Monitoring of Physical Activity in Young Children: How Much Is Enough?

Changes in physical activity over time in young children: a longitudinal study using accelerometers

Previous research has suggested that marked declines in physical activity occur during the preschool years, and across the transition into school. However, longitudinal studies using objective measures of activity have been limited by sample size and length of follow-up. The aims of this study were to determine how overall activity and time in different intensities of activity change in children followed from 3 to 7 years. Children (n = 242) wore Actical accelerometers at 3, 4, 5, 5.5, 6.5 and 7 years of age during all waking and sleeping hours for a minimum of 5 days. Time in sedentary (S), light (L), moderate (M), and vigorous (V) physical activity was determined using available cut points. Data were analyzed using a mixed model and expressed as counts per minute (cpm, overall activity) and the ratio of active time to sedentary time (LMV:S), adjusted for multiple confounders including sex, age, time worn, and weather. At 5 years, physical activity had declined substantially to around half that observed at 3 years. Although starting school was associated with a further short-term (6-month) decline in activity (cpm) in both boys (difference; 95% CI: -98; -149, -46) and girls (-124; -174, -74, both P<0.001), this proved to be relatively transient; activity levels were similar at 6-7 years as they were just prior to starting school. Boys were more physically active than girls as indicated by an overall 12% (95% CI: 2, 22%) higher ratio of active to sedentary time (P = 0.014), but the pattern of this difference did not change from 3 to 7 years. Time worn and weather variables were significant predictors of activity. In conclusion, both boys and girls show a marked decline in activity from 3 to 4 years of age, a decrease that is essentially maintained through to 7 years of age. Factors driving this marked decrease need to be determined to enable the development of targeted interventions.

A novel approach to characterize physical activity patterns in preschool-aged children

OBJECTIVE

Routine moderate-to-vigorous physical activity (MVPA) is associated with better health outcomes; the purpose of this work was to evaluate healthy preschooler physical activity patterns with objective measurement.

METHODS AND PROCEDURES

An objective prospective study of 50 normally developing children 3-5 years old who were ≥50th and <95th BMI percentile and enrolled in a family-based healthy lifestyle study in 2011-2012. Participants wore a tri-axial accelerometer for 7 continuous days. Outcome measures consisted of wear time examining four common MVPA patterns: isolated spurt (IS), isolated sustained activity (ISA), clustered spurt (CS), and clustered sustained activity (CSA).

RESULTS

Participants were 4.3 years, 56% female, 52% African-American, and 26% overweight. Forty-five children met wear time criteria. On average, children spent 14.5% of wake-wear time in MVPA, requiring 11.3 h to complete 90% of their daily MVPA. Children spent the majority of MVPA in CS (62.1%, followed by CSA (20.1%). Remaining MVPA was spent in IS (15.5%) and ISA (2.3%).

CONCLUSION

It takes most of the waking day for preschoolers to attain their PA. They engage in short spurts of small duration, in four common MVPA patterns. Utilizing this method could better characterize preschooler physical activity needs in practice and policy guidelines.

Objectively-measured physical activity and body weight in Japanese pre-schoolers

BACKGROUND

The prevalence of thinness has increased among Japanese children.

AIM

The purpose of this study was to examine the association between physical activity and body mass index (BMI) among Japanese pre-school children.

SUBJECTS AND METHODS

Subjects were 425 4-6-year-old Japanese girls and boys. Their weights were classified as normal, overweight or thin, based on Cole's international cut-offs for BMI. Physical activity was assessed using a triaxial accelerometer (ActivTracer, GMS) for 6 consecutive days.

RESULTS

Physical activity in overweight children was comparable to that in normal-weight children after controlling for age and gender. However, thin children spent significantly greater time engaged in low-intensity activities (physical activity ratio < 2) and spent less time engaged in light-intensity physical activity (2 ≤ physical activity ratio < 3) and moderate-to-vigorous physical activity (physical activity ratio  ≥ 3) than normal-weight and overweight children, and less time engaged in higher-intensity physical activity (physical activity ratio ≥ 4) than normal-weight children. Moreover, thin children spent significantly less time engaged in locomotive physical activity than normal-weight or overweight children.

CONCLUSION

This study suggests that thinness, rather than excess weight, is associated with decreased light, moderate and high intensity physical activity in Japanese pre-school children.

Quality control methods in accelerometer data processing: defining minimum wear time

BACKGROUND

When using accelerometers to measure physical activity, researchers need to determine whether subjects have worn their device for a sufficient period to be included in analyses. We propose a minimum wear criterion using population-based accelerometer data, and explore the influence of gender and the purposeful inclusion of children with weekend data on reliability.

METHODS

Accelerometer data obtained during the age seven sweep of the UK Millennium Cohort Study were analysed. Children were asked to wear an ActiGraph GT1M accelerometer for seven days. Reliability coefficients(r) of mean daily counts/minute were calculated using the Spearman-Brown formula based on the intraclass correlation coefficient. An r of 1.0 indicates that all the variation is between- rather than within-children and that measurement is 100% reliable. An r of 0.8 is often regarded as acceptable reliability. Analyses were repeated on data from children who met different minimum daily wear times (one to 10 hours) and wear days (one to seven days). Analyses were conducted for all children, separately for boys and girls, and separately for children with and without weekend data.

