Clinicl Investigtion nture publishing group Assessment of pedometer ccurcy in cpturing hbitul types of physicl ctivities in overweight nd obese children Tom J. Hzell 1, Citlin V.L. Ellery 2, Tmr R. Cohen 2, Ctherine A. Vnstone 2, Celi J. Rodd 3 nd Hope A. Weiler 2 Bckground: Currently, there is limited mount of reserch exploring physicl ctivity mesurement tools in overweight nd obese (OW/OB) children using pedometers. Thus, our objective ws to determine the ccurcy of one spring-levered (SC-T2) nd two piezoelectric pedometers (NL- 1 nd Piezo) in OW/OB children. Methods: A totl of 26 boys nd 34 girls (n = 6) prticipted. Pedometer step-counts were compred to observed step counts for wlking (wlking, stir scent nd decent) nd hopping tests. Pedometer ccurcies were compred with Friedmn tests while Blnd-Altmn plots were used to estblish the ccurcy of ech pedometer ginst direct observtions. Results: Boys (n = 26) nd femles (n = 34) were 96 nd 91% OB, respectively. The two piezoelectric pedometers (NL-1 nd Piezo) were ccurte for wlking nd stir climbing tsks, however ll pedometers were inccurte for hopping tests. Averged over ll three wlking ctivities, the NL-1 ws the most ccurte with 6.7% medin error (interqurtile rnge (IQR):. 13.3); followed by the Piezo with 1.% medin error (IQR: 3.3 18.1); SC-T2 ws the lest ccurte with 14.7% medin error (IQR: 4.8 3.). Conclusion: These results support the use of the piezoelectric pedometers for wlking nd stir climbing types of ctivities, which re typicl for OW/OB children in nonlbortory setting. Considering the incresing prevlence of obesity worldwide (1,2), obesity interventions should begin in childhood. Physicl ctivity (PA), like other determinnts such s dietry intke nd socio-economic sttus, is n importnt fctor tht ffects weight vrition (3,4). Children (ged 17 y) should ccumulte t lest 6 min of moderte- to vigorous-intensity PA per dy in multiple shorter bouts (e.g., 2 bouts of 3 min) (). Activities tht strengthen muscle nd bone should lso be performed t lest three times per week (). To meet current PA guidelines, children need to tke pproximtely 12, steps per dy (6), however reserch suggests only 9% of boys nd 4% of girls meet this recommendtion (4). Objectively evluting PA is criticl when developing interventions nd ssessing their effectiveness, prticulrly when interventions promote PA (7). Pedometers re generlly considered robust, cost-efficient, nd convenient objective PA ssessment tools (8). Although they do not mesure durtion of PA or intensity, studies hve shown pedometers correlte with other objective mesures of PA (9). However, chieving ccurte nd reproducible PA estimtes in overweight nd obese (OW/OB) children is chllenge. Reserchers need to be cogniznt of the fct obese children my be subjected to bullying; wering pedometer my single them out further resulting in reduced complince to wering the device (1,11). It hs lso been suggested tht their lrger wist circumferences, not incresed diposity (12), my cuse n incresed tilt ngle thereby inccurtely recording steps (7,1,13). Currently, studies hve investigted the ccurcy of pedometers in controlled settings (i.e., wlking on tredmills) in helthy children (9,13 16), but this does not reflect ctivities tht re typicl in the free-living environment. Determining their effectiveness in ccurtely mesuring ctivity if obese children embrk upon sports involving jumping or stepping ctivities is necessry. Further, reserch to dte is conflicting when compring norml weight nd OW/OB children. For instnce, smll study (n = 27) found n pproximte 2% (P <.1) less error in helthy-weight children (n = 16) compred to OW/OB (n = 11) using both piezoelectric (Omron HJ-1) nd spring-levered (Ymx Digi-Wlker SW-2) pedometers (13). Contrrily, nother study exmining norml nd OW/OB children (n = 8) found tht BMI, wist circumference, nd percent body ft did not significntly ffect pedometer ccurcy, but rther the style of wistbnd worn by children ffected pedometer tilt ngle nd influenced ccurcy (9). Given the complexities in studying OW/OB children, vlidtion study is wrrnted to test the use of pedometers in this popultion. Therefore, the objectives of this study were to: (i) test the ccurcy of pedometers to mesure PA in controlled yet home-like setting using different tests similr to hbitul types of PA compred to observtion; (ii) to compre the ccurcy of three different pedometer models; nd (iii) 1 Deprtment of Kinesiology nd Physicl Eduction, Wilfrid Lurier University, Wterloo, Ontrio, Cnd; 2 School of Dietetics nd Humn Nutrition, McGill University, Montrel, Québec, Cnd; 3 Children s Hospitl, University of Mnitob, Winnipeg, Mnitob, Cnd. Correspondence: Hope A. Weiler (hope.weiler@mcgill.c) Received 1 Februry 216; ccepted 11 My 216; dvnce online publiction 3 August 216. doi:1.138/pr.216.133 686 Peditric Reserch Volume 8 Number November 216 Copyright 216 Interntionl Peditric Reserch Foundtion, Inc.
