***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 This study aim ed to evaluate the associations of selected demographic , individual , social , and environmental factors with moderate-to-vigorous physical activity ( MVPA ) in a sample of children and adolescents . Methods  MVPA  was assessed among youth ( n = 294 ) 10 - 17-years-old using the ActiGraph accelerometer . Youth completed measures of demographic and individual variables related to physical activity ( PA ) , perceived social support by parents and peers , and perceived neighborhood characteristics . Parents completed the long-form of the International Physical Activity Question naire . The Physical Activity and Media Inventory was used to measure the home environment and Geographical Information Systems software was used to measure the physical neighborhood environment . Bivariate correlations and hierarchical multiple regression were conducted stratified by gender . Results Boys participated in significantly more MVPA than girls . In hierarchical analyses , peer support , home PA equipment , and temperature were significantly associated with MVPA among boys whereas distance to the school they attended was associated with MVPA among girls . The final models accounted for 25 % and 15 % of the variance in MVPA among boys and girls , respectively . Conclusions Important differences exist among the individual , social , and environmental factors related to MVPA between boys and girls . Boys ' levels of activity appear to be influenced by factors closely linked to unstructured and social types of activities whereas girls ' activities relate to internal and external barriers as well as their proximity to their schools . The prospect i ve contribution of these important individual , social , and environmental factors to changes in MVPA among children and adolescents remains to be determined PURPOSE This study examined the association of objective and perceived neighborhood environmental characteristics and parent concerns with  active commuting to school  , investigated whether parental concerns varied by environmental characteristics , and compared the association of the perceived environment , parental concerns , and objective environment on the outcome active commuting to school . METHODS R and omly selected parents of children ( aged 5 - 18 yr ) , in neighborhoods chosen for their variability in objective ly measured walkability and income , completed question naires about their neighborhood environment , concerns about children walking to school , and children 's behavior ( N = 259 ) . Objective measures of the environment were available for each participant and each neighborhood . Logistic regression analyses were used to investigate the relationships among environment , parental concerns , and walking or biking to or from school  at least once a week . RESULTS A parental concerns scale was most strongly associated with child active commuting ( odds ratio : 5.2 , 95 % CI : 2.71 - 9.96 ) . In high-income neighborhoods , more children actively commuted in high-walkable ( 34 % ) than in low-walkable neighborhoods ( 23 % ) ( odds ratio : 2.1 , 95 % CI : 1.12 - 3.97 ) , but no differences were noted in low-income neighborhoods . Parent concerns and neighborhood aesthetics were independently associated with active commuting . Perceived access to local stores and biking or walking facilities accounted for some of the effect of walkability on active commuting . CONCLUSION Both parent concerns and the built environment were associated with children 's  active commuting to school . To increase active commuting to school , interventions that include both environmental change and education campaigns may be needed PURPOSE To evaluate the reliability and validity of the CSA ( model 7164 ) accelerometer ( MTI ) in a wide walking-running speed range in laboratory and field . METHOD Twelve male subjects performed three treadmill walking/running sessions  and one field trial with the same continuous protocol involving progressively increasing velocities at 5 min per interval from 3 to 6 km x h(-1 ) ( walking ) and 8 to 20 km x h(-1 ) ( running ) . In the field trial , this protocol was terminated after 35 min ( 14 km.h(-1 ) ) , but the trial then extended with 5-km running at a freely chosen velocity . In both scenarios , two CSAs were mounted on each hip and the step frequency measured at each velocity . Oxygen uptake VO(2 ) x kg(-1 ) was measured on the last two treadmill sessions . Correlation analyses were performed for mean CSA output relationship with speed , VO(2 ) per kilogram , and step frequency . RESULTS In all trials , CSA output rose linearly ( R2 = 0.92 , P < 0.001 ) with increasing speed until 9 km.h-1 but remained at approximately 10000 counts.min-1 during running , thus underestimating VO(2 ) per kilogram at speeds > 9 km x h(-1 ) . Estimation errors increased with speed from 11 % ( P < 0.01 ) at 10 km x h(-1 ) to 48 % ( P < 0.001 ) at 16 km x h(-1 ) , when assuming a linear relationship . Freely chosen velocities in the field trial ranged from 10.9 to 16.3 km.h-1 . No difference in the CSA-speed relationship was observed between the two scenarios . Differences in CSA output between subjects could partially be attributed to differences in step frequency ( R = -0.34 ( P = 0.02 ) for walking and R = -0.63 ( P < 0.001 ) for running ) . CONCLUSION CSA output increases linearly with speed in the walking range but not in running , presumably due to relatively constant vertical acceleration in running . Between-subject reliability was related to step frequency because CSA data are filtered most at higher movement frequencies . Epidemiological CSA data should thus be interpreted with these limitations in mind PURPOSE To derive a regression equation that estimates metabolic equivalent ( MET ) from accelerometer counts , and to define thresholds of accelerometer counts that can be used to delineate sedentary , light , moderate , and vigorous activity in adolescent girls . METHODS Seventy-four healthy 8th grade girls , age 13 - 14 yr , were recruited from urban areas of Baltimore , MD , Minneapolis/St . Paul , MN , and Columbia , SC , to participate in the study .  Accelerometer and oxygen consumption (.-)VO(2 ) ) data for 10 activities that varied in intensity from sedentary ( e.g. , TV watching ) to vigorous ( e.g. , running ) were collected . While performing these activities , the girls wore two accelerometers , a heart rate monitor and a Cosmed K4b2 portable metabolic unit for measurement of (.-)VO(2 ) . A r and om-coefficients model was used to estimate the relationship between accelerometer counts and (.-)VO(2 ) . Activity thresholds were defined by minimizing the false positive and false negative classifications . RESULTS The activities provided a wide range in (.-)VO(2 ) ( 3 - 36 mL x kg x min ) with a correspondingly wide range in accelerometer counts ( 1- 3928 counts x 30 s ) . The regression line for MET score versus counts was MET = 2.01 + /- 0.00171 ( counts x 30 s ) ( mixed model R = 0.84 , SEE = 1.36 ) . A threshold of 1500 counts x 30 s defined the lower end of the moderate intensity ( approximately 4.6 METs ) range of physical activity . That cutpoint distinguished between slow and brisk walking , and gave the lowest number of false positive and false negative classifications . The threshold ranges for sedentary , light , moderate , and vigorous physical activity were found to be 0 - 50 , 51- 1499 , 1500 - 2600 , and > 2600 counts x 30 s , respectively . CONCLUSION The developed equation and these activity thresholds can be used for prediction of MET score from accelerometer counts and participation in various intensities of physical activity in adolescent girls BACKGROUND Socioeconomic status ( SES ) has well known associations with a variety of health conditions and behaviors in adults but is unknown in adolescents . METHODS Multilevel analysis was conducted to examine the associations between individual and neighborhood-level measures of SES and physical activity and body mass index in a sample of 1554 6th grade girls selected at r and om from 36 middle schools across 6 geographic regions in the United States that participated in the Trial of Activity for Adolescent Girls ( TAAG ) . Data on parental education and employment , and receipt of subsidized school lunch were collected by question naire . Neighborhood-level SES was measured by the Townsend Index . Nonschool physical activity levels were measured by accelerometer and type , location and context was measured using a 3 day physical activity recall ( 3DPAR ) . RESULTS After controlling for race , lower parental education and higher levels of social deprivation were associated with higher BMI . In a model with both variables , effects were attenuated and only race remained statistically significant . None of the indices of SES were related to  accelerometer measured physical activity . Bivariate associations with self-reported