Investigation Of Isokinetic Muscle Strength Of Knee Joint Among High Altitude Population

ObjectiveThe isokinetic muscle strength of knee joint flexors and extensors of native and immigrants at high altitude was tested.The characteristics of knee joint flexors and extensors of native and immigrants under hypoxic conditions were observed,and the correlation between peak torque of knee joint flexors and extensors and average power and total work under different exercise test speeds was observed.Whether there were differences in length and circumference of lower limbs between native and immigrants was further discussed.It provides a scientific theoretical basis and reference for sports injury and rehabilitation,selection of plateau athletes and sports training.Methods1.Meta analyses method:Pub Med,Cochrane Library,Embase,CNKI,Wanfang database and VIP database were searched for articles on isokinetic muscle strength test of 18-30-year-old healthy adults,Stata15.0software were used for meta-analyses,heterogeneity test,sensitivity analysis and publication bias test were performed.2.A cross-sectional study:Based on the meta analysis results,the research program of this project was formulated.202 college students,including 50 Tibetan men,52 Tibetan women,50 male migrants and 50Han women,were randomly selected by cluster sampling method.The test contents include questionnaire survey,physiological index（hemoglobin concentration,blood oxygen saturation and heart rate,incremental load bicycle test）and isokinetic muscle strength test.Inclusion criteria:the subjects living in the Tibetan nationality for more than three generations live in the plateau,and there is no intermarriage experience of other nationalities within three generations.The time for the subjects who emigrated to the altitude for 1-2 years.There was no history of knee injury in all subjects.The data were entered by Excel,and the statistical software Graphpad,Stata and SPSS20.0 were used for statistical analyses.The descriptive data were expressed by mean±SD;the isokinetic muscle strength indexes of different nationalities and genders were compared by independent sample t test;Pearson correlation and multivariate linear regression analysis were used to analyze the correlation among variables;The difference was set as statistically significant when P<0.05.Results1.Results of Meta analyses:There were 28 articles were included with a sample size of 1170 cases（769 males and 401 females respectively）.Meta analyses showed that normal reference values of isokinetic muscle strength test of 18-30-year-old healthy adult male left and right knee joints were:60°/s left extensor PT:93～119N*m,60°/s left flexor PT:93-119N*m,60°/s left H/Q:45%-61%;60°/s right extensor PT:174～207N*m,60°/s right flexor PT:108～131N*m,60°/s right H/Q:51%～61%;120°/s left extensor PT:139～163N*m,120°/s left flexor PT:85～101N*m,120°/s left H/Q:54%～75%;120°/s right extensor PT:138～194N*m,120°/s right flexor PT:91～105N*m,120°/s right H/Q:58%～73%;180°/s left extensor PT:117～128N*m,180°/s left flexor PT:64～85N*m,180°/s left H/Q:60%～63%;180°/s right extensor PT:108～128N*m,180°/s right flexor PT:59～96N*m,180°/s right H/Q:51%～66%;The normal reference values of isokinetic muscle strength test of female left and right knee joints were:60°/s left extensor PT:90～124N*m,60°/s left flexor PT:47～69N*m,60°/s left H/Q:41%～58%;60°/s right extensor PT:96～125N*m,60°/s right flexor PT:53～72N*m,60°/s right H/Q:46%～63%;120°/s left extensor PT:68～119N*m,120°/s left flexor PT 33～75N*m,120°/s left H/Q:39%～66%;120°/s right extensor PT:75～118N*m,120°/s right flexor PT 36～74N*m,120°/s right H/Q:45%～69%;180°/s left extensor PT:60～84N*m,180°/s left flexor PT:34～58N*m,180°/s left H/Q:43%～37%;180°/s right extensor PT:62～81N*m,180°/s right flexor PT:39～52N*m,180°/s right H/Q:52%～69%.Sensitivity analyses showed that the Meta analyses were stable.Egger’s test showed that there was publication bias in this Meta analysis.2.Cross-sectional study:（1）The body weight,BMI,blood pressure,heart rate and hemoglobin concentration of native Tibetans were lower than those of Han Chinese residents（P<0.05）;S_pO₂ of Tibetan residents was higher than that of Han residents,but the difference was not statistically significant;leg length and leg circumference of Tibetan residents were significantly lower than those of Han residents（P<0.05）;leg length and thigh circumference of Tibetan male residents were significantly higher than those of Han residents（P<0.05）.The circumference was lower than that of male Han immigrants,but the difference was not statistically significant,while there was a difference in leg circumference among women（P<0.05）;the left lower limb weight of Tibetan immigrants was lower than that of Han immigrants（P<0.05）,but the right lower limb weight had no difference.There was no significant difference in S_pO_2peak and HR_peak between Tibetan male residents and Han immigrants,but there was significant difference in S_pO_2peak between Tibetan female residents（P<0.05）.