Assessment of pedometer ccurcy in cpturing hbitul types of physicl ctivities in overweight nd obese children Articles to exmine the correltion between pedometer ccurcy nd youth body ft/wist circumference. RESULTS Prticipnt Chrcteristics Prticipnt chrcteristics re presented in Tble 1. The smple included 6 children ged 8.6 (8. 9.3) yers. There were no significnt differences in men ge (P =.69), height (P =.94), weight (P =.614), wist circumference (P =.318), nd A/G rtio (P =.72) between boys (n = 26) nd girls (n = 34); though girls hd significntly higher %BF thn boys (P =.8) nd boys hd higher BMI-z thn girls (P =.13). Pedometer Accurcy Pedometer ccurcy is presented in Tble 2. There were significnt min effects (P <.1) for the wlking, stir scent, stir descent, nd double-legged hopping tests but not the single-legged hopping test (P >.). To further confirm the wlking test results, 13 dditionl prticipnts completed 1 step-test (~2 min) to simulte longer bout of physicl ctivity. Similrly, the percent error ws significntly (P <.1) lower in the NL-1 (.% error ( 2..)) nd Piezo ( 1.% error ( 2..)) compred to the SC-T2 (1% error (77. 1.)). The overll medin percent error from ll tests ws 13.3% (3.3 27.3; IQR) for the NL-1; 19.% (7. 3) for the Piezo; nd 3.4% ( 26.7 17.9) for the SC-T2. Using only the three wlking tests (2 step wlk, stir scent, nd stir descent), the NL-1 ws the most ccurte (6.7% error (. 13.3)), followed by the Piezo (1.% error (3.3 18.1)), followed by the SC-T2 ( 14.7% ( 4.8 3.)). Blnd-Altmn plots were used to determine levels of greement between pedometer counts nd observtions for ll ctivities (Figures 1 3). Overll, the NL-1 nd Piezo were very close in terms of level of greement for ech test performed, with 1-step difference for four of five tests. The NL-1 showed highest level of greement for three of five tests (wlking, stir scent, stir descent), nd the SC-T2 showed highest greement for two of five tests (single-legged nd double-legged hopping). However, the SC-T2 hd very wide limits of greement for ech test; e.g., from 22.9 to 8.3 for the 2-step test. There were no sttisticl differences when ssessing pedometer levels of greement by gender or ge (dt not shown). Correltions Between Pedometer Accurcy nd Body Ft/Wist Circumference Wist circumference ws negtively correlted with stir scent in the NL-1 (r =.27, P =.3) such tht higher WC ws ssocited with more ccurte pedometer count (driven by older mles who hd the highest WC nd lowest error). There were no other significnt correltions found between wist circumference nd pedometer ccurcy vribles (r <.16, P >.281). There were no significnt correltions found between %BF (r <.2, P >.1) nd A/G rtio (r <.21, P >.11) mong pedometer ccurcy vribles. DISCUSSION Although reserch hs exmined the ccurcy of pedometers in children (9,13 16), there is lck of reserch exmining the use of pedometers specificlly in OW/OB children. Therefore, this study evluted pedometer ccurcy in OW/OB children nd imed to determine the ccurcy of three types of pedometers in this popultion. Overll, the piezoelectric devices (NL-1 nd Piezo) were the most vlid of the three pedometers tested on the bsis of the level of greement determined through Blnd-Altmn plots. There re severl fctors tht could explin the inccurcies ssocited with the spring-levered (SC-T2) pedometers in OW/OB children. These pedometers function with mechnicl lever rm, thus if child does not step with enough verticl ccelertion, or if the pedometer is tilted beneth lrger wist circumference, steps my not be ccurtely counted. While