Changing sensitive period in the development of Chinese students' physical fitness from the start of the Reform-and-Opening-Up policy

Sensitive period of physical-fitness development in school students in China from the start of the Reform-and-Opening-Up period was examined, to provide big data support for further improvements in student physical quality．Temporal and spatial characteristics of the changes in sensitive period of physical fitness development were subject to link comparison analogy and GIS spatial visualization．The beginning of sensitive period was found to have started earlier by 1-2 years, but ended later by 1-2 years．The sensitive period of strength quality in male students peaked at ages of 7-8 and 10-15 years but in female-students peaked at age 7-11 years．The sensitive period of endurance quality was found to peak at multiple discontinuous ages, with constant total time and alternating cycles．The sensitive period of speed quality was found to be at ages of 7-9 years and of 11-15 years in boys, but 7-11 years in girls．Sensitive period of flexibility quality showed gender and regional (urban versus rural) variations, with continuous negative growth in early school age (7-12 years)．Boys showed a single peak at 12-16 years, urban girls showed double peaks at 12-16 and 18-19 years but rural girls showed a single peak at 11-16 years．Decrease in strength, endurance and speed quality in Chinese students was noted, the magnitude was larger in girls than in boys for strength and speed, but markedly larger in boys than girls for endurance．Flexibility decreased in boys but increased in girls．Physical quality showed significant regional variations．It is concluded that the physical fitness sensitive period in Chinese students has expanded and has been prolonged．Significant gender differences were found in changes in physical fitness sensitivity period．The sensitive period for strength and speed in boys is 3 years longer than in girls, and the sensitive period of flexibility in girls is 2 years longer than in boys．The sensitive period of endurance covers the complete development period, suggesting that this quality has greater plasticity．Significant regional differences are present in changes in physical quality in Chinese students．Therefore emphasis of physical education curriculum and sports intervention in different regions should be adjusted and constructed accordingly．