human
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Spectral parameters of the surface electromyographic ( EMG ) signal from lumbar back muscles assessed during a fatiguing isometric contraction can be used to classify different categories of low back pain ( LBP ) subjects and control subjects without LBP . In the test protocol currently used at the NeuroMuscular Research Center at Boston University , subjects contract their back muscles at 80 % of their maximal voluntary contraction ( MVC ) force . This fatigue-based protocol has been successfully applied to persons with subacute or chronic LBP ; those in acute pain , however , have not been included because of their inability to perform a maximal exertion . In this paper we will examine the force sensitivity of the currently used EMG parameters and also give an overview of some of our efforts to develop new test procedures . Our goal is to develop force-insensitive surface EMG parameters that can be used for classification purpose s in population s of subjects who develop low trunk extension forces . In addition , the development of a model to predict MVC from anthropometrical measurements will be presented AIM The aim of this study was to investigate the effect of continuous ultrasound ( US ) plus exercise on the endurance of paravertebral muscles of patients with chronic non specific low back pain ( CNSLBP ) . METHODS AND MATERIAL S In this pilot , pretest-posttest study , 22 patients with CNSLBP participated . Patients received 10 sessions of treatment , including continuous US plus exercise therapy , over a period of four consecutive weeks . Median frequency slopes of Iliocostalis and Multifidus muscles as well as holding time during Biering-Sorensen test were measured using surface electromyography . In addition , function and pain were measured using Functional Rating Index ( FRI ) question naire and VAS . RESULTS Five females and 15 males with a mean age of 31.7 years completed the treatment . Descriptive data showed a decrease of 0.01 and 0.02 mean in median frequency slope of right and left Iliocostalis respectively and a mean of 0.08 decrease for both right and left Multifidus muscles . Endurance time increased 1.8 seconds mean . Both function ( 17 % ) and pain ( 24 % ) improved post treatment . CONCLUSION Larger population studies in the context of high quality , r and omized clinical trial are needed to vali date the results The rate of decline in the median frequency ( MF ) of the surface EMG power spectrum ( MFgrad ) has been evaluated for its use in monitoring the fatigability of the erector spinae muscles during the performance of submaximal isometric contractions . MFgrad consistently displayed a highly significant relationship with endurance time for the task ( p < 0.05 ) , giving a slightly better correlation for contractions performed in lordotic postures , with the back muscles in a shortened position , than in flexed postures . No significant difference existed between mean MFgrad values recorded from the right and left erector spinae muscles , at either thoracic or lumbar levels . The back extensor muscles of men were more fatigable than those of women , and this has been discussed in relation to corresponding differences in muscle fiber type relative size . Greater erector spinae muscle fatigability was associated with both the existence of , and the risk of developing , serious low back pain .  Possible mechanisms for the association , from retrospective and prospect i ve points of view , have been advanced OBJECTIVE The aim was to explore the validity and reliability of EMG for assessing lumbar muscle fatigue . DESIGN Patients with long-term low-back trouble ( n=57 ) were compared to a healthy reference group ( n=55 ) . Back muscle fatigue and recovery were studied in relation to health-related factors . BACKGROUND EMG spectral variables are important tools in the assessment of patients with low-back trouble . The influence of disability on these variables needs further investigation . METHODS  EMG from the lower back muscles was recorded during a 45 s trunk extension at 80 % of maximal voluntary contraction torque and during recovery . Disability was studied using question naires . RESULTS The reliability was high for maximal voluntary contraction torque and EMG initial median frequency , lower for the median frequency slope , and insufficient for median frequency recovery half-time . The patients had lower maximal voluntary contraction torque , higher initial median frequency at L5 level , flatter slope , and longer recovery half-time than the healthy subjects did . However , for subjects with significantly negative slope , indicating fatigue , there was no significant difference in slope between patients and healthy subjects , while , for subjects without such fatigue , patients showed significantly flatter slopes at L5 . The sensitivity/specificity of the test was 86%/78 % . The most significant variables selected with logistic regression were maximal voluntary contraction torque and initial median frequency at L5 . Patients without significantly negative slopes during contraction