How many days are enough? A study of 365 days of pedometer monitoring

Effects of ankle-foot orthoses on step activities in the community: a systematic review

PURPOSE

To determine the effects of ankle-foot orthoses (AFO) on step-based physical activities in individuals with neurological, orthopaedic, or cardiovascular disorders.

METHODS

Electronic searches of databases such as Scopus, PubMed, Web of Science, Embase, ProQuest, Cochrane Library, and EBSCO were conducted. Two evaluators independently searched with keywords focusing on step-based physical activities, and either articulated or non-articulated AFO. Study quality was assessed using a modified Downs and Black quality scale.

RESULTS

Eleven studies that met the inclusion criteria were selected, including four being classified as good, four as fair, and three as poor in quality. The majority of these trials found no significant effects of AFO on step activities. Only a few studies reported improvements in step counts and active times in step activity with a limited to moderate level of evidence. Subjective evaluations such as user satisfaction, and physical functionality during step activity, on the other hand, showed substantial changes with the use of AFO interventions, although there was no evidence of improvement in the quality of life.

CONCLUSIONS

Although the AFO did not seem to have a substantial effect on step activity, it appeared to play a vital role in improving the patient satisfaction level of step activity.IMPLICATIONS FOR REHABILITATIONAnkle-foot orthoses (AFO) may not significantly affect the step activity of individuals with impaired ankle-foot complex.AFO may enhance patient-reported satisfaction, physical functioning, participation, and fatigue level during step activity.The patient's perception that the AFO is beneficial is in contrast to objective data showing no significant increase in real-world activity.

Four Days Are Enough to Provide a Reliable Daily Step Count in Mild to Moderate Parkinson's Disease through a Commercial Smartwatch

Daily steps could be a valuable indicator of real-world ambulation in Parkinson's disease (PD). Nonetheless, no study to date has investigated the minimum number of days required to reliably estimate the average daily steps through commercial smartwatches in people with PD. Fifty-six patients were monitored through a commercial smartwatch for 5 consecutive days. The total daily steps for each day was recorded and the average daily steps was calculated as well as the working and weekend days average steps. The intraclass correlation coefficient (ICC) (3,k), standard error of measurement (SEM), Bland-Altman statistics, and minimum detectable change (MDC) were used to evaluate the reliability of the step count for every combination of 2-5 days. The threshold for acceptability was set at an ICC ≥ 0.8 with a lower bound of CI 95% ≥ 0.75 and a SAM < 10%. ANOVA and Mann-Whitney tests were used to compare steps across the days and between the working and weekend days, respectively. Four days were needed to achieve an acceptable reliability (ICC range: 0.84-0.90; SAM range: 7.8-9.4%). In addition, daily steps did not significantly differ across the days and between the working and weekend days. These findings could support the use of step count as a walking activity index and could be relevant to developing monitoring, preventive, and rehabilitation strategies for people with PD.

Monitoring physical activity using wearable technology in people with Achilles tendinopathy undergoing physiotherapy treatment: A feasibility prospective cohort study

OBJECTIVES

Physical activity modification is an important part of the management of Achilles tendinopathy. However, to our knowledge, there is a lack of evidence on objective physical activity assessment in Achilles tendinopathy. The purpose of this study is to (1) assess feasibility of using an inertial measurement unit (IMU) to monitor physical activity and IMU-derived biomechanical measures over 12-week treatment course by a physiotherapist; (2) conduct a preliminary analysis of changes in physical activity over 12-weeks.

DESIGN

A feasibility prospective cohort study SETTING: A community setting.

PARTICIPANTS

People with Achilles tendinopathy who had recently commenced (≤2 sessions), or were about to commence, treatment with a physiotherapist MAIN OUTCOME MEASURES: Participants wore a shank-mounted IMU on the affected side for one week at baseline, 6-, and 12-week follow-ups. The outcomes were pain/symptom severity, IMU-derived physical activity and biomechanical measures (stride rate, peak shank angular velocity, and peak shank acceleration).

RESULTS

Thirty participants were recruited. There was a high retention rate (97%), response rate (97%), and IMU wear compliance at each timepoint (>93%). For pain/symptom severity, a significant time effect was observed between baseline and 12-week follow-up. Physical activity and IMU-derived biomechanical measures did not change over 12 weeks. Physical activity decreased at the 6-week follow-up but only returned to the baseline level at 12-week follow-up.

CONCLUSIONS

A larger-scale cohort study assessing clinical outcomes and physical activity appears feasible. Preliminary data indicate that physical activity may not change significantly over 12-weeks in people undergoing physiotherapy management for Achilles tendinopathy. CONTRIBUTION OF THE PAPER.

How many days of indoor positioning system data are required to characterise typical movement behaviours of office workers?

Indoor Positioning Systems (IPS) appear to offer great potential to study the movement and interaction of people and their working environment, including office workplaces. But little is known about appropriate durations for data collection. In this study, location observations collected from 24 office workers on a 1220 m² office floor over a 3-month period, were analysed to determine how many days are required to estimate their typical movement and spatial behaviours. The analysis showed that up to 8 days of data was sufficient to characterise participants' typical daily movement behaviours and 10 days were required to estimate their typical spatial mobility. However, the results also indicate that 5 weeks of data collection are required to gather the necessary 10 days of data from each participant. These findings will help researchers and workplace professionals to understand the capabilities and requirements of IPS when considering their use in indoor work environments.

Evaluating daily physical activity and biomechanical measures using wearable technology in people with Achilles tendinopathy: A descriptive exploratory study

BACKGROUND

Load management is considered an important factor for prevention and treatment of Achilles tendinopathy. However, little attention has been given to monitoring daily load objectively in this population.

OBJECTIVES

We aimed to explore patterns in proxies of daily load derived from a six-axis inertial measurement unit (IMU) over a one-week period and the concordance between day-to-day fluctuation in pain intensity and IMU measures.

DESIGN

Descriptive exploratory study.

METHOD

Ten participants with Achilles tendinopathy (age: 53.00 ± 12.37) wore an IMU on the affected ankle for one week. Participants were contacted via text message three times daily to rate their worst pain intensity. Physical activity and biomechanical measures derived from the IMU signals including daily number of steps, peak stride rate, peak shank acceleration, and peak shank angular velocity were calculated.

RESULTS

The relationship between weekly worst pain and physical activity levels appeared modest; with increased steps not seeming to be linked to increased or reduced pain levels. According to the daily pain and daily IMU measures, a concordant pattern was evident in younger, highly active participants. However, in the middle-aged/older less active participants, there was either a fluctuation in pain intensity without fluctuation in the IMU measures, or a stable pattern of both pain and IMU measures.

CONCLUSIONS

Our exploratory study results suggest that continuous monitoring of proxies of daily load measures in parallel with pain may provide information about load management strategies in people with Achilles tendinopathy. Monitoring of these proxies may ultimately have a role in improving Achilles tendinopathy management.

Physical activity of physiotherapists in Germany: a cross-sectional study

Aim

We aimed to quantify the work-related physical activity of physiotherapists in Germany.

Subjects and methods

We included working physiotherapists aged between 18 and 65 years in Germany. We excluded physiotherapists working less than 20 h a week. We measured our primary outcome, work-related physical activity, by the average number of steps taken daily during work, standardized on an 8-h working day. We controlled the main outcome for potential confounders, such as working hours per week, age, weekday, and clinical setting (outpatient vs. inpatient), by multivariate linear regression analysis. We used R statistics for all statistical analyses.

Results

We included 35 participants (7 outpatient and 28 inpatient), with a median age category of 20–29 years. Our participants had a mean work-related physical activity of 6614 steps (95% confidence interval, CI [6118; 7111]) per workday. Higher age, outpatient clinical setting, and working full time were associated with lower step count, but these associations were not statistically significant.

Conclusions

The work-related physical activity of physiotherapists in Germany is comparable with results from other countries and can be regarded as ‘low’. Our result, however, might be affected by volunteer bias and gender effects. Further research should identify high-risk groups in the profession for cost-effective prevention.

