WITH the greater promotion of exercise as being good for health, there has been a substantial increase in those aged 35 years and above taking up regular physical exercise. This has led to an increasing number of those in this largely sedentary middle-aged group participating in physically demanding exercise events, including marathons.
Over the last three decades, marathon running has seen an explosive 80-fold increase in participants. It is not uncommon to hear of people dying suddenly during a marathon. Hence, it is important to understand whether it is safe to participate in vigorous exercise programmes.
While data from observational studies have suggested that regular exercise may reduce the likelihood of developing heart disease, there is now substantial evidence to show that vigorous exercise can result in the sudden development of a heart attack, sudden death, stroke and a tear in the wall of the main artery of the body (aorta). These events occur mainly in those who have underlying disease of their heart arteries, known or unknown.
Hence, for those sedentary desk-bound people who have suddenly been bitten by the exercise bug, the question is whether there is a need to seek medical clearance before plunging headlong into a vigorous exercise programme. Some professional health organisations have tried to draw up a do-it-yourself questionnaire to help the individual decide whether he needs to seek medical advice before embarking on a programme to morph from a couch potato to a six-pack speed machine burning up the tracks in the latest sports outfit.
Two commonly used self-assessment questionnaires for these new fitness enthusiasts are the American Heart Association (AHA)/American College of Sports Medicine (ACSM) Pre-participation Questionnaire (AAPQ) and the Physical Activity Readiness Questionnaire (PAR-Q). In a recent paper published by Whitfield in Circulation Journal, investigators found that for the same cohort of adults of age 40 years or more who used these two questionnaires for self screening, the PAR-Q identified 68.4 per cent and the AAPQ identified 94.5 per cent of the cohort as requiring medical clearance before embarking on vigorous exercise programmes. While the authors suggested that the AAPQ may have overly identified those at risk, nevertheless, the study showed that about two-thirds or more of those aged 40 years or older should seek medical advice before participating in exercise programmes.
Risks of exercise
As a rule of thumb, the risk of a sudden heart attack or sudden death is low with light to moderate exercises. These heart-related events tend to occur in those who are engaged in vigorous physical exercise and who push themselves beyond what their bodies can tolerate. Data from various studies suggests that the risk of sudden death varies from about one jogging death per year for about close to every 8,000 joggers to four
deaths per every million participants in half and full marathons.
What it means is that for those who do regular jogging, the death rate per hour is close to eight times that of a person who is sedentary. Data from autopsy studies suggests that the majority of deaths are due to underlying blockage of the heart arteries or an inherited abnormal thickening of the heart muscles called hypertrophic cardiomyopathy.
Hence, if underlying heart disease is detected and those who are at risk of a sudden heart attack or sudden heart death can be identified, participation in vigorous physical activity is generally safe.
For the individual, the theoretical risk of getting a heart attack is double for a person who exercises five or more times a week for about one hour each time. The upside is that during the other 23 hours when he is not doing any exercise, the risk of getting a heart attack will be halved when compared to a sedentary individual.
However, it should be noted that when the least active individuals are compared to the most active individuals when performing vigorous physical exercise, the risk of a heart attack is 50 times higher during or soon after the exercise for the least active group. Hence, an exercise programme for an individual whose lifestyle is predominantly sedentary has to be tailored to his pre-participation status and underlying medical condition.
Identifying those at risk
I am reminded of an individual who was a member of a group of runners and was extremely pleased that he ran further and faster than the others in his group. He did not have chest pain but had risk factors for heart disease. Assessment of his heart revealed the presence of significant blockage of all the three major arteries of the heart.
The fitness of the individual does not guarantee the absence of risk of a sudden heart attack or death during exercise. The American College of Sports Medicine considers it unnecessary to do any screening for those without symptoms and has less than two risk factors for heart disease. Risk factors for heart disease include high cholesterol levels, diabetes mellitus, high blood pressure, and smoking. However, for those with two risk factors or more who intend to embark on an exercise programme of moderate intensity, a medical examination is advised. This also applies to those who have known heart disease and diabetes.
Walking or jogging
I tell all my patients whose lifestyle is predominantly sedentary to walk and not run when they commence on an exercise regime. Studies show that there is a correlation between increased death and increasing intensity of exercise for sedentary individuals. Hence, for sedentary individuals, starting on a simple prescription of walking of two to three kilometres
daily may suffice to shift them from the highest risk category to a lower risk category of sudden death.
A logical step towards commencement of an exercise programme is to get them to start walking regularly. Special precautions must be taken for those who are unable to complete five metabolic equivalents (METs) of exercise as a result of symptoms.
Studies have shown that these people have a highly elevated risk of death from heart or other conditions during exercise. Activities such as recreational sports, dancing and snorkelling are considered as moderate exercises which consume about five METs of energy. These individuals will require a proper medical assessment before commencement of an exercise programme.
The first myth is that the more intense the exercise, the better it is for health. There is a tendency for many to push themselves harder and harder in the belief that the higher the intensity of the exercise, the better it must be for the body. The question often asked is: "Is there a limit to exercise where there is more harm than benefit?" Studies suggest that exercise intensity of nine METs for women and 10 METs for men are the upper limits beyond which there is no incremental survival benefit.
Increasing the exercise beyond these limits may increase the likelihood of injury without any incremental benefit for heart health. The second myth is that you can eat all you want and you can burn off the bad cholesterol by exercising. The truth is that even intense exercise will not have a beneficial effect on the bad cholesterol because bad cholesterol is mainly the result of your genetic make-up and your diet.
The third myth is that if you can complete a marathon, you are not at risk of sudden death. I recently saw Miss A who participated frequently in marathons and could routinely complete them in less than three hours. She was found to have an abnormality of the heart artery which resulted in part of it being buried deep into the heart muscle, which means that the artery gets compressed with every heart beat. This is a known cause of sudden death for those who participate in vigorous physical activities. She has since moderated the intensity of her exercises.
There was also an unfortunate case of middle-aged Mr B, who had completed a marathon but died suddenly a year later while swimming. Autopsy showed that he had severe narrowing of all his major heart arteries and there was extensive damage to the heart muscle from multiple previous heart attacks.
Hence, being able to complete a marathon does not guarantee that one is not at risk of sudden death. One of the findings of studies is that most of those who died suddenly while exercising had symptoms in the weeks preceding their death. Hence, always listen to your body. If you do not feel well, check with your doctor.
- Dr Lim is medical director at the Singapore Heart, Stroke & Cancer Centre. He is also editor-in-chief, Heart Asia (a journal of the British Medical Journal Publishing Group); chairman, scientific advisory board, Asia Pacific Heart Association; and honorary professor and senior medical adviser, Peking University Heart Centre.
This series is brought to you by Heart, Stroke and Cancer Centre.
It is produced on alternate Saturdays. .To read more of Dr Lim's previous health-related articles, please visit: http://www.btinvest.com.sg/specials/shscc