Physical inactivity and poor cardiovascular fitness are associated with an increased risk cardiovascular disease. A recent international study listed physical inactivity as a major risk factor for heart attack , but the extent to which physical inactivity affects risk factors for heart disease is still largely unknown.

A new study in the December 21, 2005 issue of the Journal of the American Medical Association found that low physical fitness was common in adolescents and adults under 50 years of age, and that low fitness was associated with other risk factors for cardiovascular disease.

About the Study

This study included 5,315 participants (3,110 adolescents ages 12-19 and 2,205 adults ages 20-49) in the National Health and Nutrition Survey (NHANES) who did not have cardiovascular disease. The participants underwent exercise treadmill testing to determine their maximal oxygen consumption (VO2max, a measure of fitness). The researchers divided the participants into three fitness levels: low (less than 20th percentile), moderate (20th-59th percentiles), and high (60th percentile or higher). Researchers measured the participants’ weight, height, waist circumference, blood pressure, cholesterol level, blood glucose level, and glycosylated hemoglobin level (a marker for diabetes ).

Overall, 33.6% of adolescents and 13.9% of adults had low fitness. In adults, low fitness was significantly more common in females than males. In all age groups, low fitness was more prevalent in blacks, Mexican Americans, and those reporting “other” ethnicities than non-Hispanic white.

Low fitness was associated with increased body mass index (a measure of weight in relation to height) and waist circumference. People with low fitness were 2-4 times more likely than those with moderate or high fitness to be overweight or obese . In addition, total cholesterol levels and blood pressure measurements were higher, and levels of high-density lipoprotein (HDL, or “good”) cholesterol were lower in people with low fitness.

These findings are limited because high-risk older adults and people with hypertension were not tested (due to risks associated with exercise treadmill testing), so the results may not apply to these groups.

How Does This Affect You?

This study confirms that low fitness is a major concern in the US. The researchers calculate that approximately 16 million adolescents and adults under age 50 in the US are in poor shape. Furthermore, since low fitness was associated with cardiovascular risk factors, we may be looking at an increasing prevalence of cardiovascular disease in this country unless the trend of physical inactivity is reversed. The study also suggests that the link between low fitness and cardiovascular disease is due, at least in part, to its effects on cardiovascular risk factors such as obesity and elevated cholesterol .

Once again, this study underscores the importance of regular exercise, which is the best way of achieving physical fitness. The Centers for Disease Control and Prevention (CDC) recommend that adults exercise moderately (e.g., walking briskly, swimming, bicycling on level terrain) for at least 30 minutes five days a week or more, or exercise vigorously (e.g., jogging, high-impact dancing, bicycling uphill) for at least 20 minutes three days a week or more. Children and adolescents should participate in moderate to high intensity activities (e.g., brisk walking, playing tag, jumping rope, swimming) for at least an hour a day.