Reporting of Physical Activity Device Measurement and Analysis Protocols in Lifestyle Interventions

This systematic review examined the extent to which lifestyle physical activity interventions that used wearable devices (eg, pedometers, accelerometers) reported on the length of device wear time requested in their protocols, criteria for analytic inclusion of data, and participant compliance with device use protocols. Literature were searches were conducted using PubMed, Cochrane Central Register, and PsychInfo. Studies were included if they were the main outcomes paper of a trial that reported on a randomized or quasi-randomized trial focused on increasing lifestyle physical activity and were published between January 1, 2006 and March 30, 2016. Titles and abstracts were screened by 2 independent reviewers; eligible full texts were retrieved and reviewed by 2 independent reviewers. A total of 104 studies used wearable devices (n = 57 pedometers, n = 47 accelerometers). Most studies (n = 65, 67.3%) asked participants to wear devices for 7 days. Almost half of the studies (n = 46, 44.2%) did not report minimum device wear time required for analytic inclusion of data, and variation existed among studies reporting these criteria. Most studies (n = 60, 57.7%) did not report average device wear time, or participant compliance with device wear. Overall, there was heterogeneity in reporting of physical activity device data. Refinement and streamlining of guidelines for device use, analysis, and reporting of data could improve comparability across studies.

Influence of the Duration and Timing of Data Collection on Accelerometer-Measured Physical Activity, Sedentary Time and Associated Insulin Resistance

Accelerometry is a commonly used method to determine physical activity in clinical studies, but the duration and timing of measurement have seldom been addressed. We aimed to evaluate possible changes in the measured outcomes and associations with insulin resistance during four weeks of accelerometry data collection. This study included 143 participants (median age of 59 (IQR9) years; mean BMI of 30.7 (SD4) kg/m²; 41 men). Sedentary and standing time, breaks in sedentary time, and different intensities of physical activity were measured with hip-worn accelerometers. Differences in the accelerometer-based results between weeks 1, 2, 3 and 4 were analyzed by mixed models, differences during winter and summer by two-way ANOVA, and the associations between insulin resistance and cumulative means of accelerometer results during weeks 1 to 4 by linear models. Mean accelerometry duration was 24 (SD3) days. Sedentary time decreased after three weeks of measurement. More physical activity was measured during summer compared to winter. The associations between insulin resistance and sedentary behavior and light physical activity were non-significant after the first week of measurement, but the associations turned significant in two to three weeks. If the purpose of data collection is to reveal associations between accelerometer-measured outcomes and tenuous health outcomes, such as insulin sensitivity, data collection for at least three weeks may be needed.

Number of daily measurements needed to estimate habitual step count levels using wrist-worn trackers and smartphones in 212,048 adults

Daily step count is a readily accessible physical activity measure inversely related to many important health outcomes. However, its day-to-day variability is not clear, especially when measured by recent mobile devices. This study investigates number of measurement days required to reliably estimate the weekly and monthly levels of daily step count in adults using wrist-worn fitness trackers and smartphones. Data were from a 5-month physical activity program in Singapore. The 5-month period was divided into 22 weekly and 5 monthly time windows. For each time window, we leveraged data sampling procedures and estimated the minimum number of measurement days needed to achieve reliable mean daily step count with intraclass correlation coefficients (ICC) above 80%. The ICCs were derived using linear mixed effect models. We examined both simple random and random consecutive measurement days and conducted subgroup analysis by participant characteristics and tracking devices. Analysis of weekly and monthly step count included 212,048 and 112,865 adults, respectively. Fewer simple random measurement days are needed than random consecutive days for weekly time windows (mean 2.5, SD 0.5 vs mean 2.7, SD 0.5; p-value = 0.025). Similarly, monthly time windows require fewer measurements of simple random days than random consecutive days (mean 3.4, SD 0.5 vs mean 4.4, SD 0.5; p-value = 0.025). Younger participants and those tracking steps via smartphones consistently required more days. Being obese was associated with more measurement days for weekly time windows. In sum, to obtain reliable daily step count level, we recommend at least 3 measurement days for weekly and 5 days for monthly time window in adults. Fewer days could be considered for adults age 60+ years, while more days are required when tracking daily step via smartphones.

Three Days of Measurement Provide Reliable Estimates of Daily Tremor Characteristics: A Pilot Study in Organic and Functional Tremor Patients

Background

Long-term tremor recording is particularly useful for the assessment of overall severity and therapeutic interventions in tremor patients. The purpose of this paper is to investigate the optimal number of days needed to obtain reliable estimates of tremor percentage, tremor frequency variability and tremor intensity in tremor patients using long-term tremor recordings.

Methods

Participants were 18 years or older and were diagnosed with tremor by a movement disorders specialist. Participants wore an accelerometer on the wrist of the most affected arm during 30 consecutive days. Tremor presence, frequency variability and intensity were calculated per day. We used reliability analysis to determine the minimum number of days needed to obtain reliable estimates of these tremor characteristics.

Results

Data from 36 adult organic (OrgT) and functional tremor (FT) patients (24 males; mean age 63.9 ± 11.9 years; 15 FT) were analyzed. Using five hours per day, one day of measurement is enough, except for tremor frequency variability in the OrgT group, where three days are needed and for tremor intensity where two days are always needed.

Discussion

Visual analysis suggested that reliability can be increased considerably by using data from three days instead of one day even when using six hours of data per day. Three days with at least three hours of tremor data provide estimates of tremor percentage, frequency variability and intensity with good to excellent reliability, both for organic and functional tremor.

Both sedentary time and physical activity are associated with cardiometabolic health in overweight adults in a 1 month accelerometer measurement

The aim of this study was to examine the associations of cardiometabolic health markers with device-measured sedentary behavior (SB) duration and different intensities of physical activity (PA) among overweight working-aged adults with low self-reported PA levels. This cross-sectional analysis included 144 subjects (42 men) with mean age of 57 (SD 6.5) years and mean BMI of 31.7 (SD 4) kg/m². SB and standing time, breaks in sedentary time, light PA (LPA) and moderate-to-vigorous PA (MVPA) were measured for 4 consecutive weeks (mean 25 days, SD 4) with hip-worn accelerometers. Fasting plasma glucose, insulin, HbA_1c, triglycerides and total cholesterol, HDL and LDL were measured from venous blood samples. HOMA-IR index was calculated as a surrogate of insulin resistance. The associations were examined using linear models. LPA, MVPA, and daily steps associated with better insulin sensitivity and favorable plasma lipid profile, when adjusted for age, sex and BMI, whereas greater proportion of SB associated with insulin resistance and unfavorable lipid profile. As all PA intensities associated with better cardiometabolic health, the total daily duration of PA may be more relevant than intensity in maintaining metabolic health in overweight adults, if the current guidelines for PA are not met.

Trial Registration: ClinicalTrials.gov NCT03101228, registered 05/04/2017, https://clinicaltrials.gov/show/NCT03101228.

Objective aerobic fitness level and neuropsychological functioning in healthy adolescents and emerging adults: Unique sex effects

Objective

Research suggests positive relationships between aerobic fitness and cognition in older adults; however, limited research has adequately investigated the relationship between objectively measured aerobic fitness and broad cognitive functioning in healthy adolescents and young adults without psychiatric or physical health disorders. Further, studies to date have disproportionately examined males and failed to examine sex differences. Here we examine the relationship between aerobic fitness and neuropsychological functioning in physically healthy youth and whether sex moderates these findings.

Design

Sixty-four healthy emerging adults (16-25 years-old; 32 female) underwent measurement of objective aerobic fitness (VO2 max) and neuropsychological assessment. Exclusion criteria included: left-handedness, prenatal medical issues or alcohol/illicit drug exposure, Axis-I psychiatric disorders, major medical disorders including metabolic conditions such as diabetes, hypertension, hyperlipidemia, major neurologic disorders, LOS greater than 2 min, intellectual disability or learning disability, regular substance use (e.g., greater than biweekly use of cannabis) or positive drug toxicology testing.

Method

Multiple regressions examined VO2 max, sex, sex*VO2interaction in relation to neurocognition, controlling for objectively measured body fat percentage.

Results

Prior to including body fat percentage, higher VO2 max related to improved working memory (Letter-Number Sequencing; p = .03) and selective attention (CPT-II hit response time standard error; p = .03). Aerobic fitness significantly interacted with sex, as higher-fit males had better performance on two sustained attention tasks while females did not demonstrate this pattern (CPT-II variability standard error, p = .047; Ruff 2&7 Total Speed, p = .02). Body fat percentage was positively slower cognitive flexibility (D-KEFS color-word switching/inhibition, p = .046).

