Background
The closing of schools and sports clubs during the COVID-19 lockdown raised questions about the possible impact on children’s motor skill development. Therefore, we compared motor skill development over a one-year period among four different cohorts of primary school children of which two experienced no lockdowns during the study period (control cohorts) and two cohorts experienced one or two lockdowns during the study period (lockdown cohorts).

Methods
A total of 992 children from 9 primary schools in Amsterdam (the Netherlands) participated in this study (age 5 – 7; 47.5% boys, 52.5% girls). Their motor skill competence was assessed twice, first in grade 3 (T1) and thereafter in grade 4 (T2). Children in control group 1 and lockdown group 1 were assessed a third time after two years (T3). Motor skill competence was assessed using the 4-Skills Test, which includes 4 components of motor skill: jumping force (locomotion), jumping coordination (coordination), bouncing ball (object control) and standing still (stability). Mixed factorial ANOVA’s were used to analyse our data.

Results
No significant differences in motor skill development over the study period between the lockdown groups and control groups (p > 0.05) were found, but a difference was found between the two lockdown groups: lockdown group 2 developed significantly better than lockdown group 1 (p = 0.008). While socioeconomic status was an effect modifier, sex and motor ability did not modify the effects of the lockdowns.

Conclusions
The COVID-19 lockdowns in the Netherlands did not negatively affect motor skill development of young children in our study. Due to the complexity of the factors related to the pandemic lockdowns and the dynamic systems involved in motor skill development of children, caution must be taken with drawing general conclusions. Therefore, children’s motor skill development should be closely monitored in the upcoming years and attention should be paid to individual differences.