helthy weight children spend pproximtely 77% of their time engging in low intensity (VO 2 < 11 ml/kg/min) types of ctivities (17), obese children tend to wlk with even slower reltive velocity nd longer stnce period between steps thn normlweight individuls (18). This my cuse pedometer recording errors due to mechnistic limittions ssocited with springlevered pedometers (19). Therefore, consistent with previous reserch evluting OW/OB prticipnts (9,12,13), cution Tble 1. Anthropometric chrcteristics of the prticipnts Vrible Boys (n = 26) Girls (n = 34) Younger: 6 8 y (n = 38) Older: 9 12 y (n = 22) All prticipnts (n = 6) Age (yers) 8. (8. 1.) 8. (8. 9.) 8. (7. 8.) 1. (9. 11.) 8. (8. 9.3) Height (meters) 1.38 (1.3 1.) 1.3 (1.31 1.43) 1.34 (1.31 1.38) 1.3 (1.39 1.7) 1.38 (1.32 1.44) Weight (kg) 49.1 (44.7 9.6) 46.4 (4.2 6.9) 44.6 (37..) 6.1 (.4 7.) 47.7 (41.3 6.4) BMI-z 3.2 (2.9 3.9) 2.8 (2.3 3.2) 2.9 (2.4 3.6) 3. (2. 3.3) 3. (2.4 3.4) % OW/OB 4/96 9/91 8/92 /9 7/93 Body ft (%) 37.3 (32.7 38.7) 37. (36. 42.6) 36.4 (33.2 4.8) 38. (36.7 41.8) 37.4 (34.6 41.1) A/G rtio 1. (.9 1.1) 1. (.9 1.) 1. (.9 1.) 1. (1. 1.1) 1. (.9 1.1) WC (cm) 87.1 (83. 96.4) 82. (77. 92.6) 8. (76.2 87.4) 96.3 (86.8 98.6) 8.3 (78. 9.6) WC >9 %ile n(%) 22 (84.6) 26 (76.) 31 (81.6) 17 (77.3) 48 (8.) All mesurements re expressed s medin (interqurtile rnge) unless otherwise noted. A/G rtio. ndroid/gynoid rtio; BMI-z, BMI z-score; OW/OB, overweight/obese; WC, wist circumference; WC >9th %ile - WC over 9th percentile. Obtined from whole body dul-energy X-ry bsorptiometry scn. Copyright 216 Interntionl Peditric Reserch Foundtion, Inc. Volume 8 Number November 216 Peditric Reserch 687
Hzell et l. Tble 2. Actul observed nd pedometer counted steps SC-T2 NL-1 Piezo WALKING Actul steps 2.3 ± 1. 2. ± 1.8 2.3 ± 1.3 Pedometer steps 12.9 ± 7.4 21. ± 2.4 21.7 ± 2.2 Accurcy (medin) 24.7% 2.4% 6.1% b Rnge (IQR) 68.9 1.8 3.9 7. 2.4 1. Stir scent Actul steps 14.9 ±.8 14.9 ±.8 14.7 ±.9 Pedometer steps 9.9 ± 6. 16. ± 1.9 16.8 ± 2. Accurcy (medin) 23.3% 8.3% 1.7% Rnge (IQR) 61. 3.4 3. 14.7 6.2 22.1 Stir descent Actul steps 14.9 ± 1. 1.2 ± 1.1 14.9 ± 1. Pedometer steps 13. ± 4.4 16.4 ± 2.2 17.7 ± 2.2 b Accurcy (medin).% 6.6% 14.3% b Rnge (IQR) 2. 1.7. 14.3 8.8 28.6 1-Leg hopping Actul steps 1.6 ±.8 1.9 ±.9 1.6 ±.6 Pedometer steps 13. ± 3.4 14.3 ± 2.7 14.1 ± 1.6 Accurcy (medin) 2.% 26.1% 29.6% Rnge (IQR). 36.8 18.2 4.2 22.3 4. 2-Leg hopping Actul steps 1.4 ±.7 1. ±.7 1. ±.8 Pedometer steps 13.2 ± 4.2 14. ± 3. 1.1 ± 3.1 b c 1 1 2 3 1 1 2 6 4 2 2 4 1 1 2 6 4 2 2 4 2 3 2 3 Accurcy (medin) 17.% 3.2% 37.2% Rnge (IQR) 1. 36. 2. 4.7 28.6 47.6 All mesurements expressed s men ± SD unless noted. IQR, interqurtile rnge. Significntly different vs. SC-T2. b Significntly different vs. NL-1. is wrrnted when using spring-levered mechnism type of pedometer with this group. These results could hve importnt implictions for smller clinicl prctice scenrios where dvnced technology such s ccelerometers is not s widely vilble. This study demonstrted tht the piezoelectric pedometers (Piezo nd NL-1) were more ccurte thn the springlevered pedometer in both wlking nd stir climbing tests. However, s seen with other studies, ll pedometers used in this study were inccurte during the hopping evlutions (2). Although OW/OB children typiclly do not spend much of their ctive time engging in vigorous-types of ctivities, this inccurcy is prticulrly importnt to note s PA recommendtions include enggement in dily moderte-tovigorous types of ctivities including weight bering ctivity 3 /week (4). Finlly, the