American Heart Association meeting report:
WASHINGTON, D.C., May 2– Do you – like millions of full-time workers – surf TV channels, play video games or boot up the computer in what little free time you have? If so, there's a good chance you're skimping on heart-healthy physical activities, scientists report at the American Heart Association's 45th Annual Conference on Cardiovascular Disease Epidemiology and Prevention.
In their study of nearly 4,500 men and women, a subset of full-time workers who spent more of their down time engaged in sedentary activities had significantly less exercise than part-time workers with the same amount of sedentary leisure pursuits.
"Many full-time workers say that one of the biggest barriers to getting enough exercise is that there's not enough time in the day," said study author Meghan Warren, P.T., M.P.H., a pre-doctoral fellow in the division of epidemiology and community health at the University of Minnesota, Minneapolis. "If they shift their interests, they would have more time for physical activity."
Many studies found that exercise can help prevent obesity, heart disease and other health problems. Warren's team evaluated the association between sedentary behaviors, physical activity and fitness using data from the large, population-based 1999-2000 National Health and Nutrition Examination Survey (NHANES) conducted by the National Center for Health Statistics, one of the Centers for Disease Control and Prevention. The survey asked the 4,498 adults if they participated in 48 different leisure-time physical activities, including walking, basketball, swimming and cycling, in the past 30 days. The 2,353 participants who indicated they participated in at least one of these activities were also asked how many minutes, on average, they engaged in each activity per session.
As part of NHANES, participants were also asked about three sedentary activities: watching TV, playing video games and leisure-time computer use. "The 1999-2000 survey was one of the first to ask about computer use and video games so that gave our study a more complete assessment of sedentary activities than studies in the past," Warren said.
The researchers assigned each activity a metabolic equivalent or MET, a standard, published measure of physical activity intensity. A MET level of 1-3 corresponds to low-intensity activity such as watching TV or sleeping; a MET value of 3-6 corresponds to moderate-intensity activity such as walking or cycling; and a MET value of 6 and over corresponds to vigorous activity such as running or skiing. Then, for each leisure-time activity, Warren's team calculated the MET-hours per day, based on frequency, duration and intensity of activities.
When the researchers looked at all 2,353 participants who reported any leisure-time physical activity, the analysis showed no statistically significant association between the amount of time spent in sedentary leisure activities and that spent exercising.
But when they compared two subgroups, 1,573 full-time workers and 508 part-time workers, a different picture emerged for those who spent the most time in sedentary activities.
Full-time workers with five or more hours of sedentary activity per day engaged in about 11 fewer minutes of physical activity such as walking or cycling each day compared to full-time workers who didn't spend any time watching TV, playing video games or using the computer in their off hours, a statistically significant finding.
In contrast, part-time workers who spent five or more hours per day engaging in sedentary activities showed a trend toward engaging in about 11 more minutes of physical activity each day than part-time workers who avoided sedentary activities in their free time. The finding did not reach the level of statistical significance, perhaps because of the smaller number in that group, she said.
"Full-time workers have less free time, so the more time spent in sedentary activity, the less time they have to exercise," Warren said. "Part-time workers have more discretionary time -- so it could be that those that watched more TV, exercised more too."
Some studies in children reveal a trend similar to that seen in part-time workers, she said. "That makes sense as both have more free time." Nearly 30 percent of the participants also took a treadmill test to determine their physical fitness, as measured by VO2 max, the maximal volume of oxygen exchanged during exercise. In this subgroup of 1,319 men and women, those who spent five or more hours watching television or using the computer during their time off were slightly less physically fit than those who didn't spend any time engaging in leisure-time sedentary activities.
All the analyses took into account factors that could skew the results, such as gender, body mass index, age, race, education and marital status.
Since this was an observational study, Warren said she doesn't know whether full-time workers exercise less because they are watching too much TV or vice versa. "But either way, they need to think about shifting their interests."
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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