# Relationship between Body Composition and Gross Motor Coordination in Six-Year-Old Boys and Girls
## 1 Introduction  
Gross motor coordination (MC) has been a commonly used term to describe the ability to execute accurate, smooth, and controlled body movement via harmonization of the nervous and musculoskeletal systems [1; 2]. In children, MC represents a fundamental movement skill and should be regarded as an important factor of health-related fitness [3; 4]. For instance, there is apparent evidence that MC strongly affects all fitness components except flexibility [5; 6; 7]. Moreover, previous studies [8; 9; 10] demonstrated that motor proficiency is an important factor underlying physical activity in children. In other words, children with a low level of MC are less prone to participate in regular physical activities compared to their motor-competent peers [8]. This is relevant given that the level of physical activity directly affects weight status; thus, a low level of MC may represent a major risk factor for obesity in children [8; 11]. Interestingly, the relationship between MC and morphological characteristics has not been extensively studied in children younger than 7-8 years of age [3], although the current literature suggests that this link tends to vary according to specific age periods [1; 5; 12; 13]. Particularly, [PERSON] and coworkers [1] found that the correlation between body mass index (BMI) and MC is moderately negative (r = 0.44-0.48) in 11-year-old boys and girls, yet non-significant (r = 0.16-0.18) during the preschool period. Neither [PERSON] et al. [12] nor [PERSON] et al. [14] observed a significant association between BMI and MC in preschool children. Still, [PERSON] et al. [14] found that both skinfold thickness and waist circumference, rather than BMI, better predict performance in the jumping sideways test (used to evaluate MC). Note that the majority of previous research utilized BMI as a proxy for weight status despite the fact that this method has some important fallacies, since BMI cannot discriminate between fat mass and lean body mass, and excess fat mass may conceal lean mass deficits [15, 16]. In that regard, body composition assessment (i.e., muscle percent and mass, fat percent and mass, fat-free mass, percent of body water, etc.) has been advocated for as it provides additional insights about morphological status [17]. Unfortunately, although weight-related studies in adults commonly use body composition assessment, it is still an evolving field, particularly in children [16]. Only [PERSON] et al. [18] and [PERSON] et al. [13] evaluated MC and some of the body composition measures in preschool boys and girls. [PERSON] et al. [13] investigated the relationship between fundamental motor skills (locomotor and object control skills) and body composition (fat mass and percent, as well as fat-free mass) in 3-10-year-old children. They found that the 23% of variance in locomotor skills (i.e., run, gallop, hop, leap, jump, and slide) may be explained by the body composition measures, although only fat-free mass contributed significantly to the regression model. [PERSON] et al. [18] noted that a level of MC (evaluated by the backward movement test) strongly predicts performance in various fitness tests (for static and dynamic strength, as well as for agility), and that \"general motor fitness\" (expressed as the summed performance of MC, strength, agility, and flexibility tests) moderately (r = 0.47-0.57) correlate with the percent of body fat. Considering the above, it seems that body composition assessment may shed a light on the relationship between weight status and MC in preschool children. Unfortunately, the abovementioned studies [13, 18] utilized motor test batteries which did not exclusively address MC and rather included several assessments of physical fitness [19]; thus, the relationship between MC and body composition in the preschool population cannot be defined.