Behavior in Children
WHAT’S KNOWN ON THIS SUBJECT: Levels of physical activity during childhood are expected to be quite stable with age. Physical activity is believed to decline markedly at adolescence, particularly for girls.
WHAT THIS STUDY ADDS: Physical activity declines before adolescence in both boys and girls. Strategies to prevent the decline in physical activity should be considered and started for both sexes before adolescence.
abstract
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 ex-plore 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 seden-tary 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 lev-els of physical activity and MVPA and increasing sedentary behavior before adolescence.Pediatrics2011;127:e24–e30
AUTHORS:Laura Basterfield, PhD,aAshley J. Adamson,
PhD,aJessica K. Frary, BSc,aKathryn N. Parkinson, PhD,a
Mark S. Pearce, PhD,band John J. Reilly, PhD,cfor the
Gateshead Millennium Study Core Team
aInstitute of Health and Society, Human Nutrition Research Centre, andbInstitute of Health and Society, Sir James Spence Institute, Royal Victoria Infirmary, Newcastle University, Newcastle Upon Tyne, United Kingdom; andcDivision of Developmental Medicine, University of Glasgow, Glasgow, United Kingdom
KEY WORDS
childhood, physical activity, sedentary behavior
ABBREVIATIONS
MVPA—moderate-to-vigorous–intensity physical activity SES—socioeconomic status
Each author is responsible for the reported research; each author has participated in the concept and design, analysis and interpretation of data, and drafting or revising of the manuscript, and each author approved the manuscript as submitted.
www.pediatrics.org/cgi/doi/10.1542/peds.2010-1935
doi:10.1542/peds.2010-1935
Accepted for publication Sep 20, 2010
Address correspondence to Laura Basterfield, PhD, Institute of Health & Society, Human Nutrition Research Centre, Newcastle University, M1.151 Leech Building Medical School, Framlington Place, Newcastle Upon Tyne NE2 4HH, United Kingdom. E-mail: laura.basterfi[email protected]
PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275).
Copyright © 2011 by the American Academy of Pediatrics
Levels of habitual physical activity and sedentary behavior are now well es-tablished as important to both the cur-rent and future health of children and adolescents,1–3and attempts to reduce
the decline in physical activity in ado-lescence have been the focus of many public health interventions in recent years.4,5
Most studies of changes in physical ac-tivity during childhood and adoles-cence have been cross-sectional rather than longitudinal. In addition, most previous studies used subjective methods of measurement of physical activity, which do not provide accurate estimates of the amount and intensity of physical activity.6In addition,
longi-tudinal studies that have used objec-tive methods7–17 have usually
mea-sured change during adolescence rather than during childhood and have usually focused on girls7–9,11,12,15,16
be-cause of concern that adolescent de-clines in physical activity are espe-cially marked in girls. Little is known about the timing, nature, and magni-tude of changes in physical activity lev-els in childhood, and even less is known about longitudinal changes in levels of objectively measured seden-tary behavior. Moreover, results of older studies conducted before the ep-idemic of pediatric obesity may not provide evidence that is readily appli-cable to contemporary children and adolescents. Finally, no studies have revealed longitudinal changes in the 3 constructs (total volume of physical activity, moderate-to-vigorous–intensity physical activity [MVPA], and seden-tary behavior6), all of which have been
identified as important to current and future health.1,2 Understanding the
timing, nature, and extent of changes in physical activity and sedentary be-havior during childhood is crucial for the development of informed, effec-tive, and evidence-based interventions aimed at preventing obesity and
pro-moting cardiometabolic health. The primary aim of this study, therefore, was to quantify changes in objectively measured habitual physical activity and sedentary behavior over a 2-year period in a sample of English children, before adolescence, by using a longitu-dinal study design. Secondary aims of this study were to identify factors as-sociated with changes in physical ac-tivity and sedentary behavior and to assess the extent to which physical activity and sedentary behavior “tracked” over time.
