Methodology Study On Monitoring Energy Expenditure Of Common Physical Activity In11-14Year-old Adolescents

PurposeTo research energy expenditure and to explode influence factor aboutenergy expenditure of the rest and command physical activity for11～14years old adolescents using the Cosmed K4b2portable indirect calorimetrysystem.Base on calibration method of the Indirect Calorimetry (Cosmed K4b2),we attempt to establish and verify physical activity energy expenditurepredictive equation of triaxial accelerometer (ActiGraph GT3X) applying to11～14yr adolescentsWe validate the validation and accuracy of the energy expenditurepredictive equation based on Actiheart Child: Group Act/Group HR bycomparing with the calibration method of the Indirect Calorimetry (CosmedK4b2).We establish the cut-points of activity counts, HR and HR%todistinguish the exercise intensity, aiming to evaluate the common physicalactivity lever of adolescents in future.MethodsRest and nine activities energy cost including Third Series of NationalBroadcast Gymnastics for Middle School Students (Flourishing Youth), ropeskipping for one minute and walking/running at the speed of3～8km/h on atreadmill were monitored in120Junior middle school students,11～14yr,subjects need wear simultaneously the portable indirect calorimetry system(Cosmed K4b2), during the whole experiment.The8011–14yr Junior middle school students were random divide toexperimental group (n=60) and validation group (n=20) by gender and age,and finished the upper nine common activities. Predictive energyexpenditure equation were established by stepwise regression analysisbasing on measured value of K4b2is dependent variable and AC, age,gender, height, mass were independent variable. We determine the ACcut-points of vertical axis, VM2and VM3for low, moderate, hard and veryhard excise intensity by the Youden value of ROC curve.The samples are66Junior middle school students age11–14yr andrequired to finish the upper rest and nine common physical activityexperiments. The research aims to verify the veracity and accuracy ofActiheart predictive equation (Child: Group Act/Group HR) by calibrationmethod of indirect calorimetry (Cosmed K4b2). Under areas of ROC curvewere using to assessment the classifying ability of HR and HR%for exciseintensity. ROC curve were using to evaluate the dividing ability of HR andHR%, and to conduct the cut-points of HR and HR%for various sportintensity.Results1These data demonstrate that EE at rest, estimated as1.0MET(recommended value3.5ml/min/kg) in adults, is higher in children and young adolescents than in adults. The highest REE were found in theyounger children and in those at an earlier stage of physical development(lower developmental stage); the gender and age difference of the REE onlyshow in the lower developmental stage.2The age element dose not effect significantly the common physicalactivity energy expenditure (relative oxygen uptake, AEE, etc); the gendereffects minor the common physical activity energy expenditure; thedevelopment stage of puberty is the significant influence factors to thewalking/running energy expenditure; the degree of obese impactssignificantly the energy expenditure of the common physical activity.3The Third Series of National Broadcast Gymnastics for Middle SchoolStudents (Flourishing Youth) and the walking at speed4km/h,5km/h,6km/hare moderate PA, and METs values are4.0、3.0、3.6、4.6, respectively; therunning at7km/h and8km/h speed are hard PA and METs values are6.3、6.9,respectively; the walking at very slow pace belongs to low PA (METs=2.6);the best-effort rope skipping for one minute is very hard PA (METs=14.0).4The index of METs isn’t influenced significantly by the effect factors ofage, gender, development stage, body mass, etc.5Vertical axis activity count was priority to the stand posture daily physicalactivity and its variation trend is similar with that of VM2and VM3.6The researcher based on dependent variable that is measured value EE orAEE mean by K4b2and the independent variable that (ACxis1、ACxis2、ACxis3)/VM2/VM3measured by GT3X acquainted six predictive energyexpenditure equations. The six predictive energy expenditure equations arevalid by stepwise regression method and apply to assess stand postureenergy expenditure for adolescents(11-14yr). The fourth， fifth and sixthpredictive equations show higher accuracy (absolute error=0.57～0.65kcal/min; relative error=9.14～13.70%； r=0.591～0.700， P<0.01) forevaluating various activity types.7Actiheart child group energy expenditure predictive equation can validlypredict the common physical exercises EE for11～14yr adolescents and thepredictive accuracy are better than Actiheart RA and Actiheart HR, butshow poor predict veracity in sedentary activity(absoluteerror=1.57kcal/min； relative error=95.61%； r=0.154， P>0.05), pure jumpaction for short time (absolute error=5.20kcal/min； relative error=22.52%；r=0.736， P<0.001） and walking at dead slow speed(absoluteerror=0.55kcal/min； relative error=23.09%； r=0.658， P<0.001). TheActiheart HR predictive equation can valid assesses the sedentary activity.8The Actiheart predictive equation based on RA and HR can valid forecastthe EE of various the daily integrated activity(absolute error=0.55～0.98kcal/min；relative error=9.91～12.31%；r=0.832～0.854，P<0.001), butcannot estimate validly the physical activity that AC equal proximity to0,for example sedentary activity.9HR, HR%and AC were the valid index to divide the exercise intensity, HR cut-points for3METs,6METs, and9METs were125,159,172beat/minrespectively; HR%cut-points for3METs,6METs, and9METs were54.75%、97.16%、118.79%; AC cut-points of vertical axis for3METs,6METs, and9METs were2151,4935,9600counts/min; VM2and VM3for3METs,6METs, and9METs were respectively3761and3783,6009and6169,9900and10296counts/min.Conclusions1METs is the perfect indicator to evaluate the physical activity intensity;the METs values of activity compendium for adults were not fit theadolescents.2The energy expenditure predictive equation for adults were not apply toadolescents; the equations (Y=-0.657+0.10522*W+5.06548E-4*ACxis1、Y=-1.579+0.10531*W+6.54427E-4*VM2�'�Y=-1.471+0.10440*W+6.15209E-4*VM3)were valid to estimate adolescents (11-14y)energyexpenditure concluding the daily activity type, the walk-run-jump activitytype, the irregular activity type and the walk-run activity type.3The predictive equation of Actiheart child group energy expenditure canpredict effectively the energy expenditure of the daily activity type and theapparatus daily common physical exercise, but the accuracy of the equationis poor to evaluate the energy cost of sedentary activity, pure jump actionfor short time and walking at dead slow speed.4The researcher can apply the HR cut-points, the HR%cut-points and theAC cut-points of uniaxial, biaxial, triaxial to distinguish the low, moderate,hard PA during monitoring the physical activity level for11-14year-oldadolescents.