Search

The primary aim of this pilot study was to assess how well the combination of global positioning system (GPS) and accelerometer data predicted different activity modes.Ten adults (seven male, three female; 23-51 yr) simultaneously wore a GPS unit and accelerometer during bouts of walking, jogging/running, bicycling, inline skating, or driving an automobile. Discriminant function analysis was used to identify a parsimonious combination of variables derived from accelerometer counts and steps and GPS speed that best classified mode. A total of 29 bouts were used to develop this classification criterion. This criterion was validated using two datasets generated from the complete collection of minute-by-minute values from all bouts.Model development with "calibration" data showed that two accelerometer variables alone (median counts and steps) resulted in 26 of 29 bouts (90%) being correctly classified. Prediction of activity mode using counts and steps in a minute-by-minute "validation" dataset (N = 200) was 86.5%. Using three variables from the accelerometer and GPS (median counts, steps and speed) resulted in correct classification in 27 of 29 activity bouts in the "calibration" data (93%). In the "validation" dataset comprising 200 min, the combination of accelerometer counts and steps and GPS speed were able to correctly classify 91% of the observations. Walking and bicycling minutes were correctly classified most frequently (96%). In another "validation" dataset consisting of activity bouts, this combination of variables resulted in correct classification in 42 of 43 bouts (98%).This pilot study provides evidence that the addition of GPS to accelerometer monitoring improves physical activity mode classification to a small degree. Larger studies among free-living individuals and with an expanded range of activities are needed to replicate the current findings and further determine the merits of using GPS with accelerometers for mode identification.

Persistent disparities suggest that multiple aspects of social context may influence leisure-time physical activity levels and weight status in multiethnic, working-class populations.Among participants in two randomized, controlled intervention trials (n = 1,969 in 10 health centers; n = 1545 in 26 manufacturing businesses) we used general linear mixed models to examine the relationship of variables posited by a social-contextual framework for behavior change with h/wk of self-reported leisure-time physical activity and with body mass index (BMI; weight [kg]/[height (m)2]) at baseline, adjusting for clustering within study site.Age, sex, race/ethnicity, and socioeconomic position were independently associated with leisure-time physical activity in both settings; multivariable models explained 15% of the variance in health centers and 11% in small businesses. Leisure-time physical activity and motivation to change lifestyle behaviors were inversely associated with BMI, adjusting for individual, interpersonal, and neighborhood factors. Models explained 12% of the variance in BMI in health centers and 10% in small businesses.A social-contextual framework highlights the contribution of social class and race/ethnicity in the variance in leisure-time physical activity and weight status but suggests other behavioral influences vary in multiethnic, working-class populations.

Objective To determine the effect of a school-based intervention to promote healthful nutrition and physical activity on disordered weight-control behaviors (self-induced vomiting or use of laxatives or diet pills to control weight) in early adolescent girls and boys. Design Using a group-randomized, controlled-trial design, we randomly assigned middle schools to an intervention or control condition. Multivariate logistic regression analyses were used to assess the effect of the intervention on the odds of reporting a new case of disordered weight-control behaviors at follow-up, adjusting for sex, school-level prevalence of disordered weight-control behaviors at baseline, and school clusters. Students reporting these behaviors at baseline were excluded from the analyses. Setting Thirteen middle schools. Participants At baseline, 749 girls and 702 boys in grades 6 and 7. Intervention The 5-2-1 Go! intervention (Planet Health obesity prevention curriculum plus School Health Index for Physical Activity and Healthy Eating: A Self-Assessment and Planning Guide, Middle/High School Version) was implemented during 2 school years, from November 2002 through May 2004. Main Outcome Measure Self-reported disordered weight-control behaviors in last 30 days at follow-up. Results At follow-up in girls, 3.6% (15 of 422) in control schools compared with 1.2% (4 of 327) in intervention schools reported engaging in disordered weight-control behaviors ( P = .04). Multivariate analyses indicated that the odds of these behaviors in girls in intervention schools were reduced by two thirds compared with girls in control schools (odds ratio, 0.33; 95% confidence interval, 0.11-0.97). No intervention effect was observed in boys. Conclusions Results add compelling support for the effectiveness of an interdisciplinary, school-based obesity prevention intervention to prevent disordered weight-control behaviors in early adolescent girls.