RESULTS

At least one hour of wear time data was obtained from 7,704 singletons. Reliability increased as the minimum number of days and the daily wear time increased. A high reliability (r = 0.86) and sample size (n = 6,528) was achieved when children with ≥ two days lasting ≥10 hours/day were included in analyses. Reliability coefficients were similar for both genders. Purposeful sampling of children with weekend data resulted in comparable reliabilities to those calculated independent of weekend wear.

CONCLUSION

Quality control procedures should be undertaken before analysing accelerometer data in large-scale studies. Using data from children with ≥ two days lasting ≥10 hours/day should provide reliable estimates of physical activity. It's unnecessary to include only children with accelerometer data collected during weekends in analyses.

Physical activity intensity, sedentary time, and body composition in preschoolers

BACKGROUND

Detailed associations between physical activity (PA) subcomponents, sedentary time, and body composition in preschoolers remain unclear.

OBJECTIVE

We examined the magnitude of associations between objectively measured PA subcomponents and sedentary time with body composition in 4-y-old children.

DESIGN

We conducted a cross-sectional study in 398 preschool children recruited from the Southampton Women's Survey. PA was measured by using accelerometry, and body composition was measured by using dual-energy X-ray absorptiometry. Associations between light physical activity, moderate physical activity (MPA), vigorous physical activity (VPA), and moderate-to-vigorous physical activity (MVPA) intensity; sedentary time; and body composition were analyzed by using repeated-measures linear regression with adjustment for age, sex, birth weight, maternal education, maternal BMI, smoking during pregnancy, and sleep duration. Sedentary time and PA were also mutually adjusted for one another to determine whether they were independently related to adiposity.

RESULTS

VPA was the only intensity of PA to exhibit strong inverse associations with both total adiposity [P < 0.001 for percentage of body fat and fat mass index (FMI)] and abdominal adiposity (P = 0.002 for trunk FMI). MVPA was inversely associated with total adiposity (P = 0.018 for percentage of body fat; P = 0.022 for FMI) but only because of the contribution of VPA, because MPA was unrelated to fatness (P ≥ 0.077). No associations were shown between the time spent sedentary and body composition (P ≥ 0.11).

CONCLUSIONS

In preschoolers, the time spent in VPA is strongly and independently associated with lower adiposity. In contrast, the time spent sedentary and in low-to-moderate-intensity PA was unrelated to adiposity. These results indicate that efforts to challenge pediatric obesity may benefit from prioritizing VPA.

The impact of ethnicity on objectively measured physical activity in children

Obesity and obesity-related diseases (cardiovascular disease/metabolic risk factors) are experienced differently in individuals from different ethnic backgrounds, which originate in childhood. Physical activity is a modifiable risk factor for obesity and related diseases. Both physical activity and metabolic risk factors track to adulthood, and thus understanding the physical activity patterns in children from different ethnic backgrounds is important. Given the limitations of self-report measures in children, this study provides a review of studies which have objectively measured physical activity patterns in children from different ethnic backgrounds. From a total of 16 studies, it can be concluded that physical activity does seem to vary amongst the ethnic groups especially South Asian and Black compared to White EU (European Union). The findings are less consistent for Hispanic/Mexican American children. However, there are several methodological limitations which need to be considered in future studies. Firstly, there is a need for consistency in the measurement of physical activity. Secondly, there are a range of complex factors such as socioeconomic status and body composition which affect both physical activity and ethnicity. Studies have failed to account for these differences limiting the ability to generalise that ethnicity is an independent risk factor for physical activity.

Objectively measured physical activity levels of children and adolescents in rural South Africa: high volume of physical activity at low intensity

There is limited evidence on objectively measured physical activity from Africa. This study quantified physical activity by accelerometry in rural South African children at ages 7, 11, and 15 years. Total physical activity was generally high (mean accelerometer counts per minute ranged 485-1017 across the 3 groups), but moderate- to vigorous-intensity physical activity was low: <1% of the sample met international recommendations. A low intensity, high volume of physical activity is present in rural South African children and adolescents.

Validity of hip-mounted uniaxial accelerometry with heart-rate monitoring vs. triaxial accelerometry in the assessment of free-living energy expenditure in young children: the IDEFICS Validation Study

One of the aims of Identification and Prevention of Dietary- and Lifestyle-Induced Health Effects in Children and Infants (IDEFICS) validation study is to validate field measures of physical activity (PA) and energy expenditure (EE) in young children. This study compared the validity of uniaxial accelerometry with heart-rate (HR) monitoring vs. triaxial accelerometry against doubly labeled water (DLW) criterion method for assessment of free-living EE in young children. Forty-nine European children (25 female, 24 male) aged 4-10 yr (mean age: 6.9 ± 1.5 yr) were assessed by uniaxial ActiTrainer with HR, uniaxial 3DNX, and triaxial 3DNX accelerometry. Total energy expenditure (TEE) was estimated using DLW over a 1-wk period. The longitudinal axis of both devices and triaxial 3DNX counts per minute (CPM) were significantly (P < 0.05) associated with physical activity level (PAL; r = 0.51 ActiTrainer, r = 0.49 uniaxial-3DNX, and r = 0.42 triaxial Σ3DNX). Eight-six percent of the variance in TEE could be predicted by a model combining body mass (partial r(2) = 71%; P < 0.05), CPM-ActiTrainer (partial r(2) = 11%; P < 0.05), and difference between HR at moderate and sedentary activities (ModHR - SedHR) (partial r(2) = 4%; P < 0.05). The SE of TEE estimate for ActiTrainer and 3DNX models ranged from 0.44 to 0.74 MJ/days or ∼7-11% of the average TEE. The SE of activity-induced energy expenditure (AEE) model estimates ranged from 0.38 to 0.57 MJ/day or 24-26% of the average AEE. It is concluded that the comparative validity of hip-mounted uniaxial and triaxial accelerometers for assessing PA and EE is similar.