METHODS
Participants, Recruitment, and Consent
The Gateshead Millennium Study is a birth cohort study of 1029 infants (born in Gateshead, northeast En-gland) and their families recruited in 1999 –2000. The details of the aims, de-sign, and sampling of this birth cohort were recently published.18In brief, the
sample population resided in Gates-head and was predominantly (98%) from the white ethnic majority group and socioeconomically representative of northeast England. For the present study, all families who had not previ-ously opted out of the cohort were sent a letter and information leaflet inviting them to take part. Baseline measures were collected between October 2006 and December 2007, when the children were aged 6 to 8 years (hereafter de-scribed as aged 7 years), and follow-up data were collected 24 months later (October 2008 to September 2009), when the children were aged 8 to 10 years (hereafter described as aged 9 years). A favorable ethical opinion was given by the Gateshead and South Tyneside Local National Health Service Research Ethics Committee for base-line data collection at 7 years of age and by the Newcastle University Fac-ulty of Medical Sciences Ethics Com-mittee for follow-up data collection
at 9 years of age. Informed written consent was obtained from the par-ent/main guardian of each child, and children provided their assent to participation.
Objective Measurement of Physical Activity and Sedentary Behavior Habitual physical activity and seden-tary behavior were measured by using Actigraph GT1M accelerometers (Acti-graph, Pensacola, FL). The Actigraph is a small, unobtrusive, and lightweight monitor worn on the right hip on an elastic waistband. The Actigraph has high validity (relative to reference measures of physical activity, direct observation, and energy expenditure), high reliability, and low reactivity in children19and has been used
success-fully in pediatric physical activity stud-ies over the past 10 years.6
Children were asked to wear the accel-erometer during waking hours for 7 days and remove them only for bed and water-based activities such as showering, bathing, or swimming. Families were also given a log sheet to note when the monitor had been worn and removed each day. The accelerom-eters were set to record data in 15-second sampling intervals (epochs) throughout the period in which the ac-celerometer was worn. Before analy-sis, the data were collapsed to 60-second epochs. Data were reduced manually by using accelerometry out-put and log sheets, as described previ-ously,20to delete occasional periods of
nonwear time (corresponding to times noted by the parent as unworn).
(percentage of daily time spent in sed-entary behavior).
To quantify MVPA and sedentary behav-ior, evidence-based cut off points from a body of pediatric calibration and val-idation studies were applied to accel-erometry output.6A cut point of 3200
cpm21and above was used to quantify
MVPA, and a cut point of 1100 cpm and below was used to quantify sedentary behavior.22The sedentary behavior
ac-tually measured in this study can be defined best as no movement of the trunk.6,22Sedentary behavior is a more
complex construct than this and one that is still evolving,23 and other
as-pects of sedentary behavior are impor-tant to health outcomes (notably television-viewing23) but were not
mea-sured in this study. Because the Acti-graph cut points used in this study were derived from studies using Acti-graph model 7164, and the more re-cent Actigraph GT1M model has been shown to have a consistent bias of 9% relative to model 7164,24a ⫹9%
cor-rection was applied to the raw accel-erometry data before applying cut points.
Previous analyses of accelerometry data have shown that 3 days of accel-erometry with a minimum of 6 hours recording per day provided acceptable reliability.25,26Analyses on the current
data set confirmed that reliability was high over any 3 days for each of the 3 constructs that were measured, and there were no differences when week-end days were included/excluded.27As
a result, measures were eligible for in-clusion in our study if at least 3 days of accelerometry of at least 6 hours/day26
were obtained at both baseline and follow-up measures. For children from the United Kingdom, there are small but significant seasonal variations in objectively measured habitual physi-cal activity28,29; therefore, follow-up
ble to match baseline and follow-up measures for season.
Anthropometrics and Descriptive Characteristics of Study
Participants
Height was measured to 0.1 cm with a Leicester portable height measure (Chasmors, London, United Kingdom), and weight was measured to 0.1 kg in light indoor clothing and percentage body fat was estimated with a Tanita TBF300MA (Chasmors). Waist circum-ference was measured to 0.1 cm at the minimum circumference between the lowest rib and the iliac crest. BMI (kg/ m2) was calculated for each child, and zscores were estimated to UK popula-tion reference data.30 Socioeconomic
status was reported by using
Townsend scores at birth,18 an
area-based measure derived from the UK census in 1991. The child’s postal code (zip code) at birth was linked to census data for the enumeration district to provide a Townsend score, a well-validated measure of socioeconomic deprivation.31The Townsend score is
based on the percentage of unem-ployed economically active 16- to 65-year-olds, household overcrowding, and not owning a car. The distribution of these scores in the northern region is known, so the scores could be di-vided into 5 ordered centiles (each comprising 20% of the population) that corresponded to the quintiles for the general population.
