Introduction:
Motor development of children is a major indicator of their physical development. Children’s motor skills show a constant decrease. The most important criteria used to assess the level of motor development include speed, jumping skills, muscle strength and endurance. These criteria are investigated by physical fitness tests, such as sprinting, long jumping, palant ball throwing, medicine ball throwing and long-distance running. These tests are an excellent tool to be used not only by researchers but also by teachers, doctors and parents.

Study objective.:
The aim of the study was to present the criteria of motor development of primary school children.

Brief description of the state of the art.:
The state of motor development of primary school children is the major manifestation of their physical fitness. Currently, the motor development of children is relatively low, which arouses concern among experts in this field. Human motor coordination can be divided into gross motor skills which involve the whole body movement, and fine motor skills allowing precise movements. The condition of gross motor coordination in children is measured by means of such criteria as speed, jumping skills, muscle strength and endurance, which are assessed by physical fitness tests. Speed is evaluated by sprinting, jumping skills by the long jump, coordination by palant ball throwing, muscle strength by medicine ball throwing and endurance by long-distance running (500m). The above tests allow diagnosis and compensation of deficiencies in children, or development of the features that may facilitate sports achievements.

Conclusions:
Proper performance of the physical fitness tests that investigate motor development of primary school children allows not only for the assessment of their current potential, but also progression or regression in the motor capacities of Polish children over the years.