Conclusions

VO2 independently predicted better working memory and selective attention. Increased aerobic fitness level related to increased performance on sustained attention tasks in males but not females. Therefore, aerobic fitness may be positively related to better cognitive functioning in physically healthy adolescents and emerging adults without metabolic conditions. Further research into factors (e.g., intensity or type of activity) that may relate to beneficial outcomes by sex are needed.

Does Online Social Connectivity Promote Physical Activity in a Wearable Tracker-Based Intervention? A Pilot Randomized Controlled Study

Wearable activity trackers have gained popularity among individuals who want to track their physical activity (PA). The features of wearable tracking technology that are known to facilitate positive behavior changes such as self-monitoring and social connectedness) are well documented; yet, the existing evidence is not conclusive in the literature requiring further investigation. This study was an 8-week pilot randomized controlled study examining the effectiveness of PA intervention incorporating a wearable activity tracker’s online connectivity feature. Forty participants were equally randomized into either an individual-based (n = 20) or a connected group (n = 20). A Jawbone UP24 tracker was provided to all participants in both groups as a means of self-monitoring PA for eight weeks, but the connected group was additionally instructed to share their PA levels with the others using the accompanying smartphone application. Participants’ weekly step counts were evaluated each week to examine the change in PA. Participants’ biometric variables such as body weight, body mass index, waist circumference, blood pressure, and psychological status, including self-efficacy (SE) and exercise motivation (EM), were measured from both groups before and after the intervention period. Additionally, the social support questionnaire (SSQ) was measured among the connected group. The statistical significance level was set at <0.05. The average step counts for eight weeks were significantly increased only in the connected group (p < 0.001). Significant differences in step count improved from the baseline to week 8 in the connected user group (p < 0.01), but only baseline vs. week 7 in the individual users. Also, no significant interaction effects for biometric variables, EM, and SE were founded. However, SSQ was significantly improved in the connected user group (p < 0.001). PA intervention combining a wearable activity tracker and online social connectivity feature shows a greater effectiveness of promoting PA than a wearable tracker alone

Sex and light physical activity impact popliteal, but not brachial artery flow-mediated dilation in physically active young adults

When controlling for baseline diameter, males have greater brachial flow-mediated dilation (BA-FMD) responses than females. It is unclear whether sex differences in baseline diameter also influences popliteal FMD (POP-FMD), which may be impacted by cardiorespiratory fitness and physical activity levels. We hypothesized that males would exhibit greater BA-FMD and POP-FMD when allometrically scaled to baseline diameter. FMD (ultrasonography), cardiorespiratory fitness (indirect calorimetry), and objectively measured physical activity were assessed in males (n = 13; age, 23 ± 3 years; peak oxygen consumption, 48.0 ± 7.1 mL·kg^-1·min^-1) and females (n = 13; age, 24 ± 2 years; peak oxygen consumption, 36.8 ± 6.0 mL·kg^-1·min^-1). Both groups had similarly high levels of moderate-to-vigorous intensity physical activity (503 ± 174 vs. 430 ± 142 min·week^-1, p = 0.25). However, males were more aerobically fit (p < 0.001) and females accumulated more light-intensity physical activity (182 ± 67 vs. 127 ± 53 min·week^-1, p = 0.03). Relative and allometrically scaled BA-FMD were similar (both, p ≥ 0.09) between sexes. In contrast, relative (6.2% ± 1.0% vs. 4.6% ± 1.4%, p = 0.001) and scaled (6.8% ± 1.7% vs. 4.7% ± 1.7%, p = 0.03) POP-FMD were greater in females. Relative POP-FMD was related to light-intensity physical activity in the pooled sample (r = 0.43; p = 0.04). However, the enhanced relative POP-FMD in females remained after adjusting for higher light-intensity physical activity levels (p = 0.01). Young females have enhanced popliteal, but not brachial, endothelial health than males with similar moderate-to-vigorous intensity physical activity levels and higher cardiorespiratory fitness. Novelty In physically active adults, females had greater POP-FMD but not BA-FMD than males. The enhanced POP-FMD in females was not related to greater vascular smooth muscle sensitivity to nitric oxide or their smaller baseline diameters. POP-FMD was associated with light physical activity levels in the pooled sample.

Minimum accelerometer wear-time for reliable estimates of physical activity and sedentary behaviour of people receiving haemodialysis

BACKGROUND

Low levels of physical activity are implicated in low life expectancies of people receiving maintenance haemodialysis. Accelerometers are increasingly being used to quantify activity behaviours of this population but guidance to quality-assure such data is lacking. The objective of this study was to provide data processing and reduction recommendations to ensure accelerometer-derived outcomes are sufficiently reliable for interpretative analysis.

METHODS

Seventy people receiving maintenance haemodialysis (age 55.9 ± 15.7 years, 34% women, 23% diabetic) from a single outpatient renal unit volunteered for the study. Participants wore Actigraph GT3x and ActivPAL monitors during waking hours over seven days. Reliability of accelerometer output (normalised to wear-time) was assessed via intraclass correlation coefficient (ICC). The Spearman-Brown prophecy formula was subsequently applied to the ICCs to derive the minimum required accelerometer wear-time for each behavioural outcome.

RESULTS

Monitor wear compliance was greater on dialysis compared to non-dialysis days (90% v 77%). Participants were significantly more active on non-dialysis days compared to dialysis days but there were no significant differences in estimated behaviours between days within the same condition. Average measure ICCs for all accelerometer outcomes were high (range 0.76-0.96). Computations indicated that habitual physical activity and sedentary behaviour could be estimated with a minimum reliability level of 0.80 from one dialysis day and two non-dialysis days, and at least eight hours monitor wear per day. Applying this rubric allowed 90% of participant data to be retained for further analysis.

CONCLUSIONS

Regardless of accelerometer, one dialysis and two non-dialysis days data with a minimum of eight hours wear each day should enable habitual activity of people receiving maintenance haemodialysis to be characterised with acceptable reliability. These recommendations reconcile the tension between wear-time criteria stringency and retention of an adequately representative sample.

Who Uses Wearable Activity Trackers and Why? A Comparison of Former and Current Users in the United States

BACKGROUND

There has been an explosion in the use of wearable activity trackers (WATs), but we do not fully understand who wears them and why. This study's purpose was to describe the characteristics of WAT users and to compare current and former users.

MATERIALS AND METHODS

A variety of internet-based resources (eg, Craigslist, Facebook) were used to recruit current and former WAT users. Respondents completed a web-based survey, where they provided information on sociodemographic characteristics, health, physical activity behavior, and about their WAT use.

RESULTS

Of the 2826 respondents who gave informed consent, 70.8% (n = 2002) met inclusion criteria for this analysis. Respondents ranged from 18 to 81 years old (mean 32.9 ± 12.2 standard deviation) with 73.8% women. Most were current WAT users (68.7%), and the average length of WAT use overall was 9.3 ± 9.7 months. On average, current users wore the device for 3.7 months longer than former users. Compared to current users, former users had a lower body mass index (1.2 kg/m² less), reported fewer medical conditions, shared data from their device less often, and received the device as a gift more frequently.

CONCLUSIONS

Current and former users varied in their reasons for using a WAT and how they used their device. Differences identified between these groups support further exploration of associations between WAT users' profiles and their physical activity behavior.

Reproducibility of objectively measured physical activity: Reconsideration needed

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.

How many days of global positioning system (GPS) monitoring do you need to measure activity space environments in health research?

This study examined the number of days of global positioning system (GPS) monitoring needed to measure attributes of an individual's routine activity space. Multiple alternative activity space representations (cumulative, mean daily), measures (kernel density, route buffer, convex hull), and attributes (area size, supermarkets, fast food restaurants, parks) were examined. Results suggested wide variability in required GPS days to obtain valid estimates of activity space attributes (1-23 days). In general, fewer days were needed for mean daily activity space representations, kernel density measures, and densities of environmental exposures (vs. counts). While kernel density measures reliably estimated between-person differences in attributes after just a few days, most variability in environmental attributes for convex hull and route buffer measures was within-person. Based on these results, a minimum of 14 days of valid GPS data is recommended to measure activity spaces.