Statistical Analysis
The sample size for our study was fixed by the size of the recruited cohort and the extent of sample attrition over the 2-year period. However, the sample size was similar to or larger than that of most previously reported longitudi-nal studies (eg, Janz et al10and
Met-calfe et al32). In addition, the accuracy
of both the reported levels of physical
period are increased by the use of ac-celerometry and the longitudinal de-sign of the study.
Data were checked for normality, and physical activity data were found to be skewed. Therefore, longitudinal changes in all 3 constructs over the 2-year period (calculated by subtract-ing 7-year data from 9-year data) were tested for significance by using Wilcoxon signed-rank tests. Mann-WhitneyU tests were used to assess the significance of differences be-tween boys and girls in levels of phys-ical activity and sedentary behavior.
Linear regression analysis was used to detect factors at baseline (age 7 years) that were associated with changes in total volume of physical activity, MVPA, and sedentary behavior. The proposed candidate explanatory variables agreed on in the analysis plan were sex, physical activity at baseline (cpm and percentage of time spent in MVPA), baseline sedentary behavior (percentage of time spent sedentary), socioeconomic status (SES) (Town-send score quintiles), and child BMIz
score at 7 years of age as an index of weight status. Spearman rank correla-tions between baseline and follow-up measures were used to assess the ex-tent to which tracking occurred over the 2-year period for all 3 constructs. SPSS 17 (SPSS Inc, Chicago, IL) and Stata 10 (Stata Corp, College Station, TX) were used for statistical analyses. Significance was set atP⬍.05.
RESULTS
Characteristics of Study Sample and Dropout, Including Age and Accelerometry Variables
had both baseline (age 7 years) and follow-up (age 9 years) measurements were included in our analysis (n ⫽
405). A total of 105 children studied at baseline were lost to follow-up because they did not have consent to take part or were unable to be traced (n⫽55), were missing accelerometry log sheets (n⫽
9), were not wearing the accelerometer (n⫽6), did not reach the minimum wear criteria (n⫽8), lost their accelerome-ters (n⫽14), or had malfunctioning ac-celerometers (n⫽13).
Participants followed up to 9 years of age were not significantly different to those lost to follow-up with respect to initial levels of physical activity and sedentary behavior, BMI, or SES. At baseline, when children were aged 7 years, mean duration of accelerom-etry was 6.4 days and 11.1 hours/day; at follow-up when children were aged
9 years, mean duration of accelerom-etry was 6.1 days and 11.3 hours/day.
Overall physical activity levels were low (median: 26 minutes of MVPA daily at 7 years of age and 24 minutes at 9 years of age [both sexes combined]). Only 26 of 405 (6.4%) children achieved a mean of 60 minutes of MVPA daily at 7 years of age and only 23 of 405 (5.7%) at 9 years of age. Nine children (2.2%) achieved an average of 60 minutes of MVPA at both time points.
Longitudinal Changes in Physical Activity and Sedentary Behavior Changes in total volume of physical ac-tivity, MVPA, and sedentary behavior over the 2-year period are summarized in Table 2. In summary, over the 2-year period the total volume of physical ac-tivity declined significantly, MVPA de-clined significantly, and sedentary
be-havior increased significantly (Table 1). There were significant differences between boys and girls for change in the 3 constructs of physical activity (mean cpm,P⫽.020; MVPA minutes/ day,P⫽.012; percentage of MVPA,P⫽
.006) but no difference in the percent-age of time spent sedentary (P⫽.274) (Table 2).
