## 4 Discussion
### The Associations Between MC and PFI in Aordance with FMR  
Studies assessing body weight status with MC and PFI show that parameters based on fat accumulation--BMI and WC values--are negatively correlated with PFI and MC [4, 6, 38]. Our results align with previous findings, and add to the research by showing that the association between MC and PFI is positive despite the FMR.  
There is strong evidence for a positive association between MC and PF, specifically musculoskeletal fitness (strength) and cardiorespiratory fitness (endurance) [39]. This is because mastery of MC in a vigorous physical activity context (eg. sport) requires a high level of PF, including endurance (CRF), strength (UBMS, LBMS), and speed-agility [40]. The relative importance of these physical qualities depends on the skills (locomotion and control skills) involved in each particular action. Considering that MC is a complex parameter, defined as the sum of skills required to adapt to an environment, [PERSON] et al. [41] showed that healthy weight status is related to only certain MC skills. Children with a higher fat mass than muscle mass could face more difficulties with this functional movement. For example, excessive fat mass might be a morphological constraint hindering efficient locomotor performance because it makes it difficult to transport the body through space. On the other hand, object manipulation performance might not be significantly predicted through body composition when it is not performed simultaneously with locomotion skills. [PERSON] et al. [4] state that the development of motor competence is linked directly to neuromuscular function and physiological adaptations, and is indirectly conditioned via physical activity participation and other factors.  
In this way, children with mastery in MC could have more muscle mass and better muscular function (biomechanics and metabolic), which may support their skeletal structures and regulate the intensive crosstalk between muscle, bone and fat metabolism through myokines, osteoblasts and adipocytes [24], implying increases in PFI and metabolic health parameters. This is consistent with our evidence, which shows that MC is positively associated with PFI independently of the FMR level, and that children with higher FMRs show lower levels of MC and PFI.  
The abovementioned results may suggest another paradigm based on the FMR. In our proposal, the role of skeletal muscle contraction is a determining factor regarding increasing physical fitness and health, because of the production of myokines [29]. Skeletal muscle is recognized as a highly energy-demanding tissue, significantly contributing to the basal metabolic rate. Enhancing muscular fitness may indicate increases in skeletal muscle mass, improvements in muscle metabolic efficiency (such as enhanced lipid oxidation and glucose transport capacity), or a combination of both, leading to higher total daily energy expenditure [42].  
These results suggest that improving motor competence could be a regulator of body composition. The underlying explanations could be related to (a) the improvement in the skeletal muscle's efficiency (metabolic) and efficacy (neuromuscular), and (b) the mastery of motor skills, which will provide an individual the opportunity to participate in moderate and vigorous physical activity contexts that are highly metabolically demanding.