A systematic literature review of reviews on techniques for physical activity measurement in adults: a DEDIPAC study

The links between increased participation in Physical Activity (PA) and improvements in health are well established. As this body of evidence has grown, so too has the search for measures of PA with high levels of methodological effectiveness (i.e. validity, reliability and responsiveness to change). The aim of this “review of reviews” was to provide a comprehensive overview of the methodological effectiveness of currently employed measures of PA, to aid researchers in their selection of an appropriate tool. A total of 63 review articles were included in this review, and the original articles cited by these reviews were included in order to extract detailed information on methodological effectiveness.

Self-report measures of PA have been most frequently examined for methodological effectiveness, with highly variable findings identified across a broad range of behaviours. The evidence-base for the methodological effectiveness of objective monitors, particularly accelerometers/activity monitors, is increasing, with lower levels of variability observed for validity and reliability when compared to subjective measures. Unfortunately, responsiveness to change across all measures and behaviours remains under-researched, with limited information available.

Other criteria beyond methodological effectiveness often influence tool selection, including cost and feasibility. However, researchers must be aware of the methodological effectiveness of any measure selected for use when examining PA. Although no “perfect” tool for the examination of PA in adults exists, it is suggested that researchers aim to incorporate appropriate objective measures, specific to the behaviours of interests, when examining PA in free-living environments.

Reproducibility of objectively measured physical activity and sedentary time over two seasons in children; Comparing a day-by-day and a week-by-week approach

Introduction

Knowledge of reproducibility of accelerometer-determined physical activity (PA) and sedentary time (SED) estimates are a prerequisite to conduct high-quality epidemiological studies. Yet, estimates of reproducibility might differ depending on the approach used to analyze the data. The aim of the present study was to determine the reproducibility of objectively measured PA and SED in children by directly comparing a day-by-day and a week-by-week approach to data collected over two weeks during two different seasons 3–4 months apart.

Methods

676 11-year-old children from the Active Smarter Kids study conducted in Sogn og Fjordane county, Norway, performed 7 days of accelerometer monitoring (ActiGraph GT3X+) during January-February and April-May 2015. Reproducibility was calculated using a day-by-day and a week-by-week approach applying mixed effect modelling and the Spearman Brown prophecy formula, and reported using intra-class correlation (ICC), Bland Altman plots and 95% limits of agreement (LoA).

Results

Applying a week-by-week approach, no variables provided ICC estimates ≥ 0.70 for one week of measurement in any model (ICC = 0.29–0.66 not controlling for season; ICC = 0.49–0.67 when controlling for season). LoA for these models approximated a factor of 1.3–1.7 of the sample PA level standard deviations. Compared to the week-by-week approach, the day-by-day approach resulted in too optimistic reliability estimates (ICC = 0.62–0.77 not controlling for season; ICC = 0.64–0.77 when controlling for season).

Conclusions

Reliability is lower when analyzed over different seasons and when using a week-by-week approach, than when applying a day-by-day approach and the Spearman Brown prophecy formula to estimate reliability over a short monitoring period. We suggest a day-by-day approach and the Spearman Brown prophecy formula to determine reliability be used with caution.

Trial Registration

The study is registered in Clinicaltrials.gov 7^th April 2014 with identification number NCT02132494.

Developing a Clinical Protocol for Habitual Physical Activity Monitoring in Youth With Cerebral Palsy

PURPOSE

The StepWatch (SW) has been used to monitor physical activity (PA) in youth with cerebral palsy; however, there is no standard collection protocol. The goal was to develop such a protocol.

METHODS

Data were examined from patients who wore the SW for 8 to 14 days. The Spearman-Brown prediction formula determined the minimum number of days for reliable PA. Weekdays were compared to weekends and 10- and 60-second collection intervals were examined.

RESULTS

The PA data were collected from 98 youth with cerebral palsy. Results showed 3 days would provide reliable representation of PA, participants took significantly more steps during school days compared with weekends, and there were no differences between collection intervals.

CONCLUSIONS

We recommend setting the SW for 7 days at 10-second collection rate. Data should be analyzed if at least 3 days of data are present. Weekdays and weekend days should be noted, and both included when possible.

Reliability and validity of daily physical activity measures during inpatient spinal cord injury rehabilitation

Objectives:

To assess the test–retest reliability and convergent validity of daily physical activity measures during inpatient spinal cord injury rehabilitation.

Design:

Observational study.

Setting:

Two inpatient spinal cord injury rehabilitation centres.

Subjects:

Participants (n = 106) were recruited from consecutive admissions to rehabilitation.

Methods:

Physical activity during inpatient spinal cord injury rehabilitation stay was recorded on two days via (1) wrist accelerometer, (2) hip accelerometer if ambulatory, and (3) self-report (Physical Activity Recall Assessment for People with Spinal Cord Injury questionnaire). Spearman’s correlations and Bland–Altman plots were utilized for test–retest reliability. Correlations between physical activity measures and clinical measures (functional independence, hand function, and ambulation) were performed.

Results:

Correlations for physical activity measures between Day 1 and Day 2 were moderate to high (ρ = 0.53–0.89). Bland–Altman plots showed minimal bias and more within-subject differences in more active individuals and wide limits of agreement. None of these three physical activity measures correlated with one another. A moderate correlation was found between wrist accelerometry counts and grip strength (ρ = 0.58) and between step counts and measures of ambulation (ρ = 0.62). Functional independence was related to wrist accelerometry (ρ = 0.70) and step counts (ρ = 0.56), but not with self-report.

Conclusion:

The test–retest reliability and convergent validity of the instrumented measures suggest that wrist and hip accelerometers are appropriate tools for use in research studies of daily physical activity in the spinal cord injury rehabilitation setting but are too variable for individual use.

Physical activity, body mass index and heart rate variability-based stress and recovery in 16 275 Finnish employees: a cross-sectional study

BACKGROUND

Physical inactivity, overweight, and work-related stress are major concerns today. Psychological stress causes physiological responses such as reduced heart rate variability (HRV), owing to attenuated parasympathetic and/or increased sympathetic activity in cardiac autonomic control. This study's purpose was to investigate the relationships between physical activity (PA), body mass index (BMI), and HRV-based stress and recovery on workdays, among Finnish employees.

METHODS

The participants in this cross-sectional study were 16 275 individuals (6863 men and 9412 women; age 18-65 years; BMI 18.5-40.0 kg/m(2)). Assessments of stress, recovery and PA were based on HRV data from beat-to-beat R-R interval recording (mainly over 3 days). The validated HRV-derived variables took into account the dynamics and individuality of HRV. Stress percentage (the proportion of stress reactions, workday and working hours), and stress balance (ratio between recovery and stress reactions, sleep) describe the amount of physiological stress and recovery, respectively. Variables describing the intensity (i.e. magnitude of recognized reactions) of physiological stress and recovery were stress index (workday) and recovery index (sleep), respectively. Moderate to vigorous PA was measured and participants divided into the following groups, based on calculated weekly PA: inactive (0 min), low (0 < 150 min), medium (150-300 min), and high (>300 min). BMI was calculated from self-reported weight and height. Linear models were employed in the main analyses.

RESULTS

High PA was associated with lower stress percentages (during workdays and working hours) and stress balance. Higher BMI was associated with higher stress index, and lower stress balance and recovery index. These results were similar for men and women (P < 0.001 for all).

CONCLUSION

Independent of age and sex, high PA was associated with a lower amount of stress on workdays. Additionally, lower BMI was associated with better recovery during sleep, expressed by a greater amount and magnitude of recovery reactions, which suggests that PA in the long term resulting in improved fitness has a positive effect on recovery, even though high PA may disturb recovery during the following night. Obviously, several factors outside of the study could also affect HRV-based stress.

Statistical approaches to account for missing values in accelerometer data: Applications to modeling physical activity

Physical inactivity is a recognized risk factor for many chronic diseases. Accelerometers are increasingly used as an objective means to measure daily physical activity. One challenge in using these devices is missing data due to device nonwear. We used a well-characterized cohort of 333 overweight postmenopausal breast cancer survivors to examine missing data patterns of accelerometer outputs over the day. Based on these observed missingness patterns, we created psuedo-simulated datasets with realistic missing data patterns. We developed statistical methods to design imputation and variance weighting algorithms to account for missing data effects when fitting regression models. Bias and precision of each method were evaluated and compared. Our results indicated that not accounting for missing data in the analysis yielded unstable estimates in the regression analysis. Incorporating variance weights and/or subject-level imputation improved precision by >50%, compared to ignoring missing data. We recommend that these simple easy-to-implement statistical tools be used to improve analysis of accelerometer data.

