Objective To understand the characteristics of surface electromyography (sEMG)of vastus medialis muscle fatigue induced by isokinetic flexion and extension movement, and to further provide references for the application of sEMG on dynamical movements.Methods Arial isokinetic equipment and ME6000 equipment were combined to analyze the time domain indices including root mean square (RMS ) integrated electromyography (iEMG)and spectrum indices including median frequency (MF)and mean power frequency (MPF)for vastus medialis from ten students from Shenyang Sport University during isokinetic fatigue.Results During the isokinetic muscle fatigue the RMS and iEMG were significantly increased (P<0.05),accompanying with higher effect sizes for iEMG than for RMS. As for the spectrum indices,MF and MPF were significantly decreased (P<0.05)with larger effect sizes for MPF than for MF. The increase rate of iEMG was significantly higher in iEMG than RMS (P<0.05),and the decline rate of MPF was larger than MF (P<0.05).Conclusion The iEMG as a time domain index and MPF as a spectrum index can be sensitive indexes to assess the dynamic muscle fatigue.

Objective To establish a simple and practical regression equation for estimating maximal oxygen uptake(VO2max),so as to provide a base and reference for epidemiological studies.Methods Totally 128 freshmen(88 males and 40 females) were randomly recruited majoring in social sports and physical education to conduct the correlation analysis between VO2max and the weight,body surface area,body mass index(BMI) and vital capacity.Then 34 freshmen(17 males and 17 females) were chosen from them randomly to compare whether there was a significant difference between the two VO2max relative values measured by Astrand estimation and direct measurement respectively.Based on the results,the multiple linear regression analysis was conducted:independent variables entered theregression equation in turn according to the Forward method and the significance test of the regression equation,the regression coefficients and the fitting degree was conducted.We got the regression equation finally according to the Durbin-Watson and VIF values.Another 17 male freshmen were recruited to verify the efficient of the regression equation.Results Significant differences were observed in the relative VO2max value of females,being 45.14 ± 8.08 ml/kg/min and 32.63 ± 5.87 ml/kg/min by Astrand and direct measuring respectively,but not in that of the male,being 47.24 ± 6.46 ml/kg/min and 51.62 ± 6.91 ml/kg/min accordingly.There was very significant correlation between VO2max and weight,body surface area,BMI and vital capacity of the male freshmen(P＜0.01),but not of the female freshmen (P＞0.05).The regression equation of estimating the relative VO2max of the boy freshmen was y=34.812+0.015×vital capacity(ml)-40.403×body surface area(m2).No significant differences were found between the value calculated using this equation and that measured directly (P＞0.05).Conclusions The regression equation found in this study is simple,practical and efficient,and it can be used to estimate the relative VO2max of male freshmen majoring in physical education and social sports in epidemiologic study,so as to evaluate their cardiopulmonary fitness.