Back to school after lockdown: The effect of COVID-19 restrictions on children’s device-based physical activity metrics

Background:The coronavirus disease-2019(COVID-19) pandemic and national lockdowns took away opportunities for children to be physically active.This study aimed to determine the effect of the COVID-19 lockdown on accelerometer-assessed physical activity(PA) in children in Wales.Methods:Eight hundred participants(8-18 years old),stratified by sex,age,and socio-economic status,wore Axivity AX3 accelerometers for7 days in February 2021,during the lockdown,and in May 2021,while in school.Raw accelerometer data were processed in R-package GGIR,and cut-point data,average acceleration(AvAcc),intensity gradient,and the acceleration above which the most active X minutes are accumulated(MX) metrics were extracted.Linear mixed models were used to assess the influence of time-point,sex,age,and socioeconomic status(SES) on PA.Results:During lockdown,moderate-to-vigorous PA was 38.4±24.3 min/day;sedentary time was 849.4±196.6 min/day;mean± SD.PA levels increased significantly upon return to school(all variables p <0.001).While there were no sex differences during lockdown(p=0.233),girls engaged in significantly less moderate-to-vigorous PA than boys once back in school(p <0.001).Furthermore,boys had more favorable intensity profiles than girls(intensity gradient:p <0.001),regardless of time-point.PA levels decreased with age at both time-points;upper secondary school girls were the least active group,with an average M30 of 195.2 mg(while in school).Conclusion:The lockdown affected boys more than girls,as reflected by the disappearance of the typical sex difference in PA levels during lockdown,although these were re-established on return to school.Upper secondary school(especially girls) might need specific COVID-recovery intervention.