Number of Days Required to Estimate Habitual Activity Using Wrist-Worn GENEActiv Accelerometer: A Cross-Sectional Study

Introduction

Objective methods like accelerometers are feasible for large studies and may quantify variability in day-to-day physical activity better than self-report. The variability between days suggests that day of the week cannot be ignored in the design and analysis of physical activity studies. The purpose of this paper is to investigate the optimal number of days needed to obtain reliable estimates of weekly habitual physical activity using the wrist-worn GENEActiv accelerometer.

Methods

Data are from a subsample of the Mitchelstown cohort; 475 (44.6% males; mean aged 59.6±5.5 years) middle-aged Irish adults. Participants wore the wrist GENEActiv accelerometer for 7-consecutive days. Data were collected at 100Hz and summarised into a signal magnitude vector using 60s epochs. Each time interval was categorised according to intensity based on validated cut-offs. Spearman pairwise correlations determined the association between days of the week. Repeated measures ANOVA examined differences in average minutes across days. Intraclass correlations examined the proportion of variability between days, and Spearman-Brown formula estimated intra-class reliability coefficient associated with combinations of 1–7 days.

Results

Three hundred and ninety-seven adults (59.7±5.5yrs) had valid accelerometer data. Overall, men were most sedentary on weekends while women spent more time in sedentary behaviour on Sunday through Tuesday. Post hoc analysis found sedentary behaviour and light activity levels on Sunday to differ to all other days in the week. Analysis revealed greater than 1 day monitoring is necessary to achieve acceptable reliability. Monitoring frame duration for reliable estimates varied across intensity categories, (sedentary (3 days), light (2 days), moderate (2 days) and vigorous activity (6 days) and MVPA (2 days)).

Conclusion

These findings provide knowledge into the behavioural variability in weekly activity patterns of middle-aged adults. Since Sunday differed from all other days in the week this suggests that day of the week cannot be overlooked in the design and analysis of physical activity studies and thus should be included in the study monitoring frames. Collectively our data suggest that six days monitoring, inclusive of Saturday and Sunday, are needed to reliably capture weekly habitual activity in all activity intensities using the wrist-worn GENEActiv accelerometer.

Long-term Surveillance of Physical Activity Habits of Latinas Enrolled in a 12-Month Physical Activity Intervention

BACKGROUND

Long-term physical activity surveillance has not been conducted among Latinas. This study explored the variability of daily physical activity habits of inactive adult Latinas participating in a 12-month physical activity intervention.

METHODS

We collected objective physical activity data (pedometer) from 139 Spanish speaking Latinas (age = 41.6 ± 10.1 years; BMI = 29.6 ± 4.3 kg/m2) enrolled in a 12-month physical activity intervention. Total and aerobic steps (>100 steps/minute) were computed by year, season, month, day of week, time of day, and hour.

RESULTS

Participants walked an average of 6509 steps/day of which 1303 (20%) were aerobic steps. Significant physical activity differences were observed for subgroups including generational status, education, employment, income, marital status and health literacy. Significant and similar differences were observed for both total steps and aerobic steps for day of the week (weekdays > weekends) and season (summer > spring > fall > winter). Opposing trends were observed over the course of the day for total steps (early afternoon > late morning > late afternoon > early morning > evening) and aerobic steps (early morning > evening > late morning > late afternoon > early afternoon).

CONCLUSIONS

Both seasonality and week day predicted physical activity habits of Latinas. This is the first long-term study to track daily physical activity habits of Latinas. These data have potential to inform the design of future physical activity interventions targeting Latinas.

Reliability of accelerometer-determined physical activity and sedentary behavior in school-aged children: a 12-country study

OBJECTIVES

Focused on the accelerometer-determined physical activity and sedentary time metrics in 9-11-year-old children, we sought to determine the following: (i) number of days that are necessary to achieve reliable estimates (G⩾0.8); (ii) proportion of variance attributed to different facets (participants and days) of reliability estimates; and (iii) actual reliability of data as collected in The International Study of Childhood Obesity, Lifestyle and Environment (ISCOLE).

METHODS

The analytical sample consisted of 6025 children (55% girls) from sites in 12 countries. Physical activity and sedentary time metrics measures were assessed for up to 7 consecutive days for 24 h per day with a waist-worn ActiGraph GT3X+. Generalizability theory using R software was used to investigate the objectives i and ii. Intra-class correlation coefficients (ICC) were computed using SAS PROC GLM to inform objective iii.

RESULTS

The estimated minimum number of days required to achieve a reliability estimate of G⩾0.8 ranged from 5 to 9 for boys and 3 to 11 for girls for light physical activity (LPA); 5 to 9 and 3 to 10, for moderate-to-vigorous physical activity (MVPA); 5 to 10 and 4 to 10 for total activity counts; and 7 to 11 and 6 to 11 for sedentary time, respectively. For all variables investigated, the 'participant' facet accounted for 30-50% of the variability, whereas the 'days' facet accounted for ⩽5%, and the interaction (P × D) accounted for 50-70% of the variability. The actual reliability for boys in ISCOLE ranged from ICCs of 0.78 to 0.86, 0.73 to 0.85 and 0.72 to 0.86 for LPA, MVPA and total activity counts, respectively, and 0.67 to 0.79 for sedentary time. The corresponding values for girls were 0.80-0.88, 0.70-0.89, 0.74-0.86 and 0.64-0.80.

CONCLUSIONS

It was rare that only 4 days from all participants would be enough to achieve desirable reliability estimates. However, asking participants to wear the device for 7 days and requiring ⩾4 days of data to include the participant in the analysis might be an appropriate approach to achieve reliable estimates for most accelerometer-derived metrics.

Fruit and Vegetable Consumption, Fat Intake, and Physical Activity Participation in Relation to Socio-demographic Factors Among Medically Underserved Adults

Fruit and vegetable intake as well as physical activity participation in Mississippi is consistently lower than recommendations. We conducted a cross-sectional study to examine fruit and vegetables consumption, fat intake, and moderate-intensity physical activity participation and how these variables relate to socio-demographic factors among medically underserved adults in south Mississippi. Fruit and vegetable consumption and fat intake along with physical activity participation and socio-demographic characteristics was collected from a sample of 161 (48 male and 113 female) adults in south Mississippi. A majority (81.9%) of participants reported consuming less than five servings of fruits and vegetables per day and 54% reported exercising less than three times a week. Only 14% of participants reported eating a low fat diet. Bivariate correlations revealed no significant relationships between fruit and vegetable consumption and fat intake as well as no significant relationships between fruit and vegetable consumption and gender, ethnicity, income, marital status, or education. However, there were significant correlations between physical activity and fat intake (r = -0.21, p = 0.01), and physical activity with fruit and vegetable consumption (r = 0.16, p = 0.05). Higher physical activity rates were associated with decreased fat intake and increased fruit and vegetable consumption. Physical activity was also higher among men (r = -0.16, p = 0.05) and positively correlated with income level (r = 0.21 p = 0.01). In order to effectively identify or develop strategies to improve health by promoting increased fruit and vegetable intake and physical activity, further research is needed to understand the factors that affect behavior choices regarding nutrition and physical activity in this medically underserved adult population.

Agreement of objectively measured physical activity and sedentary time in preschool children

OBJECTIVE

To determine the intra-individual agreement for objectively measured physical activity (PA) and sedentary behavior (SED) over two subsequent weeks in preschool children.

METHOD

Ninety-one children aged 3 to 5 years (49% boys) from three preschools in Sogn og Fjordane, Norway, provided 14 consecutive days of accelerometer data (Actigraph GT3X +) during the autumn of 2014. Week-by-week reliability was assessed using intraclass correlation (ICC), Bland-Altman plots and 95% limits of agreement for different wear time criteria (≥ 6, 8 and 10 h/day and ≥ 3 and 5 days/week).