dditionl 1-steps wlking test performed in this study found tht the two piezoelectric pedometers demonstrted improved ccurcy over the longer distnce (1- steps) compred to the 2-step test. It is therefore possible 6 1 1 2 2 3 Figure 1. Blnd-Altmn plots of the difference (pedometer count observer count) vs. observtion for the 2-step test. () SC -T2, (b) NL-1, nd (c) Piezo. Hshed lines represent the men. Dotted lines represent men + 2SD (upper) nd men 2SD (lower). tht the error ssocited with the piezoelectric pedometers during the 2-step test my be reduced with incresing durtion or number of steps nd my thus ccurtely cpture longer durtion ctivities such s wlking to the prk or to school. Strengths This study included vrious types of tests chrcteristic of dily living ctivities nd ws conducted in controlled reserch setting s well s the use of both piezoelectric nd spring-levered pedometers. Unlike tredmill testing tht restricts child s movement, the tests performed in this study permitted for children to wlk t their own pce nd stride, encourging usul displcement nd ccelertion t the hip (13). As seen with other studies (12), this study did not find ny significnt correltions with mesures of diposity (%BF, A/G rtio); only stir scent ws negtively correlted with mesured wist circumference (driven by older boys with highest WC nd pedometer ccurcy). 688 Peditric Reserch Volume 8 Number November 216 Copyright 216 Interntionl Peditric Reserch Foundtion, Inc.
Assessment of pedometer ccurcy in cpturing hbitul types of physicl ctivities in overweight nd obese children Articles 1 d 1 1 1 2 1 1 2 2 2 1 1 2 2 b 1 e 1 1 1 2 1 2 1 1 2 2 c 1 f 1 1 1 2 2 1 1 2 2 Figure 2. Blnd-Altmn plots of the difference (pedometer count observer count) vs. observtion for the stir scent: () SC -T2, (b) NL-1, (c) Piezo nd stir descent: (d) SC -T2, (e) NL-1, nd (f) Piezo tests. Hshed lines represent the men. Dotted lines represent men + 2SD (upper) nd men 2SD (lower). This study incorported stir climbing nd hopping exercises, of which hopping ws considered to be n exmple of moderte-to-vigorous type of ctivity. Including hopping llowed for n evlution of different movements other thn wlking tht my ffect pedometer ccurcy in controlled setting. To decrese bis nd/or error, two observers counted steps nd ech test ws performed twice. The smple size ws firly lrge (n = 6) s it included children between ges 6 nd 12 y nd focused solely on OW/OB individuls (93% of prticipnts being obese). Limittions Although pedometers re simple devices, they re chllenging to use in consistent mnner in children. The tests used in this study were over reltively short time frme which could overestimte the potentil mesurement error, however considering the overll lck of PA performed by OW/OB children, these short intermittent types of ctivity re relistic. Ech pedometer ws worn during its own individul test nd therefore ws not exposed to the exct sme stimulus. Further, multiple speeds were not employed s only self-pced wlking ws performed. Future studies tht reserch childhood obesity nd physicl ctivity re wrrnted to thoroughly exmine differences in pedometer ccurcy with ge. A finl limittion ws we did not test the pedometer units for relibility prior to the study. Conclusion This study suggests tht lthough pedometers re convenient devices for mesuring PA, not ll pedometer technology is ccurte in OW/OB children. Of the three tested in this study, the NL-1 ws the most ccurte pedometer, followed closely by the Piezo, in mesuring wlking nd stir climbing ctivities, which re typicl of n OW/OB child s dily movements. The spring-levered (SC-T2) pedometer ws the most inccurte for ll ctivities mesured. All of the pedometers hd high level of inccurcy when mesuring hopping. This is concern s children s PA recommendtions include vigorous types of PA tht my include hopping movements. Reserchers nd helth cre prctitioners should tke note of the potentil Copyright 216 Interntionl Peditric Reserch Foundtion, Inc. Volume 8 Number November 216 Peditric Reserch 689