The importance of Active Transportation to and from school for daily physical activity among children

OBJECTIVE

To investigate if students who use of Active Transportation (AT) to and from school among urban and rural Canadian children are more likely to meet physical activity recommendations.

METHODS

The Raising healthy Eating and Active Living in Alberta (REAL Kids Alberta) study is a population-based health survey among Grade 5 students. In 2009, physical activity levels were measured using time-stamped pedometers (number of steps/hour) among 688 children. Parents reported mode of transportation to and from school (AT/non-AT). Multilevel multiple linear regression analyses with corresponding β coefficients were conducted to quantify the relationship between mode of transportation to and from school with (1) overall step count, and (2) the likelihood of achieving at least 13,500 steps per day recommended for optimal growth and development.

RESULTS

Among urban children, those who used AT to and from school accumulated more steps [β=1124(95% CI=170,2077)] and although not significant, were more likely to achieve the recommended 13,500 steps/day compared to those not using AT to and from school [OR=1.61(95% CI=0.93,2.81)].

CONCLUSION

Using AT to and from school appears to be beneficial to children by supplementing their physical activity, particularly those living in urban regions. Strategies to promote physical activity are needed, particular for children residing in rural regions and smaller towns.

A systematic review of the clinimetric properties of habitual physical activity measures in young children with a motor disability

Aim. To identify and systematically review the clinimetric properties of habitual physical activity (HPA) measures in young children with a motor disability. Method. Five databases were searched for measures of HPA including: children aged <6.0 years with a neuromuscular disorder, physical activity defined as "bodily movement produced by skeletal muscles causing caloric expenditure", reported HPA as duration, frequency, intensity, mode or energy expenditure, and evaluated clinimetric properties. The quality of papers was assessed using the COSMIN-checklist. A targeted search of identified measures found additional studies of typically developing young children (TDC). Results. Seven papers assessing four activity monitors met inclusion criteria. Four studies were of good methodological quality. The Minimod had good ability to measure continuous walking but the demonstrated poor ability to measure steps during free-living activities. The Intelligent Device for Energy Expenditure and Activity and Ambulatory Monitoring Pod showed poor ability to measure activity during both continuous walking and free-living activities. The StepWatch showed good ability to measure steps during continuous walking in TDC. Interpretation. Studies assessing the clinimetric properties of measures of HPA in this population are urgently needed to allow assessment of the relationship between HPA and health outcomes in this group.

Early predictors of objectively measured physical activity and sedentary behaviour in 8-10 year old children: the Gateshead Millennium Study

BACKGROUND

With a number of studies suggesting associations between early life influences and later chronic disease risk, it is suggested that associations between early growth and later physical activity (PA) may be a mediator. However, conflicting evidence exists for association between birth weight and childhood PA. In addition, it is important to know what other, potentially modifiable, factors may influence PA in children given its' association with childhood and later adiposity. We used the Gateshead Millennium Study (GMS) to identify predictors of childhood PA levels.

METHODS

The GMS is a cohort of 1029 infants born in 1999-2000 in Gateshead in northern England. Throughout infancy and early childhood, detailed information was collected. Assessments at age 9 years included body composition, objective measures of habitual PA and a range of lifestyle factors. Mean total volumes of PA (accelerometer count per minute, cpm) and moderate-vigorous intensity PA (MVPA), and the percentage of time spent in sedentary behaviour (%SB) were quantified and related to potential predictors using linear regression and path analysis.

RESULTS

Children aged 8-10 years were included. Significant differences were seen in all three outcome variables between sexes and season of measurement (p<0.001). Restricting children's access to television was associated with decreased MVPA. Increased paternal age was associated with significant increases in %SB (p = 0.02), but not MVPA or total PA. Increased time spent in out of school sports clubs was significantly associated with decreased %SB (p = 0.02). No significant associations were seen with birth weight.

CONCLUSION

A range of factors, directly or indirectly, influenced PA and sedentary behaviour. However, associations differed between the different constructs of PA and %SB. Exploring further the sex differences in PA would appear to be useful, as would encouraging children to join out of school sports clubs.

Comparison of Actical and activPAL measures of sedentary behaviour in preschool children

OBJECTIVES

The purpose of this study was to examine the convergent validity of the Actical and activPAL to measure sedentary behaviour (SB) and non-SB in preschoolers in a free-living environment.

DESIGN

A convenience sample of 49 preschoolers (22 boys; 4.0 ± 0.5 years) from six early childhood centres in Auckland, New Zealand were included in data analysis.

