Each year, almost 20 million people die of cardiovascular or coronary diseases around the world. In Turkey, coronary artery disease (CHD) is still the main cause of death, based on the Turkish Statistical Institute's (TurkStat) 2015 data. To what extent winter raises the risk of a heart attack is a matter of debate, but several studies have shown that the prevalence of heart attacks increases in the December-January timeframe. Studies say cold weather puts increased pressure and strain on the heart by causing the arteries to constrict. Certain studies put the increase in the overall incidence of heart attacks at more than 50 percent in the winter when compared to the summer. This is why being exposed to cold weather and strenuously exercising can bring about a "bad end" for at-risk patients.Physicians agree that exercising, even just 30 minutes a day, increases artery activity, increases blood flow and strengthens the cardiovascular system and the heart. Regular exercise also improves muscle function and helps to better take in and use oxygen. Around three hours of weekly cardio exercise will be enough to keep capillaries healthy and plump. For healthy people, the American Heart Association (AHA) advises that walking four to five times a week can reduce the risk of heart disease. Physical activity also helps to shape up the waistline, and reduces the risk of other diseases including fatty liver, diabetes and cancer.However, exercising for more than 12 hours a week poses a health risk. When it comes to patients with heart disease, the scenario turns into a delicate situation. Normally, such patients who exercise on a regular basis have increased self-confidence in performing physical tasks, a better sense of well-being as well as less stress and anxiety. Physicians prohibit working out for these patients or recommend a limited exercise regimen.Dr. Osman Sönmez, an associate professor of cardiology at the Medical Park Hospitals Group, said a certain group of patients with heart disease cannot play sports or exercise. The group includes patients with angina pectoris, especially when they perform an effortful physical task, patients with coronary failure, uncontrolled hypertension, diabetic target organ disease, heart valve disease and pulmonary hypertension. Sönmez added that certain patients with heart disease and patients with cardiomyopathy must avoid participating in sports competitions as well as lifting weights and bodybuilding. Diving and high altitude sports are not recommended for patients who are under physical control due to atrial septal defect (ASD). Exercises that increase abdominal pressure are also dangerous for patients with pulmonary hypertension and heart valve disease. Of course, such limitations do not mean that patients with heart disease cannot - or should not - exercise. Sönmez stressed that aside from the specific aforementioned group, such patients can play sports under physician supervision. Extreme sports, however, are not recommended for any patient with heart problems.There are four main signs that such patients should be aware of while exercising: New onset or recurring angina pain, unaccustomed or unusual shortness of breath, dizziness or lightheadedness and heart rhythm abnormalities. In such cases, exercise should be discontinued and medical attention must be sought.Sönmez also discussed how patients with heart disease can pay better attention to their bodies while exercising. "A warm-up should be the first stage as with other forms of physical activity. After a 15 minute warm-up session, a 30-minute cardio exercise is sufficient. While working out, you should reach a target heart rate, which can be measured according to the patient's age," he said. He also advised to check with a physician before starting an exercise program or to find a program that suits the patient's physical condition. Sönmez added that patients with heart disease who are allowed to exercise are recommended to do 30 minute workout sessions every day. They should also exercise five days per week. When exercising on cold winter days, do not forget to dress warmly and wear layers to keep body temperature high.