Factors Associated With
Longitudinal Changes in Physical Activity and Sedentary Behavior The regression analysis of factors as-sociated with change in total volume of physical activity, MVPA, and sedentary behavior is shown in Table 3. In sum-mary, after adjustment for baseline levels of physical activity and seden-tary behavior (which had significant influences on changes in these vari-ables), longitudinal declines in total
TABLE 1 Participant Characteristics
Anthropometry, Mean (SD)
All Children (N⫽401–405) Boys (n⫽195–198) Girls (n⫽205–207)
Baseline Follow-up Baseline Follow-up Baseline Follow-up
Age (range), y 7.4 (6.4–8.4) 9.3 (8.4–10.2) 7.4 (6.4–8.4) 9.3 (8.4–10.2) 7.4 (6.5–8.4) 9.3 (8.4–10.2) Height, cm 124.8 (0.3) 135.5 (0.3) 125.0 (0.4) 135.5 (0.5) 124.6 (0.4) 135.4 (0.4) Weight, kg 26.2 (0.3) 33.1 (0.4) 26.1 (0.4) 32.7 (0.5) 26.2 (0.4) 33.5 (0.5) Waist, cm 56.4 (0.3) 60.7 (0.3) 56.8 (0.4) 60.9 (0.5) 56.0 (0.4) 60.4 (0.4)
BMI 16.7 (0.1) 17.9 (0.1) 16.6 (0.2) 17.7 (0.2) 16.8 (0.2) 18.1 (0.2)
BMIzscore 0.37 (0.05) 0.53 (0.05) 0.39 (0.08) 0.53 (0.08) 0.36 (0.07) 0.52 (0.07) Physical activity/sedentary behavior
data, median (IQR)
Total physical activity, mean cpm 721 (601–864) 643 (523–785)a 731 (623–876) 688 (569–831)a 710 (588–848) 612 (496–728)a,b MVPA, min 26 (18–37) 24 (15–37)a 28 (19–43) 28 (20–43) 24 (17–34)b 21 (13–30)a,b Time spent in sedentary behavior, % 78.0 (73.9–81.9) 81.1 (76.8–84.4)a 77.2 (72.6–80.9) 79.5 (75.5–83.2)a 78.6 (74.6–82.9)b 82.3 (78.4–85.3)a,b Time spent in MVPA, % 3.8 (2.6–5.7) 3.6 (2.4–5.2)a 4.1 (2.8–6.3) 4.3 (2.9–6.2) 3.7 (2.5–5.4)b 3.0 (2.1–4.5)a,b aPaired longitudinal data: 9 years significantly different from 7 years.
bResults for the girls were significantly different from those of the boys.
TABLE 2 Longitudinal Changes in Total Physical Activity, MVPA, and Sedentary Behavior From 7 to 9 Years of Age
All Children (N⫽405) Boys (n⫽198) Girls (n⫽207)
Median (IQR) P Median (IQR) P Median (IQR) P
Change in total physical activity, mean cpm
⫺83 (⫺189 to 31)a ⬍.001 ⫺55 (⫺153 to 52)a ⬍.001 ⫺100 (⫺227 to 22)a,b ⬍.001
Change in MVPA, min/d ⫺2 (⫺10 to 7)a .012 ⫺1 (⫺8 to 8) .970 ⫺4 (⫺11 to 5)a,b ⬍.001 Change in time spent in MVPA, % ⫺0.3 (⫺1.4 to 0.9)a .003 0.03 (⫺1.1 to 1.1) .878 ⫺0.62 (⫺1.7 to 0.6)a,b ⬍.001 Change in time spent sedentary, % 3.1 (⫺0.29 to 6.0)a ⬍.001 2.9 (⫺0.6 to 5.6)a ⬍.001 3.6 (⫺0.2 to 7.1)a ⬍.001 aNine-year measurement significantly different from 7-year measurement.
bResults for the girls were significantly different from those of the boys.
volume of physical activity (accelerom-etry cpm) were greater in girls than boys but were not related to BMI z
scores or SES. Longitudinal declines in MVPA were significantly greater in girls than boys and in those with higher initial BMIzscore but were not related to SES. Longitudinal increases in sedentary behavior were signifi-cantly greater in girls but not related to BMIz score or SES. There was no interaction between sex and any base-line variable.