METHODS

Participants wore a hip-mounted Actical and a thigh-mounted activPAL accelerometer simultaneously during centre attendance for one day and data were collected in 15s epochs. Bland-Altman tests were used to assess differences in group mean minutes and percentage of time in (non-)SB between both monitors. Agreement between binary coded (SB vs. non-SB) 15s-by-15s Actical and activPAL data was evaluated by calculating percentage agreement and κ statistic.

RESULTS

The monitors were worn on average for 294.8 ± 46.3 min resulting in a total of 57,780 15s epochs. Bland-Altman tests suggested a small group mean difference in (non-)SB (1.3 min; 0.1%) and a wide prediction interval (121.3 min; 39.2%). No obvious systematic bias was observed in the Bland-Altman plot. Percentage agreement between the 15s-by-15s Actical and activPAL data of all participants was 73.0% (inter-child range: 36.8-93.8%). The κ statistic showed moderate agreement with a value of 0.46 (95% CI: 0.45-0.47).

CONCLUSIONS

Although the group mean estimate of (non-)SB was similar between the Actical and activPAL, the output of both monitors cannot be considered convergent as meaningful random disagreement was found between both monitors.

Validity and reliability of physical activity questionnaire for Japanese students

BACKGROUND

Self-administered questionnaires about physical activity are useful for collecting data to develop public health policies. There is currently no validated physical activity questionnaire, however, for Japanese children and adolescents. The purpose of the present study was to evaluate the validity and reliability of self-administered, physical activity questionnaires for Japanese students.

METHODS

Fifth- and eighth-grade students were asked to complete two questionnaires that estimated the intensity and time of moderate-to-vigorous physical activities in which they participated, and the frequency and duration spent performing sports activities. Students also wore triaxial accelerometers to compare their actual activity levels to their estimates, to investigate the validity and reliability of the questionnaires.

RESULTS

The intensity and time spent performing moderate-to-vigorous physical activity that were estimated from the questionnaire were higher than those measured by accelerometry (9-161% of accelerometry). Questionnaire data were highly correlated with accelerometer data for eighth graders (Spearman correlation, 0.642-0.754), but the correlations were lower for fifth graders (≤ 0.331). Furthermore, there was higher repeatability in the data collected from eighth graders (intraclass correlation, 0.625-0.645) than from fifth graders (0.136-0.194).

CONCLUSIONS

Questionnaires may be useful in epidemiological studies for ranking physical activity levels of adolescents, such as a confounding factor for other lifestyle surveys, but these surveys are less accurate for younger children.

Effects of a physical education intervention on cognitive function in young children: randomized controlled pilot study

BACKGROUND

Randomized controlled trials (RCT) are required to test relationships between physical activity and cognition in children, but these must be informed by exploratory studies. This study aimed to inform future RCT by: conducting practical utility and reliability studies to identify appropriate cognitive outcome measures; piloting an RCT of a 10 week physical education (PE) intervention which involved 2 hours per week of aerobically intense PE compared to 2 hours of standard PE (control).

METHODS

64 healthy children (mean age 6.2 yrs SD 0.3; 33 boys) recruited from 6 primary schools. Outcome measures were the Cambridge Neuropsychological Test Battery (CANTAB), the Attention Network Test (ANT), the Cognitive Assessment System (CAS) and the short form of the Connor's Parent Rating Scale (CPRS:S). Physical activity was measured habitually and during PE sessions using the Actigraph accelerometer.

RESULTS

Test- retest intraclass correlations from CANTAB Spatial Span (r 0.51) and Spatial Working Memory Errors (0.59) and ANT Reaction Time (0.37) and ANT Accuracy (0.60) were significant, but low. Physical activity was significantly higher during intervention vs. control PE sessions (p < 0.0001). There were no significant differences between intervention and control group changes in CAS scores. Differences between intervention and control groups favoring the intervention were observed for CANTAB Spatial Span, CANTAB Spatial Working Memory Errors, and ANT Accuracy.

CONCLUSIONS

The present study has identified practical and age-appropriate cognitive and behavioral outcome measures for future RCT, and identified that schools are willing to increase PE time.

TRIAL REGISTRATION NUMBER

ISRCTN70853932 (http://www.controlled-trials.com).

Factors associated with bone turnover and speed of sound in early and late-pubertal females

This cross-sectional study examines whether maturity, body composition, physical activity, dietary intake, and hormonal concentrations are related to markers of bone turnover and tibial speed of sound (tSOS) in premenarcheal (n = 20, 10.1 ± 1.1 years) and postmenarcheal girls (n = 28, aged 15.0 ± 1.4 years). Somatic maturity was evaluated using years from age of peak height velocity (aPHV). Daily dietary intake was assessed with a 24-h recall interview, and moderate to very vigorous physical activity (MVPA) was measured using accelerometry. Plasma levels of 25-OH vitamin D, serum levels of insulin-like growth-factor 1 (IGF-1) and leptin, and serum levels of bone turnover markers including osteocalcin (OC), bone-specific alkaline phosphatase (BAP) and cross-linked N-teleopeptide of type I collagen (NTX) were measured using ELISA. OC, BAP, and NTX were significantly higher while IGF-1 and tSOS were lower in the premenarcheal group. The premenarcheal girls were more active and had higher daily energy intake relative to their body mass but there were no group differences in body mass index percentile. Maturity predicted 40%-57% of the variance in bone turnover markers. Additionally, daily energy intake was a significant predictor of OC, especially in the postmenarcheal group. IGF-1 and MVPA were significant predictors of BAP in the group as a whole. However, examined separately, IGF-1 was a predictor of BAP in the premenarcheal group while MVPA was a predictor in the postmenarcheal group. Adiposity and leptin were both negative predictors of tSOS, with leptin being specifically predictive in the postmenarcheal group. In conclusion, while maturity was the strongest predictor of bone markers and tSOS, dietary intake, physical activity, body composition, and hormonal factors further contribute to the variance in bone turnover and bone SOS in young Caucasian females. Further, the predicting factors of bone turnover and tSOS were different within each maturity group.