and /or not exponential-like EMG recovery scored worse on several items concerning disability and self-efficacy . CONCLUSIONS EMG spectral variables in combination with torque might be used for classification . For patients with long-term low-back trouble , the ability to fatigue the lumbar muscles sufficiently to obtain a significantly negative slope during an 80 % maximal voluntary contraction may be a sign of better functioning . RELEVANCE The ability to fatigue the back muscles during a test requiring a high force output might be achieved with back muscle training focused on increasing strength and self-efficacy PURPOSE To determine whether dynamic back muscle endurance exercises in a semisitting position induce more fatigue in back muscles than that in hip extensors in healthy controls as well as in patients with nonspecific chronic low back pain . METHODS Sixteen healthy volunteers and 18 volunteers with nonspecific chronic low back pain performed trunk flexion-extension cycles until exhaustion at 60 % of their strength in a machine design ed for back exercise in a semisitting position with knees ' angle at 135 degrees . The number of cycles and perceived muscle fatigue ( Borg CR-10 scale ) at five areas ( upper and lower back , gluteus , hamstrings , and quadriceps ) were used as fatigue criteria . EMG signals were recorded bilaterally on four back muscles , two hip extensors ( gluteus maximus and biceps femoris ) , and the vastus medialis . The slope values of the instantaneous median frequency values computed over time were retained as EMG indices of fatigue . RESULTS The number of cycles was equivalent in healthy controls ( n = 23 + /- 13 ) and patients with back pain ( n = 27 + /- 16 ) . EMG indices of fatigue disclosed evidence of muscle fatigue in all the back muscles and the vastus medialis , contrary to hip extensors . EMG revealed significantly more muscle fatigue of lower back muscles , which was further corroborated by the Borg scale assessment . No between-group difference was obtained in any EMG comparison . CONCLUSION These results showed that this type of exercise machine can specifically train the back muscles , and this as much in subjects with nonspecific chronic low back pain as in healthy controls . This has implication s for the training of back muscle endurance , especially in patients with back pain for whom poor back muscle endurance is sometimes of concern PURPOSE Roman chair exercises are popular for improving back muscle endurance but do not specifically target back muscles . This study aim ed to determine whether an adaptation of the Roman chair exercise would induce more fatigue in back muscles than in hip extensors . METHODS For this study , 16 healthy subjects and 18 patients with nonspecific chronic low back pain performed trunk flexion-extension cycles until exhaustion in a Roman chair with hips flexed at 40 ° . Surface EMG signals  were recorded bilaterally on four back muscles and two hip extensors ( gluteus maximus and biceps femoris ) . Motion analysis of the trunk segments ( pelvis , lumbar , and thoracic spines ) was also carried out . RESULTS In both groups , EMG revealed clear evidence of muscle fatigue for the gluteus maximus , less clear evidence of fatigue for the lower back muscles , and motor unit recruitment ( without fatigue ) for the upper back muscles and biceps femoris . A change of muscle activation pattern was emphasized throughout the exercise bout , with some lower back muscles showing an increase followed by a decrease or leveling off of activation and with upper back muscles showing an increased activation at the end . Kinematic analyses revealed a progressive decrease ( 11 ° ) in the lumbar range of motion ( ROM ) and a progressive increase in hip ( 2 ° ) and thoracic ( 7 ° ) ROM during the exercise bout . CONCLUSIONS Roman chairs allow more freedom to change the kinematics of the spine during the exercise ( less lumbar and more thoracic motion ) to delay lower back muscle fatigue by sharing the load between the lower and upper back muscles . Even with adaptations to reduce hip extensors fatigue , this may make this exercise not as specific as wanted for fatiguing lower back muscles Study Design . Investigative case control study . Objectives . To determine whether excessive paraspinal muscle fatigue in chronic low back pain results from a paucity of muscle type I fiber content . Summary of Background Data . Paraspinal muscle function is vital for spinal protection . Prospect i ve studies suggest that excessive paraspinal muscle fatigability may increase risk of first-time low back pain . As contractile performance of the paraspinal muscles is governed by their constitutionally determined fiber composition , the question arises whether a constitutionally determined “ adverse ” composition could predispose to low back pain through impaired spinal protection . Methods . Thirty-five male patients with chronic low back pain were compared with 32 male control patients of similar age and anthropometry . During Sorensen and 60 % of maximum voluntary isometric contraction fatigue tests , median frequency declines in the  paraspinal muscle surface electromyograph signal were monitored and correlated with muscle histomorphometry . Results . Patients were weaker than controls during maximum voluntary isometric contractions ( 84.47 [28.44]vs . 