| Objective :To study the age-related changes and gender difference of muscle strenth which included maximal muscle strength,explosive force,endurance force in teens aged12~25 years in China in static isometric conditions,and to analyze the correlation and difference between muscle strength with age and sex.Specifically included:1)Research on reliability and validity of digital testing system of isometric muscle contraction;2)To explore the characteristics of age-related changes of body shape(height,weight,lean body mass,upper arm circumference)and physical fitness(the sitted ball throw,vertical jump,height,standing long jump);3)To explore the characteristics of age-related changes of muscle strength in elbow and knee joints among teens in China aged 12 to 25 years old,including the age-related changes and sex factors of maximum muscle strength,muscle explosive force and muscle endurance between men and women.4)analyzing the muscle strength data(maximal muscle strength,explosive force,endurance force)of each age group and analyzed the correlation between muscle strength and body shape(height,weight,lean body mass,upper arm circumference)and physical fitness i(the sitted ball throw,vertical jump,height,standing long jump);5)The research could provide the basis for data collection and statistics of muscle movement ability of teens in China.Methods:To design isometric muscle strength testing system based on the principle of muscle isometric contraction by adopting engineering technology,it can precisely measure the muscle strength of elbow and knee joints.Using average number and standard deviation to count the concerned indexes including the figures index of different ages,the index of body shape,the index of physical fitness and the index about muscle strengths,explosive force and endurance force.The descriptive statistics,the trend analysis,the correlation analysis with correlation network analysis,two-way ANOVA test analysis were employed to distinguish the gender differences and the ageing-related variations.Results:(1)The reliability test of the test system indicates: The two measurements were compared,The correlation coefficient of the right extensor of the knee joint was lower than 0.75(0.695),and the other positions were greater than 0.75.The comparison between the two test data was not statistically significant(P>0.05).After correction,the validity showed that the test system error decreases.There was no significant differencebetween the measured value and the fixed load(P > 0.05).(2)The body shape indicators(height and weight of body weight and upper arm and thigh circumference)and the quality index(vertical jump of standing jump and small ball throwing distance)all increased with age;(3)The muscle strength of the flexion and extensor muscles of the knee joint showed an increasing trend with increasing age.In addition to the muscle group and 12,13,male and female elbow flexion and extension knee extensor muscle strength,no significant difference(P > 0.05),other all ages male subjects elbow knee joint group of flexor muscle strength there were significant differences(P < 0.05,P < 0.01);There was a positive correlation between the muscle strength of the left and right elbow flexion muscle group and the body circumference of the weight and weight of the body weight,there was significant statistical significance(P<0.05,P<0.01),The muscle strength of the flexion muscle of the knee joint was positively correlated with the vertical jump and the vertical jump,there was significant statistical significance(P<0.05,P<0.01).(4)In the 100 ms 200ms,the muscle strength of the flexion muscles of the knee joint of the knee joint was not significantly increased,and the maximum explosive force showed the trend of increasing with age.There was a significant difference between male and female subjects(P<0.05).There was a positive correlation between the strength of the knee flexion and the maximum explosive force and the body circumference of the body weight.there was significant statistical significance(P<0.05);There was a significant correlation between the explosive force of the elbow flexion muscle group and the sitting ball,but there was not show statistical significance(P>0.05).There was a positive correlation between the explosive force of the knee flexion muscle group and the vertical jump and the standing long jump,which was statistically significant(P<0.05).(5)There was no significant increase in the fatigue index of the knee flexion.There was a significant difference in the fatigue index of the elbow flexion muscle group in all ages(P<0.05),There was no significant difference in the fatigue index of knee flexion muscle group(P >0.05).Subjects muscles fatigue index and elbow flexion and extension was positively correlated with lean body mass and the degree of upper arm circumference of weight for height,it have significant statistical significance(P < 0.05),knee flexion muscle fatigue index was positively related but it showed no statistical significance(P > 0.05).(6)The strength of muscle strength and muscle endurance of the knee flexion muscles of the knee joint wereshown to show significant age effect gender maineffect and age sex interaction effect(P<0.05).Conclusion: This research is independently developed isometric muscle strength testing system based on the principle of muscle isometric contraction,which has better stability and consistency,and the test results is accurate and reliable.The height,weight,lean body mass,Upper arm circumference and thigh circumference of 12 to25 years old shows a regular increase with age.In the same age group,male height,weight,lean body mass and upper arm circumference are greater than female,and thigh circumference does not show the regularity of male than female.And the seated ball throw,vertical jump,standing long jump all shows a regular increase with age.In the same age group,male upper and lower limb strength qualities are greater than female except upper limb strength on the left.The maximal muscle strenth(Fmax)all showed a gradual increase in teens aged 12~25 years.Muscle strength was significantly affected by age and sex;The maximal explosive force(EFmax)all showed a gradual increase in teens aged12 ~ 25 years,explosive force at the time of 100 ms and 200 ms did not show obvious ageing characteristics.At the same time corresponding to the same age,the explosive force of of the elbow and knee flexors and extensors of the male was greater than that of the female,and the right side was greater than the left side.So,the subject”s muscle strength was significantly affected by age and sex.The endurance force(FMI)did not showed a gradual increase in teens aged 12~25 years,the elbow and knee joint flexors and extensors of the endurance force women were better than men.The knee flexors were better than men before the age of 19,and the rules were not obvious after the age of 19,and the knee extensors did not have obvious rules.The correlation analysis showed the highest significant correlation among the muscle strength and explosive force of the elbow and knee flexors and extensors and the index of body shape,the index of physical fitness. |
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