Cardiovascular fitness levels among American workers.

Many Americans are suffering from the spectrum of coronary artery and cardiovascular diseases (CAD/CVD). Collectively, these diseases are the number one killer responsible for 30% of all global deaths, which was approximately 17.5 million deaths in 2005.1–3 The co-morbid conditions associated with CAD/CVD, such as obesity, diabetes, and cardiometabolic syndrome, have emerged as widespread epidemics crippling the United States and many other parts of the world.4–11 CAD/CVD and these co-morbid conditions warrant further study for causative factors and preventive strategies, given that these epidemics predict early death and disability. A physically-active lifestyle and a moderate to high degree of cardiovascular fitness (CVF) have been associated with health benefits that include reducing: (1) risk factors for CAD/CVD and diabetes (e.g., hypertension, obesity, hyperglycemia, and hyperlipidemia) and (2) overall morbidity and mortality.12–14 Moreover, CVF, as measured by the internationally- recognized standard of maximum oxygen consumption (VO2max), expressed in milliliters (ml) of oxygen/kilogram (kg) of bodyweight/minute (min), is a better predictor of CAD/CVD risk compared to self-reported physical activity levels.15 A recent meta-analysis determined that a higher level of CVF was related to lower risk of all-cause mortality and CAD/CVD,16 while low CVF has been shown to be a significant modifiable risk factor for many diseases and untimely death.17 Population-level findings also reveal that CVF is inversely related to CAD/CVD risk.18;19 Thus, CVF is a key characteristic to consider relative to morbidity and mortality from CAD/CVD and other co-morbid conditions and is superior to self-reported physical activity levels. A paucity of data exists examining the relationship between CVF and occupation with few studies making comparisons between occupation categories. A study of healthy men in sedentary occupations (i.e., professional, technical, and administrative workers) in Singapore found that those who were regular exercisers had significantly higher VO2max (40.9 ml/kg/min) compared to their non-exercising counterparts (34.3 ml/kg/min).20 The regular exercisers had VO2max values that approximated the ability to perform heavy physical work. In a similar study, VO2max values obtained from submaximal bicycle ergometry and other cardiovascular risk factors were assessed among women employees in the United States.21 In this study, academic faculty had the highest average VO2max (29.1 ml/kg/min), followed by registered nurses and nursing assistants (both 27.0 ml/kg/min) and telephone personnel (22.4 ml/kg/min); however even among the academic faculty over 40% were classified as having below-average CVF levels.21 A recent study found a mean VO2max of 46.6 ml/kg/min among firefighters, but 25% of the sample were unable to attain a minimally-acceptable level of CVF according to the Bruce treadmill protocol.22 Fifteen percent of the sample met diagnostic criteria for cardiometabolic syndrome, which was significantly and inversely related to CVF.22 While the aforementioned studies have reported CVF levels among specific occupation groups, it is virtually unknown how CVF compares across multiple occupations. Additionally, these data suggest an overall low to moderate CVF level among these occupation groups, which may portend a greater risk of CAD/CVD and other co-morbidities, given the links found between poor fitness and incidence of disease. CVF data across many occupations are needed to understand if these trends are indicative of poor fitness levels on a wider scale. Such information can also be used to identify worker groups that are at particular risk of CAD/CVD for the purpose of creating workplace fitness and other health promotion programs. Thus, the objective of this study was to assess CVF levels among employees in 40 different occupation categories using a nationally-representative sample of the United States population and to examine how those fitness levels compared to standard CVF recommendations.