The Center for Disease Control and Prevention (CDC) and the American College of Sports Medicine (ACSM) recommend that adults engage in at least 30 minutes of moderate-intensity exercise on most days, preferably all days, to have a beneficial effect on their health [2].

 

One of the Healthy People 2010 objectives of the US Department of Health and Human Services (objectives 22-1) is to increase the proportion of adults who engage in regular moderate or vigorous activity to at least 50% [17]. A recent report released by the CDC compared the nationwide exercise level in non-institutionalized population aged >18 years throughout the United States in two years: activity level in 2003 was based on data from 264,684 respondents to a phone interview, and was compared to the activity level in the year 2000, based on 214,500 respondents to the same interview. Respondents were classified as active at the minimum recommended level if they reported moderate-intensity activity for at least 30 minutes per day, 5 or more days per week, or vigorous-intensity activity at least 20 minutes per day, 3 or more days per week. Respondents were classified as inactive if they reported less than 10 minutes or more per week of moderate or vigorous intensity.

 

The results indicated that more than half of U.S. adults do not participate in physical activity at a level recommended as beneficial to health: from 2001 to 2003, the age-adjusted prevalence of adults participating in physical activity at the minimum recommended level remained similar (45.3% in 2001 and 45.9% in 2003), a trend which seems far from achieving the quoted Healthy People 2010 objective. In the same report, also the overall prevalence of lifestyle inactivity in 2003 was similar to 2001 (15.6%) [3].

 

CDC also released age and gender stratified data, collected from 1994 to 2004. Physical inactivity was defined as lack of participation in physical activities or exercise, such as running, calisthenics, golf, gardening, or walking for exercise, during the previous month. Among women, at every observation during the follow-up physical inactivity increased with age, and in 2004 around 30% of women >50 years old were inactive [18]. Several studies investigated barriers to physical activity maintenance in adult women across different age and ethnic groups. The most consistently referred barriers are lack of time due to work or family obligations and lack of motivation [4-7].