The sensitive period of sports quality development means that each kind of sports quality develops faster at certain ages on the basis of the natural growth and development of children and adolescents, showing the best period of development. The sensitive period of quality development is an important basis for athletes to select materials. Physical fitness training must make timely use of this period, fully develop the sports quality that can meet the special needs or can directly serve the special services, and lay the foundation for creating excellent results.
Sensitive period of strength development
Power quality refers to the ability of the human neuromuscular system to overcome or resist resistance at work.
When the muscles work, the tension generated by the contraction overcomes the resistance. The resistance that muscle work overcomes includes external resistance and internal resistance. External resistance, such as object weight, friction and air resistance; internal resistance, such as muscle viscosity, resistance between muscles, mainly from moving organs such as bones, muscles, joint capsules, ligaments, aponeurosis Resistance to tissues such as fascia.
The sensitive period of development of children's strength is 11 to 15 years old and 12 to 16 years old. The main basis is: First, in the process of children's natural growth and development, the total amount of muscle increased sharply from the age of 12 years. For example, the period in which the girl's muscle mass increases particularly sharply is 11 to 13 years old; the boy is 12 to 14 years old, and when it is 14 to 15 years old, the difference in muscle characteristics and adults has narrowed. The weight and weight percentage of the main age group in childhood are: - 16.6% at birth, 3 years - 21% , 6 years old - 21.7% , 8 years old - 27% , 12 years old - 29% , 15 years old - Close to 33.3% . Adult men are 43.5% and women are 35% . Second, the "longitudinal splitting theory of muscle fibers" also provides a basis for this. Scholars have found that muscle cells in adult animals, including humans, have lost the ability to synthesize DNA and re-divide, while young animals retain this ability. When the latter is muscular, the number of muscle units and capillaries are increased, and the density of muscle fibers is significantly increased. This is caused by the "longitudinal splitting" of muscle fibers caused by strength training (the former Soviet Union Vorobiev "Modern training Some ideas, 1978 ).
(1) Absolute power
The absolute strength of girls can be divided into the following four stages: 10~13 years old, the strength grows rapidly (especially flexor), the absolute strength can be increased by 46% ; 13~15 years old, the growth rate decreases, only increase 8% ; 15 to 16 years old, an increase of 14% ; 16 to 21 years old, an increase of 6% .
The age at which the boy's absolute strength increases is sexual maturity ( 12-16 years), with an average increase of 57.5% ; the growth rate of 17-20 years is reduced to 36.6% ; and the 21-22 year old only increases by 9.6% . At the age of 25 , the greatest strength that adults can perform (Devolk et al., "Changes in Muscle Strength and Speed ​​Strength of Different Ages", 1983 ).
(two) relative strength
The relative strength of men and girls has grown more slowly. For example, from 12 to 14 years old, it only grows by 2% to 3% per year . The main cause of this phenomenon is faster weight gain; the increase in muscle cross-sectional area during the fastest period of height growth; and the increase in muscle growth as the height growth rate slows.
(3) Speed ​​power
The speed of 7~14 years old is growing rapidly. After 14 years old, the boy still grows at a faster rate, while the growth rate of girls is relatively small. The growth rate of 16 to 17 years old began to slow down. This phenomenon is related to the rapid secretion of secretory glands in men and girls during the period of youthful maturity (Yan, 1990 ).
(4) Strength endurance
Girls are in a straight-line trend before the age of 7 to 13. They begin to develop slowly after the age of 13 and even decline after the age of 14. This is because the arrival of the sexual maturity period has made the strength endurance more seriously affected. The boy is 7 to 17 years old, and his strength endurance is basically in a straight upward trend.
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