulin in advance, if you know you'll be working out within a few hours.

Since physical activity can deplete your glucose stores, you may experience a low between 30 minutes and two hours afterward. To prevent it, cap your workout with a snack that's a combination of protein, fat, and carbs, says Colberg, who has had type 1 diabetes for more than 40 years and snacks on yogurt after exercising. "It doesn't make my blood sugar spike, but it keeps me from going low after," she says. After-dinner workouts may cause nighttime hypoglycemia in people taking insulin, so if you just started working out in the evening, set an alarm and check your glucose levels in the middle of the night.

You may also need glucose during a workout, especially a long-duration activity. Even people without diabetes who exercise for more than 90 minutes need to supplement with carbohydrates, like an energy bar or glucose gels. Start by eating 15 grams of carbs every 30 minutes to an hour, then test your blood glucose to ensure you don't dip too low. "It's a little bit trial and error," says Colberg. "It depends on how much insulin you're using [and] how hard that activity is."

Still, exercise is a critical aspect of diabetes management, and fear shouldn't dissuade you from being active. "Cutting it out shouldn't be an option," says Colberg.



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