Abstract: Objective To analyze the physical fitness monitoring results of different body fat and muscle mass in children aged 3 to 6 years old, and to understand the influence of body fat and muscle mass changes on physical development level. Methods Using random cluster sampling, 573 children aged 3 to 6 from four township kindergartens in Fangshan District were selected for monitoring of body morphology and physical fitness indicators using bioelectrical impedance analysis, and variance analysis was conducted. Results There were statistically significant differences in the physical fitness monitoring quality indexes of different body fat and muscle mass in children aged 3 to 6 years old: grip strength, standing long jump, continuous jump with both feet, 15-meter obstacle course, and balance beam (P<0.05). With different degrees of increase in body fat and muscle mass, the trends of increasing or decreasing of different physical quality indexes were different. Conclusion With the increase of body fat in a certain range, it is beneficial to the monitoring results of physical quality indexes: grip strength, 15-meter obstacle course, standing long jump, continuous jump with both feet, and balance beam. With the increase of body muscle mass, the monitoring results of physical quality indexes: grip strength, standing long jump show an increasing trend.

Key words: children, body composition, physical development status