Relationship between plantar pressures, physical activity and sedentariness among preschool children

It has been speculated that high plantar pressures might cause foot pain and discomfort which, in turn, may discourage children from being physically active and result in them spending more time in sedentary activities. The purpose of this study was to determine whether plantar pressure distributions generated by preschool children were correlated with objectively measured time spent in physical activity and sedentary behaviour. Dynamic plantar pressures were measured for 33 preschool children (age=4.3±0.6 years; height=1.06±0.1 m; mass=18.4±2.9 kg; 17 boys) as they walked across an emed AT-4 pressure platform. Physical activity was objectively assessed using MTI ActiGraph accelerometers. Total physical activity (counts per minute), percentage of time spent in moderate-to-vigorous physical activity (MVPA), light activity and sedentary behaviour were then calculated. Peak pressures across the heel were found to significantly correlate with total physical activity (r=-0.53; p=0.03) and time in MVPA (r=-0.47; p=0.05) in boys. Similarly, the correlation data suggested that girls who generated higher peak pressures in the toe region spent more time in sedentary behaviour (r=0.53; p=0.04). As high plantar pressures appear to be a potential negative correlate of physical activity and sedentary behaviour, it is recommended that further research be conducted to design, test and evaluate the potential of interventions to reduce plantar pressures in inactive children so they can enjoy the benefits associated with participating in a more active lifestyle.

Correlates of objectively measured physical activity and sedentary behaviour in English children

BACKGROUND

Evidence on the correlates of objectively measured physical activity and sedentary behaviour in childhood is limited. This study aimed to identify correlates of physical activity and sedentary behaviour among 7-year-old children in England.

METHODS

Physical activity was measured using Actigraph accelerometry in 480 participants as part of the Gateshead Millennium Study during 2006-07. Twenty-two potential correlates across five domains (demographic and biological; psychological, cognitive and emotional; behavioural; social and cultural; physical environmental) were tested for associations with total volume of habitual physical activity, moderate-vigorous intensity physical activity (MVPA) and sedentary behaviour. Multiple linear regression analysis was used.

RESULTS

Seven correlates, including four that are potentially modifiable, were significantly associated with total physical activity, MVPA and sedentary behaviour in final models: gender, child weight status, maternal age, child interest in active play, active commuting to school, parenting practice and season. Four of these variables were significantly associated with all three constructs in final models. The final models explained 18, 18 and 24% of variance in total volume of physical activity, MVPA and sedentary behaviour, respectively.

CONCLUSION

A number of potentially modifiable factors are associated with increased physical activity and/or reduced sedentary behaviour in English children. These could be valuable targets of future interventions.

Active children use more locations for physical activity

We examined frequency of use of 11 physical activity (PA) locations among 539 San Diego children (45.0% males, 41.2% Latinos; mean ± SD age: 6.6 ± 0.7 years) and explored associations between location use, PA and potential correlates. Parents reported child's use (visits/week) of 11 locations. Child PA was assessed by accelerometry (subsample n = 178). The most frequently used locations (mean ± SD times/week) were homes (3.2 ± 2.3) and parks/playground (1.6 ± 1.3). Children used 4.0 ± 2.0 locations in a typical week, and made a total of 12.5 ± 6.8 visits/week to all locations. Latinos used fewer locations regularly (3.6 ± 2.1 vs. 4.3 ± 1.9 locations; p < 0.001) and had fewer visits to all locations (11.4 ± 7.4 vs. 13.2 ± 6.4 visits/week; p = 0.003) than non-Latinos. Accelerometry-assessed vigorous PA (VPA) was positively associated with the number of locations regularly used (ß = 0.04, p = 0.03) and total visits to all locations among Latinos (ß = 0.09, p = 0.005). Parental PA support was positively associated with locations used (ß = 0.64, p < 0.001) and visits to all locations (ß = 2.56, p < 0.001). Children using a greater variety of locations did more VPA. Latinos making more total visits to all locations had higher VPA.

Impact of methodological decisions on accelerometer outcome variables in young children

BACKGROUND

The impact of accelerometer-related methodological decisions relating to the assessment of physical activity and sedentary time has not been conclusively determined in young children.

OBJECTIVES

To determine the effects of epoch and cutoff points on the assessment of physical activity and sedentary time and to determine the accelerometer wear time required to achieve reliable accelerometer data in children.

DESIGN

Children were recruited from centres at Ghent, Glasgow, Gothenburg and Zaragoza.

