Comparing physical activity estimates in children from hip-worn Actigraph GT3X+ accelerometers using raw and counts based processing methods

This study examined differences in physical activity (PA) estimates provided from raw and counts processing methods. One hundred and sixty-five children (87 girls) wore a hip-mounted ActiGraph GT3X+ accelerometer for 7 days. Data were available for 129 participants. Time in moderate PA (MPA), vigorous PA (VPA) and moderate-vigorous PA (MVPA) were calculated using R-package GGIR and ActiLife. Participants meeting the wear time criteria for both processing methods were included in the analysis. Time spent in MPA (?21.4 min.d^?1, 95%CI ?21 to ?20) and VPA (?36 min.d^?1, 95%CI ?40 to ?33) from count data were higher (P < 0.001) than raw data. Time spent in MVPA between the two processing methods revealed significant differences (All P < 0.001). Bland-Altman plots suggest that the mean bias for time spent in MPA, VPA and MVPA were large when comparing raw and count methods. Equivalence tests showed that estimates from raw and count processing methods across all activity intensities lacked equivalence. Lack of equivalence and poor agreement between raw and count processing methods suggest the two approaches to estimate PA are not comparable. Further work to facilitate the comparison of findings between studies that process and report raw and count physical activity data may be necessary.     

Reproducibility of objectively measured physical activity: Reconsideration needed

ABSTRACT

Reliability of accelerometer-determined physical activity (PA), and thus the required length of a monitoring period, appears to depend on the analytic approach used for its calculation. We compared reliability of objectively measured PA using different resolution of data in a sample of 221 Norwegian 2–6-year-old children providing 2–3 valid 14-day periods of accelerometer monitoring (ActiGraph GT3X+) during September–October, January–February, and May–June 2015–2016. Reliability (intra-class correlation [ICC]) was measured for 1–14 days of monitoring across the measurement periods using linear mixed effect modelling. These results were compared to reliability estimated using different resolution of data using the Spearman–Brown formula. The measured reliability improved only marginally with increased monitoring length and levelled off after 5–6 days. Estimated reliability differed substantially when derived from different resolution of data: 3.9–5.4, 6.7–9.2, 13.4–26.7 and 26.3–87.7 days of monitoring was required to achieve an ICC = 0.80 using an hour-by-hour, a day-by-day, a week-by-week and a period-by-period approach, respectively. Reliability could not be correctly estimated from any single resolution of data. We conclude that reconsideration is needed with regard to how reproducibility of objectively measured PA is analysed and interpreted.     

Wear compliance,sedentary behaviour and activity in free-living children from hip-and wrist-mounted ActiGraph GT3X+ accelerometers

The GT3X+ worn at the wrist promotes greater compliance than at the hip. Minutes in SB and PA calculated from raw accelerations at the hip and wrist provide contrasting estimates and cannot be directly compared.

Wear-time for the wrist (15.6 to 17.4 h.d^?1) was greater than the hip (15.2 to 16.8 h.d^?1) across several wear-time criteria (all P < 0.05). Moderate-strong associations were found between time spent in SB (r = 0.39), LPA (r = 0.33), MPA (r = 0.99), VPA (r = 0.82) and MVPA (r = 0.81) between the two device placements (All P < 0.001). The wrist device detected more minutes in LPA, MPA, VPA and MVPA whereas the hip detected more SB (all P = 0.001). Estimates of time in SB and all activity outcomes from the wrist and hip lacked equivalence.

One hundred and eighty-eight 9–12-year-old children wore a wrist- and hip-mounted accelerometer for 7 days. Data were available for 160 (hip) and 161 (wrist) participants. Time spent in SB and PA was calculated using GGIR.

This study examined the compliance of children wearing wrist- and hip-mounted ActiGraph GT3X+ accelerometers and compared estimates of sedentary behaviour (SB) and physical activity (PA) between devices.     