98.74 [ 18.11 ] kg , respectively ; P = 0.02 ) and more fatigable during their Sorensen tests ( endurance time 105.29 [28.53]vs . 137.50 [ 40.38 ] sec , respectively ; P < 0.01 ) . There were no between-group differences in median frequency declines during the Sorensen ( −0.37 [0.16]vs . −0.36 [0.12]%.sec−1 ) or 60 % maximum voluntary isometric contraction ( −0.42 [0.31]vs . −0.51 [0.29]%.sec−1 ) tests , for patients and controls , respectively . There were no between-group differences in the percent number of paraspinal muscle type I fibers ( 64 [11]vs . 64 [9]% ) or the percent area occupied by type I fibers ( 67 [11]vs . 69 [9]% ) , for patients and controls , respectively . Type I and II muscle fiber narrow diameters were similar for both groups . Conclusion . In the patients with chronic low back pain tested , their associated paraspinal muscle dysfunctionwas not the result of a constitutionally determined “ adverse ” fiber type composition Abstract Of the various methods for measuring pain the  visual analogue scale seems to be the most sensitive . For assessing response to treatment a pain-relief scale has advantages over a pain scale . Pain can not be said to have been relieved unless pain or pain relief has been directly measured & NA ; We asked 78 chronic low back pain patients to report on their usual pain intensity , and on the lifestyle changes caused by their pain , on a horizontally‐oriented visual analogue scale ( VAS ) . Also , the usual and the current pain  intensities were examined on a vertical VAS . Statistical analysis showed normal distribution of data in the measurement of usual pain on the horizontal VAS , but no homogeneous distribution on the vertical VAS . Therefore , in the measurement of chronic low back pain VAS should be used horizontally rather than vertically , because of higher sensitivity . The intensity of usual pain was significantly correlated with the degree of lifestyle change . No correlation was found between current and usual pain . There was no significant difference in the failure rate between the vertical and horizontal VAS . Also , there was no reduction of the failure rate by giving additional oral explanations in the use of the scale to the patient . Owing to a negative influence in distribution of rates and an increase in the failure rate , complex questions should be avoided . A short written introduction to the scale is sufficient , and oral explanations are not essential The paravertebral muscles ( PM ) act together with the hamstrings and calf muscles as important postural muscles . Both the histochemistry , biochemistry , strength and endurance of the PM were studied . Moreover attention was drawn to the exposure of PM , in particular the internal exposure level but to a certain degree repetitiveness and duration , in various job elements , and their various physiological acute responses . The thesis also deal with possible relations between the function of the PM and the magnitude of low-back trouble ( LBP ) , and if PM muscle fatigue may play a role as a mediating factor for the occurrence of work related LBP . The lumbar PM is dominated by relatively small ST fibers with a well-developed network of capillaries , especially distinct in the central sections of PM ( lumbar longissimus muscle ) in females . It is remarkable that ST fibers are of the same size or larger compared to the FT fibers even in well-trained subjects . Further on PM is characterized by high activity levels of enzymes , oxidative as well as non-oxidative , important for the re synthesis of ATP and CrP. Also the level of muscles glycogen concentration is high . Altogether the PM have seemingly a potential for different metabolic pathways which may be selectively activated for a given activity . The average trunk extensor MVC varies in the different studies from 194 - 342 Nm and 252 - 450 Nm in females and males respectively . This is in accordance with predictions based specific strength , muscle cross sections and lever arms from the literature . The large range in strength due to dimension , age and training have to be considered when such data are used for e.g. ergonomic st and ardization and biomechanical modelling . The sex difference is smaller ( female : male trunk extensor strength ratio = 0.7 - 0.8 ) than reported earlier . The small age reduction ( 25 - 60 year ) of the trunk extensor strength , 0.5 % per year , is probably caused by the fact that the ST dominated 
    Output:
    
agent
We found conflicting data regarding the validity of methods used to examine back muscle fatigue .
The Biering-Sorensen test  , performed in conjunction with surface electromyography spectral analysis , turned out to be the most widely used and comparatively , the most optimal modality currently available to assess objective back muscle fatigue in daily clinical practise , even though critical limitations are discussed .