METHODS

Physical activity was assessed for 1 week in 86 children (41 girls, 45 boys; mean age 7±2 years) by uniaxial accelerometry. The epoch was set at 15 s and reintegrated to 30 and 60 s. Time spent sedentary and in moderate and vigorous physical activity (MVPA) was assessed using a range of cutoff points. Number of days required to achieve 80% reliability was predicted using the Spearman-Brown Prophecy formula.

RESULTS

The Reilly cutoff points (<1100 counts per min (CPM)) indicated less sedentary time per day when comparing 15 vs 30 s and 15 vs 60 s epochs: 570±91 vs 579±93 min and 570±91 vs 579±94 min, respectively; P<0.05. Pate cutoff points (>420 counts per 15 s) reported more MVPA time per day compared with Sirard (890 counts per 15 s) and Puyau cutoff points (>3200 counts per min) using 15 s epoch: 78 (4-197) min (median (range) vs 18 (1-80) min and 24 (1-100) min, respectively; P<0.001. Compliance with guidelines of at least 60 min MVPA was 84, 78 and 73% for Pate cutoff points using 15, 30 and 60 s epochs, respectively, but 0% for Sirard and Puyau cutoff points across epochs. The number of days required to achieve 80% reliability for CPM, sedentary and MVPA time was 7.4-8.5 days.

CONCLUSION

Choice of epoch and cutoff point significantly influenced the classification of sedentary and MVPA time and observed compliance to the MVPA guidelines.

MVPA is associated with lower weight gain in 8-10 year old children: a prospective study with 1 year follow-up

BACKGROUND

Studies relating physical activity (PA) to weight gain in children have produced mixed results, although there is some evidence for stronger associations with more intense physical activities. The present study tested the hypothesis that weight gain over one year in 8-10 year olds would be more strongly predicted by moderate and vigorous physical activity (MVPA) than total physical activity (total PA) or sedentary behaviour.

METHODOLOGY

Participants were 280 children taking part in the Physical Exercise and Appetite in Children Study (PEACHES). Weight status was assessed using body mass index (BMI), fat mass index (FMI), and waist circumference (WC) in school Year 4 (baseline; age 8.7 yrs) and Year 5 (follow-up; age 9.7 yrs). Physical activity was measured at baseline using the Actigraph GT1M accelerometer to assess total PA (mean accelerometers counts per minute), MVPA; ≥ 4000 counts per minute) and sedentary time (<100 counts per minute).

PRINCIPAL FINDINGS

After adjustment for baseline BMI, SES, sex and ethnicity, MVPA was significantly associated with follow-up BMI (adjusted β  = -0.07; p = 0.002). This association was independent of total PA or sedentary time. Similar results were observed for FMI; again MVPA was significantly associated with follow up FMI (β = -0.16; p = 0.001) independent of total PA or sedentary time. The pattern was similar for WC (β = -0.07), but the association between MVPA and WC did not reach significance at p = 0.06.

CONCLUSION

The results of this study strongly support promotion of MVPA in children.

Validity, practical utility and reliability of Actigraph accelerometry for the measurement of habitual physical activity in dogs

OBJECTIVES

To test the validity, practical utility, and reliability of the Actigraph GT3-X accelerometer for measurement of habitual physical activity in pet dogs.

METHODS

In the validation study, 30 dogs wore the accelerometer for 1 day while being filmed. Accelerometer and film were synchronised and 10-minute periods of the filmed records were extracted with dogs in continuous periods of sedentary behaviour, light intensity physical activity indoors, light to moderate intensity physical activity outdoors and vigorous physical activity outdoors. For the practical utility and reliability studies, 20 dogs wore the GT3-X accelerometers for 1 week: practical utility was quantified as data loss and was also assessed by owner questionnaire; reliability was determined by 2 to 7 days of monitoring using the Spearman-Brown prophecy formula.

RESULTS

In the validation study, accelerometry output differed significantly between activity intensities (Friedman test, P<0·01). In the practical utility study, no data were lost from any dogs and dog owners reported that accelerometry was well tolerated. Reliability of accelerometry output was high: for 3 days of wear, it was 91% [95% confidence interval (CI) 82 to 96] and for 7 days of wear, it was 94% (CI 88 to 97).

CLINICAL SIGNIFICANCE

The GT3-X accelerometer is valid, practical and reliable for the measurement of habitual physical activity in dogs.

An open study of the effectiveness of a multi-component weight-loss intervention for adults with intellectual disabilities and obesity

Adults with intellectual disabilities experience high rates of obesity. Despite this higher risk, there is little evidence on the effectiveness of weight-loss interventions for adults with intellectual disabilities and obesity. The present study examined the effectiveness of the TAKE 5 multi-component weight-loss intervention. Adults with obesity were invited using specialist intellectual disability services to participate in the study. Obesity was defined as a BMI of 30 kg/m2 or greater. TAKE 5 included a daily energy-deficit diet of 2510 kJ (600 kcal), achieved via a personalised dietary prescription. Participants' body weight, BMI, waist circumference and levels of physical activity and sedentary behaviour were measured before and after the intervention. A total of fifty-four individuals consented to participate, of which forty-seven (87 %) completed the intervention in the study period. There was a significant decrease in body weight (mean difference − 4·47 (95 % CI − 5·91, − 3·03) kg; P < 0·0001), BMI ( − 1·82 (95 % CI − 2·36, − 1·29) kg/m2; P < 0·0001), waist circumference ( − 6·29 (95 % CI − 7·85, − 4·73) cm; P < 0·0001) and daily sedentary behaviour of participants ( − 41·40 (95 % CI − 62·45, − 20·35) min; P = 0·00 034). Of the participants who completed the intervention, seventeen (36·2 %) lost 5 % or more of their initial body weight. Findings from the study suggest that TAKE 5 is an effective weight-loss intervention for adults with intellectual disabilities and obesity. The effectiveness of TAKE 5 should be examined further in a controlled study.