Impact of the choice of threshold on physical activity patterns in free living conditions among adolescents measured using a uniaxial accelerometer: The HELENA study

Abstract

The aim of this study was to assess the impact of the choice of threshold on physical activity patterns measured in adolescents under free living conditions (FLC) using a uniaxial accelerometer. The study comprised 2043 adolescents (12.5–17.5 years) participating in the HELENA Study. Participants wore a uniaxial accelerometer for 7 days. The PA patterns were assessed using thresholds determined from six different studies. For each of the thresholds used, the number of adolescents fulfilling the recommendation of 60 min of moderate to vigorous PA (MVPA) per day was also calculated. A significant difference was found between thresholds regardless of the activity level: differences of 38%, 207%, 136%, and 2780% for sedentary, light, moderate, and vigorous intensity PA, respectively (P < 0.001). Time of MVPA varied between methods from 25.3 to 55.2 min · day^–1. The number of adolescents fulfilling the recommendation varied from 5.9% to 37% according to the thresholds used. The kappa coefficient for concordance in the assessment of the number of adolescents achieving the PA recommendations was generally low. The definition of the threshold for PA intensity may considerably affect the PA patterns in FLC when assessed using a uniaxial accelerometer and the number of participants fulfilling the recommendations.     

Accelerometry-Based Characteristics of Overall Sedentary Behavior and Sitting in Middle-Aged Adults

ABSTRACT

The purpose of this study was to describe the accelerometry-based characteristics of overall sedentary behavior (SB) and sitting among adults under free-living conditions. Thirty-six (mean age 47.6 years) volunteers carried a waist-worn accelerometer for ≥4 days with data ≥600 min/d during 14 consecutive days. A machine learning (ML) based method was used to classify the patterns of SB and sitting from raw 3D acceleration. The participants spent most (69.3%) of their waking time in SB, and a half (52.2%) of the SB was performed in a sitting posture. Men broke their overall sedentary time less often (4.1 vs. 6.1 bouts/h), but women sat more; however, women broke their sitting time as often as men (7.6 bouts/h). This study confirms that SB and sitting can be distinguished using ML methods, and more information about SB can be achieved when overall SB and sitting are analyzed separately in free-living conditions.     

The translation of preschoolers’ physical activity guidelines into a daily step count target

This study aimed at translating the physical activity (PA) guideline (180 min of total PA per day) into a step count target in preschoolers. 535 Flemish preschoolers (mean age: 4.41 ± 0.58) wore an ActiGraph accelerometer (GT1M, GT3X and GT3X+) – with activated step count function – for four consecutive days. The step count target was calculated from the accelerometer output using a regression equation, applying four different cut-points for light-to-vigorous PA: Pate, Evenson, Reilly, and Van Cauwenberghe. The present analysis showed that 180 min of total PA per day is equivalent to the following step count targets: 5,274 steps/day using the Pate cut-point, 4,653 steps/day using the Evenson cut-point, 11,379 steps/day using the Reilly cut-point and 13,326 steps/day using the Van Cauwenberghe cut-point. Future studies should focus on achieving consensus on which cut-points to use in preschoolers before a definite step count target in preschoolers can be proposed. Until then, we propose to use a provisional step count target of 11,500 steps/day as this step count target is attainable, realistic and helpful in promoting preschoolers’ PA.     

Frequent sit-to-stand transitions and several short standing periods measured by hip-worn accelerometer are associated with smaller waist circumference among adults

