(School of Physical Education,Zhengzhou University,Zhengzhou 450044,China) Abstract: In order to study the natural development pattern of the knee joint flexor and extensor strength of females as the age grows, the author used the Kinitech isokinetic test system to perform isokinetic tests at the speeds of 60 (°)/s, 120 (°)/s and 240 (°)/s on the strength of the flexor and extensor at both sides of common elementary school, middle school and college girls at the age of 10-12, and revealed the following findings: the peak torque (PT) value of the knee joint flexor and extensor of females increases as the age grows, the muscle strength of females at the age of 14-17 grows faster, and the PT value of the knee joint flexor and extensor of females at the same age decreases as the test speed increases; as for females in various age groups, the PT value of their extensor of is greater than the PT value of their flexor at the same side; as for females at the same age, there is no significant difference in the PT value measured at the same speed between the homonymous muscles at different sides; the ratio of knee joint flexor strength to knee joint extensor strength (H/Q) tested at the same speed shows a trend of decreasing as the age grows; the H/Q ratio of females in the same age group shows a trend of increasing as the speed increases. The said findings indicate the followings: the knee joint flexor and extensor strength of females at the age of 10-20 grows naturally as the age grows, and the knee joint flexor and extensor strength of females in the age group of 14-17 grows faster, es-pecially their extensor strength grows significantly faster; the H/Q ratio shows a trend of gradually decreasing as the age grows, which forms the sign of increasing of the difference in muscle strength between the flexor and extensor under the condition of natural growth. Key words: sports biomechanics;knee joint flexor and extensor strength;dynamic isokinetic test;teenage girls |