RESUMO
BACKGROUND:As an effective method to evaluate the muscle functional level in humans,isokinetic testing system is applied in more and more researches.However,reports remain few in which isokinetic muscle strength test is used to study the effect of movement training on the development of muscle groups in teenagers.OBJECTIVE:To make a comparison and analysis on the muscle strength of knee joints between the two different teenager populations of the same age,namely,the one with jump testing and the one without.DESIGN,TIME AND SETTING:A contrast observation was performed at the Laboratory of Hebel Physical Education Science Institute between October and Decamber in 2008.PARTICIPANTS:The 20 volunteers without sport training were selected randomly from Hebei Normal University Affiliated Middle School in Shijiazhuang,and were classified as the control group;the other 20 volunteers with high jump and long jump training were randomly selected from Shijiazhuang Sports School,and were used as the training group.All participants are males.METHODS:Cybex-6000 isokinetic testing system was used to test the knee joints of all participants,with the concentdc contraction going first and then the eccentric contraction.The slow,middle and high testing speeds were 60(°)/s,120(°)/s and 240(°)/s respectively.MAIN OUTCOME MEASURES:Relative peak torque(PT)values of flexor and extensor groups in knee joints.RESULTS:All 40 volunteers were involved in the result analysis.Compared with the control group,knee joints in the training group showed much higher flexor and extensor PT values during the concantric contraction and the eccentric contraction at the speed of either 60(°)/s or 120(°)/s or 240(°)/s,and the difference between the two groups was of significance(P＜0.01).The PT value ratios between flexor and extensor of both the left and the right knee joints were lower in the training group than in the control group at any of the three speeds.CONCLUSION:Jump exercise has a distinctively positive effect on increasing the muscle strength of knee joints in teenagers,while it is limited in the coordinated development of extensor and flexor,leading to the decreased ratios between the two which may be caused by the inappropriate training method.