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HEART Insight:
doi: 10.1097/01.HEARTI.0000363809.36165.a1
Features: Fit & Happy

Baby, It's Cold Outside!

Fuerst, Mark L.

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But That's No Excuse To Hibernate All Winter

There's a nip in the air, and the first snow has fallen, two clear signs it's time to rev up your physical activity during the cold winter months ahead. If you have heart disease, it's important for you to stay fit and keep your heart pumping, even in the dead of winter.

Some winter sports, such as downhill skiing, ice-skating, hiking and indoor swimming or walking, offer ample opportunity to safely get in the 2 hours and 30 minutes per week of moderate-intensity aerobic physical activity recommended by the American Heart Association. Other sports, such as cross-country skiing or snowshoeing, may be more dangerous for your heart.

If you have heart disease or diabetes, you need at least 150 minutes of moderate-intensity physical activity a week to maintain health. The activity should be done in blocks of at least 10 minutes, and preferably spread throughout the week. If you don't have large blocks of time, try to get 30 minutes on most days of the week, with 10-minute blocks three times a day. “Heart patients and diabetics can't just take a break from exercise until the weather warms up,” Gerald Fletcher, M.D., Professor of Medicine at the Mayo Clinic in Jacksonville, FL. “It will be easier to adapt to almost any environment, cold or otherwise, if you are already physically active most days of the week.”

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Heart disease risk factors may be harder to control during cold weather, cautions Fletcher. Blood pressure is often higher in cold weather, and going out into the frigid air can trigger a condition known as cold-air angina, which is chest pain and discomfort caused by inhaling cold air. Cold temperatures may also trigger life-threatening cardiac events, such as heart attack — even if you live someplace where it's not especially bone-chilling. In fact, a recent study done in Munich, Germany, found that those with congestive heart failure were at higher risk of dying as temperatures became colder.

“[When you] exercise in the cold...blood vessels tend to constrict, [which] increases resistance to blood flow, [causing] increase[d] blood pressure and demands on the heart,” explains Barry Franklin, Ph.D., Director of the Cardiac Rehabilitation and Exercise Laboratories at William Beaumont Hospital in Royal Oak, MI. In addition, heart rate tends to be higher in cold weather, and blood vessels feeding the heart may go into spasm, which reduces blood flow to the heart, says Franklin.

Certain high blood pressure and heart medications may also make it harder for your body to handle the cold, particularly diuretics, beta-blockers and vasodilators, which can alter heart rate, exacerbate the tendency of blood pressure to rise in the cold and interfere with the ability to maintain safe body temperatures during physical activity, says Franklin. Body temperatures below normal can lead to hypothermia. This occurs when your body can't produce enough energy to keep the internal body temperature warm enough, which may lead to deadly heart failure.

An added complication is that many heart patients and diabetics don't watch their diets as closely during the “holiday season,” which — let's face it — runs from Halloween through Super Bowl Sunday in early February. Excess weight adds its own stress to the body, apart from the effect of single-digit temperatures.

“Enjoy holiday food as long as you don't eat too much,” says Stephen Rosen, M.D., Chief of Endocrinology and Metabolism at Pennsylvania Hospital in Philadelphia. “If you have diabetes and you gain weight during the holidays, you will need to work it off.” And the sooner you start losing weight, the easier it will be to control your blood sugar and blood pressure — and to maintain that control.

A Kaiser Permanente study of 2,574 type 2 (adult-onset) diabetes patients found that those who lost about 10 percent of their weight within 18 months of diagnosis were more likely to have normal blood sugar and blood pressure levels when the study ended four years later, as compared with those who gained weight or stayed at the weight they were in the beginning.

And for those who have high blood pressure, working up a sweat could be a key lifestyle change to prevent complications, such as stroke or kidney disease. A recent look at data from the seventh National Health and Nutrition Examination Survey, conducted by the National Center for Health Statistics of the Centers for Disease Control and Prevention, found that 71 percent of the patients with high blood pressure who took their physician's advice and increased physical activity saw an average 3–4 mmHg (millimeters of mercury) drop in systolic blood pressure (the top number in the blood pressure reading).

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Aside from walking, that is. Downhill skiing, ice-skating and hiking are outdoor winter activities that promote heart health and fitness. Like all aerobic workouts, these sports keep the heart pumping at a high enough rate for long enough to boost “good” high-density lipoprotein cholesterol, and help keep high blood pressure in check. These activities also build endurance and help maintain normal weight or aid weight loss, says Fletcher.