Implication s for Rehabilitation Despite its limitations , the Biering-Sorensen test is currently the most used , convenient and easily available fatiguing test for lumbar muscles .
Pooled mean frequency and half-width of the spectrum are currently the most valid electromyographic parameters to assess fatigue in chronic non-specific low back pain .
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Spectral parameters of the surface electromyographic ( EMG ) signal from lumbar back muscles assessed during a fatiguing isometric contraction can be used to classify different categories of low back pain ( LBP ) subjects and control subjects without LBP . In the test protocol currently used at the NeuroMuscular Research Center at Boston University , subjects contract their back muscles at 80 % of their maximal voluntary contraction ( MVC ) force . This fatigue-based protocol has been successfully applied to persons with subacute or chronic LBP ; those in acute pain , however , have not been included because of their inability to perform a maximal exertion . In this paper we will examine the force sensitivity of the currently used EMG parameters and also give an overview of some of our efforts to develop new test procedures . Our goal is to develop force-insensitive surface EMG parameters that can be used for classification purpose s in population s of subjects who develop low trunk extension forces . In addition , the development of a model to predict MVC from anthropometrical measurements will be presented AIM The aim of this study was to investigate the effect of continuous ultrasound ( US ) plus exercise on the endurance of paravertebral muscles of patients with chronic non specific low back pain ( CNSLBP ) . METHODS AND MATERIAL S In this pilot , pretest-posttest study , 22 patients with CNSLBP participated . Patients received 10 sessions of treatment , including continuous US plus exercise therapy , over a period of four consecutive weeks . Median frequency slopes of Iliocostalis and Multifidus muscles as well as holding time during Biering-Sorensen test were measured using surface electromyography . In addition , function and pain were measured using Functional Rating Index ( FRI ) question naire and VAS . RESULTS Five females and 15 males with a mean age of 31.7 years completed the treatment . Descriptive data showed a decrease of 0.01 and 0.02 mean in median frequency slope of right and left Iliocostalis respectively and a mean of 0.08 decrease for both right and left Multifidus muscles . Endurance time increased 1.8 seconds mean . Both function ( 17 % ) and pain ( 24 % ) improved post treatment . CONCLUSION Larger population studies in the context of high quality , r and omized clinical trial are needed to vali date the results The rate of decline in the median frequency ( MF ) of the surface EMG power spectrum ( MFgrad ) has been evaluated for its use in monitoring the fatigability of the erector spinae muscles during the performance of submaximal isometric contractions . MFgrad consistently displayed a highly significant relationship with endurance time for the task ( p < 0.05 ) , giving a slightly better correlation for contractions performed in lordotic postures , with the back muscles in a shortened position , than in flexed postures . No significant difference existed between mean MFgrad values recorded from the right and left erector spinae muscles , at either thoracic or lumbar levels . The back extensor muscles of men were more fatigable than those of women , and this has been discussed in relation to corresponding differences in muscle fiber type relative size . Greater erector spinae muscle fatigability was associated with both the existence of , and the risk of developing , serious low back pain .  Possible mechanisms for the association , from retrospective and prospect i ve points of view , have been advanced OBJECTIVE The aim was to explore the validity and reliability of EMG for assessing lumbar muscle fatigue . DESIGN Patients with long-term low-back trouble ( n=57 ) were compared to a healthy reference group ( n=55 ) . Back muscle fatigue and recovery were studied in relation to health-related factors . BACKGROUND EMG spectral variables are important tools in the assessment of patients with low-back trouble . The influence of disability on these variables needs further investigation . METHODS  EMG from the lower back muscles was recorded during a 45 s trunk extension at 80 % of maximal voluntary contraction torque and during recovery . Disability was studied using question naires . RESULTS The reliability was high for maximal voluntary contraction torque and EMG initial median frequency , lower for the median frequency slope , and insufficient for median frequency recovery half-time . The patients had lower maximal voluntary contraction torque , higher initial median frequency at L5 level , flatter slope , and longer recovery half-time than the healthy subjects did . However , for subjects with significantly negative slope , indicating fatigue , there was no significant difference in slope between patients and healthy