Moderate-Vigorous Physical Activity ( MVPA ) location and type ( 3DPAR ) varied by SES . CONCLUSION Among adolescent girls in the TAAG Study , the prevalence of overweight is high and inversely related to individual and neighborhood SES 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 UNLABELLED The absence of comparative validity studies has prevented research ers from reaching consensus regarding the application of intensity-related accelerometer cut points for children and adolescents . PURPOSE This study aim ed to evaluate the classification accuracy of five sets of independently developed ActiGraph cut points using energy expenditure , measured by indirect calorimetry , as a criterion reference st and ard . METHODS A total of 206 participants between the ages of 5 and 15 yr completed 12 st and ardized activity trials . Trials consisted of sedentary activities ( lying down , writing , computer game ) , lifestyle activities ( sweeping , laundry , throw and catch , aerobics , basketball ) , and ambulatory activities ( comfortable walk , brisk walk , brisk treadmill walk , running ) . During each trial , participants wore an ActiGraph GT1 M , and V˙O2 was measured breath-by-breath using the Oxycon Mobile portable metabolic system . Physical activity intensity was estimated using five independently developed cut points : Freedson/Trost ( FT ) , Puyau ( PU ) , Treuth ( TR ) , Mattocks ( MT ) , and Evenson ( EV ) . Classification accuracy was evaluated via weighted κ statistics and area under the receiver operating characteristic curve ( ROC-AUC ) . RESULTS Across all four intensity levels , the EV ( κ=0.68 ) and FT ( κ=0.66 ) cut points exhibited significantly better agreement than TR ( κ=0.62 ) , MT ( κ=0.54 ) , and PU ( κ=0.36 ) . The EV and FT cut points exhibited significantly better classification accuracy for moderate- to vigorous-intensity physical activity ( ROC-AUC=0.90 ) than TR , PU , or MT cut points ( ROC-AUC=0.77 - 0.85 ) . Only the EV cut points provided acceptable classification accuracy for all four levels of physical activity intensity and performed well among children of all ages . The widely applied sedentary cut point of 100 counts per minute exhibited excellent classification accuracy ( ROC-AUC=0.90 ) . CONCLUSIONS On the basis of these findings , we recommend that research ers use the EV ActiGraph cut points to estimate time spent in sedentary , light- , moderate- , and vigorous-intensity activity in children and adolescents PURPOSE We established accelerometer count ranges for the Computer Science and Applications , Inc. ( CSA ) activity monitor corresponding to commonly employed MET categories . METHODS Data were obtained from 50 adults ( 25 males , 25 females ) during treadmill exercise at three different speeds ( 4.8 , 6.4 , and 9.7 km x h(-1 ) ) . RESULTS Activity counts and steady-state oxygen consumption were highly correlated ( r = 0.88 ) , and count ranges corresponding to light , moderate , hard , and very hard intensity levels were < or = 1951 , 1952 - 5724 , 5725 - 9498 , > or = 9499 cnts x min(-1 ) , respectively . A model to predict energy expenditure from activity counts and body mass was developed using data from a r and om sample of 35 subjects ( r2 = 0.82 , SEE = 1.40 kcal x min(-1 ) ) . Cross validation with data from the remaining 15 subjects revealed no significant differences between actual and predicted energy expenditure at any treadmill speed ( SEE = 0.50 - 1.40 kcal x min(-1 ) ) . CONCLUSIONS These data provide a template on which patterns of activity can be classified into intensity levels using the CSA accelerometer PURPOSE Objective measurement with body worn instrumentation is a preferred and increasingly common way to gather information about young people 's physical activity . Measured sample s have been typically small and recruited through schools . The purpose of this article was to present the descriptive epidemiology of children and youth pedometer-determined  physical activity on the basis of a large national sample . METHODS Children and youth ( 19,789 ) were recruited through r and om digit dialing . Participants were asked to wear the pedometer for seven consecutive days and to log daily steps . Of the 58 % of participants who returned pedometer data ,  
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Conclusions Children do not benefit to the same extent as adolescents from built-environment features that encourage walking and those design ed or used for neighbourhood play