Effect Of Knee Flexion And Extension Muscle Strength And Ratio On Balance Ability

Research objective: Currently,the influence of knee flexion and extension muscle strength on balance ability is mainly focused on the condition of normal muscle strength,while the antagonistic relationship of knee flexion and extension muscle strength and the deterioration of knee function caused by neuromuscular fatigue are ignored,because specific tasks must be performed in many exercises under the condition of muscle fatigue.In this study,by testing the centrifugal contraction torque of the knee hamstring muscle and the centripetal contraction torque of the quadriceps muscle as well as its torque ratio and balance ability,the correlation analysis was carried out to explore the general rule of the ratio of flexor and extensional muscle of the knee and balance ability,so as to provide certain data support for the development of the knee function and balance ability.In order to further test the influence of muscle fatigue on the deterioration of knee joint performance,this paper reduces the flexor and extensor strength of knee joint through fatigue exercise,analyzes the degree of decline of knee flexor and extensor muscle strength and its fatigue index,and explores whether the degree of decline of knee flexor and extensor muscle strength after fatigue affects the H/Q ratio and the influence on balance ability.Methods: Sixteen healthy males(age: 22.75±1.73,height: 175.56±3.77,weight:69.11±8.63,BMI: 22.38±2.35)were selected as subjects in this study.The Biodex balance System SD dynamic and static balance instrument made in the United States was used to test the dynamic and static balance ability of the subjects on the dominant side and the non-dominant side.In order to prevent the balance difference brought by visual feedback,static closed-eye standing and dynamic closed-eye standing were selected for the balance test.The balance index is OSI(Overall Stability Index),APSI(Anterior-Posterior Stability Index)and MLSI(Medial-Lateral Stability Index).Isokinetic muscle strength test Con-Trex isokinetic muscle strength tester was used to perform isokinetic muscle strength tests of 60°/s,180°/s and 240°/s on the dominant and non-dominant side of knee joints for all subjects to determine the strength of knee flexor and extensor muscles of subjects.The isokinetic indexes were: Peak moment of centrifugal contraction of hamstring muscle,peak moment of centripetal contraction of quadriceps muscle,ratio of centrifugal contraction moment of hamstring muscle to centripetal contraction moment of quadriceps muscle(Ratio of eccentric hamstring strength to concentric quadriceps strength,H/Q function ratio).Fatigue test was performed with an iso-velocity muscle strength tester set at 180°/s,and the maximum muscle strength of knee joint was repeated50 times.In order to further test the impact of fatigue on performance degradation,a time period was established every 10 times,a total of 5 times(i.e.the initial 1-10 times,11-20 times,21-30 times,31-40 times,41-50 times).Perform a balance test immediately after fatigue exercise.Fatigue muscle strength indexes are: maximum torque of quadriceps muscle centripetal contraction,maximum force distance of hamstring muscle centripetal contraction,ratio of knee flexor extensor muscle centripetal moment(H/Q traditional ratio)and flexor extensor fatigue index at each time.Research results:(1)The centripetal moment of quadriceps knee decreases with the increase of angular velocity,the ratio of H/Q functional ratio increases with the increase of angular velocity,and the centrifugal moment of hamstring muscle does not change significantly with the increase of angular velocity.The centriotropic moment of the quadriceps muscle on the dominant side was higher than that on the non-dominant side,there was no significant difference in the comparison of centrifugal moment of the knee and hamstring muscle on both sides,and the ratio of H/Q functional ratio on the non-dominant side was higher than that on the dominant side.(2)The centriolar moment of the quadriceps muscle at the three angular velocities on the dominant side was correlated with the static equilibrium OSI,APSI and MLSI,and was negatively correlated;The H/Q function ratio at 60°/s is correlated with MLSI,and the H/Q function ratio at 240°/s is correlated with OSI and APSI.The centriotropic moment of the dominant quadriceps muscle at 60°/s and 240°/s was negatively correlated with the OSI of dynamic equilibrium.There was no correlation between the centrifugal torque of the dominant hamstring muscle and the dynamic and static balance ability.(3)The 60°/s centriolar contraction torque of the quadriceps muscle on the non-dominant side was correlated with the OSI,APSI and MLSI of static balance,and the180°/s and 240°/s centriolar contraction torque was correlated with the OSI of static balance.The centrifugal contraction torque of the hamstring muscle at 60°/s is correlated with the static equilibrium OSI and APSI.The centripetal contraction torque of the quadriceps muscle at 60°/s and the centrifugal contraction torque of the hamstring muscle on the non-dominant side were correlated with the dynamic balance OSI and APSI.The centrifugal contraction torque of the hamstring muscle at 180°/s is correlated with the OSI of dynamic balance.(4)After fatigue exercise,knee flexor and extensor muscle strength decreased significantly,the degree of decline of extensor muscle strength was higher than that of flexor muscle,and the traditional ratio of H/Q on the non-dominant side increased significantly.The fatigue index increased with the increase of exercise time intensity.After 50 times of fatigue exercise,the strength of dominant extensor muscle decreased by about 48.72% and that of flexor muscle decreased by about 45.56%.The muscle strength of the non-dominant extensor muscle decreased by 53.46% and that of the flexor muscle decreased by 44.24%.The balance ability of the dominant side and the non-dominant side decreased significantly before and after fatigue.Research conclusion:(1)There was no difference in the centrifugal contraction torque of knee hamstring muscle,quadriceps centristral contraction torque,H/Q function ratio and balance ability between dominant and non-dominant side of healthy men.After fatigue exercise,knee flexion and extension muscle strength decreased obviously,and the decreasing degree increased with the extension of exercise time.The strength of the quadriceps muscle decreased more than that of the hamstring muscle,and the ratio of traditional H/Q ratio did not decrease due to knee flexor extensor fatigue.(2)The centrioforce moment of the quadriceps muscle on the dominant side has a significant negative correlation with the static balance ability of the human body;the H/Q function ratio on the dominant side has a significant positive correlation with the static balance;the centrifugal moment of the hamstring muscle on the non-dominant side has a significant negative correlation with the balance ability OSI and APSI.(3)The balance ability of the dominant side and the non-dominant side decreased significantly after fatigue.The results showed that the balance ability was more affected by the flexion and extension strength of knee joint,and the balance ability decreased obviously after the flexion and extension strength decreased.But the balance ability is not affected by the traditional H/Q ratio.