# Relationship between Body Composition and Gross Motor Coordination in Six-Year-Old Boys and Girls
## 4 Discussion
A higher level of strength mastery and the presence of explosive movements earlier in their activities led to a better development of basic motor skills, which has been implied to improve their dexterity, or better said, the mechanism for structuring movement, which manifests itself in coordination. Today, this is not the case due to the large presence of disturbing and uncontrolled factors in children's development, such as mobile phones and various computer games, among others, to which boys are more prone than girls, and thus the differences in motor competence today has been reduced to a minimum or does not exist. Conversely, with respect to body composition, several dissimilarities between boys and girls were observed in this study. Specifically, boys were taller, with greater muscle and protein mass, and total body water levels. Inversely, greater mineral mass was observed in girls. Previously, it was postulated that sex differences in body composition at the preschool age should be considered negligible [34], preferentially due to the fact that marked differences in sex hormone levels do not occur before puberty [35]. However, this theory has been contested since recent studies noted significant sex differences in lean muscle mass, even at the ages of 3 and 10 years old [13; 36; 35; 37]. Particularly, both [PERSON] [35] and [PERSON] et al. [13] found that 6-year-old boys have about 5% greater muscle mass than female peers, which corresponds well with our results (Table 1). Thus, our findings further support the idea that sex dimorphism is present at an early age, before puberty [13; 35], and that other factors besides sex hormone accretion may be responsible for sex differences in body composition. Contrary to our hypothesis, the present results revealed that neither body composition nor BMI was significantly related to the scores obtained on the OCB test, suggesting that morphological features have a negligible influence on MC. Concerning BMI, our findings are consistent with previous studies [1; 12; 14] in which BMI did not correlate with MC in 6-year-old children. On the other hand, our results do not support previous reports [13; 14; 38] that body composition status significantly affects MC (and vice versa) in children. The possible reason for these discrepancies may be twofold, being related to the sample characteristics and methodological approach to evaluate MC. In the current study, the sample included less than 5% of excessive-weight (overweight and obese; based on BMI) children, whereas in other studies [13; 14; 38] the percentage of excessive-weighted children was quite larger (i.e., 15-20%). This is relevant, since a low level of motor competence may indirectly affect obesity status in children through reduced physical activity [8; 11]. Hence, it is quite possible that a link between some morphological factors (BMI, skinfold thickness, body fat mass, etc.) and MC may be present in the overweight and obese population; however, this association is not apparent in normal and underweight children, as our results suggest. Moreover, note that the MC is a multidimensional construct and there are different aspects of MC (i.e., coordination in rhythm, speed performance in complex motor tasks, etc. ), which can be assessed by various motor tests [2; 39]. For instance, [PERSON] et al. [13] utilized the Test of Gross Motor Development (TGMD), which includes skills such as running, jumping, sliding, etc. Although this test primarily evaluates MC, it is partially related to physical fitness (presumably strength and agility) [19]; hence, it is not surprising why [13] identified muscle mass as an important predictor of TGMD scores. In the current study, we applied the OCB test, which is a reliable tool for assessing MC through movement structure factors [22; 40] and requires a significant level of perceptual skills [40] since the motion is performedin a backward direction and also includes movements such as climbing and crawling.