Characteristics Of Motor Coordination Ability In Children Aged 10-12 Years With Moderate To Severe Mental Retardation

Due to the influence of their own conditions and environment, movement coordination ability of children with Intellectual Disabilities (ID) such as motor control and motor learning ability lag behind the typically development children(TD) seriously. Motor coordination disorder of children with ID has a negative impact to their life style and learning ability. Study showed there is a significant correlation between sports ability and intelligence in children with ID. What is the characteristics of movement coordination ability of children with moderate to severe ID? This article will further explorate on this question:Movement coordination can be divided into the displacement ability and operational skill. According to the above classification, this study selected walking, counter-movement jump, throwing with both hands as test of movement coordination ability. This study integrated the kinematic-biomechanics-dynamic measurement method and synchronous test technology, to characterize movement coordination of children with ID and the characteristics of limb muscle force in different movement phase.Results of gait test showed that in the aspect of kinematics, the parameter-based analysis found significant group differences for cadence, peak ankle dorsiflexion in swing, peak plantar flexion angle and moment, hip range of motion, peak hip flexion in stance and swing, and peak hip flexor moments. In terms of dynamics, the knee joint torque, foot ground reaction force are lower than typically development children, ankle bending angle are less than typically development children. In terms of sEMG, there are several differences between the children with ID and typically development children, mainly has the following several problems:muscle activation sequence is different from those of typically development children, muscle tension is too high. Mainly activated muscle unlike those of typically development children, there is an obvious phenomenon of muscle compensatory.Results of counter-movement jump test showed that individuals without ID jumped higher than their counterparts with ID. Besides the lower take-off velocity, the group with ID demonstrated lower knee joint power, knee joint extension angle and angular velocity and longer braking and propulsion phase compared to the group without ID. Finally, individuals with ID presented lower agonist and higher antagonist EMG activity.Results of throwing test showed the elbow angle of children with ID is significantly higher and shoulder joint angle is significantly lower than TD children. In the process of throwing, shoulder joint angle and elbow joint angle showed the power features of cut shape. Children with ID present lower agonist and higher antagonist EMG activity in uplimb too. In the whole development of throwing sequence,TD children have already reached to the fourth and the fifth stage at the same age of children with ID. But children with ID did not develop a block mode of action. Muscle strength an joint flexibility of children with ID is poor. Movement coordination ability of children with ID only reached to the first stage of the throwing development sequence.In conclusion, when children complete displacement action and operate action, there is significant differences in the action pattern from TD children. The characteristics of coordination ability of children with ID rigidity and small range of joint, lower muscle strength, dysfunction of agonist and antagonist muscle, irregular foot-ground forces. According to the division of the coordinated development, of Bernstein and Newell, TD children of 10-12 years old have already developed to the releasing stage of the degrees of freedom, and the movement pattern of children with ID only reached to the first stage(freezing stage) of development sequence.