Hzell et l. 1 1 d 2 1 1 1 1 1 2 1 1 2 b 1 e 1 1 1 1 1 2 1 1 2 c 1 f 1 8 6 4 2 1 1 1 2 1 1 2 Figure 3. Blnd-Altmn plots of the difference (pedometer count observer count) vs. observtion for the single-leg hops: () SC -T2, (b) NL-1, (c) Piezo nd double-leg hops: (d) SC -T2, (e) NL-1, (f) Piezo tests. Hshed lines represent the men. Dotted lines represent men + 2SD (upper) nd men 2SD (lower). dvntges/disdvntges of pedometers for mesuring PA in OW/OB children nd select pedometer models tht re best suited for this popultion. Future reserch should exmine the use of pedometers in OW/OB children in free-living conditions nd compred them to other objective tools, such s ccelerometers. METHODS Prticipnts A totl of n = 6 children 6 to 12 y of ge (n = 26 boys, n = 34 girls) who were clssified s overweight or obese (OW/OB) ccording to the World Helth Orgniztion BMI cut-off criteri (21) prticipted in the study. Prticipnts were recruited from lrger study (NCT12916) known s the McGill Youth Lifestyle Intervention for Food nd Exercise (MYLIFE) Study (22). Briefly, prticipnts were recruited through public nd privte elementry schools, primry helth cre orgniztions, locl dvertisements, nd word of mouth. The subgroup for the present study ws designed to represent the group, with trget of 4% of the totl prticipnts from the prent study (ctully recruited 43%, 6 of 138). Ethics pprovl ws received through McGill University Fculty of Medicine Institutionl Review Bord. Prticipnts were recruited from Montrél (QC) nd surrounding res. All study visits were crried out t the Mry Emily Clinicl Nutrition Reserch Unit (McGill University, Ste-Anne-de- Bellevue, Québec) nd were offered in English or French. Inclusion criteri included helthy children with no known disese or illness. In ddition to prentl consent, prticipnts provided written informed ssent by reding nd signing n ssent written t the grde 1 level. Anthropometric Mesurements Height nd weight were mesured (in light clothing without shoes) using stdiometer (Sec 214, Hmburg, Germny) nd clibrted blnce-bem scle (Detecto, MO), respectively. An experienced investigtor mesured wist circumference using stndrd mesuring tpe between the lowest rib nd ilic crest t the level of the umbilicus (23). Wist circumference percentiles were determined using the NHANES III dt (24). All nthropometric mesures were mde to the nerest.1 units. Percent body ft (%BF) nd ndroid/gynoid rtio (A/G rtio) were ssessed using fn-bem dul-energy X-ry bsorptiometry (DXA) device (APEX version 13.3:3, Hologic 4A Discovery Series, Bedford, MA). Both %BF nd A/G rtio re vlid prmeters for body composition ssessment in children (2,26). DXA qulity control ws performed throughout the study using the lumbr spine phntom (Hologic #14774), with coefficient of vribility of.% for bone minerl content nd.3% for bone minerl density. Accurcy Tests All tests were performed twice (1 originl nd 1 repet) using ech of three pedometers (3 totl tests): the SC-T2 (Dibeters, Deep River, 69 Peditric Reserch Volume 8 Number November 216 Copyright 216 Interntionl Peditric Reserch Foundtion, Inc.
