CORRESPONDENCE: LETTER TO THE EDITOR
The Other Face of the Medal: The Risks of Exercise Training
Erdem Kasikcioglu, MD, PhD, FESC*
* Istanbul University, Istanbul Faculty of Medicine, Department of Sports Medicine, Istanbul, Turkey (Email: ekasikcioglu{at}yahoo.com).
I read with interest the recent study in the Journal by Noda et al. (1) who concluded that exercise training might reduce the risk of mortality from coronary heart disease and stroke in Asian populations. However, several limitations of the study need to be considered. Indeed, except for walking, both intensive and prolonged exercises may have harmful effects on the cardiovascular system regardless of the time spent participating in sporting activities. In particular, acute heavy exercise may cause myocardial ischemia, myocardial infarction, and cardiovascular stroke because of suddenly increasing blood pressure, uncontrolled heart rate, and oxygen demand (2). Noda et al. (1) should perhaps clarify the role of intense physical activity in postponing mortality in the cardiac patient.
Although there is strong epidemiological evidence that a dose-response relationship exists between physical activity and all-cause mortality, there is a consistent inverse dose-response relationship between physical activity and both the incidence and mortality rates from all types of cardiovascular and coronary heart disease (3,4). Previously, it was reported that a U-shaped association existed between physical activity and incidences of stroke or mortality. In the Harvard Alumni Study, highly active men had elevated stroke risk when compared with moderately active men but lower risk when compared with low-active men (4). Contrary to the investigators, a previously published study even showed a positive association between physical activity and stroke incidence in a Japanese population (5).
Moreover, data from an integrated activity questionnaire and from recall diaries are converted to amount of energy expenditure, but this may lead to a source of bias. Ideally, except for frequency and duration components of physical activity, exercise intensity is important for a preventative approach. The method carries many difficulties, particularly for estimating different levels of physical activity.
Related to these arguments is the following question: What is the true path of the dose-response curve regarding physical activity and cardiovascular mortality in cardiac patients (3)?
Finally, the intensity of physical activity should be taken into consideration because it is a major contributor to exercise-induced medical complications. The intensity of such activities should be estimated and accurately prescribed to reduce health risks before participation in sports exercises.
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References
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- Noda H, Iso H, Toyoshima H, et al. Walking and sports participation and mortality from coronary heart disease and stroke J Am Coll Cardiol 2005;46:1761-1767.[Abstract/Free Full Text]
- Tanasescu M, Leitzmann MF, Rimm EB, Willett WC, Stampfer MJ, Hu FB. Exercise type and intensity in relation to coronary heart disease in men JAMA 2002;288:1994-2000.[Abstract/Free Full Text]
- Kesaniemi YK, Danforth E, Jensen MD, Kopelman PG, Lefebvre P, Reeder BA. Dose-response issues concerning physical activity and healthan evidence-based symposium. Med Sci Sports Exerc 2001;33:S351-S358.[CrossRef][ISI][Medline]
- Lee IM, Paffenbarger RS. Physical activity and stroke incidencethe Harvard Alumni Health Study. Stroke 1998;29:2049-2054.[Abstract/Free Full Text]
- Nakayama T, Date C, Tokoyama T, Yoshiike N, Yamaguchi M, Tanaka H. A 15.5-year follow-up of stroke in Japanese provincial citythe Shibata study. Stroke 1997;28:45-52.[Abstract/Free Full Text]
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