Special articleLess Sitting, More Physical Activity, or Higher Fitness?
Section snippets
Sitting and All-Cause Mortality
The independent role of sedentary behavior as a risk factor for poor health and premature mortality has received considerable attention in recent years.6, 7 Sedentary behavior has been defined as any waking behavior characterized by an energy expenditure that is less than or equal to 1.5 times the resting metabolic rate while in a sitting or reclining posture.8 It has been operationalized in several ways in scientific studies, including the use of television viewing as a marker of sedentary
Physical Activity and All-Cause Mortality
The role of physical activity in the prevention of chronic disease and premature mortality is well established.2 More than 50 years of systematic epidemiological and intervention research contributed to the development of the 2008 Physical Activity Guidelines for Americans,4 which call for 150 minutes of moderate activity, 75 minutes of vigorous activity, or some combination of moderate and vigorous activity. Similar guidelines have been promoted by other countries and by the World Health
Cardiorespiratory Fitness and All-Cause Mortality
The first studies on cardiorespiratory fitness and mortality were published more than 30 years ago.23 Cardiorespiratory fitness is defined here as either maximal oxygen uptake or maximal work capacity and is measured typically with a treadmill or cycle ergometer test. Cardiorespiratory fitness can also be estimated by submaximal exercise tests. The first study to use maximal exercise tests with all-cause mortality as the outcome was published in 1989.24 The results revealed that low
Intrinsic and Acquired Cardiorespiratory Fitness
Low cardiorespiratory fitness is a powerful predictor of health problems and premature death. To better understand the public health implications of this observation, one would need to untangle the intrinsic and acquired components of cardiorespiratory fitness at the individual level. The intrinsic level of cardiorespiratory fitness can be measured by testing for maximal oxygen uptake adjusted for body mass in a person who has a life history of being sedentary with no history of exercise
Implications of the Evidence for Public Health Recommendations
In the earlier sections of this article, we provided succinct reviews of the scientific evidence that sedentary behavior, regular physical activity, and cardiorespiratory fitness have strong associations with premature mortality (Figure 2). Low cardiorespiratory fitness may be the strongest of these risk factors because the associations with mortality indicators remain strong even after adjustment for physical activity level. We certainly have ample evidence that cardiorespiratory fitness has a
Conclusion
This review illustrates the importance of sedentary behavior, physical activity level, and cardiorespiratory fitness to health outcomes and premature death. There are associations among these variables, but there also is evidence supporting their independence as health-related variables. Additional research is needed to address several outstanding questions that would help clarify their public health implications. We encourage health authorities and funding agencies to focus more attention on
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Potential Competing Interests: Dr Bouchard has received book royalties from Elsevier, CRC Press, and Human Kinetics; has received honoraria for lectures from Gatorade, Inc, DASA SA, and Biogenetika; has served on advisory boards for Pathway Genomics, Nike, Inc, and Weight Watchers International, Inc; has received research funding from the National Institutes of Health (grant HL-45670) and the King Faisal Foundation of Saudi Arabia; and is partially funded by the John W. Barton Sr Chair in Genetics and Nutrition.
Dr Blair has received book royalties from Human Kinetics; has received honoraria for lectures and consultations from scientific, educational, and lay groups that are donated to the University of South Carolina or not-for-profit organizations; is a consultant on research projects with the University of Texas Southwestern Medical School and the University of Miami; and has received research grants from BodyMedia, Inc, The Coca-Cola Company, the National Institutes of Health, and the Department of Defense.
Dr Katzmarzyk is supported in part by the Marie Edana Corcoran Endowed Chair in Pediatric Obesity and Diabetes and grant 1 U54 GM104940 from the National Institute of General Medical Sciences of the National Institutes of Health, which funds the Louisiana Clinical and Translational Science Center.