Study On The Balance Between Quadriceps And Hamstrings Of Female College Students By Perturbation Trainin

Anterior Cruciate Ligament(ACL)injuries are common knee injuries,and female athletes are 3.5 times more likely to develop ACL injuries than male athletes,and approximately 70% of ACL injuries are non-contact.It is usually due to the small angle of knee flexion when landing,and the ratio of hamstring to quadriceps strength is too small,this unbalanced muscle condition leads to athletes using the quadriceps to stabilize the knee joint when landing,that is,quadriceps priority activation(Quadriceps Dominance,Q.D).Priority activation of the quadriceps muscles leads to insufficient hamstring and gastrocnemius muscle recruitment at landing,resulting in excessive extension moment,thereby increasing stress on the ACL and increasing the risk of ACL injury.Daily rehabilitation mostly uses neuromuscular control training and muscle strength training to adjust the imbalanced quadriceps and hamstrings in this population.Several studies have proven that perturbation training is an effective neuromuscular training program.However,there is little literature on its application to people with quadriceps and hamstring muscle imbalance,and its balance function,coordination ability and muscle activation mode during the leg jumping landing process need to be further explored,which can provide a reliable experimental basis for preventing ACL injury.Purpose of the study:The intervention effect of disturbance training on adjusting the strength of hamstring and quadriceps muscles and the uneven activation order of female college students when landing was observed,and the mechanism of disturbance training to improve Q.D population was discussed,which provided a method and basis for preventing ACL injury in Q.D female college students.Research methods:A total of 24 female college students who met the inclusion criteria for priority activation of the quadriceps muscles were randomly divided into two groups,the experimental group(n=12)and the control group(n=12),the experimental group carried out conventional strength training and disturbance training,and the control group underwent conventional strength training and neuromuscular control training,each time for 60 minutes,3times a week,intervention for 6 weeks.Noraxon electronic goniometer was used to test the angle change of knee joint in the longitudinal jump stage and knee holding jump stage(initial contact,landing peak,angle change during movement);Cybex isokinetic muscle strength was used to measure the muscle strength of the subject’s lower extremities(peak torque,peak torque ratio);Noraxon surface EMG tester was used to test the degree of activation of lower limb muscles and muscle activatio n time(medial femoris muscle,rectus femoris muscle,lateral femoral muscle,medial hamstring muscle and lateral hamstring)in the preparation and reaction stage of vertical jump;Y-balance was used to test the balance of the lower extremities(anterior,posterolateral,posteromedial,and composite scores).Indicators were measured before and after the intervention.SPSS22.0 statistical software was used to analyze the test data,and the independent sample t-test was used for the between-group comparison,and the paired-sample t-test was used for the intra-group comparison,and the significance level was P<0.05.Research results:1.Change in knee angle in the jump test between the two groups after 6weeks of intervention.Intra-group comparison: the knee angle during the vertical jump was increased between the experimental group and the control group compared with before the intervention(P<0.05).Comparison between groups: The initial contact angle(29.54±1.33°)and landing peak angle(68.11±6.28°)o f the experimental group after the intervention were more obvious than the initial contact angle(26.52±1.32°)and the landing peak angle(64.06±8.12°)in the experimental group after the intervention,with significant differences(P<0.05),but there was n o significant difference in the range of motion of knee flexion angle in the landing stage(P>0.05).2.Changes in isokinetic muscle strength in both groups after 6 weeks of intervention.Intra-group comparison: Compared with before the intervention,the peak torque and peak torque ratio of 60°/s and 180°/s increased between the experimental group and the control group,and there were significant differences before and after the intervention(P<0.05).Comparison between groups: There was no significant diff erence between the peak torque and the peak torque ratio at 60°/s and 180°/s between the experimental group and the control group after intervention(P>0.05).3.Changes in muscle activation in the preparation and response stages of the two groups after 6 weeks of intervention.Intra-group comparison: Compared with before the intervention,the degree of medial femoral muscle activation,the degree of rectus femoral muscle activation decreased,the degree of lateral femoral muscle activation decreased,the d egree of semitendon muscle activation increased,and the degree of biceps activation decreased in the preparation and response stages between the experimental group and the control group before the intervention were significantly different(P<0.05).Comparison between groups: After the intervention,the activation degree of medial femoral muscle and semitendon muscle in the experimental group increased more significantly than that in the control group,and the difference was significant(P<0.05).After the intervention,the degree of activation of rectus femoris,lateral femoral muscle,and biceps muscles in the experimental group was greater than that of the control group,and the difference was significant(P<0.05).4.After 6 weeks of intervention,the ti ming of muscle activation changed during the vertical jump in both groups.Intra-group comparison: Compared with before the intervention,the activation time of medial femoral muscle,the activation time of rectus femoris muscle decreased,the activation t ime of lateral femoral muscle decreased,the activation time of semitendon muscle increased,and the activation time of biceps femoris muscle increased between the experimental group and the control group compared with before the intervention,the differen ce was significant(P<0.05).Comparison between groups: After the intervention,the activation time of medial femoral muscle and semitendon muscle in the experimental group increased more significantly than that in the control group,and the difference was significant(P<0.05).After the intervention,the rectus femoris,lateral femoral muscle,and biceps femoris muscle in the experimental group had a more significant reduction in activation time than that of the control group,and the difference was significant(P<0.05).5.Change in balance ability between the two groups after 6 weeks of intervention.Intra-group comparison: Compared with before the intervention,the experimental group and the control group had an increase in anterior score,posteromedial score,posterolateral score and comprehensive score,and there were very significant differences before and after the intervention(P<0.05).Comparison between groups: There were no significant differences in anterior scores,posteromedial scores,posterol ateral scores and comprehensive scores between the experimental group and the control group after intervention(P>0.05).Research conclusion:1.6 weeks of disturbance training and neuromuscular control training can improve the hamstring strength and balan ce of female college students with priority activation of the quadriceps muscles,and the two have the same effect.2.6 weeks of disturbance training can improve the activation degree of hamstring muscles during exercise,increase the knee flexion angle w hen landing,enhance the cushioning capacity of the knee joint,reduce the load,reduce the risk of anterior cruciate ligament injury,and the effect is better than neuromuscular control training.3.6 weeks of perturbation training can adjust the muscle a ctivation time of the longitudinal jump process,increase the hamstring activation time,reduce the quadriceps activation time,this change can activate the hamstring muscles first,thereby reducing the load of the anterior cruciate ligament,and the effect is better than neuromuscular control training.