subjects , while , for subjects without such fatigue , patients showed significantly flatter slopes at L5 . The sensitivity/specificity of the test was 86%/78 % . The most significant variables selected with logistic regression were maximal voluntary contraction torque and initial median frequency at L5 . Patients without significantly negative slopes during contraction and /or not exponential-like EMG recovery scored worse on several items concerning disability and self-efficacy . CONCLUSIONS EMG spectral variables in combination with torque might be used for classification . For patients with long-term low-back trouble , the ability to fatigue the lumbar muscles sufficiently to obtain a significantly negative slope during an 80 % maximal voluntary contraction may be a sign of better functioning . RELEVANCE The ability to fatigue the back muscles during a test requiring a high force output might be achieved with back muscle training focused on increasing strength and self-efficacy PURPOSE To determine whether dynamic back muscle endurance exercises in a semisitting position induce more fatigue in back muscles than that in hip extensors in healthy controls as well as in patients with nonspecific chronic low back pain . METHODS Sixteen healthy volunteers and 18 volunteers with nonspecific chronic low back pain performed trunk flexion-extension cycles until exhaustion at 60 % of their strength in a machine design ed for back exercise in a semisitting position with knees ' angle at 135 degrees . The number of cycles and perceived muscle fatigue ( Borg CR-10 scale ) at five areas ( upper and lower back , gluteus , hamstrings , and quadriceps ) were used as fatigue criteria . EMG signals were recorded bilaterally on four back muscles , two hip extensors ( gluteus maximus and biceps femoris ) , and the vastus medialis . The slope values of the instantaneous median frequency values computed over time were retained as EMG indices of fatigue . RESULTS The number of cycles was equivalent in healthy controls ( n = 23 + /- 13 ) and patients with back pain ( n = 27 + /- 16 ) . EMG indices of fatigue disclosed evidence of muscle fatigue in all the back muscles and the vastus medialis , contrary to hip extensors . EMG revealed significantly more muscle fatigue of lower back muscles , which was further corroborated by the Borg scale assessment . No between-group difference was obtained in any EMG comparison . CONCLUSION These results showed that this type of exercise machine can specifically train the back muscles , and this as much in subjects with nonspecific chronic low back pain as in healthy controls . This has implication s for the training of back muscle endurance , especially in patients with back pain for whom poor back muscle endurance is sometimes of concern PURPOSE Roman chair exercises are popular for improving back muscle endurance but do not specifically target back muscles . This study aim ed to determine whether an adaptation of the Roman chair exercise would induce more fatigue in back muscles than in hip extensors . METHODS For this study , 16 healthy subjects and 18 patients with nonspecific chronic low back pain performed trunk flexion-extension cycles until exhaustion in a Roman chair with hips flexed at 40 ° . Surface EMG signals  were recorded bilaterally on four back muscles and two hip extensors ( gluteus maximus and biceps femoris ) . Motion analysis of the trunk segments ( pelvis , lumbar , and thoracic spines ) was also carried out . RESULTS In both groups , EMG revealed clear evidence of muscle fatigue for the gluteus maximus , less clear evidence of fatigue for the lower back muscles , and motor unit recruitment ( without fatigue ) for the upper back muscles and biceps femoris . A change of muscle activation pattern was emphasized throughout the exercise bout , with some lower back muscles showing an increase followed by a decrease or leveling off of activation and with upper back muscles showing an increased activation at the end . Kinematic analyses revealed a progressive decrease ( 11 ° ) in the lumbar range of motion ( ROM ) and a progressive increase in hip ( 2 ° ) and thoracic ( 7 ° ) ROM during the exercise bout . CONCLUSIONS Roman chairs allow more freedom to change the kinematics of the spine during the exercise ( less lumbar and more thoracic motion ) to delay lower back muscle fatigue by sharing the load between the lower and upper back muscles . Even with adaptations to reduce hip extensors fatigue , this may make this exercise not as specific as wanted for fatiguing lower back muscles Study Design . Investigative case control study . Objectives . To determine whether excessive paraspinal muscle fatigue in chronic low back pain results from a paucity of muscle type I fiber content . Summary of Background Data . Paraspinal muscle function is vital for spinal protection . Prospect i ve studies suggest that excessive paraspinal muscle fatigability may increase risk of first-time low back pain . As contractile performance of the paraspinal muscles is governed by their constitutionally determined fiber composition , the question arises whether a constitutionally determined “ adverse ” composition could predispose to low back pain through impaired spinal protection . Methods . Thirty-five male patients with chronic low back pain were compared with 32 male control patients of similar age and anthropometry . During Sorensen and 60 % of maximum voluntary isometric contraction fatigue tests , median frequency declines in the  paraspinal muscle surface electromyograph signal were monitored and correlated with muscle histomorphometry . Results . Patients were weaker than controls during maximum voluntary isometric contractions ( 84.47 [28.44]vs . 