In all children and adolescents, we found that activity composition was significantly associated with DC overall, process, and time scores. Among primary school participants, activity composition was associated with time score only, while in secondary school participants it was associated with overall, process, and product scores. Overall, relative to other activity behaviours, MVPA had the greatest association with motor competence outcomes. The largest positive estimated differences in motor competence outcomes occurred when MVPA hypothetically replaced LPA.
Congruent with previous systematic review evidence supporting positive isolated associations between PA levels and motor competence [2, 7], these findings reinforce the key role of MVPA for children’s and adolescents’ motor competence. They also support previous compositional studies examining associations between activity behaviours and motor competence in preschool and primary school children [10, 11]. These showed that reallocating time to MVPA, elicited the largest positive estimated difference in overall motor competence scores [10, 11]. However, contrary to our findings, another compositional study found that relocating time to LPA or sleep, at the expense of ST, was associated with positive differences in motor competence in primary school children from a low socioeconomic status area . Nevertheless, despite one recent systematic review revealing that most previous studies did not find a significant prospective association between PA and subsequent motor competence , our findings, as well as others [10, 11] provide cross-sectional evidence that MVPA, relative to other behaviours is associated with motor competence outcomes. Potential reasons for the difference between our findings and studies included within the systematic review evidence , are that there were differences in the statistical approach (i.e., time-use compositional analysis), differences in the study measures within our study (e.g., a hybrid measure of motor competence, wrist-worn devices), differences in statistical power, or some combination of these factors.
Among girls, reallocating time to sleep was associated with negative estimated differences and increasing MVPA or LPA was associated with positive differences in DC scores. These findings may reflect that, while sleep plays an important contribution towards healthy 24-h activity behaviours , more time spent in sleep is likely not to play a key role in developing motor competence given that it does not provide appropriately challenging opportunities to practice and develop movement skill competency [2,3,4,5, 8]. For boys, reallocating time spent to MVPA was associated with positive estimated differences, whereas, increasing time in LPA was associated with negative differences in DC scores. These negative estimated differences may be due to the types of activities that are associated with LPA (e.g., slow walking) and only more intense activities association with MVPA may benefit the development of motor competence [7, 10]. Overall, MVPA had the greatest associations with motor competence outcomes in both boys and girls across school type. The largest positive and negative estimated differences in motor competence outcomes occurred, when MVPA hypothetically replaced LPA or sleep and when LPA or sleep hypothetically replaced MVPA, respectively. Again, consistent with previous systematic reviews showing various associations between PA and motor competence in boys and girls [2, 7], these findings further emphasise the key role of MVPA for both sexes’ motor competence. Notably, no other compositional analysis study [10,11,12,13] has investigated sex-stratified associations between activity composition and motor competence outcomes. Thus, we provide new evidence for the contention that time spent in MVPA (relative to other activities) is positively associated with motor competence outcomes irrespective of sex, which could guide the focus of motor competence interventions. For example, practical approaches to increase MVPA are advocated (e.g., active classroom breaks, physically active learning, outdoor play, high quality PE, structured sport/exercise, family activities) [28, 29].
Using a hybrid-based assessment [1, 6], our findings represent a holistic view on the association between activity behaviours and motor competence . The largest estimated increases in overall, process, and time scores were observed when MVPA hypothetically replaced LPA or sleep, whilst the largest estimated decreases occurred when LPA hypothetically replaced MVPA. Further, the largest estimated increases in product score were observed when LPA hypothetically replaced MVPA, and greatest decreases were when sleep or LPA hypothetically replaced MVPA. Previous research utilising compositional data analysis has only considered motor competence outcomes using a process-based approach [10,11,12,13], and whilst positive differences in motor competence were found [10,11,12,13], the current study provides further evidence that associations exist between MVPA (relative to other activity behaviours) and both process- and product-based motor competence outcomes. Thus, irrespective of a process- or product-based assessment approach used to assess motor competence, our findings suggest that enabling engagement in MVPA is beneficial for motor competence in all children and adolescents.
Interestingly, the estimated differences in motor competence outcomes were greatest when MVPA was hypothetically replaced by sleep or LPA, rather than when MVPA hypothetically replaced these behaviours. These asymmetrical associated differences in physical outcomes involving MVPA have previously been observed in youth studies considering adiposity and fitness . Furthermore, some studies have reported negative associations between ST and motor competence [7, 31]. We found that ST, relative to the other activity behaviours was not significantly associated with any of the motor competence outcomes. However, in Table 2, a negative association was present for the full sample, but inconsistent in the sub-group analyses, therefore, the lack of consistent significant association may be a combination of low statistical power and potential misclassification of LPA as ST. Nonetheless, further studies on the potential negative effects of ST on the development of motor competence are warranted.
In line with the recent review evidence reporting that most previous studies did not find a significant prospective association between PA and subsequent motor competence , it is noteworthy, that there were no significant associations observed between the activity compositions and numerous DC scores (Table 2). These non-significant associations between activity behaviours and outcomes require further investigation, but it may mean that other associated factors better estimate motor competence outcomes [3, 4, 8]. Therefore, children/adolescents may benefit from other interventions such as appropriately challenging opportunities, instruction, and feedback during activities, to complement increases in MVPA, as opposed to just time reallocated to MVPA [2,3,4,5, 8].
Strengths of this study included wrist-worn device-based assessment of 24-h activity behaviours and use of compositional data analysis to examine how the full activity composition related to motor competence outcomes. Moreover, this is the first compositional analysis study to investigate motor competence outcomes, measured using a hybrid-based assessment that evaluates proficiency in fundamental, combined, and complex movement skills, with a large enough sample size to stratify the data by sex and school type.
However, the study is not without limitations. The cross-sectional design precludes any claims of causal inferences and directionality between the activity composition and motor competence outcomes. There is also longitudinal evidence for a motor competence to subsequent PA association, thus there is a possibility of reverse causality or bi-directional associations [2, 3, 5]. We also had an imbalanced sample of primary and secondary school participants, who were relatively homogenous in terms of area-level socioeconomic status, which limits generalisability. Therefore, future studies should extend this work across the full spectrum of area-level socioeconomic status/neighbourhood deprivation. Finally, although the activity behaviours were defined using validated wrist-worn acceleration cut-points for LPA and MVPA, these reflect absolute intensity rather than relative intensity for each participant (intensity related to individual energy expenditure instead of absolute energy expenditures, and consideration is made towards age-, sex-, and fitness-related differences in the intensities of effort during PA ), and therefore, may have resulted in some misclassification of activity behaviours. Cut-point free accelerometer metrics, or machine learning to label activity behaviours and intensities, could be used in future studies to potentially address this issue.