The Importance of Physical Fitness versus Physical Activity for Coronary Artery Disease Risk Factors: A Cross-Sectional Analysis
Young, Deborah Rohm, Steinhardt, Mary A., Research Quarterly for Exercise and Sport
Numerous epidemiological investigations have shown that low physical fitness and low physical activity are related to the incidence of coronary artery disease (CAD). Most studies, however, have not examined both variables concurrently to determine which has the strongest association with CAD risk. The purpose of this investigation was to cross-sectionally examine the relationships among physical fitness, physical activity, and risk factors for CAD. Male law enforcement officers (N = 412) from the City of Austin, Texas, were subjects for this study. Physical fitness, physical activity, and risk factors for CAD were assessed through health screenings and from data collected as part of an annual physical fitness assessment. Multivariate analysis of covariance revealed that physical fitness, but not physical activity, was related to several single CAD risk factors. Percent body fat, smoking habits, and Type A behavior score were negatively related to physical fitness level, and high density lipoprotein (HDL) cholesterol was positively related to physical fitness level. Univariate analysis of variance found both physical fitness and physical activity to be significantly related to a composite CAD risk score. Low physical fitness and low physical activity were associated with a high CAD risk score. These data suggest that physical activity must be sufficient to influence physical fitness before statistically significant risk-reducing benefits on single CAD risk factors are obtained, although minimal engagement in weekly vigorous activity provides a significant benefit for the composite CAD risk score. It is plausible, however, that physical fitness is a stronger measure than physical activity and optimally characterizes the relationship among physical activity and CAD risk factors.
Key words: physical fitness, physical activity, cardiovascular disease
It is well accepted that habitual physical activity is related to reduced incidence of coronary artery disease (CAD). Numerous epidemiological studies have documented this association (Leon, Connett, Jacobs, & Rauramaa, 1987; Morris, Everitt, Pollard, Chase, & Semmence, 1980; Morris, Heady, Raffle, Roberts, & Parks, 1953; Paffenbarger & Hale, 1975; Paffenbarger, Hyde, Wing, & Hsieh, 1986; Paffenbarger et al., 1993). Based on these and other investigations, physical inactivity is thought to be an independent predictor of a magnitude similar to the more "traditional" risk factors such as hypertension, hypercholesterolemia, and smoking history (Powell, Thompson, Caspersen, & Kendrick, 1987).
Epidemiological investigations also have documented a relationship between physical fitness and CAD. Low physical work capacity was related to CAD incidence in a large, predominantly white, upper middle-class population (Blair, Kohl, et al., 1989); a sample of Los Angeles County fire and law enforcement employees (Peters, Cady, Bischoff, Bernstein, & Pike, 1983); a population of men with high serum cholesterol levels (Ekelund et al., 1988); and Belgian male factory workers (Sobolski et al., 1987).
Although physical fitness and physical activity are related (e.g., activity at a level that meets specified requirements for intensity, duration, and frequency will result in improved physical fitness; American College of Sports Medicine, 1990), many epidemiological investigations have examined only one of these variables, most commonly physical activity. This is presumably due to the time and expense required to test large populations for fitness and the relative ease in assessment of physical activity. To our knowledge, only one study has looked simultaneously at both variables. Lochen and Rasmussen (1992) found a stronger relationship between physical fitness and coronary risk factors than between leisure-time physical activity and coronary risk factors.
Scientific evidence regarding these relationships is sparse; less-than-optimal information is available to public health professionals on the potential health benefits of physical activity and/or physical fitness. …