98.74 [ 18.11 ] kg , respectively ; P = 0.02 ) and more fatigable during their Sorensen tests ( endurance time 105.29 [28.53]vs . 137.50 [ 40.38 ] sec , respectively ; P < 0.01 ) . There were no between-group differences in median frequency declines during the Sorensen ( −0.37 [0.16]vs . −0.36 [0.12]%.sec−1 ) or 60 % maximum voluntary isometric contraction ( −0.42 [0.31]vs . −0.51 [0.29]%.sec−1 ) tests , for patients and controls , respectively . There were no between-group differences in the percent number of paraspinal muscle type I fibers ( 64 [11]vs . 64 [9]% ) or the percent area occupied by type I fibers ( 67 [11]vs . 69 [9]% ) , for patients and controls , respectively . Type I and II muscle fiber narrow diameters were similar for both groups . Conclusion . In the patients with chronic low back pain tested , their associated paraspinal muscle dysfunctionwas not the result of a constitutionally determined “ adverse ” fiber type composition Abstract Of the various methods for measuring pain the  visual analogue scale seems to be the most sensitive . For assessing response to treatment a pain-relief scale has advantages over a pain scale . Pain can not be said to have been relieved unless pain or pain relief has been directly measured & NA ; We asked 78 chronic low back pain patients to report on their usual pain intensity , and on the lifestyle changes caused by their pain , on a horizontally‐oriented visual analogue scale ( VAS ) . Also , the usual and the current pain  intensities were examined on a vertical VAS . Statistical analysis showed normal distribution of data in the measurement of usual pain on the horizontal VAS , but no homogeneous distribution on the vertical VAS . Therefore , in the measurement of chronic low back pain VAS should be used horizontally rather than vertically , because of higher sensitivity . The intensity of usual pain was significantly correlated with the degree of lifestyle change . No correlation was found between current and usual pain . There was no significant difference in the failure rate between the vertical and horizontal VAS . Also , there was no reduction of the failure rate by giving additional oral explanations in the use of the scale to the patient . Owing to a negative influence in distribution of rates and an increase in the failure rate , complex questions should be avoided . A short written introduction to the scale is sufficient , and oral explanations are not essential The paravertebral muscles ( PM ) act together with the hamstrings and calf muscles as important postural muscles . Both the histochemistry , biochemistry , strength and endurance of the PM were studied . Moreover attention was drawn to the exposure of PM , in particular the internal exposure level but to a certain degree repetitiveness and duration , in various job elements , and their various physiological acute responses . The thesis also deal with possible relations between the function of the PM and the magnitude of low-back trouble ( LBP ) , and if PM muscle fatigue may play a role as a mediating factor for the occurrence of work related LBP . The lumbar PM is dominated by relatively small ST fibers with a well-developed network of capillaries , especially distinct in the central sections of PM ( lumbar longissimus muscle ) in females . It is remarkable that ST fibers are of the same size or larger compared to the FT fibers even in well-trained subjects . Further on PM is characterized by high activity levels of enzymes , oxidative as well as non-oxidative , important for the re synthesis of ATP and CrP. Also the level of muscles glycogen concentration is high . Altogether the PM have seemingly a potential for different metabolic pathways which may be selectively activated for a given activity . The average trunk extensor MVC varies in the different studies from 194 - 342 Nm and 252 - 450 Nm in females and males respectively . This is in accordance with predictions based specific strength , muscle cross sections and lever arms from the literature . The large range in strength due to dimension , age and training have to be considered when such data are used for e.g. ergonomic st and ardization and biomechanical modelling . The sex difference is smaller ( female : male trunk extensor strength ratio = 0.7 - 0.8 ) than reported earlier . The small age reduction ( 25 - 60 year ) of the trunk extensor strength , 0.5 % per year , is probably caused by the fact that the ST dominated 
    Output:
    