This cross-sectional study analysed the association of sedentary behaviour (SB) and standing with waist circumference. Finnish adults aged 30-75 years from a sub-sample of population-based Health 2011 Study used a hip-worn tri-axial accelerometer (Hookie AM20, Traxmeet, Ltd, Espoo, Finland) for seven days. Those 1405 participants (57% women) who used accelerometer at least four days, minimum of 10 hours/day, were included. SB and standing were analysed in 6s epochs using validated algorithm. Daily total time, daily number and accumulated time from bouts (30s–5min,30s–10min,30s–15min,30s 30min,>5min,>10min,>15min, >30min) as well as daily number of sit-to-stand transitions were determined. Waist circumference (cm) was measured in standardized way. Participants’ mean age was 52 years (SD 12.2). Mean waist circumference was 97cm (SD 12.3) in men and 87cm (SD 12.7) in women. According to multivariable stepwise linear regression analysis, sit-to-stand transitions [standardised regression coefficient (β)= -0.14, 95%CI -0.20 to -0.09], standing bouts of 30s–5min (β= -0.21, 95%CI -0.26 to -0.15) and number of 30s-30min SB bouts (β=0.12, 95%CI 0.06 to 0.17) were most strongly associated with waist circumference. Besides assessing total SB time, future studies should assess also different bout lengths of SB and sit-to-stand transitions and standing times should be assessed separately.     

Evaluation of wrist and hip sedentary behaviour and moderate-to-vigorous physical activity raw acceleration cutpoints in older adults

Wrist-based accelerometers are now common in assessing physical activity (PA) and sedentary behaviour (SB) in population-based studies, but there is a scarcity of raw acceleration cutpoints in older adults. The study aimed to determine and evaluate wrist-based GENEActiv (GA) and hip-based ActiGraph GT3X+ (AG) raw acceleration cutpoints for SB and moderate-to-vigorous PA (MVPA) in older adults ≥60 years of age. A laboratory-based calibration analyses of 34 healthy older adults involved receiver operator characteristic (ROC) curves to determine raw acceleration cutpoints for SB and MVPA. ROC analysis revealed an area under the curve (AUC) of 0.88 for GA SB and MVPA, and 0.90 for AG SB and 0.94 for AG MVPA. Sensitivity optimised SB and specificity optimised MVPA GA cutpoints of 57 mg and 104 mg, and AG cutpoints of 15 mg and 69 mg were also generated, respectively. Cross-validation analysis revealed moderate agreement for GA and AG SB cutpoints, and fair to substantial agreement for GA and AG MVPA cutpoints, respectively. The resultant cutpoints can classify older adults as engaging in SB or not engaging in MVPA but the sensitivity optimised SB cutpoints should be interpreted with a degree of caution due to their modest cross-validation results.     

Accelerometer data requirements for reliable estimation of habitual physical activity and sedentary time of children during the early years - a worked example following a stepped approach

This study presents a worked example of a stepped process to reliably estimate the habitual physical activity and sedentary time of a sample of young children. A total of 299 children (2.9 ± 0.6 years) were recruited. Outcome variables were daily minutes of total physical activity, sedentary time, moderate to vigorous physical activity and proportional values of each variable. In total, 282 (94%) provided 3 h of accelerometer data on ≥1 day and were included in a 6-step process: Step-1: determine minimum wear-time; Step-2: process 7-day-data; Step-3: determine the inclusion of a weekend day; Step-4: examine day-to-day variability; Step-5: calculate single day intraclass correlation (ICC) (2,1); Step-6: calculate number of days required to reach reliability. Following the process the results were, Step-1: 6 h was estimated as minimum wear-time of a standard day. Step-2: 98 (32%) children had ≥6 h wear on 7 days. Step-3: no differences were found between weekdays and weekend days (P ≥ 0.05). Step-4: no differences were found between day-to-day variability (P ≥ 0.05). Step-5: single day ICC’s (2,1) ranged from 0.48 (total physical activity and sedentary time) to 0.53 (proportion of moderate to vigorous physical activity). Step-6: to reach reliability (ICC = 0.7), 3 days were required for all outcomes. In conclusion following a 7 day wear protocol, ≥6 h on any 3 days was found to have acceptable reliability. The stepped-process offers researchers a method to derive sample-specific wear-time criterion.     