RESULTS

The week-by-week ICC was ≥ 0.75 for all variables across all wear criteria applied, except for absolute sedentary time (ICC 0.61-0.81). Using a ≥ 8 h/day and ≥ 3 days/week criterion (n = 78), limits of agreement were ± 209.5 cpm for overall PA, ± 68.6 min/day for SED, ± 43.8 min/day for light PA, ± 20.2 min/day for moderate-to-vigorous PA, and ± 55.9 min/day for light-to-vigorous PA, equaling 1.0-1.6 standard deviation units.

CONCLUSION

Considerable week-by-week variability was found for all variables. Researchers need to be aware of substantial intra-individual variability in accelerometer-measurements and take necessary actions according to the hypothesis under study, as noise in any measurement will preclude researchers' ability to arrive at valid conclusions in epidemiology.

Physical Activity Levels in College Students With Chronic Ankle Instability

CONTEXT

Ankle sprains are the most common orthopaedic pathologic condition, and more concerning is the high percentage of persons who develop chronic ankle instability (CAI). Researchers have reported that patients with CAI are restricted occupationally, have more functional limitations, and have a poorer health-related quality of life. We do not know if these limitations decrease physical activity levels.

OBJECTIVE

To assess total weekly steps taken between persons with CAI and persons with healthy ankles.

DESIGN

Case-control study.

SETTING

University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 20 participants with unilateral CAI (9 men, 11 women; age = 21.2 ± 1.9 years, height = 174.3 ± 6.9 cm, mass = 71.9 ± 11.7 kg) and 20 healthy participants (9 men, 11 women; age = 20.4 ± 2.1 years, height = 172.1 ± 5.5 cm, mass = 73.1 ± 13.4 kg) volunteered.

MAIN OUTCOME MEASURE(S)

We provided all participants with a pedometer and instructed them to wear it every day for 7 days and to complete a daily step log. They also completed the Foot and Ankle Ability Measure (FAAM), the FAAM Sport version, and the International Physical Activity Questionnaire. A 2-way analysis of variance (group × sex) was used to determine if differences existed in the total number of weekly steps, ankle laxity, and answers on the International Physical Activity Questionnaire between groups and between sexes.

RESULTS

We found no group × sex interaction for step count (F range = 0.439-2.108, P = .08). A main effect for group was observed (F(1,38) = 10.45, P = .04). The CAI group took fewer steps than the healthy group (P = .04). The average daily step count was 6694.47 ± 1603.35 for the CAI group and 8831.01 ± 1290.01 for the healthy group. The CAI group also scored lower on the FAAM (P = .01) and the FAAM Sport version (P = .01).

CONCLUSIONS

The decreased step count that the participants with CAI demonstrated is concerning. This decreased physical activity may be secondary to the functional limitations reported. If this decrease in physical activity level continues for an extended period, CAI may potentially be a substantial health risk if not treated appropriately.

Intra-individual and inter-individual variability in daily sitting time and MVPA

OBJECTIVES

Little is known about how much variability exists in free-living sitting time within individuals. The purpose of this study was to examine intra-individual variability of objectively determined daily sitting time and to determine if this variability was related to weekly averages of sitting duration or recommended moderate-vigorous physical activity (MVPA). Also, this study determined the reliability of free-living sitting and MVPA time as it useful for guiding researchers in determining how many days of monitoring are needed.

DESIGN

An activPAL monitor was worn for 7 consecutive days by 68 women (52±8 years).

METHODS

Intra-individual range of daily sitting time was calculated. Generalizability theory analysis determined the reliability of daily sitting and recommended MVPA.

RESULTS

Mean sitting time was 9.0±1.8h/day and the within individual weekly mean range was 4.5±1.7h/day. Similarly, there was a 4.5h/day difference in sitting time between the mean of the lowest sitting (6.7±0.8) and highest sitting (11.3±1.1h/day) quartiles. The intra-individual range in daily sitting did not differ among quartiles of sitting time (i.e., 4.9±1.9, 4.1±1.9, 5.1±1.5, 3.9±1.1h/day for the 1st-4th quartiles) nor among quartiles of MVPA (i.e., 4.2±1.8, 4.7±2.0, 4.6±1.5, 4.4±1.3h/day for the 1st-4th quartiles). A reliability coefficient of 0.80 was achieved with 4 days of objectively measured sitting time and 7 days for MVPA.

CONCLUSIONS

The findings suggest exposure to relatively high levels of sedentary time may occur in people regardless of weekly averages in sitting and regular exercise due to the high day-to-day variation in daily sitting time (4.5h/d range within a week).

Effectiveness of a web-based, computer-tailored, pedometer-based physical activity intervention for adults: a cluster randomized controlled trial

BACKGROUND

Computer-tailored physical activity (PA) interventions delivered through the Internet represent a promising and appealing method to promote PA at a population level. However, personalized advice is mostly provided based on subjectively measured PA, which is not very accurate and might result in the delivery of advice that is not credible or effective. Therefore, an innovative computer-tailored PA advice was developed, based on objectively pedometer-measured PA.

OBJECTIVE

The study aim was to evaluate the effectiveness of a computer-tailored, pedometer-based PA intervention in working adults.

METHODS

Participants (≥18 years) were recruited between May and December 2012 from eight Flemish workplaces. These workplaces were allocated randomly to an intervention or control group. Intervention group participants (n=137) received (1) a booklet with information on how to increase their steps, (2) a non-blinded pedometer, and (3) an Internet link to request computer-tailored step advice. Control group participants (n=137) did not receive any of the intervention components. Self-reported and pedometer-based PA were assessed at baseline (T0), and 1 month (T1) and 3 months (T2) months post baseline. Repeated measures analyses of covariance were used to examine intervention effects for both the total sample and the at-risk sample (ie, adults not reaching 10,000 steps a day at baseline).

RESULTS

The recruitment process resulted in 274 respondents (response rate of 15.1%) who agreed to participate, of whom 190 (69.3%) belonged to the at-risk sample. Between T0 and T1 (1-month post baseline), significant intervention effects were found for participants' daily step counts in both the total sample (P=.004) and the at-risk sample (P=.001). In the at-risk sample, the intervention effects showed a daily step count increase of 1056 steps in the intervention group, compared to a decrease of 258 steps in the control group. Comparison of participants' self-reported PA revealed a significant intervention effect for time spent walking in the at-risk sample (P=.02). Intervention effects were still significant 3 months post baseline for participants' daily step counts in both the total sample (P=.03) and the at-risk sample (P=.02); however, self-reported PA differences were no longer significant.

CONCLUSIONS

A computer-tailored, pedometer-based PA intervention was effective in increasing both pedometer-based and self-reported PA levels, mainly in the at-risk participants. However, more effort should be devoted to recruit and retain participants in order to improve the public health impact of the intervention.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02080585; https://clinicaltrials.gov/ct2/show/NCT02080585 (Archived by WebCite at http://www.webcitation.org/6VvQnRQSy).

Objectively measured physical activity in Finnish employees: a cross-sectional study

OBJECTIVES

To objectively measure the amount of intensity-specific physical activity by gender and age with respect to body mass index (BMI) during workdays and days off among Finnish employees.

DESIGN

A cross-sectional study.

SETTING

Primary care occupational healthcare units.

PARTICIPANTS

A sample of 9554 Finnish employees (4221 men and 5333 women; age range 18-65 years; BMI range 18.5-40 kg/m(2)) who participated in health assessments related to occupational health promotion.

MAIN OUTCOME MEASUREMENTS

The amount of moderate-to-vigorous (MVPA) and vigorous (VPA) physical activity (≥3 and ≥6 metabolic equivalents, respectively) was assessed by estimating the minute-to-minute oxygen consumption from the recorded beat-to-beat R-R interval data. The estimation method used heart rate, respiration rate and on/off response information from R-R interval data calibrated by age, gender, height, weight and self-reported physical activity class. The proportion of participants fulfilling the aerobic physical activity recommendation of ≥150 min/week was calculated on the basis of ≥10 min bouts, by multiplying the VPA minutes by 2.

RESULTS

Both MVPA and VPA were higher among men and during days off, and decreased with increasing age and BMI (p<0.001 for all). Similar results were observed when the probability of having a bout of MVPA or VPA lasting continuously for ≥10 min per measurement day was studied. The total amount of VPA was low among overweight (mean ≤2.6 min/day), obese (mean ≤0.6 min/day) and all women in the age group 51-65 years (mean ≤2.5 min/day) during both types of days. The proportion of participants fulfilling the aerobic physical activity recommendation was highest for normal weight men (65%; 95% CI 62% to 67%) and lowest for obese women (10%; 95% CI 8% to 12%).

