Introduction and objectives:
Motor and cognitive development of children with Down syndrome (DS) is delayed and inharmonic. Neuro–muscular abnormalities, such as hypotonia, retained primary reflexes, and slow performance of volitional reaction, result in difficulties with body balance. The aim of the presented study is to assess the global motor functions and body balance of children with DS in relation to age and mental development.

Material and Methods:
The study group consisted of 79 children with DS (42 boys, 37 girls), average age 6 years and 3 months ± 4 years and 6 months. Participants were divided according to age range into 3 groups: <3 years old, 3 – 6 years old, >6 years old. Children were assessed using Gross Motor Function Measure-88 (GMFM-88) and Paediatric Balance Scale (PBS). Psychological diagnosis served to determine the degree of mental development using the Brunet–Lezine Scale for children younger than 3 years old, and the Wechsler Intelligence Scale for Children (WISC) for those who are older than 3 years. Nine children in research group had not been diagnosed by psychologists, which is the reason why the analysis referring to mental development was performed in 70 children (34 girls, 36 boys), with an average age of 4 years and 6 months.

Results:
GMFM–88 scores were significantly lower in children with moderate psychomotor delay than in children with mild psychomotor delay, or normally developed children, p=0.043. GMFM-88 scores in children with profound mental impairment were lower than in children with mild or moderate mental impairment. There was a statistical significant correlation between GMFM-88 scores and the PBS scores, r= 0.7, p<0.0001.

Conclusions:
Motor development of children with Down syndrome from towns and villages in the Greater Poland region is associated with cognitive development, especially in the first three years of life, with the balance functions being closely related to motor skills.