（2）With the increase of angular velocity,Pt decreased gradually.At the same angular velocity,Pt in male was significantly higher than that in female（P<0.001）.The PT of extensor muscle of Tibetan male was higher than that of Han male,the PT of left extensor muscle of Tibetan male was higher than that of Han male（P<0.05）,the PT of right extensor muscle of Tibetan male was higher than that of Han male（P<0.001）,the PT of flexor and extensor muscle of Tibetan female was higher than that of Han female,and the PT of Tibetan female was higher than that of Han female at 120°/s and 180°/s angular velocity The results showed that the left extensor muscle was larger than that of the Han nationality female immigrants（P<0.05）,and there was no significant difference in other angular velocities;the flexor muscle of the Tibetan nationality male immigrants was larger than that of the Han nationality male immigrants at60°/s and 120°/s angular velocity（P<0.01）,and the right flexor muscle of the Tibetan nationality male immigrants was larger than that of the Han nationality male immigrants at 60°/s angular velocity（P<0.05）;the left flexor muscle pt of the Tibetan nationality female immigrants was larger than that of the Han nationality male immigrants at 60°/s angular velocity There was no significant difference in other angular velocity.（3）With the increase of angular velocity,PT/BW gradually decreased,and the ratio of native Tibetan males was higher than that of immigrant Han males.At 60°/s angular velocity,the left and right extensors were significantly different from those of immigrant Han residents（P<0.05）;the right extensors were significantly different from those of immigrant Han residents（P<0.05）;there was no difference in the ratio of female extensors;at 60°/s and 120°/s angular velocity,the left extensors of native Tibetan males were significantly different from those of immigrant Han residents（P<0.05）.There was significant difference in flexor muscle between the native Tibetan male and the immigrated Han nationality（P<0.001）.At 180°/s angular velocity,there was significant difference in flexor muscle between the native Tibetan male and the immigrated Han nationality（P<0.01）.At 60°/s and 120°/s angular velocity,there was significant difference in flexor muscle between the native Tibetan male and the immigrated Han nationality（P<0.01）Flexor muscle was larger than that of Han nationality female（P<0.05）.（4）With the increase of angular velocity,H/Q increased gradually;there was difference in male when the angular velocity was 120°/s on the left side（P<0.05）;there was difference in female when the angular velocity was 60°/s,120°/s,180°/s on the left side and 60°/s on the right side（P<0.05）.（5）With the increase of angular velocity,AP increased gradually;the AP of native Tibetan male was higher than that of immigrant Han male,and there was difference in angular velocity of 60°/s left flexion and60°/s right flexion（P<0.05）,but there was no difference in extensor under different angular velocity;here was no difference in flexor AP of native Tibetan and immigrant Han female under different angular velocity,and there was no difference in angular velocity of 120°/s and 180°/s The left extensor of lower Han women was larger than that of Tibetan women（P<0.05）.（6）TW decreased with the increase of angular velocity,and the extensor muscle was larger than the flexor muscle.TW of native Tibetan male was larger than that of immigrant Han male（P<0.05）when the angular velocity was 60°/s left flexion and 60°/s right flexion;TW of immigrant Han female was larger than that of native Tibetan female（P<0.05）when the angular velocity was 120°/s left extension and 180°/s right extension.