Purpose: To assess test-retest reliability and validity of the Youth Risk Behavior Survey (YRBS) items for moderate and vigorous physical activity in middle school students. Methods: Students (N = 125; 12.7 ± 0.6 yr) wore Actigraph accelerometers for 6.1 ± 1.0 d and twice completed surveys that included YRBS moderate and vigorous physical activity items. Accelerometer counts were transformed into minutes of moderate (3-6 METs) and vigorous (> 6 METs) physical activity. Days per week meeting moderate and vigorous physical activity recommendations were estimated using four summary methods. Reliability was assessed using intraclass correlation coefficients (ICC) from the two surveys. Validity was assessed as percent concordance, kappa coefficients, and sensitivity and specificity using binary YRBS and Actigraph outcomes. Results: Test-retest ICC for the moderate and vigorous physical activity items were 0.51 and 0.46, respectively. Twenty-two percent of students met the recommended level of moderate physical activity (= 30 min·d-1, = 5 d·wk-1) according to self-reports, whereas 90.4 and 66.4% met the recommendation according to accumulated accelerometer minutes and 5-min-bout criteria, respectively. Concordance between YRBS and Actigraph moderate physical activity measures was highest using accumulated accelerometer minutes. Sensitivity of the moderate YRBS item ranged from 0.19 to 0.23 for four comparisons, and specificity was 0.74-0.92. More than two thirds of students reported vigorous physical activity at recommended levels (= 20 min·d-1, = 3 d·wk-1), whereas the highest prevalence according to Actigraph monitoring was 22.4%. Sensitivity of the YRBS vigorous item was high (0.75-0.92) compared with the four Actigraph measures; specificity was low (0.23-0.26). Conclusion: YRBS questions underestimate the proportion of students attaining recommended levels of moderate physical activity and overestimate the proportion meeting vigorous recommendations. Use of accelerometry for physical activity surveillance seems to be indicated. At the minimum, new questions demonstrating greater validity are needed.

Background Promotion of transportation-related physical activity is consistent with current national recommendations. However, few studies have simultaneously examined correlates of recreational and transportation physical activity. Methods Surveys were mailed to 1002 adults residing in a Massachusetts suburb. The survey included measures of self-reported recreational and transportation-related physical activity and demographic, cognitive, interpersonal, and environmental variables potentially correlated with activity. Multiple linear regression was used to examine the associations between environmental variables and the two outcomes. Results Respondents (n = 413) who averaged 51.2 ± 16.8 years of age reported 132.3 ± 140.5 min/week recreational physical activity and 142.1 ± 180.9 min/week transportation activity. Sidewalks (P = 0.02) and traffic (P = 0.01) were each associated with higher levels of recreational physical activity in unadjusted analyses, but in models that controlled for age, self-efficacy for physical activity and family social support for physical activity, these environmental variables were nonsignificant. Three perceived environmental variables (enjoyable scenery, sidewalks, traffic) and one objective environmental variable (distance from home to a community rail-trail) each showed associations (P ≤ 0.05) with transportation-related physical activity in models that controlled for age and self-efficacy. Conclusions Neighborhood physical environmental variables were associated with transportation physical activity, but not with recreational physical activity. Further research is needed to identify shared and unique correlates of recreational and transportation physical activity in urban, suburban, and rural settings.

The Massachusetts WISEWOMAN Project is a cardiovascular disease (CVD) risk reduction program targeting older uninsured and underinsured women. The cost-effectiveness of providing CVD screening and enhanced lifestyle interventions (EI), compared with providing CVD screening and a minimum intervention (MI), was assessed at five El and six MI healthcare sites.Cost calculations were based on data collected during screenings and intervention activities conducted with 1586 women in 1996. Risk factor data, including cholesterol and blood pressure measures, were used to create a summary effectiveness outcome, the 10-year probability of developing coronary heart disease (CHD). The cost-effectiveness ratio of the EI, compared with the MI, was calculated by dividing the incremental cost of the EI by the incremental effectiveness of the EI.The incremental cost of the EI was $191. During the 1-year study period, the 10-year probability of CHD decreased from 9.4% to 9.2% in the MI group and from 10.3% to 9.8%in the El group. Based on these results, it would cost $637 to achieve a 1 percentage point larger decrease in the 10-year probability of CHD for women enrolled in the El. However, because differences between groups were not statistically significant, we cannot reject the hypothesis that the El results in no greater reductions in CHD risk.Although women enrolled in both the MI and El showed decreases in CHD risk during the study period, future research is needed to assess the impact of lifestyle interventions targeting financially disadvantaged women.

The belief that significant others (referents) felt the subjects should exercise (normative beliefs) was the strongest in subjects in the maintenance stage and weakest for subjects in the inactive stage. This pattern occurred in all the referent groups and for both male and female subjects. Women's normative beliefs were stronger than men's for all the stages and referent groups. For men, motivation to comply with referents was strongest in the maintenance stage and weakest in the inactive stage. This pattern was not as clearly visible in female subjects. Inactive women had higher motivation to comply then did men for all conditions and referent groups, but this motivation was most pronounced in the inactive stage.