ActivPAL™ determined sedentary behaviour,physical activity and academic achievement in college students

The aim of this study was to examine relationships between activPAL?-determined sedentary behavior (SB) and physical activity (PA) with academic achievement. A total of 120 undergraduates (N = 57 female; 20.6 ± 2.3 years) participated in the study. Academic achievement was measured as the grade point average obtained from all completed courses. Participants wore on the right tight an activPAL? for 7 days to determine total sedentary time, total number of sedentary breaks, sedentary bouts, standing time, light and moderate-to-vigorous physical activity (MVPA). Separate multiple linear regression models were performed to examine associations between SB variables and academic achievement. Light PA, MVPA, total sedentary time, total standing time, or total number of sedentary breaks were not related to academic achievement. Independently of PA, the amount of time spent in sedentary bouts of 10-20min during weekdays was positively related to academic achievement. Given that college students spend the majority of their workday in environments that encourage prolonged sitting, these data suggest that interruptions in prolonged periods of sitting time every 10-20min via short breaks may optimize cognitive operations associated with academic performance.     

Validity and Reliability of the Global Physical Activity Questionnaire (GPAQ)

There is limited published validity and reliability evidence to support using the Global Physical Activity Questionnaire. Two studies were conducted to evaluate validity and reliability evidence for the Global Physical Activity Questionnaire. In Study 1: 69 adults completed the Global Physical Activity Questionnaire (three months apart; n?=?54), International Physical Activity Questionnaire, fitness and anthropometric measures. All participants wore a pedometer and 53 participants wore an accelerometer for seven days at baseline. In Study 2, 16 adults completed the Global Physical Activity Questionnaire 10 days apart. Global Physical Activity Questionnaire moderate and vigorous minutes were correlated with the accelerometer moderate (r?=?0.28) and vigorous (r?=?0.48) physical activity. The Global Physical Activity Questionnaire and International Physical Activity Questionnaire were related for sedentary behaviors (r?=?0.51), moderate-to-vigorous (r?=?0.48) and vigorous (r?=?0.63) PA. Global Physical Activity Questionnaire moderate-to-vigorous physical activity was associated with percent fat (r =??0.32), estimated VO₂ max (r?=?0.26), and step count (r?=?0.39). The Global Physical Activity Questionnaire demonstrated graded differences across categories for step count, body mass index, waist circumference, percent fat, fitness, and accelerometer measured activity. Short-term test–retest reliability (10 days) ranged from 0.83 to 0.96 while long-term reliability (three months) was 0.53 to 0.83. These data provide low-to-moderate validity and generally acceptable reliability evidence for the Global Physical Activity Questionnaire.     

Age-related differences in daily physical activity divided by bout duration: preliminary findings in female convenience samples

The purpose of the present investigation was to clarify the relationship between age and bout duration of physical activity (PA) under free-living conditions in female adults. Forty-three females wore an accelerometer (Lifecorder) for seven consecutive days in order to determine the time spent in PA at light intensity (LPA), at moderate intensity (MPA), and at vigorous intensity (VPA). The PA was divided according to the bout duration, such as PA lasting longer than 16 s, 32 s, 60 s, 3 min, >5 min, and >10 min (PA16s, PA32s, PA1m, PA3m, PA5m, PA10m). The time for LPA32s, LPA1m, MPA16s, VPA16s, and the total time for MPA and VPA were significantly associated with age (P < 0.05). There were no significant associations between age and PA lasting >60 s, regardless of intensity category. The results of the present pilot study suggest that the age-associated differences in PA occur mainly in PA lasting 1 min or shorter duration.     

Evaluation of an unstructured afterschool physical activity programme for disadvantaged youth