CONCLUSIONS

Objectively measured physical activity is higher among men and during days off, and decreases with increasing age and BMI. The amount of VPA is very low among obese, overweight and older women.

The minimum number of days required to establish reliable physical activity estimates in children aged 2-15 years

The purpose of this study was to determine the minimum number of days needed to assess reliable estimates of step-count data for children based on age and gender. A total of 428 developing children (at least 30 boys and 30 girls in seven two-year intervals from 2-3 years to 14-15 years of age) wore a StepWatch accelerometer for 7 consecutive days. Following data screening, the 422 children's data were finally analyzed by age and sex groups using the Generalizability theory. Single-facet crossed designs (i.e. Participant (P) × Days (D)) were applied for each of 14 datasets. G-studies were performed to quantify the percentage of variance associated with the facet and interaction in the model. Follow-up D-studies were performed to determine the minimum number of days of step-count data collection needed to achieve a desirable reliability coefficient (G ≥ 0.80). The results from the G-studies show that P explained a large percentage of the total variance (26-71%) while D had little effect on the total variance (0-5%). A relatively large percentage of variance was unidentified (i.e. the P × D interaction). The minimum number of days necessary to achieve a desirable reliability coefficient (G ≥ 0.80) ranged from 2 to 12 d. On average, boys required less days of monitoring than girls. Researchers should use the findings of this study to design data collection that ensures reliable data.

Introducing novel approaches for examining the variability of individuals' physical activity

Tudor-Locke and colleagues previously assessed steps/day for 1 year. The aim of this study was to use this data set to introduce a novel approach for the investigation of whether individual's physical activity exhibits periodicity fluctuating round a mean and, if so, the degree of fluctuation and whether the mean changes over time. Twenty-three participants wore a pedometer for 365 days, recorded steps/day and whether the day was a workday. Fourier transform of each participant's daily steps data showed the physical activity had a periodicity of 7 days in half of the participants, matching the periodicity of the workday pattern. Activity level remained stable in half of the participants, decreased in ten participants and increased in two. In conclusion, the 7-day periodicity of activity in half of the participants and correspondence with the workday pattern suggest a social or environmental influence. The novel analytical approach introduced herein allows the determination of the periodicity of activity, the degree of variability in activity that is tolerated during day-to-day life and whether the activity level is stable. Results from the use of these methodologies in larger data sets may enable a more focused approach to the design of interventions that aim to increase activity.

Separating bedtime rest from activity using waist or wrist-worn accelerometers in youth

Recent interest in sedentary behavior and technological advances expanded use of watch-size accelerometers for continuous monitoring of physical activity (PA) over extended periods (e.g., 24 h/day for 1 week) in studies conducted in natural living environment. This approach necessitates the development of new methods separating bedtime rest and activity periods from the accelerometer recordings. The goal of this study was to develop a decision tree with acceptable accuracy for separating bedtime rest from activity in youth using accelerometer placed on waist or wrist. Minute-by-minute accelerometry data were collected from 81 youth (10-18 years old, 47 females) during a monitored 24-h stay in a whole-room indirect calorimeter equipped with a force platform covering the floor to detect movement. Receiver Operating Characteristic (ROC) curve analysis was used to determine the accelerometer cut points for rest and activity. To examine the classification differences, the accelerometer bedtime rest and activity classified by the algorithm in the development group (n = 41) were compared with actual bedtime rest and activity classification obtained from the room calorimeter-measured metabolic rate and movement data. The selected optimal bedtime rest cut points were 20 and 250 counts/min for the waist- and the wrist-worn accelerometer, respectively. The selected optimal activity cut points were 500 and 3,000 counts/min for waist and wrist-worn accelerometers, respectively. Bedtime rest and activity were correctly classified by the algorithm in the validation group (n = 40) by both waist- (sensitivity: 0.983, specificity: 0.946, area under ROC curve: 0. 872) and wrist-worn (0.999, 0.980 and 0.943) accelerometers. The decision tree classified bedtime rest correctly with higher accuracy than commonly used automated algorithm for both waist- and wrist-warn accelerometer (all p<0.001). We concluded that cut points developed and validated for waist- and wrist-worn uniaxial accelerometer have a good power for accurate separation of time spent in bedtime rest from activity in youth.

Steps/day and metabolic syndrome in African American adults: the Jackson Heart Study

OBJECTIVE

To examine the relationship between pedometer-measured step count data and the Metabolic Syndrome (MetS) in African American adults.

METHOD

379 African American adults (mean age 60.1 years; 60% female) enrolled in the Jackson Heart Study (Jackson, MS) from 2000 to 2004 provided sufficient pedometer data for inclusion in this analysis. MetS was classified according to the International Diabetes Federation Task Force on Epidemiology and Prevention.

RESULTS

Using steps/day categorized as tertiles (<3717 (referent), 3717-6238, >6238), participants taking 3717-6238 (Odds Ratio (OR)(95% Confidence Interval (CI))=0.34 (0.19, 0.61)) and >6238 steps/day (OR(95% CI)=0.43 (0.23, 0.78)) had lower odds of having MetS compared to participants in the lowest tertile. Using previously suggested steps/day cut-points (<2500 (referent), 2500-4999, 5000-7499, ≥7500), the odds of having MetS were lower for participants taking 2500-4999 (OR(95% CI)=0.32 (0.14, 0.72)), 5000-7499 (OR(95% CI)=0.22 (0.09, 0.53)), and >7500 (OR(95% CI)=0.26 (0.11, 0.65)) steps/day compared to those taking <2500 steps/day.

CONCLUSION

Compared to lower levels, higher levels of steps/day are associated with a lower prevalence of MetS in this older African American population.

Fully automated waist-worn accelerometer algorithm for detecting children's sleep-period time separate from 24-h physical activity or sedentary behaviors

Analysis of 24-h waist-worn accelerometer data for physical activity and sedentary behavior requires that sleep-period time (from sleep onset to the end of sleep, including all sleep epochs and wakefulness after onset) is first identified. To identify sleep-period time in children in this study, we evaluated the validity of a published automated algorithm that requires nonaccelerometer bed- and wake-time inputs, relative to a criterion expert visual analysis of minute-by-minute waist-worn accelerometer data, and validated a refined fully automated algorithm. Thirty grade 4 schoolchildren (50% girls) provided 24-h waist-worn accelerometry data. Expert visual inspection (criterion), a published algorithm (Algorithm 1), and 2 additional automated refinements (Algorithm 2, which draws on the instrument's inclinometer function, and Algorithm 3, which focuses on bedtime and wake time points) were applied to a standardized 24-h time block. Paired t tests were used to evaluate differences in mean sleep time (expert criterion minus algorithm estimate). Compared with the criterion, Algorithm 1 and Algorithm 2 significantly overestimated sleep time by 43 min and 90 min, respectively. Algorithm 3 produced the smallest mean difference (2 min), and was not significantly different from the criterion. Relative to expert visual inspection, our automated Algorithm 3 produced an estimate that was precise and within expected values for similarly aged children. This fully automated algorithm for 24-h waist-worn accelerometer data will facilitate the separation of sleep time from sedentary behavior and physical activity of all intensities during the remainder of the day.

Accuracy of uploadable pedometers in laboratory, overground, and free-living conditions in young and older adults

Purpose

The purpose of this study was to examine the accuracy of uploadable pedometers to accurately count steps during treadmill (TM) and overground (OG) walking, and during a 24 hour monitoring period (24 hr) under free living conditions in young and older adults.

Methods

One hundred and two participants (n=53 aged 20–49 yrs; n=49 aged 50–80 yrs) completed a TM protocol (53.6, 67.0, 80.4, 93.8, and 107.2 m/min, five minutes for each speed) and an OG walking protocol (self-determined “< normal”, “normal”, and “> normal” walking speeds) while wearing two waist-mounted uploadable pedometers (Omron HJ-720ITC [OM] and Kenz Lifecorder EX [LC]). Actual steps were manually tallied by a researcher. During the 24 hr period, participants wore a New Lifestyles-1000 (NL) pedometer (standard of care) attached to a belt at waist level over the midline of the left thigh, in addition to the LC on the belt over the midline of the right thigh. The following day, the same procedure was conducted, replacing the LC with the OM. One-sample t-tests were performed to compare measured and manually tallied steps during the TM and OG protocols, and between steps quantified by the NL with that of the OM and LC during the 24 hr period. Mean error step scores (MES, criterion – device) and 95% Limits of Agreement (LoA) were calculated.

