Research On Ergonomic Load And Muscle Fatigue And Its Biomarkers

Objective The relationship between self-induced fatigue,physiological,blood biomarkers and ergonomic load was analyzed by simulating repetitive lifting in laboratory.To explore the evaluation method of local muscle fatigue,sensitive biomarkers in fatigue process were screened and their correlation was analyzed.It provides a data basis for the early prevention and diagnosis of musculoskeletal injury and a reference for the further study on the pathogenesis of work-related musculoskeletal disorders(WMSDs).Methods Thirteen healthy male volunteers were selected as subjects to simulate repetitive manual lifting in the laboratory.Lifting task was divided into 4 time periods(T1?T4).Lifting activity lasted for 12 min in each time period,then suspended for 3 min for sampling.The total amount of work done in the lifting process reflects the external load of the operation.The internal load was reflected by the subjective fatigue sensation of local muscles and the change of surface electromyography(sEMG)signal during lifting.The subjective fatigue rating of perceived exertion(RPE)score was used as the subjective evaluation method for local muscle fatigue,the joint analysis of sEMG spectrum and amplitude(JASA)method was used as the objective evaluation method for fatigue,and the results of subjective and objective methods were taken as the fatigue evaluation method in this study to reflect the overall fatigue condition of the body.RPE score was performed on local muscles every 6 min(except pause time)during the lifting process,and changes in subjects'heart rate(HR)and respiratory rate(RR)were monitored throughout.Surface EMG signals of brachioradialis muscle(BR)of forearm,biceps brachii of upper arm(BB),deltoid muscle(DM)of shoulder,left and right spinal erector muscle(ES)of waist and lateral femur muscle(VL)of leg were collected in the whole lifting process,and time domain mean square root value(RMS)and frequency domain median frequency(MF)of EMG signals were analyzed.Before the trial and the time of each move lift suspension was collected venous blood during 5 mL,a total of five times,using ELISA method,optical and electrochemical method(automatic biochemistry analyzer)to detect 4 kinds of biochemical markers in serum levels,including:metabolic markers ammonia(AMM),lactic acid(LAC),creatine kinase(CK),lactate dehydrogenase(LDH),serum cartilage oligomeric matrix protein(COMP)and type ? collagen carboxyl terminal telopeptide(CTX-?),type ? collagen carboxyl terminal telopeptide(CTX-1),calcium(Ca2+);Oxidative stress marker glutathione(GSH);Inflammatory markers c-reactive protein(CRP),prostaglandin E2(PG-E2),interleukin 6(IL-6),tumor necrosis factor(TNF-?)and pain marker neuropeptide Y(NPY)were 14 indicators in total.SPSS22.0 software was used for statistical analysis of the data of each index,and the test level a=0.05.Results I.The RPE of all parts showed a linear increase trend with the increase of accumulated work(P<0.01),especially the waist.Heart rate and respiratory rate increased linearly with the increase of cumulative work(P<0.01).2.The RMS values of local muscles in different parts were slightly different with the changes in the cumulative amount of work,and the BR,BB,DM,and ES presented a rising and then falling trend in the static and dynamic mixed work muscle.The dynamic operating muscle DM showed the trend of first descending and then ascending,and the VL showed the trend of continuous ascending.MF values of most muscles(such as BR,BB,DM,and ES)showed a downward trend with the accumulation of work,and only the VL gradually increased with the load.When muscle fatigue occurred,the amplitude increased(RMS increased)and frequency spectrum shifted to the left(MF decreased).Therefore,these results indicated that the statically mixed working muscles(BR,BB,and ES)were more prone to fatigue than the dynamic working muscles(DM,VL).3.Changes in blood biomarkers:AMM,CK,LDH,COMP,Ca2+ and NPY presented a linear increase trend with the accumulation of work(P<0.01).CTX-II and CTX-I showed a binomial change trend(P<0.05).LAC showed a trend of trinomial change(P<0.01).PG-E2 showed a significant difference with the change of cumulative work(P<0.05),but no significant change trend(P>0.05).CRP and GSH showed no difference with the cumulative work(P>0.05).No changes in IL-6,TNF-? were detected and the results were negative.Most of the biomarkers showed a low positive correlation with the external load,among which AMM,CK,COMP,and Ca2+ metabolic indexes were low positively correlated with the external load,and a linear regression model could be further established.The above results indicated that there was a certain relationship between some blood biomarkers and external load,and the changes of blood biomarkers could reflect the effect of external load,laying a foundation for fatigue analysis.4.There was also a certain degree of correlation between each marker.Metabolic markers:AMM was positively correlated with LAC,LDH;LAC was positively correlated with CTX-I,Ca2+;CK was moderately positively correlated with LDH,CTX-? and Ca2+.AMM and COMP;LAC and LDH,COMP,CTX-?:LDH and COMP,Ca2+;CTX-? and Ca-2+ were low positive correlation.Metabolic marker LDH was positively correlated with inflammatory marker PG-E2 and pain marker NPY,respectively.The inflammatory marker PG-E2 was highly positively correlated with the pain marker NPY.These results demonstrate the association of various markers in the fatigue process.5.Fatigue assessment:subjective fatigue(RPE scale)appeared in the second task segment of lifting operation(13?24 min).Objective fatigue(JASA evaluation)appeared in the second task segment of lifting operation(13?24 min),and the results of the two methods were consistent.6.There were significant changes in most biomarkers before and after fatigue,with statistically significant differences in AMM,LAC,CK,LDH,COMP,CTX-II,Ca2+ and NPY before and after fatigue(P<0.01),and no statistically significant differences in CTX-?,PG-E2,GSH,and CRP before and after fatigue(P>0.05).In the process of fatigue,AMM and LAC were most sensitive to fatigue,CTX-II,COMP,CK,LDH and NPY were more sensitive,and Ca2+ was generally sensitive.Conclusions There is a certain relationship between subjective fatigue,physiological,blood biochemical indexes and external load.Metabolic biomarkers(blood AMM,LAC,CK.LDH,COMP,CTX-?,Ca2+)and pain biomarkers(blood NPY)are sensitive to fatigue,can objectively and effectively reflect muscle fatigue,and can be used as sensitive indicators to evaluate fatigue in repetitive activities.There is a good correlation between metabolic biomarkers,between metabolic biomarkers and pain biomarkers,and between inflammatory biomarkers and pain biomarkers,which could jointly reflect muscle fatigue during operation.