Longitudinal study of physical activity and sedentary behavior in children

OBJECTIVE

Physical activity is thought to decline during childhood, but the extent of the decline is unknown. We made objective measures of 2-year changes in physical activity and sedentary behavior in English children who participated in the Gateshead Millennium Study to explore the nature, timing, and extent of changes in physical activity and sedentary behavior before adolescence.

METHODS

We conducted a longitudinal study of 405 children (207 girls), aged 7 years, in 2006/2007 and again 24 months later. Physical activity and sedentary behavior were measured with the Actigraph GT1M accelerometer. Data were analyzed in 2010. Changes in total volume of physical activity (accelerometer counts per minute [cpm]), moderate-to-vigorous-intensity physical activity (MVPA), and sedentary behavior were quantified. Factors associated with changes in physical activity and sedentary behavior were tested by using linear regression. Tracking of physical activity and sedentary behavior over the 2-year period was assessed by rank-order correlation.

RESULTS

Mean daily volume of physical activity declined by 83 cpm (interquartile range [IQR]: -189 to 31) over 2 years; the percentage of daily time spent in MVPA was low at baseline and declined by 0.3% (IQR: -1.4 to 0.9). The percentage of daily time in sedentary behavior was high at baseline and increased from 78.0% to 81.1% of the day (change 3.1% [IQR: -0.3 to 6.0]). The decline in MVPA and increase in sedentary behavior were significantly greater in girls and in those with higher BMI z scores at baseline. Physical activity and sedentary behavior showed moderate tracking over the 2-year period.

CONCLUSIONS

We report here new evidence of low and declining levels of physical activity and MVPA and increasing sedentary behavior before adolescence.

Utility of accelerometers to measure physical activity in children attending an obesity treatment intervention

Objectives. To investigate the use of accelerometers to monitor change in physical activity in a childhood obesity treatment intervention. Methods. 28 children aged 7-13 taking part in "Families for Health" were asked to wear an accelerometer (Actigraph) for 7-days, and complete an accompanying activity diary, at baseline, 3-months and 9-months. Interviews with 12 parents asked about research measurements. Results. Over 90% of children provided 4 days of accelerometer data, and around half of children provided 7 days. Adequately completed diaries were collected from 60% of children. Children partake in a wide range of physical activity which uniaxial monitors may undermonitor (cycling, nonmotorised scootering) or overmonitor (trampolining). Two different cutoffs (4 METS or 3200 counts·min(-1)) for minutes spent in moderate and vigorous physical activity (MVPA) yielded very different results, although reached the same conclusion regarding a lack of change in MVPA after the intervention. Some children were unwilling to wear accelerometers at school and during sport because they felt they put them at risk of stigma and bullying. Conclusion. Accelerometers are acceptable to a majority of children, although their use at school is problematic for some, but they may underestimate children's physical activity.

Changes in children's physical activity over 12 months: longitudinal results from the SPEEDY study

OBJECTIVE

We measured physical activity changes among 10-year-old British children over 12 months and assessed biological and demographic determinants.

METHODS

Physical activity was measured with accelerometers (counts per minute) over ≥3 days at baseline and 1 year later in a prospective study of 844 children (41.6% male; mean±SD baseline age: 10.2±0.3 years) from 92 schools. Meeting physical activity recommendations was defined as ≥60 minutes/day at ≥2000 counts per minute. Biological (height, weight, and fat percentage) and demographic factors (gender, rural/urban home location, and socioeconomic status) were assessed at baseline. Associations between physical activity changes and multiple factors were studied.

RESULTS

Physical activity decreased over 1 year (baseline: 665.7±209.8 counts per minute; follow-up: 623.2±179.2 counts per minute; P<.001), with 70.4% of children meeting physical activity recommendations at the baseline evaluation and 65.8% at the follow-up evaluation (P<.001). The decrease occurred mainly on weekends (-47.2±395.8 counts per minute; P=.002), with no significant change on weekdays (8.0±201.6 counts per minute; P=.20). Girls (P<.001), participants with greater body fat percentage (P=.001), and participants of higher socioeconomic status (P=.008) were more likely to exhibit physical activity decreases.

CONCLUSIONS

Physical activity decreased over 1 year among children in primary school, predominantly during the weekend. Because these children were relatively active at baseline, prevention of physical activity decreases in childhood, particularly among girls and on weekends, may be a suitable health promotion target.

Validity and prognostic value of parental ratings of children's activity

OBJECTIVE

To determine whether parental reports of children's physical activity are stable over time and correlate with objectively-measured physical activity.

METHODS

Participants were 322 twin children from a large UK twin cohort. When the children were aged 4 (1999) and 11 (2006), mothers rated their activity levels using four different measures. These included children's enjoyment of active pastimes, their habitual activity level, their activity compared with others of the same age and sex and a standard scale for 'fidgetiness'. Children wore an Actigraph (model 7164) for 7 consecutive days at the 11 year follow up from which total physical activity was calculated.