Tracking of Physical Activity and Sedentary Behavior Over a 2-Year Period
Rank-order correlations between baseline and follow-up measures of to-tal volume of physical activity, MVPA minutes/day, percentage of time spent in MVPA, and percentage of time spent in sedentary behavior werer⫽0.54, 0.57, 0.58, and 0.57, respectively (all
P⬍.001).
DISCUSSION
Main Findings, Implications, and Comparisons With Other Evidence We found low levels of habitual physi-cal activity and high levels of sedentary behavior in participating children at 7 years of age, with declines in physical activity and increases in sedentary behavior by 9 years of age. Recent evidence, based on contemporary samples of children and adolescents that have used accelerometry with evidence-based cut points,6 suggests
that levels of physical activity are typi-cally very low and levels of sedentary
behavior very high. In addition, small numbers of longitudinal studies of children with objective measures10,17
and 1 recent cross-sectional study with objective measures33 suggested
that declines in physical activity may typically occur well before adoles-cence. Our results, therefore, add to the body of evidence that low levels of physical activity are established early in childhood and decline further dur-ing childhood and before adolescence.
The 2-year changes in physical activity and sedentary behavior observed in this study were significant and, al-though relatively modest in magni-tude, are a great cause for concern be-cause of the low level of baseline physical activity and high level of base-line sedentary behavior. In this study, unfavorable changes in physical activ-ity and sedentary behavior occurred in both sexes, but these changes were generally more severe in girls than boys and in those with higher baseline weight status. Identifying factors asso-ciated with declines in objectively measured physical activity and with increases in objectively measured sed-entary behavior would be useful to in-form the development of future public health interventions aimed at modify-ing these behaviors.9Our results
sug-gest that public health interventions aimed at preventing declines in physical activity should be targeting elementary school–aged children, because unfavor-able trends in health behaviors seem to be already established before puberty. In Scotland, for example, as in some other countries, public health policy is based
on the assumption that physical activity is high during childhood but declines markedly only during adolescence. Pre-vention of declines in physical activity in adolescent girls is a Scottish public health priority,34but according to our
re-sults, we would question the assump-tions on which this policy was based.
Tracking of physical activity and sed-entary behavior was moderately strong in this study, which is broadly consistent with other recent stud-ies14,35 of tracking of physical activity
and sedentary behavior measured ob-jectively during childhood. However, even for the most physically active chil-dren, levels of objectively measured physical activity at both time points were low (Table 2).
Study Strengths and Weaknesses There are several methodologic strengths to this study: The study sam-ple was relatively large and represen-tative of children recruited from the Gateshead Millennium Study longitudi-nal birth cohort study; measurements were made during a period of relative social and educational stability; physi-cal activity and sedentary behavior were objectively and accurately mea-sured; the longitudinal design allowed the measures to be repeated after a 2-year period; and, in terms of SES, the sample was representative of families living in northeast England.18
Potential weaknesses include the is-sue of generalizability to other settings and samples, and there was some sample attrition from baseline to the
Mean cpm
(95% CI) P (95% CI) P (95% CI) P
Baseline BMIzscore ⫺14.7 (⫺31.0 to 1.7) .078 ⫺0.2 (⫺0.4 to⫺0.1) .011 0.3 (⫺0.1 to 0.7) .148 Sexa ⫺50.4 (⫺85.3 to⫺15.6) .005 ⫺0.8 (⫺1.2 to⫺0.4) ⬍.001 1.6 (0.7–2.5) ⬍.001 Baseline test variable ⫺0.6 (⫺0.6 to⫺0.5) ⬍.001 ⫺0.4 (⫺0.5 to⫺0.4) ⬍.001 ⫺0.5 (⫺0.6 to⫺0.5) ⬍.001 Constant 422.2 (338.4–506.0) ⬍.001 3.0 (2.2–3.7) ⬍.001 41.1 (35.5–46.6) ⬍.001
2-year follow-up. However, there was no difference in SES, BMI, BMIzscore, or physical activity/sedentary behav-ior levels between those who partici-pated in the follow-up and those who did not.
