**1. Introduction**

Physical inactivity represents a global health problem and is related to higher risk for morbidity and mortality [1]. Evidence has shown that inactive children are exposed to increased cardiometabolic risk [2,3]. Physical activity in childhood and adolescence is important to attain appropriate bone mineral content [4]. Although the influence of physical activity as a measure of movement quantity has been examined extensively, very few studies have examined the movement quality through the sensitive period of adolescence. However, these studies pointed out the importance of proper development of the optimal functional movement patterns through adolescence [5–16]. Since functional movement is considered the clinical measure of movement quality [17,18] and potentially the essential component for optimal motor development, the investigation of the optimal functional movement in childhood and adolescence needs special attention.

Functional movement can be defined as optimal flexibility of the soft tissue, mobility of the joints, and neuromuscular control of the body regions involved in the particular motor task [17,18]. On the other hand, dysfunctional movement (DFM) is characterized by movement compensations evident across the kinematic chain with a significant loss in mobility, observed asymmetry, and poor movement control of the particular motor task [17,18]. The importance of functional movement patterns has been studied widely [19–21] and they represent the basic foundation for the execution of more complex motor tasks [17,18]. A higher incidence of musculoskeletal injury has been associated with DFM patterns among the athletic population [19–21], while some studies reported the opposite [22–24]. The most common diagnostic tool to assess functional movement is Functional Movement Screen (FMSTM) which evaluates mobility and stability in seven functional movement patterns: deep squat, hurdle step, inline lunge, shoulder mobility, active straight leg raise (ASLR), trunk stability push-up, and rotary stability [17,18]. FMSTM can detect movement asymmetries if a difference between the right and left side of the uni/contralateral movement patterns is observed [17,18]. What is more, the literature shows that movement asymmetries detected via FMSTM have been associated with higher injury risk [5] which could possibly contribute to the development of musculoskeletal deformities in later life.

The presence of the DFM patterns and movement asymmetries in childhood could facilitate postural abnormalities in the period of mid-adolescence. Indeed, evidence shows that neuromuscular control of the movement is not properly developed by the time of the adolescent period [25]. Therefore, identifying DFM patterns and movement asymmetries in this period of a child's growth needs special attention. Still, only a few studies have investigated sex differences in functional movement in an average or athletic adolescent population. These studies sugges<sup>t</sup> that, in both the general and athletic population, girls exhibit better functional movement compared to boys [8–10,12,15,16], while some studies reported opposite or no difference between sexes [6,11,13,14]. However, these were either small-scale studies [11–13] or included only active adolescents [5–10,14] or adolescents with overweight/obesity [7] and did not analyze movement asymmetries.

However, to this date, none of the studies have investigated sex differences in functional movement and movement asymmetries in a large representative sample of school-aged mid-adolescents. Therefore, the purpose of this study was to examine sex dimorphism in functional movement patterns and movement asymmetries in the representative sample of mid-adolescents.

### **2. Materials and Methods**