Of course, people who have diabetes need to be careful about injury, but that shouldn't rule out downhill skiing. “If you do regular physical activity and are a diabetic who has good blood pressure, good blood sugar control, no increase in blood cholesterol and no diabetic complications, there's no reason you can't go downhill skiing,” says Rosen. However, he does caution skiers who have diabetes to pay particular attention to their hands and feet. Diabetes commonly causes peripheral neuropathy, a condition that often interferes with nerve signals and makes it hard to sense coldness in the hands and feet, thereby making diabetics more prone to frostbite.

In addition, research conducted at the University of Freiberg, Germany, found that cross-country skiing a distance of four miles at a moderate pace for 90 minutes (equal to a brisk walk) caused abnormal heart rhythms in 10 study participants who had already had a heart attack and were new to the sport. The study suggests that it's probably not a good idea to wake up one morning and decide to take up cross-country skiing if you've already had an adverse coronary event.

Cross-country skiing and snowshoeing may be dangerous for heart patients. “Physical activities that use the upper extremity (hand, wrist, elbow, arm, shoulder and neck) like cross-country skiing and snowshoeing tend to increase blood pressure and put added pressure on the heart, which could lead to a heart attack,” explains Fletcher.

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For this reason, people with known or hidden heart disease can have a sudden, fatal heart attack after shoveling snow. “People who have underlying heart disease and are unaccustomed to vigorous physical activity are predisposed to a heart attack during snow shoveling,” says Franklin. It's not just lifting a shovel laden with snow with your arms that increases risk, but also the blood vessel constriction that causes a dangerous spike in blood pressure or a spasm in the coronary arteries. In other words, the whole megillah. Franklin's research shows that just 10 minutes of shoveling heavy, wet snow can raise the heart rate up to its maximal level, which can be dangerously high for heart patients.

“You don't have to hibernate in winter. Be more cautious about the weather conditions and the potential environmental stresses on your heart,” says Franklin. HI

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Cold Weather Precautions

If you have heart disease risk factors or type 2 diabetes, and have not performed physical activity regularly, you should see your doctor and begin increasing daily physical activity before going on that long-planned ski vacation, or engaging in other vigorous activities. A medical checkup might lead your doctor to advise an exercise test. If you are in good physical condition, winter sports can be invigorating, particularly if you take the following safety measures:

▪ Dress appropriately. Wear a hat and several layers of light, loose, water- and wind-resistant clothing for warmth and protection — as well as a scarf, if cold air is a known trigger for your angina symptoms. Even when it's below freezing out, your body perspires under your clothes, especially if you're active. Use fabrics that wick moisture away from the body, such as polypropylenes. Cotton soaks up sweat and holds onto it.

▪ Wear heavy, properly-fitting socks and footwear, and gloves and mittens that provide warmth and dryness, which is particularly important for diabetics.

▪ Don't push too hard. If you feel light-headed, out of breath or have a fast or irregular heartbeat, slow down or take a break and be sure to follow up with your doctor about the symptoms you experienced.

▪ Cardiac rehabilitation expert Barry Franklin, Ph.D., advises giving yourself 24 hours or more to adapt to high altitude. As altitude increases, the air becomes “thinner,” which means there is less oxygen in the atmosphere to draw into your lungs with each breath and the amount of oxygen in your blood declines. Both heart and breathing rate increase as the body tries to send more oxygen to its tissues. If you have heart disease, high-altitude activity can increase the heart rate to potentially dangerous levels.

▪ Warm up thoroughly beforehand. Cold muscles, tendons and ligaments are vulnerable to injury. Do a warm-up activity (jog in place or take a brisk walk for five minutes) before putting on gear, which will increase your performance and reduce the risk of pulling a muscle or tearing a ligament.

▪ Drink plenty of water before, during and after activity to prevent dehydration, which happens faster at higher altitudes. Dehydration may not seem like an obvious hazard of winter sports. But as you perform physical activity, your body uses water and produces sweat — making it crucial to replace lost fluids.

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Of course if you really can't stand being outdoors when the weather is cold, wet and generally unpleasant, all is not lost. Many people simply take their physical activity program indoors during the winter. For instance, many malls offer free walking time before stores open for business. Instead of having to contend with icy sidewalks or knee-deep snowdrifts just to get in your morning constitutional, malls offer a flat, even walking surface and a climate-controlled, comfortable environment. The only danger: Instead of walking fast enough to get a workout, you'll give in to the temptation to window-shop the colorful and imaginative holiday displays, Rosen admonishes. Swimming in an indoor pool is another good winter alternative. “People with arthritis — and many of those with diabetes also have arthritis — do better with water-based exercise, which is less stressful on the joints,” says Rosen. Of course, you could always hit the gym and watch the winter wonderland through the window as you walk on the treadmill.

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© 2009 American Heart Association, Inc.