The purpose of the study was to conduct an evaluation of an unstructured afterschool physical activity (PA) programme (Keep it Moving!; KIM) in an ethnically diverse and low socio-economic status (SES) school district. PA of students in 3rd–5th grades (N = 205) at four elementary schools were assessed during spring 2012. An ActiGraph accelerometer was utilised to examine objectively measured time and steps in differing intensity levels. Standard data reduction procedures were used to process collected data and characterise PA. Students averaged approximately 54 min of accelerometer wear-time during the KIM programme, 10.4 ± 6.1 min (19.2%) of which were spent in sedentary behaviour, 28.2 ± 8.3 min (52.1%) in light PA and 15.6 ± 6.6 min (28.7%) in moderate-to-vigorous intensity PA. Within the cadence band of 1–19 steps/min participants accumulated the highest time-derived PA (16.4 ± 6.3 min). In total, children averaged 1811.9 ± 527.5 steps during the entire KIM programme. Results from the programme indicated that elementary-aged students received additional PA through the KIM programme. The mean value of accumulated steps during the afterschool PA programme represented 12–16.5% of the minimum steps/day target (depending upon gender) identified for elementary-aged school children. These data represent unique findings from a high-need population that may be helpful for researchers and practitioners alike.     

Accelerometer and GPS Data to Analyze Built Environments and Physical Activity

ABSTRACT

Purpose: Most built environment studies have quantified characteristics of the areas around participants’ homes. However, the environmental exposures for physical activity (PA) are spatially dynamic rather than static. Thus, merged accelerometer and global positioning system (GPS) data were utilized to estimate associations between the built environment and PA among adults. Methods: Participants (N = 142) were recruited on trails in Massachusetts and wore an accelerometer and GPS unit for 1–4 days. Two binary outcomes were created: moderate-to-vigorous PA (MVPA vs. light PA-to-sedentary); and light-to-vigorous PA (LVPA vs. sedentary). Five built environment variables were created within 50-meter buffers around GPS points: population density, street density, land use mix (LUM), greenness, and walkability index. Generalized linear mixed models were fit to examine associations between environmental variables and both outcomes, adjusting for demographic covariates. Results: Overall, in the fully adjusted models, greenness was positively associated with MVPA and LVPA (odds ratios [ORs] = 1.15, 95% confidence interval [CI] = 1.03, 1.30 and 1.25, 95% CI = 1.12, 1.41, respectively). In contrast, street density and LUM were negatively associated with MVPA (ORs = 0.69, 95% CI = 0.67, 0.71 and 0.87, 95% CI = 0.78, 0.97, respectively) and LVPA (ORs = 0.79, 95% CI = 0.77, 0.81 and 0.81, 95% CI = 0.74, 0.90, respectively). Negative associations of population density and walkability with both outcomes reached statistical significance, yet the effect sizes were small. Conclusions: Concurrent monitoring of activity with accelerometers and GPS units allowed us to investigate relationships between objectively measured built environment around GPS points and minute-by-minute PA. Negative relationships between street density and LUM and PA contrast evidence from most built environment studies in adults. However, direct comparisons should be made with caution since most previous studies have focused on spatially fixed buffers around home locations, rather than the precise locations where PA occurs.     

Social correlates of sedentary behavior in young people:The UP&DOWN study

Purpose:The aim of the present study was to analyze the associations of youths' sedentary behavior(SB) with parents' and siblings' SB and physical activity(PA),as well as the associations of youths' coparticipation with parents,siblings,and friends in PA and SB with youths' SB.Methods:The sample consisted of 1543 youths(12.02±2.51 years;788 boys) enrolled in the baseline cohort of the UP&DOWN study.SB was assessed by accelerometry and questionnaire.Participants reported the time spent by their parents and siblings watching television,playing videogames,surfing the Internet,sitting/resting,and doing PA.Further,participants reported coparticipation with parents,siblings,and friends in these activities.Linear mixed models,including school and city as random effects,were performed.Results:Parents' television time was positively associated with youths' screen-based SB.Coparticipation with friends in playing videogames(in boys) and in surfing the Internet(in girls) showed a positive association with screen-based SB and a negative association with educational-based SB.Moreover,coparticipation with siblings and friends in PA was inversely associated with accelerometer-based SB in boys and girls.Conclusion:Our results emphasize the important role of social modeling in the development of sedentary lifestyles in youths.Interventions aimed at reducing health risk behaviors in youths could be more effective if they are oriented from a social perspective that involves their families and networks of their closest friends.     