Assessment of pedometer ccurcy in cpturing hbitul types of physicl ctivities in overweight nd obese children Articles ON, Cnd), NL-1 (New-Lifestyles, Lees Summit, MO) nd Piezo (Dibeters) in rndom order. These three pedometers were chosen in order to test vrying low cost pedometers nd different mechnisms; these were lso chosen s they re redily vilble to the generl public. The SC-T2 functions vi spring-levered horizontl lever rm, while the Piezo functions vi piezoelectric technology. The NL-1 lso uses piezoelectric technology nd hs been previously used in reserch s reltively low cost nd ccurte step counter (12,27,28). Pedometer step-counts were compred to direct observtion by two observers (observer 1 nd observer 2). Pedometers were positioned on the front of ech child s trousers wistbnd t the right hip in line with the foot nd knee (29). Pedometers were identiclly plced one t time; prctice 2 step-test ws used to both count steps while lso observing for correct positioning. Children were encourged to wlk or perform ctivities normlly s they would in the schoolyrd or t the prk for ll three sessions. Different ctivities included wlking (2-step test), stir scent/stir descent, single-leg hop nd double-leg hop. Between ech test, children rested for 1 2 min. The 2-step test hd prticipnts tke 2 self-pced steps (~3 s in durtion) in stright line in the first floor of the reserch fcility. Children were sked to wlk like they would every dy to go to clss, encourging self-pce nd stride, usul displcement nd ccelertion t the hip (13). As the 2-step test hd durtion of ~3 s, 13 children (6 boys, 7 girls) tht were lredy recruited performed 1-step test (~2 min) to simulte longer bout of physicl ctivity. The stir scent hd prticipnts climb set of 14 stirs (~3 s), which would be typicl of stndrd house or stirs in school. Children were instructed to lternte feet, stepping one foot per step nd were permitted to hold the riling if necessry. The stir descent hd prticipnts wlk down the sme set of 14 stirs (~3 s) with the sme instructions s the scent. To mimic free ply types of movement ptterns nd skills, the single-leg hops test hd prticipnts hop from one foot to the other (side-to-side) over verticl line of tpe on the floor ten times (~2 s). The double-leg hops test hs prticipnts hop with both feet together (side-to-side) over the sme line ten times (~2 s). Sttisticl Anlysis Dt ws nlyzed using observer one-step counts s there were no significnt differences from observer 2 for ll tests (P >.284). The men differences between observer 1 nd 2 were less thn.7 counts (9% CI:.16 to.2) for ech test. Dt ws nlyzed using SAS version 9.2 (SAS Institute, Cry, NC); sttisticl significnce ws set t P =.. Normlity testing using Shpiro-Wilk s W sttistic reveled dt ws not norml; therefore, nonprmetric sttistics were used throughout the nlysis. As observtion is the gold stndrd method (3) for counting steps tken (31), pedometer ccurcy ws clculted s: ((pedometer count observed steps)/observed steps *1), where pedometer count re the steps recorded from the pedometer nd observed steps reflect the number of observed steps counted by observers (1,32); the eqution is multiplied by 1 to evlute pedometer ccurcy s percentge. Pedometer ccurcy ws clculted for ll five tests. A score of % represented perfect pedometer count of ctul steps tken, negtive number represented n underestimtion of ctul steps tken, nd positive number represented n overestimtion of ctul steps tken. Differences in pedometer ccurcy, steps observed, nd steps counted for ech test were tested with Friedmn s test (nonprmetric lterntive to one-wy ANOVA with repeted mesures). To determine the level of greement between pedometer nd observer step-counts, Blnd-Altmn plots were creted using GrphPd Prism version.4 (GrphPd Softwre, L Joll, CA) where the difference (pedometer count observed count) ws plotted on the y-xis ginst the verged step-count (pedometer + observed count/2) on the x-xis. In order to determine ssocitions between body composition nd pedometer