| Research purposes：The role of the posterior cruciate ligament is to prevent the tibiabackward shift, in sports and everyday life, The pressure on the posterior cruciateligament is very strong, and the posterior cruciate ligament will be creep. Ligament inaddition to maintaining the mechanical stability of the joint, many studies haveconfirmed that there is reflex arc, creep on the reflex arc will produce what kind ofimpact? This is a problem worthy of further exploration. In this study, subjects inlaboratory condition , static loading on the knee and make the posterior cruciateligament creep. Analysis flexor and extensor muscle torque and EMG before and aftercreep, co-activation of thigh flexion and extension movements after posterior cruciateligament creep, in order to investigate the damage mechanism.Methods: 25 subjects in this study, including 11 male subjects(age 22±2,height179.8±2.7cm, weight 76.2±16.2kg) and 14 female subjects(age 21±1,height164.3±5.0cm,weight 55.9±8.3kg), physical condition is good and knees no injuryhistory. The experimental apparatus used in this study have CON-TREX muscleassessment and training system , Germany Biovision EMG tester, digital camera(Sony-DCR-TRV17E), light-emitting diodes, electronic vernier caliper, dumbbells, aone-time use of EMG electrodes. Experimental steps: 1) subjects in the CON-TREXmuscle assessment and training system with 60°/ s to do the greatest strength of thethree knee flexion and extension activities, rest one minute, with 120°/ s greateststrength to do the three knee flexion and extension activities, the instrumentalrecorded muscle torque. EMG data recorded by EMG tester, Digital video camera(Sony-DCR-TRV17E) synchronization shooting screen. 2) the subjects were sitting ina chair, leg fixed and placed on another same chair, keep the legs parallel to theground and knee vacant. In the top of the tibia static load of 20kg, for 10min.Electronic vernier caliper to record the distance between the knee and the groundchange after loading is completed. 3) like 1). Make average of the peak muscle torque what from knee flexion and extension threetimes; EMG data were normalized; APAS motion analysis system were used in videoprocessing, and come to the range of flexion and extension of the knee joint angle;Select the rectus and biceps femoris EMG data as objects when the knee in 20°, 40°,60°and 80°. Data were compared using single factor analysis of variance (one-wayANOVA), the difference significant level was set at P = 0.05, the difference is verysignificant level was set at P = 0.01.Results: 1) after loading, the creep of male and female have significant differences（P=0.01）. 2）Muscular torque at unloading flexion, loading flexion, unloadingextension, loading extension, male subjects were larger than females and havesignificant differences（P<0.01）; In two different angular velocity , the difference isnot significant; at low-speed, extension muscular torque of female subjects beforeloading is larger than after loading（P=0.003）, at hign-speed, extension musculartorque of female subjects before loading is larger than after loading（P=0.003）．3) atlow-speed, The BF / BF at 20°, 60°, 80°before and after loading have nosignificant differences, at 40°there are significant differences（P=0.035）; BF/RF-flexion at 20°, 80°before and after loading have no significant differences, at 40°and60°there are significant differences（P=0.044）（P=0.039）; RF / RF, BF/RF- extensionat 20°, 40°, 60°, 80°have no significant differences before and after loading. 4) athigh-speed, BF, / BF, RF / RF, BF/RF- flexion, BF/RF- extension at 20°, 40°, 60°,80°, have no significant differences before and after loading. 5) male subjects beforeand after loading, at low-speed and high-speed ,BF / BF, RF / RF, BF/RF- flexion,BF/RF- extension at 20°, 40°, 60°, 80°have no significant differences. 6) Femalebefore and after loading, at low-speed when the BF / BF, RF / RF, BF/RF- extensionat 20°, 40°, 60°, 80°have no significant differences; BF/RF-flexion at 20°and 80°,have no significant difference before and after loading, at 40°and 60°, havesignificant differences before and after loading（P=0.045）（P=0.044）; high-speedwhen the BF / BF, BF/RF-flexion, BF/RF- extension at 20°, 40°, 60°, 80°have nosignificant difference before and after loading; RF / RF at 40°, 60°, 80°have nosignificant differences before and after loading , at 20°have very significant differences before and after loading（P=0.008）. 7) Before male and female loading, atlow-speed when the BF / BF at 40°, 60°, 80°have no significant differences beforeand after loading, at 20°have significant differences（P=0.04）; RF / RF, BF/RF--flexion, BF/RF- extension at 20°, 40°, 60°, 80°, have no significant differencesbefore and after loading; at high-speed when the BF / BF, RF / RF, BF/RF-flexion,BF/RF- extension at 20°, 40°, 60°, 80°have no significant differences before andafter loading. 8) After male and female loading, at Low-speed when the BF / BF, RF /RF, BF/RF-- extension at 20°, 40°, 60°, 80°have no significant differences beforeand after loading; BF/RF-flexion at 20°, 60°, 80°have no significant differencesbefore and after loading, at 40°have significant differences（P=0.039）; at high-speedwhen the BF / BF, RF / RF, BF/RF-flexion, BF/RF- extension at 20°, 40°, 60°, 80°have no significant differences before and after loading.Conclusion: 1) The creep of posterior cruciate ligament, female was larger than male.compared with male, intensity of posterior cruciate ligament should be small andhave better knee flexibility. 2) Compared with female, muscle torque of male waslarger than female at low-speed and high-speed. There was no difference in themuscle torque before and after the creep. 3) at low speed, after cruciate ligament creep,flexion and extension movement co-activation was changed but at high speed is not. 4)after cruciate ligament creep of male subjects, co-activation does not change, femalehave changed.Suggestion:1）Compared with male, intensity of posterior cruciate ligament offemale should be small and have better knee flexibility. So pay attention to thestrength of the load in daily life and sports, to avoid injury. 2) In daily life and sports,the knees to withstand greater loads to rest for some time, so that the cruciate ligamentcreep have been restored. 3) Sports warm-up activities such as stretching, knee to giveappropriate support to avoid the creep of the posterior cruciate ligament, in order toreduce the risk of injury. |
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