ABSTRACT Background Fundamental motor skills (FMS) are critical for child health and development and are commonly assessed using either process‐oriented assessment or product‐oriented assessments. Although previous studies have examined cross‐sectional relationships between these assessments, little is known about their longitudinal and reciprocal associations. Therefore, the purpose of this study was to examine the longitudinal and reciprocal relationships of two FMS assessments (Test of Gross Motor Development–3rd edition TGMD‐3 and Movement Assessment Battery for Children–2nd edition MABC‐2) in preschool‐age children. Methods A diverse sample of 117 children ( Mage = 3.4 years) completed both assessments at baseline, with 72 completing follow‐up. Spearman correlations were conducted to assess cross‐sectional relationships, and linear mixed‐effects models (LMMs) were used to model longitudinal associations, adjusting for race, BMI, SES, screen time, moderate‐to‐vigorous physical activity (MVPA) and childcare centre. Results At baseline, significant positive associations were found between TGMD‐3 and MABC‐2 total and subscale percentile scores ( r s = 0.20–0.41, all p 0.05). LMMs revealed that MABC‐2 scores at baseline significantly predicted TGMD‐3 scores at baseline ( β = 0.57), explaining 14.2% of the variance, but not at follow‐up ( β = −0.02). Each assessment significantly predicted its own follow‐up performance: TGMD‐3 ( β = 0.42; 27% variance explained) and MABC‐2 ( β = 0.52; 20.3% variance explained). Conclusions These findings suggest that TGMD‐3 and MABC‐2 measure distinct constructs of FMS performance that may diverge as children develop. The study highlights the importance of selecting FMS assessments based on the developmental stage, purpose and context and emphasizes the need for longitudinal research to better understand how early FMS influence long‐term outcomes. Trial Registration ClinicalTrials.gov ID: NCT02751788
Webster et al. (Thu,) studied this question.