Assessing free-living physical activity using accelerometry : practical issues for researchers and practitioners

Physical activity is an integral component of a healthy lifestyle, with relationships documented between physical activity, chronic diseases, and disease risk factors. There is increasing concern that many people are not sufficiently active to benefit their health. Consequently, there is a need to determine the prevalence of physical activity engagement, identify active and inactive segments of the population, and evaluate the effectiveness of interventions. The aim of the present study was to identify and explain a number of methodological and decision-making processes associated with accelerometry, which is the most commonly used objective measure of physical activity in child and adult research.Specifically, this review addresses:(a) pre-data collection decisions,(b) data collection procedures,(c) processing of accelerometer data, and(d) outcome variables in relation to the research questions posed.An appraisal of the literature is provided to help researchers and practitioners begin field-based research, with recommendations offered for best practice. In addition, issues that require further investigation are identified and discussed to inform researchers and practitioners of the surrounding debates.Overall, the review is intended as a starting point for field-based physical activity research using accelerometers and as an introduction to key issues that should be considered and are likely to be encountered at this time.<br /

Effect of a school-based active play intervention on sedentary time and physical activity in preschool children

Early childhood is a critical time for promoting physical activity. Few studies have investigated the effect of interventions in this population. The aim of this study was to investigate the effect of a school-based active play intervention on preschool children&rsquo;s sedentary time and physical activity. Preschool children were recruited from randomly selected preschools. Schools were randomly assigned to an intervention or comparison group. One teacher per intervention school received training from active play professionals in the delivery of a 6-week active play programme. Comparison schools continued their usual practice. Children wore a uni-axial accelerometer for 7 days at baseline, immediately after and at 6-month post-intervention. No significant intervention effects were observed for sedentary time or physical activity. However, sex and hours spent at school were significant predictors of physical activity. Children who spent fewer hours (half-day children) at school were significantly more active than their full-day counterparts. Physical activity during the intervention classes was high even though neither daily physical activity nor sedentary time changed. Notably children who spent more time at preschool were less active suggesting that preschool was not as conducive to physical activity engagement as other environments

Reproducibility of Heart Rate Variability Indices in Children with Cystic Fibrosis

Fundamental to the potential utilisation of heart rate variability (HRV) indices as a prognostic tool is the reproducibility of these measures. The purpose of the present study was therefore to investigate the reproducibility of 24-hour derived HRV indices in a clinical paediatric population. Eighteen children (10 boys; 12.4 ± 2.8 years) with mild to moderate Cystic Fibrosis (CF; FVC: 83 ± 12% predicted; FEV1: 80 ± 9% predicted) and eighteen age- and sex-matched controls (10 boys; 12.5 ± 2.7 years) wore a combined ECG and accelerometer for two consecutive days. Standard time and frequency domain indices of HRV were subsequently derived. Reproducibility was assessed by Bland-Altman plots, 95% limits of agreement and intra-class correlation coefficients (ICC). In both groups, there was no systematic difference between days, with the variables demonstrating a symmetrical, homoscedastic distribution around the zero line. The time domain parameters demonstrated a good to excellent reproducibility irrespective of the population considered (ICC: 0.56 to 0.86). In contrast, whilst the frequency domain parameters similarly showed excellent reproducibility in the healthy children (ICC: 0.70 to 0.96), the majority of the frequency domain parameters illustrated a poor to moderate reproducibility in those with CF (ICC: 0.22 to 0.43). The exceptions to this trend were the normalised LF and HF components which were associated with a good to excellent reproducibility. These findings thereby support the utilisation of time and relative frequency domain HRV indices as a prognostic tool in children with CF. Furthermore, the present results highlight the excellent reproducibility of HRV in healthy children, indicating that this may be a useful tool to assess intervention effectiveness in this population

Compensation or displacement of physical activity in middle-school girls: the Trial of Activity for Adolescent Girls

The “activitystat” hypothesis suggests that increases in moderate-to-vigorous physical activity (MVPA) are accompanied by a compensatory reduction in light physical activity (LPA) and/or an increase in inactivity in order to maintain a consistent total physical activity level (TPA).ObjectiveThe purpose of this study was to identify evidence of compensation in middle school girls.SubjectsParticipants were 6,916, 8th grade girls from the Trial of Activity for Adolescent Girls (TAAG).DesignInactivity and physical activity were measured over 6- consecutive days using accelerometry (MTI Actigraph). A within-girl, repeated measures design was used to assess associations between physical activity and inactivity using general linear mixed models.ResultsWithin a given day, for every one MET-minute more of inactivity, there was 3.18 MET-minutes (95% confidence interval: −3.19, −3.17) less of TPA (activity > 2 METS) on the same day. Daily inactivity was also negatively associated with TPA on the following day. Each additional minute of MVPA was associated with 1.85 minutes less of inactivity on the same day (95% confidence interval: −1.89, −1.82). Daily MVPA was also negatively associated with inactivity the following day.ConclusionOur results, based on 6-days of observational data, were not consistent with the “activitystat” hypothesis, and instead indicated that physical activity displaced inactivity, at least in the short term. Longer intervention trials are needed, nevertheless our findings support the use of interventions to increase physical activity over discrete periods of time in middle school girls

Covert Neurological Symptoms Associated With Silent Infarcts From Midlife to Older Age: The Atherosclerosis Risk in Communities Study

Unrecognized or unreported stroke-like symptoms, called covert symptoms, occur in persons free of clinical stroke. Whether covert symptoms are associated with subclinical brain infarcts (SBI) is unknown. This study examined the association between covert stroke-like symptoms and SBI/stroke in persons with no history of stroke or TIA

Risk of dementia hospitalisation associated with cardiovascular risk factors in midlife and older age: the Atherosclerosis Risk in Communities (ARIC) study

Cardiovascular risk factors are associated with a higher risk of developing dementia. Studies in older populations, however, have often failed to show this relationship. We assessed the association between cardiovascular risk factors measured in midlife and risk of being hospitalized with dementia and determined whether this association was modified by age and ethnicity

Tracking of Physical Activity and Inactivity in Middle School Girls

The purpose of this study was to describe and compare the levels of tracking of physical activity and inactivity as assessed by self-report and accelerometry in middle school girls over a 2-year period

Public Parks and Physical Activity Among Adolescent Girls

Proximity to routine destinations is an important correlate of physical activity. We examined the association between distance from school and physical activity in adolescent girls

Associations between Patterns of Objectively Measured Physical Activity and Risk Factors for the Metabolic Syndrome

Determine whether certain patterns of objectively measured physical activity (PA) are associated with the risk factors for or the diagnosis of the metabolic syndrome (MS)

Blood Pressure and White-Matter Disease Progression in a Biethnic Cohort: Atherosclerosis Risk in Communities (ARIC) Study

Blood pressure (BP) is a predictor of concurrent and subsequently measured white matter hyperintensity (WMH), but longitudinal studies of WMH change and data in black participants are lacking. We hypothesized that WMH progression would be 1) strongly related to BP in blacks and whites, and 2) predicted more strongly by earlier (midlife) or cumulative BP measurements than by measures at older ages