Purpose: To investigate potential time drift between devices when using Global Positioning Systems (GPS) and accelerometers in field-based research. Methods: Six Qstarz BT-Q1000XT GPS trackers, activPAL3 accelerometers, and ActiGraph GT3X+ and GT3X accelerometers were tested over 1–3 waves, each lasting 9–14 days. Once per day an event marker was created on each pair of devices concurrently. The difference in seconds between the time stamps for each event marker were calculated between each pair of GPS and activPAL devices and GPS and ActiGraph devices. Mixed-effects linear regression tested time drift across days and waves and between two rooms/locations (in an inner room vs. on a windowsill in an outer room). Results: The GPS trackers remained within one second of the computer clock across days and waves and between rooms. The activPAL devices drifted an average of 8.38 seconds behind the GPS devices over 14 days (p < .001). The ActiGraph GT3X+ devices drifted an average of 11.67 seconds ahead of the GPS devices over 14 days (p < .001). The ActiGraph GT3X devices drifted an average of 28.83 seconds behind the GPS devices over 9 days (p < .001). Time drift did not differ across waves but did differ between rooms and across devices. Conclusions: Time drift between the GPS and accelerometer models tested was minimal and is unlikely to be problematic when addressing many common research questions. However, studies that require high levels of precision when matching short (e.g., 1-second) time intervals may benefit from consideration of time drift and potential adjustments.
Chelsea Steel, Carolina Bejarano and Jordan A. Carlson
Jordan A. Carlson, J. Aaron Hipp, Jacqueline Kerr, Todd S. Horowitz and David Berrigan
Objectives: To document challenges to and benefits from research involving the use of images by capturing examples of such research to assess physical activity– or nutrition-related behaviors and/or environments. Methods: Researchers (i.e., key informants) using image capture in their research were identified through knowledge and networks of the authors of this paper and through literature search. Twenty-nine key informants completed a survey covering the type of research, source of images, and challenges and benefits experienced, developed specifically for this study. Results: Most respondents used still images in their research, with only 26.7% using video. Image sources were categorized as participant generated (n = 13; e.g., participants using smartphones for dietary assessment), researcher generated (n = 10; e.g., wearable cameras with automatic image capture), or curated from third parties (n = 7; e.g., Google Street View). Two of the major challenges that emerged included the need for automated processing of large datasets (58.8%) and participant recruitment/compliance (41.2%). Benefit-related themes included greater perspectives on obesity with increased data coverage (34.6%) and improved accuracy of behavior and environment assessment (34.6%). Conclusions: Technological advances will support the increased use of images in the assessment of physical activity, nutrition behaviors, and environments. To advance this area of research, more effective collaborations are needed between health and computer scientists. In particular development of automated data extraction methods for diverse aspects of behavior, environment, and food characteristics are needed. Additionally, progress in standards for addressing ethical issues related to image capture for research purposes is critical.
James F. Sallis, Jacqueline Kerr, Jordan A. Carlson, Gregory J. Norman, Brian E. Saelens, Nefertiti Durant and Barbara E. Ainsworth
Neighborhood environment attributes of walkability and access to recreation facilities have been related to physical activity and weight status, but most self-report environment measures are lengthy. The 17-item PANES (Physical Activity Neighborhood Environment Scale) was developed to be comprehensive but brief enough for use in multipurpose surveys. The current study evaluated test-retest and alternate-form reliability of PANES items compared with multi-item subscales from the longer NEWS-A (Neighborhood Environment Walkability Scale—Abbreviated).
Participants were 291 adults recruited from neighborhoods that varied in walkability in 3 US cities. Surveys were completed twice with a 27-day interval.
Test-retest ICCs for PANES items ranged from .52 to .88. Spearman correlations for the PANES single item vs NEWS-A subscale comparisons ranged from .27 to .81 (all P < .01).
PANES items related to land use mix, residential density, pedestrian infrastructure, aesthetic qualities, and safety from traffic and crime were supported by correlations with NEWS-A subscales. Access to recreation facilities and street connectivity items were not supported. The brevity of PANES allows items to be included in studies or surveillance systems to expand knowledge about neighborhood environments.
Jordan A. Carlson, James F. Sallis, Nicole Wagner, Karen J. Calfas, Kevin Patrick, Lisa M. Groesz and Gregory J. Norman
Psychosocial factors have been related to physical activity (PA) and are used to evaluate mediation in PA interventions.
Brief theory-based psychosocial scales were compiled from existing measures and evaluated. Study 1 assessed factor structure and construct validity with self-reported PA and accelerometry in overweight/obese men (N = 441) and women (N = 401). Study 2 assessed 2-week reliability and internal consistency in 49 college students.
Confirmatory factor analysis indicated good fit in men and women (CFI = .90; RMSEA = .05). Construct validity was supported for change strategies (r = .29–.46), self-efficacy (r = .19–.22) and enjoyment (r = .21–.33) in men and women, and for cons in women (r = –.19 to –.20). PA pros (r = –.02 to .11) and social support (r = –.01 to .12) were not supported for construct validity. Test-retest reliability ICCs ranged from .49–.81. Internal consistency alphas ranged from .55–.90. Reliability was supported for most scales with further testing needed for cons (alphas = .55–.63) and enjoyment (ICC = 49).
Many of the brief scales demonstrated adequate reliability and validity, while some need further development. The use of these scales could advance research and practice in the promotion of PA.