step-count ccurcy, Spermn correltions were computed between pedometer ccurcy nd ech of: %BF, wist circumference, nd A/G rtio. For body composition prmeters, Wilcoxon-Mnn-Whitney test were performed to determine whether or not the prmeters differed between ge groups. Two ge groups were defined s prt of the lrger MY LIFE Study (i.e., young (6 8 y), older (9 12 y)) (Clinicltrils.org: NCT12916). Dt is presented s medin (interqurtile rnge) unless specified. STATEMENT OF FINANCIAL SUPPORT This study ws funded in prt by the Diry Reserch Cluster (Diry Frmers of Cnd, Agriculture nd Agri-Food Cnd, Cndin Diry Commission). As well, Dr. Weiler is supported by funding from Cnd Reserch Chirs Progm (Montrel, Cnd). Infrstructure support for the DXA ws from the Cndin Foundtion for Innovtion (Montrel, Cnd. Disclosure: The uthors declre no conflict of interest. References 1. Gurnni M, Birken C, Hmilton J. Childhood obesity: cuses, consequences, nd mngement. Peditr Clin North Am 21;62:821 4. 2. Lobstein T, Jckson-Lech R, Moodie ML, et l. Child nd dolescent obesity: prt of bigger picture. Lncet 21;38:21 2. 3. Shields M. Overweight nd obesity mong children nd youth. Helth Rep 26;17:27 42. 4. Trembly MS, Wrburton DE, Jnssen I, et l. New Cndin physicl ctivity guidelines. Appl Physiol Nutr Metb 211;36:36 46.. World Helth Orgniztion. Globl recommendtions on physicl ctivity for helth. Switzerlnd: WHO Press; 21. 6. Colley RC, Jnssen I, Trembly MS. 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Hills AP, Prker AW. Git chrcteristics of obese children. Arch Phys Med Rehbil 1991;72:43 7. 19. Chen KY, Jnz KF, Zhu W, Brycht RJ. Redefining the roles of sensors in objective physicl ctivity monitoring. Med Sci Sports Exerc 212;44(1 Suppl 1):S13 23. 2. Smith JD, Schroeder CA. Assessing pedometer ccurcy while wlking, skipping, glloping, sliding, nd hopping. J Strength Cond Res 28;22:276 82. Copyright 216 Interntionl Peditric Reserch Foundtion, Inc. Volume 8 Number November 216 Peditric Reserch 691
Hzell et l. 21. World Helth Orgniztion. Growth reference 19 yers. 27 (http:// www.who.int/growthref/who27_bmi_for_ge/en/.). 22. Cohen TR, Hzell TJ, Vnstone CA, Plourde H, Rodd CJ, Weiler HA. A fmily-centered lifestyle intervention to improve body composition nd bone mss in overweight nd obese children 6 through 8 yers: rndomized controlled tril study protocol. BMC Public Helth 213;13:383. 23. Rudolf MC, Wlker J, Cole TJ. Wht is the best wy to mesure wist circumference? Int J Peditr Obes 27;2:8 61. 24. Fernández JR, Redden DT, Pietrobelli A, Allison DB. Wist circumference percentiles in ntionlly representtive smples of Africn-Americn, Europen-Americn, nd Mexicn-Americn children nd dolescents. J Peditr 24;14:439 44. 2. Aucouturier J, Meyer M, Thivel D, Tillrdt M, Duché P. Effect of ndroid to gynoid ft rtio on insulin resistnce in obese youth. Arch Peditr Adolesc Med 29;163:826 31. 26. Scheffler C, Obermüller J. Development of ft distribution ptterns in children nd its ssocition with the type of body shpe ssessed by the Metric- Index. Anthropol Anz 212;69:4. 27. Crouter SE, Schneider PL, Krbulut M, Bssett DR Jr. Vlidity of 1 electronic pedometers for mesuring steps, distnce, nd energy cost. Med Sci Sports Exerc 23;3:14 6. 28. Schneider PL, Crouter S, Bssett DR. Pedometer mesures of freeliving physicl ctivity: comprison of 13 models. Med Sci Sports Exerc 24;36:331. 29. Trost SG, McIver KL, Pte RR. Conducting ccelerometer-bsed ctivity ssessments in field-bsed reserch. Med Sci Sports Exerc 2;37(11 Suppl):S31 43. 3. Vnhees L, Lefevre J, Philipperts R, et l. How to ssess physicl ctivity? How to ssess physicl fitness? Eur J Crdiovsc Prev Rehbil 2;12: 12 14. 31. Krouwer JS. Why Blnd-Altmn plots should use X, not (Y+X)/2 when X is reference method. Stt Med 28;27:778 8. 32. Le Msurier GC, Lee SM, Tudor-Locke C. Motion sensor ccurcy under controlled nd free-living conditions. Med Sci Sports Exerc 24;36: 9 1. 692 Peditric Reserch Volume 8 Number November 216 Copyright 216 Interntionl Peditric Reserch Foundtion, Inc.