There has been no consensus on the appropriate accelerometer cut points to use for children to quantify intensity of physical activity. The value of 3200 cpm21used in our study was based on
a previous pediatric study in which ac-celerometer output was calibrated against energy expenditure and is sim-ilar to the cut point suggested by a number of other pediatric calibration studies.6Other studies have used both
higher and lower cut points (eg, 2000 cpm36), but these cut points have not
usually been based on calibration studies that aimed to identify the most appropriate cut point for MVPA.6 The
1100-cpm cut point used to quantify sedentary behavior in our study is higher than that used by some other pediatric studies (some have used 100 cpm to define sedentary behavior) and was based on a calibration study on younger children,22but empirical
evi-dence suggests that it is appropriate for older children.6The use of different
cut points has a moderately large im-pact on objective measurement of MVPA and a less marked effect on mea-surement of sedentary behavior in children.6
We used individualized manual accel-erometer data reduction in the present study, as in previous studies6:
we chose not to exclude strings of ze-ros unless they corresponded with re-ported nonwear time, despite parents not being with their children during
the entire monitoring period. This de-cision was made on the basis of trying to include as much data as possible, although it may reduce the proportion of time spent in MVPA and increase the proportion of time spent in sedentary behavior. The absolute time spent in
MVPA should not be so greatly
affected.
However, taking into account these limitations, the reported findings were consistent with several other recent studies that also used objective meth-ods to measure physical activity. In ad-dition, the levels of total physical activ-ity and MVPA observed in the present study were similar to those observed in recent studies of both slightly younger and slightly older samples within the United Kingdom.14,17,28,32,37,38
These findings also question the hy-pothesis that physical activity levels only decline markedly during adoles-cence, especially taken alongside the recent studies reporting the levels of objectively measured physical activity during adolescence in the United King-dom.39 Longer-term follow-up will be
required to investigate the extent to which the patterns observed in the present study are generalizable to other groups of children and to assess whether most of the decline in physical activity that occurs before adulthood occurs before, rather than during, adolescence.
CONCLUSIONS
The low levels of childhood MVPA and high levels of sedentary behavior re-ported here present a major public health concern. These findings, if rep-licated in other groups of preadoles-cents, suggest that efforts to prevent
declines in physical activity should be directed at children not just at adolescents.
ACKNOWLEDGMENTS
This work was supported by grants from the Scottish Government Chief Scientist Office (grant CZH/4/484), the UK National Prevention Research Initia-tive (incorporating funding from Brit-ish Heart Foundation, Cancer Re-search UK, Diabetes UK, English Department of Health, Economic and Social Research Council, Food Stan-dards Agency, Medical Research Coun-cil, Research and Development Office for the Northern Ireland Health and So-cial Services, Chief Scientist Office of the Scottish Government Health Direc-torate, Welsh Assembly Government, and World Cancer Research Fund), and Gateshead PCT. The funding bodies had no role in the decision to publish or the content of the article. The cohort was first set up with funding from the Henry Smith Charity and Sport Aiding Medical Research for Kids.
Members of the Gateshead Millennium Study Core Team are Ashley Adamson, Anne Dale, Robert Drewett, Ann Le Cou-teur, Paul McArdlev, Kathryn Parkin-son, Mark Pearce, John Reilly, and Charlotte Wright.
We acknowledge the support of an ex-ternal reference group in conducting the present study. We appreciate the support of Gateshead Health National Health Service Foundation Trust, Gateshead Education Authority, and lo-cal schools. We thank members of the research team for their effort. We es-pecially thank the families and chil-dren who participated in the Gates-head Millennium Study.
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DOI: 10.1542/peds.2010-1935 originally published online December 20, 2010;
2011;127;e24
Pediatrics
S. Pearce, John J. Reilly and for the Gateshead Millennium Study Core Team
Laura Basterfield, Ashley J. Adamson, Jessica K. Frary, Kathryn N. Parkinson, Mark
Longitudinal Study of Physical Activity and Sedentary Behavior in Children
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DOI: 10.1542/peds.2010-1935 originally published online December 20, 2010;
2011;127;e24
Pediatrics
S. Pearce, John J. Reilly and for the Gateshead Millennium Study Core Team
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