（7）With the increase of angular velocity,TPT decreased gradually.At the angular velocity of 180°/s left flexion and 180°/s left extension,the male of Han nationality was larger than that of Tibetan nationality（P<0.05）;at the angular velocity of 60°/s left flexion,120°/s left flexion,180°/s left flexion,60°/s right flexion,120°/s right flexion,180°/s left extension,120°/s right extension and 180°/s right extension,the female of Han nationality was larger than that of Tibetan nationality female（P<0.05）,there was no difference in other angular velocity.（8）There was no difference between the male living in Tibetan nationality and the male of immigrated Han nationality.Under the angular velocity of 120°/s left bend and 180°/s left bend,the AOPT of the female emigrated Han nationality was higher than that of the Tibetan women（P<0.05）,and the AOPT of the female in the Tibetan nationality was larger than that of the immigrant Han women（P<0.05）,and the other movement angular velocity was higher than that of the immigrant Han women（P<0.05）There was no difference in degrees.（9）The peak torque of knee flexor and extensor was positively correlated with average power and total work,which could reflect the explosive force of the subjects to a certain extent.（10）At the speed of 60°/s,there was a negative correlation between PT/BW and TL in bilateral knee flexion of Tibetan men.At 120°/s and180°/s,there was a negative correlation between PT/BW and TL in left knee flexion of Tibetan men.Compared with other angular velocity,PT/BW and TL were positively correlated,but the difference was not significant;compared with Tibetan men,PT/BW and TL in Han men showed significant correlation（P>0.05）.There was a negative correlation between PT/BW and TL at 60°/s and 120°/s,and a positive correlation between PT/BW and TL at 60°/s and 120°/s.There was a positive correlation between PT/BW and LL in both Tibetan and Han males at three different angular velocities.At 60°/s,there was a significant correlation between PT/BW and LL in Tibetan males at right flexor,120°/s left extensor,180°/s left extensor,right extensor,right flexor and Tibetan males at right flexor（P<0.05）.No matter male or female,Tibetan or Han nationality,the correlation coefficient between PT/BW and thigh circumference gradually decreased with the increase of thigh circumference.Only Han nationality female subjects showed more obvious performance（P<0.05）.Compared with the thigh circumference of8cm,10cm and 12cm,the correlation coefficient between PT/BW and thigh circumference of 6cm reached the maximum.Compared with the minimum circumference of lower leg,the correlation between PT/BW and the maximum circumference of lower leg was significant（P<0.05）.There was no significant correlation between PT/BW and T/L at different angular velocity.Conclusion1.Conclusion of Meta analyses:Isokinetic muscle strength test indicator of knee joint were important reference in rehabilitation medicine and sports medicine,but in the future research,we still need high-quality and large sample of isokinetic muscle strength test to further study and determine the normal reference value range according to the condition of Chinese people.2.Cross-sectional conclusion:（1）in the isokinetic concentric muscle strength test of knee flexors and extensors under different angular velocities,the peak torque of concentric contraction of knee muscles of native Tibetan and Han Chinese subjects gradually decreased with the increase of angular velocity.（2）The overall strength of the knee joint of the native Tibetan subjects is better than that of the Han subjects,and the strength of the knee extensor is greater than that of the knee flexor.（3）The peak torque of male knee flexors and extensors is greater than that of female knee flexors and extensors.When the weight factor is excluded,the difference will narrow.Therefore,the relative peak torque is more used when comparing the muscle strength between male and female.（4）Peak torque has a high correlation with average power and total work,so it has a good consistency in reflecting muscle function.（5）The difference of muscle strength between the native Tibetan and the immigrated Han subjects may be closely related to the difference of lower limb length and circumference,and the reason for this difference may be related to the high altitude chronic hypobaric hypoxia.