THURSDAY, Dec. 4 (HealthDay News) -- An estimated 65 percent of people in the United States last year met the 2008 Physical Activity Guidelines for Americans. And 49 percent of those people met the Healthy People 2010 physical activity objectives, according to a federal report released Thursday.

According to the 2008 guidelines, released in October by the U.S. Department of Health and Human Services, the minimum recommended aerobic physical activity required to produce substantial health benefits in adults is 150 minutes of moderate-intensity activity or 75 minutes of vigorous activity per week, or an equivalent combination of moderate and vigorous physical activity. In addition, muscle-strengthening exercises are recommended at least twice a week.

The 2010 guidelines call for adults to do at least 30 minutes of moderate-intensity activity five days per week, or 20 minutes of vigorous activity three days a week.

For this study, U.S. Centers for Disease Control and Prevention researchers analyzed data from 399,107 adults aged 18 and older who took part in the 2007 Behavioral Risk Factor Surveillance System (BRFSS) survey. The 64.5 percent of respondents who met the 2008 guidelines included 68.9 percent of men and 60.4 percent of women. By age group, the percentage classified as physically active ranged from 51.2 percent of those older than 65, to 74 percent of those ages 18 to 24.

Among racial/ethnic groups, rates were lower for non-Hispanic blacks (56.5 percent) than for non-Hispanic whites (67.5 percent). By education levels, rates were lowest for those with less than a high school diploma (52.2 percent) and highest for college graduates (70.3 percent). By region, rates were lowest in the South (62.3 percent) and highest in the West (67.8 percent). The study also found that 68.8 percent of normal weight people were physically active, compared with 67.3 percent of those who were overweight and 57.1 percent of those who were obese.

The 48 percent of respondents who met the Healthy People 2010 objectives included 50.7 percent of men and 47 percent of women.

The study was published in the Dec. 5 Morbidity and Mortality Weekly Report, a publication of the CDC.

In the BRFSS survey, moderate physical activity was assessed by asking respondents, "When you are not working, in a usual week, do you do moderate activities for at least 10 minutes at a time, such as brisk walking, bicycling, vacuuming, gardening, or anything else that causes some increase in breathing or heart rate?"

Those who answered yes were then asked, "How many days per week do you do these moderate activities for at least 10 minutes at a time?" Finally, they were asked, "On days when you do moderate activities for at least 10 minutes at a time, how much total time per day do you spend doing these activities?"

To assess participation in vigorous-intensity activities, respondents were asked, "When you are not working, in a usual week, do you do vigorous activities for at least 10 minutes at a time, such as running, aerobics, heavy yard work, or anything else that causes large increases in breathing or heart rate?"

Those who answered yes were then asked, "How many days per week do you do these vigorous activities for at least 10 minutes at a time?" Finally, they were asked, "On days when you do vigorous activities for at least 10 minutes at a time, how much total time per day do you spend doing these activities?"

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