Environmental correlates of total and domain-specific sedentary behaviour in young people. The UP&DOWN study

This study investigated the associations between the characteristics of the nearby physical environment with the total and domain-specific leisure-time sedentary behaviour (SB) in young people. The study included 1578 youth (9–18 years) from the UP&DOWN study. Total leisure-time SB was objectively-assessed by accelerometers. Participants self-reported the time spent during leisure-time in different domains of SB (i.e. screen-based, educational-based, social-based, and other-based SB). Information regarding the basic characteristics of the house, the perceived neighbourhood environment, the amount of physical activity facilities, equipment and materials attainable at home, and the media equipment available at home and in the own bedroom was collected. Linear mixed models were performed, including school and city as random effects. The availability of yard was related to lower total SB and time spent surfing the Internet in boys, but not in girls. More favourable perceived neighbourhood environment was associated with lower total SB and time spent playing video games in girls, but not in boys. The amount of physical activity materials at home was negatively associated with screen-based SB, while the availability of a computer in the own bedroom was positively related to the time spent surfing the Internet in boys and girls. The number of televisions at home and having a computer in the own bedroom was associated with lower time in educational-based SB in boys and girls, respectively. Increasing the number of PA materials at home and decreasing the number of TVs at home and the availability of a computer in the bedroom could improve SB profiles of youth.     

Patterns of accelerometer-derived sedentary time across the lifespan

ABSTRACT

We aimed to describe ST and its patterns on a national level. A hip-worn accelerometer (ActiGraph GT1M) was used to collect data during waking hours from 4575 Portuguese’ participants from 2007–2009 (2683 females) aged 10–102 years old. Data was presented by sex, in 5-years age intervals, and by adolescents (n=2833), adults (n=1122), and older adults (n=620). Lambda-mu-sigma (LMS) smoothed percentile curves were estimated. Girls, women, and older women spent 61, 57, and 64% of wear time in ST, respectively. In males, ST represented 57, 60, and 62% of wear time respectively for boys, men, and older men. Comparing to other age groups, older adults spent a larger amount of ST in bouts ≥30-min (women: 33%, men: 39% of total ST). The number of breaks/ST hour were: 10.6 in girls, 11.7 in women, and 9.6 in older women. In males, the number of breaks/ST hour were: 11.2, 10.5, and 8.5 for boys, men, and older men. In conclusion, ST was not consistently higher at older ages. Instead, we found that the potential critical moments in which ST may be higher are during adolescence and in the transition from adulthood into older adulthood, which represents critical periods for interventions.     

Is a single question of the Global Physical Activity Questionnaire (GPAQ) valid for measuring sedentary behaviour in the Chilean population?

A study was conducted to assess the validity of the Global Physical Activity Questionnaire (GPAQ) for measuring sedentary behaviour (SB) in the Chilean adult population. About 217 adults (93/124 male/female, 43.8 ± 15.75 years) who were randomly selected during National Health Survey 2009–2010 completed the protocol. The participants wore an ActiGraph GT3X (AG) for 7 consecutive days and then completed the GPAQ (single-item question for measuring time spent sitting in a usual day). Validity was examined using Spearman’s correlation, mean bias and limits of agreement (LoA), with AG (vertical axis <100 counts · min^?1) as the reference standard for estimates of SB in bouts of 1 (AG1), 5 (AG5) and 10 (AG10) min. Agreement between the GPAQ and AG for classifying data into quartiles and tertiles was assessed with kappa method. The GPAQ showed fair correlation with AG1, AG5 and AG10 (range = 0.23–0.26), with large mean biases (range = ?293.9, ?76.12 min · day^?1). Agreement between the GPAQ and AG1, AG5 and AG10 was poor for categorising time spent in SB into tertiles and quartiles. The single question from the GPAQ has shown fair validity for measuring SB and poor ability for correctly classifying individuals into tertiles or quartiles of SB in a Chilean population.