Abstract: Objective: To integrate the basic movement skills that young children should master into a set of rhythmic physical activities and then compare the effect of the activities with that of existing ones through analyzing the change in young children's lower limb iEMG. Methods: 38 children were randomly divided into the experimental group and the control group by age. The experimental group participated in the designed rhythmic physical activities from Monday to Friday, 20-30 minutes a day, and the motor intervention lasted for one year, while the control group participated in only common rhythmic activities. Before and after the intervention, The electromyographic activities during children's slide steps were recorded and assessed by the iEMG and the iEMG contribution of the main muscles of lower limbs. Results: (1) After the intervention, the general change in the lower limb iEMG contribution in both groups lies in the rise of agonistic muscle iEMG contribution and the drop of antagonistic muscle iEMG contribution; (2) After the intervention, in the first phase of slide steps, the iEMG contribution of Gas (right) in the experimental group was significantly higher than that of the control group while the iEMG contribution of RF(right) in the experimental group was significantly lower than that of the control group; the iEMG contribution of Gas (left) in the experimental group of 5-year-old children was significantly higher than that of the control group while the iEMG contribution of BF(left) in the experimental group was significantly lower than that of the control group. Conclusion: After the intervention, both groups presented obvious improvement in slide step movement, and showed better control over the coordinated movement of agonistic muscle and antagonistic muscle. The change of lower limb iEMG contribution in the experimental group was better than that of the control group on the whole. This shows that the rhythmic physical activities based on motor development are better than common physical activities in improving muscle discharge of lower limbs during slide steps and in promoting the development of young children's slide steps.

Key words: Young Children, Electromyographic Activities of Lower Limbs, Rhythmic Physical Activities, iEMG Contribution, Motor Development