***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background Few studies have investigated both the self-perceived and measured environment with objective ly determined physical activity in older adults . Accordingly , the aim of this study was to examine measured and perceived environmental associations with physical activity of older adults residing across different neighborhood types . Methods One-hundred and forty-eight older individuals , mean age 64.3 ± 8.4 , were r and omly recruited from one of four neighborhoods that were pre-determined as either having high- or low walkable characteristics . Individual residences were geocoded and 200 m network buffers established . Both objective environment audit , and self-perceived environmental measures  were collected , in conjunction with accelerometer derived physical activity behavior . Using both perceived and objective environment data , analysis consisted of a macro-level comparison of physical activity levels across neighborhood , and a micro-level analysis of individual environmental predictors of physical activity levels . Results Individuals residing in high-walkable neighborhoods on average engaged in 11 min of moderate to vigorous physical activity per day more than individuals residing in low-walkable neighborhoods . Both measured access to non-residential destinations ( b = .11 , p < .001 ) and self-perceived access to non-residential uses ( b = 2.89 , p = .031 ) were significant predictors of time spent in moderate to vigorous physical activity . Other environmental variables significantly predicting components of physical activity behavior included presence of measured neighborhood crime signage ( b = .4785 , p = .031 ) , measured street safety ( b = 26.8 , p = .006 ) , and perceived neighborhood satisfaction ( b = .5.8 , p = .003 ) . Conclusions Older adult residents who live in high-walkable neighborhoods , who have easy and close access to nonresidential destinations , have lower social dysfunction pertinent to crime , and generally perceive the neighborhood to a higher overall satisfaction are likely to engage in higher levels of physical activity behavior . Efforts aim ed at promoting more walkable neighborhoods could influence activity levels in older adults OBJECTIVES . Physical activity may be constrained or facilitated by local environments . The availability of neighborhood facilities for physical activity may be particularly relevant for youth , who are unable to drive and whose activity is often limited to the immediate distance they are able to walk or bicycle . Several studies have shown that proximity to recreational facilities and parks is one of the most important predictors of physical activity . Because the United States already has an extensive infrastructure of parks , with 70 % of adults indicating that they live within walking distance of a park or playground , parks may be a potential venue for increasing physical activity . This might be particularly important for adolescent girls , whose physical activity levels decline substantially as they go through puberty . The goal of this study was to examine the association between park proximity , park type , and park features and physical activity in adolescent girls . PATIENTS AND METHODS . This was a cross-sectional study using baseline data from the Trial of Activity for Adolescent Girls . It included 1556 grade 6 girls who were r and omly selected from 6 middle schools in each of the following 6 field site areas : Washington , DC , and Baltimore , Maryl and ; Columbia , South Carolina ; Minneapolis , Minnesota ; New Orleans , Louisiana ; Tucson , Arizona ; and San Diego , California . Girls wore accelerometers for 6 days to measure metabolic equivalent – weighted moderate-to-vigorous physical activity , a measure accounting for the volume and intensity of activity . Metabolic equivalent – weighted moderate-to-vigorous physical activity was calculated for the hours outside of school time using 2 different cutpoints , activity levels ≥3.0 metabolic equivalents and ≥4.6 metabolic equivalents , the latter indicating activity at the intensity of a brisk walk or higher . We mapped all of the parks within 1 mile of each girl 's home . Trained staff used a checklist to document the presence of facilities and amenities at each park , including passive amenities , such as drinking fountains , restrooms , and areas with shade , as well as active amenities like basketball courts , multi purpose fields , playgrounds , and tennis courts . RESULTS . Mean nonschool metabolic equivalent – weighted moderate/vigorous physical activity , using the 4.6 metabolic equivalent cutoff , was 611.1 minutes ( range : 49.7–4718.6 metabolic equivalent minutes per 6 days ) and 1704.8 metabolic equivalent minutes per 6 days ( range : 276.2–5792.6 metabolic equivalent minutes per 6 days ) when using the 3.0 metabolic equivalent cutpoint . Many girls had multiple parks within a 1-mile radius of their homes : 57 % had ≥1 type of park , the majority being neighborhood or community parks ; 42 % had between 1 and 3 parks , 37 % had ≥4 parks , and 14 % had ≥8 parks . The type , number , and specific parks features were associated with girls ' nonschool metabolic equivalent – weighted moderate/vigorous physical activity . At the 4.6 metabolic equivalent cutpoint , higher levels of nonschool metabolic equivalent – weighted moderate/vigorous physical activity  were associated with both neighborhood and community parks ( 22 metabolic equivalent minutes ) and miniparks ( 40 metabolic equivalent minutes ) . Each park , regardless of type , in the half-mile around each girl 's home was associated with an increase in nonschool metabolic equivalent – weighted moderate/vigorous physical activity by 2.8 % or 17.2 nonschool minutes of metabolic equivalent – weighted moderate/vigorous physical activity per 6 days . Beyond a half-mile , each park increased nonschool metabolic equivalent – weighted moderate/vigorous physical activity by 1.1 % or 6.7 metabolic equivalent minutes per 6 days . For the average girl with 3.5 parks within a 1-mile radius of home , the presence of parks accounted for 36.5 extra nonschool metabolic equivalent minutes per 6 days , ∼6 % of total nonschool metabolic equivalent – weighted moderate/vigorous physical activity . Using the 3.0 metabolic equivalent cutpoint , this sums to an additional 68 metabolic equivalent minutes of nonschool metabolic equivalent – weighted moderate/vigorous physical activity over 6 days , or 4 % of the total . The most common amenities in the parks were playgrounds , multi purpose fields , and picnic areas . Slightly more than one third of girls lived within a half-mile of a park with a basketball court , and > 20 % had