Preventing exercise-related cardiovascular events: is a medical examination more urgent for physical activity or inactivity?

P hysical inactivity is a serious health problem worldwide, contributing to early development of obesity, diabetes mellitus, hypertension, and cardiovascular diseases (CVD). 1 In fact, our hypokinetic lifestyle is now widely recognized among the most proximal risk factors for heart disease (Figure 1), along with poor dietary habits and cigarette smoking. 2–4 To address these concerns, public health strategies commonly incorporate the goal of safely increasing physical activity levels in the populations of industrialized societies. Accordingly, the number of health/fitness facilities and members is expected to increase exponentially over the next decade. Current market research indicates that the fastest-growing user subsets are those aged 35 to 54 years and those ≥55 years of age. These data, coupled with the recent finding that regular exercise prevents cellular senescence, have led an increasing number of adults, many of whom have known or occult chronic disease, to the conclusion that " more exercise is better. " Marathon running, for example, has increased in popularity over the past 3 decades, with participation increasing from 25 000 runners in 1976 to ≈2 million in 2010. Thus, we have a population paradox in which there is an expansion in the number of habitually sedentary individuals paralleling a concomitant increase in those taking part in unprecedented hours of vigorous exercise. Although numerous epidemiological studies suggest that regular physical activity or moderate to high levels of cardio-respiratory fitness, expressed as metabolic equivalents (METs; 1 MET=3.5 mL O 2 ·kg −1 ·min −1), may protect against the development of CVD, considerable evidence now indicates that cardiovascular events, including acute myocardial infarction, sudden cardiac death (SCD), stroke, and aortic dissection, can be triggered by vigorous physical activity. 5 To a large extent, the major cause of exertion-related cardiovascular events is the combination of vigorous physical exertion and known or occult CVD, rather than the activity per se. Thus, efforts to identify adults at increased risk generally focus on medical history, including symptomatology, cardiovascular risk factors , or diagnostic testing to identify underlying CVD. Because " do no harm " remains a cardinal tenet of the Hippocratic Oath, professional organizations have increasingly championed preparticipation self-screenings to identify " at risk " individuals who should seek medical clearance, specially qualified supervisory staff/facilities, or both before embarking on an exercise program. The ingenious study by Whitfield et al, 6 published in the current issue of Circulation, evaluated 2 commonly recommended self-screening exercise preparticipation …