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Effects of Frequency Filtering on Intensity and Noise in Accelerometer-Based Physical Activity Measurements.

ABSTRACT: In objective physical activity (PA) measurements, applying wider frequency filters than the most commonly used ActiGraph (AG) filter may be beneficial when processing accelerometry data. However, the vulnerability of wider filters to noise has not been investigated previously. This study explored the effect of wider frequency filters on measurements of PA, sedentary behavior (SED), and capturing of noise. Apart from the standard AG band-pass filter (0.29-1.63 Hz), modified filters with low-pass component cutoffs at 4 Hz, 10 Hz, or removed were analyzed. Calibrations against energy expenditure were performed with lab data from children and adults to generate filter-specific intensity cut-points. Free-living accelerometer data from children and adults were processed using the different filters and intensity cut-points. There was a contribution of acceleration related to PA at frequencies up to 10 Hz. The contribution was more pronounced at moderate and vigorous PA levels, although additional acceleration also occurred at SED. The classification discrepancy between AG and the wider filters was small at SED (1-2%) but very large at the highest intensities (>90%). The present study suggests an optimal low-pass frequency filter with a cutoff at 10 Hz to include all acceleration relevant to PA with minimal effect of noise.

SUBMITTER: Fridolfsson J

PROVIDER: S-EPMC6539652 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Effects of Frequency Filtering on Intensity and Noise in Accelerometer-Based Physical Activity Measurements.

Fridolfsson Jonatan J Börjesson Mats M Buck Christoph C Ekblom Örjan Ö Ekblom-Bak Elin E Hunsberger Monica M Lissner Lauren L Arvidsson Daniel D

Sensors (Basel, Switzerland) 20190511 9

In objective physical activity (PA) measurements, applying wider frequency filters than the most commonly used ActiGraph (AG) filter may be beneficial when processing accelerometry data. However, the vulnerability of wider filters to noise has not been investigated previously. This study explored the effect of wider frequency filters on measurements of PA, sedentary behavior (SED), and capturing of noise. Apart from the standard AG band-pass filter (0.29-1.63 Hz), modified filters with low-pass ...[more]

PMID: 31083538

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Project description:ImportanceDementia risk may be attenuated by physical activity (PA); however, the specific activity levels optimal for dementia prevention are unclear. Moreover, most older adults are unable to meet the nationally recommended PA guidelines, set at 150 minutes of moderate to vigorous PA per week.ObjectiveTo assess the association of total steps walked per day and total dose (intensity?×?duration) of PA with brain volumes on magnetic resonance imaging (MRI) among Framingham Heart Study participants.Design, setting, and participantsThis cross-sectional, community-based cohort study of the association of accelerometry-determined PA with brain MRI measures in Framingham, Massachusetts, included the Framingham Heart Study third-generation (examination 2, 2008-2011) and offspring (examination 9, 2011-2014) cohorts. Of 4021 participants who agreed to wear an accelerometer and had valid data (?10 hours/day for ?3 days), 1667 participants who did not undergo brain MRI (n?=?1604) or had prevalent dementia or stroke (n?=?63) were excluded. Data analysis began in 2016 and was completed in February 2019.ExposuresPhysical activity achieved using accelerometry-derived total activity (steps per day) and 2 intensity levels (light intensity and moderate to vigorous intensity).Main outcomes and measuresDifferences in total brain volume and other MRI markers of brain aging.ResultsThe study sample of 2354 participants had a mean (SD) age of 53 (13) years, 1276 (54.2%) were women, and 1099 (46.7%) met the PA guidelines. Incremental light-intensity PA was associated with higher total brain volume; each additional hour of light-intensity PA was associated with approximately 1.1 years less brain aging (? estimate, 0.22; SD, 0.07; P?=?.003). Among individuals not meeting the PA guidelines, each hour of light-intensity PA (? estimate, 0.28; SD, 0.11; P?=?.01) and achieving 7500 steps or more per day (? estimate, 0.44; SD, 0.18; P?=?.02) were associated with higher total brain volume, equivalent to approximately 1.4 to 2.2 years less brain aging. After adjusting for light-intensity PA, neither increasing moderate to vigorous PA levels nor meeting the threshold moderate to vigorous PA level recommended by the PA guidelines were significantly associated with total brain volume.Conclusions and relevanceEvery additional hour of light-intensity PA was associated with higher brain volumes, even among individuals not meeting current PA guidelines. These data are consistent with the notion that the potential benefits of PA on brain aging may accrue at a lower, more achievable level of intensity or duration.