access to walking paths and tennis courts in their local park . Higher levels of nonschool metabolic equivalent – weighted moderate/vigorous physical activity per 6 days were associated with walking paths ( 13 metabolic equivalent minutes ) , running tracks ( 82 metabolic equivalent minutes ) , playgrounds ( 28 metabolic equivalent minutes ) , and basketball courts ( 30 metabolic equivalent minutes ) . Parks with streetlights and floodlights were also associated with an increase of 18 and 22 minutes of nonschool metabolic equivalent – weighted moderate/vigorous physical activity , respectively . With the 3.0 metabolic equivalent cutoff for metabolic equivalent – weighted moderate/vigorous physical activity , additional nonschool metabolic equivalent minutes more than doubled when girls had miniparks ( 92 metabolic equivalent minutes ) , natural re source areas ( 36 metabolic equivalent minutes ) , walking paths ( 59 metabolic equivalent minutes ) , and running tracks ( 208 metabolic equivalent minutes ) within a half-mile of their homes . Skateboard areas and special-use parks were negatively associated with nonschool metabolic equivalent – weighted moderate/vigorous physical activity in adolescent girls . CONCLUSIONS . Adolescent girls who live near more parks , particularly near those with amenities that are conducive to walking and with active features , engage in more nonschool metabolic equivalent – weighted moderate/vigorous physical activity than those with fewer parks . Whether this is because of actual use of the parks or neighborhood choice could not be determined . Although the magnitude of the association between parks and additional minutes of metabolic equivalent – weighted moderate/vigorous physical activity was small for an individual , amounting to an average of 4%–6 % of a girl 's total nonschool metabolic equivalent – weighted moderate/vigorous physical activity , it is likely to have a large population -level association . Because of the potential population level impact , the use of parks to promote physical activity should be further studied BACKGROUND Regular physical activity is known to help prevent chronic disease and promote healthy aging . Yet , most older women are not regularly active . This study attempts to identify objective ly measured attributes of the neighborhood environment that may be associated with physical activity levels in older women . METHODS Sociodemographics and  physical activity level , as measured by pedometer , were assessed in 158 overweight Caucasian and African-American postmenopausal women from southwestern Pennsylvania at the baseline evaluation of a r and omized clinical trial in 2002 - 2003 .  Geographic information systems technology was used to obtain neighborhood-level data , including  neighborhood socioeconomic status  ( SES ) indicators , the median year that homes were built ( as a proxy measure for urban form ) , and proximity to businesses and facilities . Multiple linear regression was used to test associations between individuals ' physical activity level and neighborhood characteristics . RESULTS After controlling for individual age , race/ethnicity , education , smoking status , and body mass index , indicators of low neighborhood SES , living in a neighborhood with homes built between 1950 and 1969 ( representing an urban form that is more pedestrian-friendly than after 1969 ) , and living within walking distance ( 1500 m ) of specific types of businesses and facilities were positively associated with individuals ' physical activity level measured by pedometer ( p < 0.05 ) . CONCLUSIONS Results suggest that certain aspects of the neighborhood environment may have an important influence on the physical activity levels of postmenopausal women . Results warrant future research to clarify the role of these environmental attributes in other population Locational data , logged on portable GPS units and matched with accelerometer data , was used to examine associations of the built environment with physical activity and  sedentary behaviors of adolescent females . In a sample of 293 adolescent females aged 15 to 18 years old in Minneapolis and San Diego , the built environment around each GPS point and its corresponding sedentary , light , and moderate-to-vigorous intensity physical activity was examined using r and om intercept multinomial logistic regression models . The odds of higher physical activity intensity ( 3-level outcome : sedentary , light , MVPA ) were higher in places with parks , schools , and high population density , during weekdays , and lower in places with more roads and food outlets . Underst and ing the places where physical activity and sedentary behaviors occur appears to be a promising strategy to clarify relationships and inform policy aim ed at increasing physical activity and reducing sedentary behaviors BACKGROUND This study examined predictors of adoption and maintenance of vigorous physical activity over time in a sample of 1,719 r and omly selected women and men . METHODS Based on reported frequency of vigorous exercise in a mail survey at baseline , subjects were classified as sedentary ( zero sessions per week ) , intermediate ( one to two sessions per week ) , or active ( three or more sessions per week ) . RESULTS On the same survey subjects reported on 25 potential determinants of physical activity based on a comprehensive learning model . Twenty-four months later , 85 % of subjects were resurveyed , and their physical activity levels were classified . Within each baseline category and gender subgroup , predictors of follow-up physical activity were identified . In multivariate analyses , adoption of  vigorous exercise by sedentary men was predicted by self-efficacy , age ( inverse ) , and neighborhood environment ( inverse ) . Adoption by sedentary women was predicted by education , self-efficacy , and friend and family support for exercise . Maintenance of vigorous physical activity  was predicted by self-efficacy and age ( inverse ) for initially active men and by education for initially active women . CONCLUSION These results suggest that factors influencing adoption are different for men and women , and there may be different factors influencing adoption versus maintenance of vigorous physical activity 
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Our review found that even among studies with objective ly measured physical activity , the association between access to parks and physical activity varied between studies , possibly due to heterogeneity of exposure measurement .
Self-reported ( vs. independently-measured ) neighborhood park environment characteristics and smaller ( vs. larger ) buffer sizes were more predictive of physical activity .