RESULTS

From age 4 to 11 amount and enjoyment of physical activity declined, but significant temporal correlations over the 7 year interval (range r=0.19 to 0.52) suggested that relative activity level was maintained. Habitual physical activity level, enjoyment of activity and fidgetiness at age 11 were all significantly associated with activity counts (all p values<0.05).

CONCLUSIONS

These results indicate that parental ratings can be valid indicators of children's physical activity, and that children who are perceived to be more active at 4 years are still more active at 11 years.

Objectively measured habitual physical activity in a highly obesogenic environment

BACKGROUND

While the prevalence of overweight and obesity among children continues to grow nationally, prevalence in the North-East of England is among the highest in the UK. The objective of this study was to investigate the habitual physical activity levels in a particularly obesogenic environment in the North-East of England.

METHODS

Eight primary schools were selected using a stratified random sampling frame ranking average deprivation levels. Participating children (n = 246, mean age 10 years) wore an accelerometer (Actigraph, GT-256) over five consecutive days (weekend plus three weekdays). Total daily moderate-to-vigorous intensity physical activity was calculated using thresholds by Puyau and colleagues.

RESULTS

Only 7% (17/246) of children were sufficiently active. Boys were more physically active than girls (766 +/- 268 vs. 641 +/- 202 counts/min, 95% CI for the difference 63-186 cpm.). Total physical activity was not influenced significantly by deprivation levels or weight status, and there were no significant differences in physical activity between school or weekend days.

CONCLUSIONS

The North-East of England is a recognized 'hot spot' for paediatric obesity and the present study shows that low levels of habitual physical activity are typical. Choice of accelerometry threshold affects both the apparent amount of physical activity and the ability to detect groups with particularly low levels of physical activity.

Methodological considerations in using accelerometers to assess habitual physical activity in children aged 0-5 years

This paper reviews the evidence behind the methodological decisions accelerometer users make when assessing habitual physical activity in children aged 0-5 years. The purpose of the review is to outline an evidence-guided protocol for using accelerometry in young children and to identify gaps in the evidence base where further investigation is required. Studies evaluating accelerometry methodologies in young children were reviewed in two age groups (0-2 years and 3-5 years) to examine: (i) which accelerometer should be used, (ii) where the accelerometer should be placed, (iii) which epoch should be used, (iv) how many days of monitoring are required, (v) how many minutes of monitoring per day are required, (vi) how data should be reduced, (vii) which cut-point definitions for identifying activity intensity should be used, and (viii) which physical activity outcomes should be reported and how. Critique of the available evidence provided a basis for the development of a recommended users protocol in 3-5-year olds, although several issues require further research. Because of the absence of methodological studies in children under 3 years, a protocol for the use of accelerometers in this age range could not be specified. Formative studies examining the utility, feasibility and validity of accelerometer-based physical activity assessments are required in children under 3 years of age. Recommendations for further research are outlined, based on the above findings, which, if undertaken, will enhance the accuracy of accelerometer-based assessments of habitual physical activity in young children.

Assessment of physical activity in youth

Despite much progress with physical activity assessment, the limitations concerning the accurate measurement of physical activity are often amplified in young people due to the cognitive, physiological, and biomechanical changes that occur during natural growth as well as a more intermittent pattern of habitual physical activity in youth compared with adults. This mini-review describes and compares methods to assess habitual physical activity in youth and discusses main issues regarding the use and interpretation of data collected with these techniques. Self-report instruments and movement sensing are currently the most frequently used methods for the assessment of physical activity in epidemiological research; others include heart rate monitoring and multisensor systems. Habitual energy expenditure can be estimated from these input measures with varying degree of uncertainty. Nonlinear modeling techniques, using accelerometry perhaps in combination with physiological parameters like heart rate or temperature, have the greatest potential for increasing the prediction accuracy of habitual physical activity energy expenditure. Although multisensor systems may be more accurate, this must be balanced against feasibility, a balance that shifts with technological and scientific advances and should be considered at the beginning of every new study.

Accelerometers and pedometers: methodology and clinical application

PURPOSE OF REVIEW

The relationship between physical activity and health varies considerably, partly due to the difficulty of assessing physical activity accurately. This review examines recent literature on the validation of movement sensors to assess habitual physical activity. Recommendations are given for the use of movement sensors during free-living conditions and methods of data analysis and interpretation are discussed.

RECENT FINDINGS

Recent progress in physical-activity research includes detailed comparative studies of different monitor brands. The move away from using linear-regression equations and the use of novel data-analysis strategies is increasing the accuracy with which energy expenditure can be estimated from accelerometry. New technologies, including the combination of accelerometry with the measurement of physiological parameters, have great potential for the increased accuracy of physical-activity assessment.

SUMMARY

Accelerometry is able to adequately assess physical activity and its association with health outcomes but currently methods have limited accuracy for the estimation of free-living energy expenditure. Pedometers provide an inexpensive overall measure of physical activity but are unable to assess intensity, frequency and duration of activity or to estimate energy expenditure. Interpretation of monitor output is best kept as close to the measurement domain as possible.