Results

There were no significant differences between the OM and tallied steps for any of the TM speeds for either the young or older adult groups. The LC significantly underestimated steps for the young adult group during the 53.6 m/min TM speed (MES 31.4 [14.5, 48.3]) and during the OG < normal walking speed (MES 12.0 [0.9, 23.1] (p<0.01 for both age groups). The LC also significantly underestimated steps for the older adult group during the TM speeds of 53.6 m/min (MES 64.5 [45.6, 83.4]), 67.0 m/min (MES 15.1 [6.1, 24.0]), and 80.4 m/min (MES 3.2 [0.6, 5.9]) (p<0.01 for all speeds), in addition to the OG < normal walking speed (MES 14.7 [−13.3, 42.6] (p<0.01). The OM reported significantly lower steps during the 24 hr period for the young adult group by 949.1 steps (t=6.111, p<0.025) and for the older adult group by 612.9 steps (t=2.397, p<0.025).

Conclusion

Both the OM and LC pedometers were more accurate as TM and OG walking speed increased. The OM significantly underestimated steps during the 24 hr compared with a standard of care evaluation. Overall, both uploadable pedometers appear acceptable to use in young or old age groups to measure walking behavior.

Impact of accelerometer wear time on physical activity data: a NHANES semisimulation data approach

BACKGROUND

Current research practice employs wide-ranging accelerometer wear time criteria to identify a valid day of physical activity (PA) measurement.

OBJECTIVE

To evaluate the effects of varying amounts of daily accelerometer wear time on PA data.

METHODS

A total of 1000 days of accelerometer data from 1000 participants (age=38.7 ± 14.3 years; body mass index=28.2 ± 6.7 kg/m(2)) were selected from the 2005-2006 National Health and Nutrition Examination Study data set. A reference data set was created using 200 random days with 14 h/day of wear time. Four additional samples of 200 days were randomly selected with a wear time of 10, 11, 12 and 13 h/day(1). These data sets were used in day-to-day comparison to create four semisimulation data sets (10, 11, 12, 13 h/day) from the reference data set. Differences in step count and time spent in inactivity (<100 cts/min), light (100-1951 cts/min), moderate (1952-5724 cts/min) and vigorous (≥5725 cts/min) intensity PA were assessed using repeated-measures analysis of variance and absolute percent error (APE).

RESULTS

There were significant differences for moderate intensity PA between the reference data set and semisimulation data sets of 10 and 11 h/day. Differences were observed in 10-13 h/day(1) for inactivity and light intensity PA, and 10-12 h/day for steps (all p values <0.05). APE increased with shorter wear time (13 h/day=3.9-14.1%; 12 h/day=9.9-15.2%, 11 h/day=17.1-35.5%; 10 h/day=24.6-40.3%).

DISCUSSION

These data suggest that using accelerometer wear time criteria of 12 h/day or less may underestimate step count and time spent in various PA levels.

Reliably measuring ambulatory activity levels of children and adolescents with cerebral palsy

OBJECTIVE

To identify sources of variance in step counts and to examine the minimum number of days required to obtain a stable measure of habitual ambulatory activity in the cerebral palsy (CP) population.

DESIGN

Cross-sectional.

SETTING

Free-living environments.

PARTICIPANTS

Children and adolescents with CP (N=209; mean age ± SD, 8y, 4mo ± 3y, 4mo; n=118 boys; Gross Motor Function Classification System [GMFCS] levels I-III) were recruited through 3 regional pediatric specialty care hospitals.

INTERVENTIONS

Daily walking activity was measured with a 2-dimensional accelerometer over 7 consecutive days. An individual information-centered approach was applied to days with <100 steps, and participants with ≥3 days of missing values were excluded from the study. Participants were categorized into 6 groups according to age and functional level. Generalizability theory was used to analyze the data.

MAIN OUTCOME MEASURES

Mean step counts, relative magnitude of variance components in total step activity, and generalizability coefficients (G coefficients) of various combinations of days of the week.

RESULTS

Variance in step counts attributable to participants ranged from 33.6% to 65.4%. For youth ages 2 to 5 years, a minimum of 8, 6, and 2 days were required to reach acceptable G coefficient (reliability) of ≥.80 for GMFCS levels I, II, and III, respectively. For those ages 6 to 14 years, a minimum of 6, 5, and 4 days were required to reach stable measures of step activity for GMFCS levels I, II, and III, respectively.

CONCLUSIONS

The findings of the study suggest that an activity-monitoring period should be determined based on the GMFCS levels to reliably measure ambulatory activity levels in youth with CP.

Convergent validity of the international physical activity questionnaire (IPAQ): meta-analysis

OBJECTIVE

The purpose of the present study was to use a meta-analytic approach to examine the convergent validity of the international physical activity questionnaire (IPAQ).

DESIGN

Systematic review by meta-analysis.

SETTING

The relevant studies were surveyed from five electronic databases. Primary outcomes of interest were the product-moment correlation coefficients between IPAQ and other instruments. Five separate meta-analyses were performed for each physical activity (PA) category of IPAQ: walking, moderate PA (MPA), total moderate PA (TMPA), vigorous PA (VPA) and total PA (TPA). The corrected mean effect size (ESρ) unaffected by statistical artefacts (i.e., sampling error and reliability) was calculated for each PA category. Selected moderator variables were length of IPAQ (i.e., short and long form), reference period (i.e., last 7 d and usual week), mode of administration (i.e., interviewer and self-reported), language (i.e., English and translated) and instruments (i.e., accelerometer, pedometer and subjective measure).

SUBJECTS

A total of 152 ESρ across five PA categories were retrieved from twenty-one studies.

RESULTS

The results showed small- to medium-sized ESρ (0.27-0.49). The highest value was observed in VPA while the lowest value was found in MPA. The ESρ were differentiated by some of the moderator variables across PA categories.

CONCLUSIONS

The study shows the overall convergent validity of IPAQ within each PA category. Some differences in degree of convergent validity across PA categories and moderator variables imply that different research conditions should be taken into account prior to deciding on use of the appropriate type of IPAQ.

[Objective measurement tools for the assessment of physical activity]

The aim of the present study was to provide an overview about the various measurement options for the quantitative assessment of physical activity in daily life. After briefly discussing the importance of physical activity in this era of civilization-related health problems characterized by increasing malnutrition problems in combination with increasing lack of movement in daily life, the different types of measurement systems available and their applicability are described. It is hoped that this information will assist the potential user or buyer of a new measurement system to make a well-informed decision about the appropriate tool for a specific research interest.

Pedometer determined physical activity tracks in African American adults: the Jackson Heart Study

Background

This study investigated the number of pedometer assessment occasions required to establish habitual physical activity in African American adults.

Methods

African American adults (mean age 59.9 ± 0.60 years; 59 % female) enrolled in the Diet and Physical Activity Substudy of the Jackson Heart Study wore Yamax pedometers during 3-day monitoring periods, assessed on two to three distinct occasions, each separated by approximately one month. The stability of pedometer measured PA was described as differences in mean steps/day across time, as intraclass correlation coefficients (ICC) by sex, age, and body mass index (BMI) category, and as percent of participants changing steps/day quartiles across time.

Results

Valid data were obtained for 270 participants on either two or three different assessment occasions. Mean steps/day were not significantly different across assessment occasions (p values > 0.456). The overall ICCs for steps/day assessed on either two or three occasions were 0.57 and 0.76, respectively. In addition, 85 % (two assessment occasions) and 76 % (three assessment occasions) of all participants remained in the same steps/day quartile or changed one quartile over time.

Conclusion

The current study shows that an overall mean steps/day estimate based on a 3-day monitoring period did not differ significantly over 4 – 6 months. The findings were robust to differences in sex, age, and BMI categories. A single 3-day monitoring period is sufficient to capture habitual physical activity in African American adults.