Project description:BackgroundOverweight and low levels of physical activity (PA) in preschoolers are major public health concerns. However, to date only few studies have investigated subjective and objective correlates of PA across different socioecological domains in preschoolers. We therefore simultaneously investigate associations between preschoolers' objectively measured leisure-time PA and a comprehensive set of subjective and objective potential PA correlates across the behavioral, social and physical environmental domains on both family- and community-level.MethodsIn this cross-sectional study time spent in moderate-to-vigorous PA (MVPA) and total PA (TPA) were measured by combined accelerometry and heart rate monitoring in 735 3-6 year-old children from 52 preschools in Southern Germany. Family- and community-level potential correlates of PA from different domains (behavioral, social and physical environmental) were subjectively (i.e. by parent proxy-report) and objectively assessed. Their associations with PA on weekend days and weekday afternoons were tested by covariate-adjusted multilevel regression models.ResultsWhile none of the objective social and physical environmental factors showed associations with PA, subjective parental traffic safety perceptions were positively associated with MVPA and TPA on weekends. Also, preschoolers' participation in organized sports was positively correlated with MVPA (on weekends) and TPA (both on weekends and weekday afternoons).ConclusionSubjective traffic safety perceptions and participation in organized sports, an indicator and a result of parental support towards PA - i.e. subjective parental perceptions of environmental factors and family-level correlates which are more proximal to preschoolers - might be more central to PA in preschool age than objectively assessed community-level environmental features which tend to be more distal correlates. If replicable, targeting parental perceptions of environmental factors and parental support for PA in preschool age might be powerful leverages for public health policy.

Project description:BackgroundTo investigate the influence of shoulder immobilization on daily physical activity.IntroductionThe harmful effect of sedentary behavior does not receive much attention in orthopedic surgery even though immobilization, especially of the lower extremity, has been associated with reduced physical activity. Immobilization of the shoulder is common after reconstructive shoulder surgery and could also potentially lead to reduced physical activity and have a negative effect on a patient's general health.MethodTwenty-one healthy volunteers were immobilized in an orthosis (DJO Ultrasling III) for 10 h on two consecutive days. In the following week, activity was measured on the same days without the orthosis. Activity including gait cycles per minute and total gait cycles per day was measured by accelerometer based step count StepWatchTMActivity Monitor. Average age was 26 +/- 3 years. A questionnaire was administered to evaluate subjective activity.ResultsParticipants wearing the shoulder orthosis were significantly less active than without immobilization by 2227.5 gait cycles/day (5501.2 with SO, 7728.7 without SO). Also, significantly more time in sedentary behavior occurred (< 400 steps/h) when the shoulder was immobilized. Patients were significantly more active without shoulder orthosis in medium level activities (800-999 steps/h). Differences for low (400-799 steps/h) and high activity levels (> 1000 steps/h) were not statistically significant. Subjective limitations while wearing the orthosis were graded at 2.343 on a scale of 0-4.ConclusionResults of this study show that even in young, healthy volunteers immobilization of the shoulder in an orthosis for 2 days leads to significantly reduced activity levels. A negative influence on general health, especially in older patients who are immobilized for up to 6 weeks, can potentially occur. Promoting physical activity during the immobilization period should be part of rehabilitation after injuries/surgery of the shoulder.Trial registrationRetrospectively registered in DRKS (DRKS00017636).

Dataset Information

Effects of Frequency Filtering on Intensity and Noise in Accelerometer-Based Physical Activity Measurements.

Publications

Effects of Frequency Filtering on Intensity and Noise in Accelerometer-Based Physical Activity Measurements.

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