***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: The aim of this study was to compare the recruitment patterns and latencies of the scapular muscles , as well as the isokinetic performance  of the shoulder rotators in 10 subjects with unilateral impingement syndrome who comprised the impingement group ( IG ) with a control group ( CG ) of 10 asymptomatic subjects . The recruitment patterns and latencies were evaluated by  electromyographic activity during arm elevation in the scapular plane . Isokinetic work ratios of the shoulder rotator muscles were used to analyze muscular performance . A 2 x 2 ANOVA detected that muscular performance and recruitment patterns were similar for both groups and sides . However , the ANOVA revealed a significant side and group interaction , indicating that the scapular muscle latencies of the affected shoulder was greater than that of the nonaffected side only for the IG ( p < .001 ) . These findings indicated that subjects with light to moderate impingement syndrome showed late recruitment of the scapular muscles during arm elevation . However , muscular performance of the shoulder rotator muscles was not affected Little consensus exists in the literature regarding methods for determination of the onset of electromyographic ( EMG ) activity . The aim of this study was to compare the relative accuracy of a range of computer-based techniques with respect to EMG onset determined visually by an experienced examiner . Twenty-seven methods were compared which varied in terms of EMG processing ( low pass filtering at 10 , 50 and 500 Hz ) , threshold value ( 1 , 2 and 3 SD beyond mean of baseline activity ) and the number of sample s for which the mean must exceed the defined threshold ( 20 , 50 and 100 ms ) . Three hundred r and omly selected trials of a postural task were evaluated using each technique . The visual determination of EMG onset was found to be highly repeatable between days . Linear regression equations were calculated for the values selected by each computer method which indicated that the onset values selected by the majority of the parameter combinations deviated significantly from the visually derived onset values . Several methods accurately selected the time of onset of EMG activity and are recommended for future use OBJECTIVE Since 2002 , an epidemiologic surveillance system of work-related , upper-limb musculoskeletal disorders ( MSDs ) has been implemented in France 's Pays de la Loire region to assess the prevalence of MSDs and their risk factors in the working population . METHODS The surveillance was based on a network of occupational physicians ( OPs ) and used the recommendations of a group of European experts ( criteria document consensus ) . In 2002 - 2003 , 80 of 400 OPs volunteered to participate . All underwent a training program to st and ardize the physical examination .  Health status was assessed by self-administered question naire and physical examination . Occupational risk factors were assessed by self-administered question naire .  Exposure scores were computed for each anatomic zone by summing the risk factors taken into account by the criteria document . RESULTS More than 50 % of the 2,685 men and women r and omly included in 2002 - 2003 experienced nonspecific musculoskeletal symptoms during the preceeding 12 months and approximately 30 % experienced them in the preceeding week . The prevalence of clinical ly diagnosed MSDs was high : approximately 13 % of workers experienced at least 1 of the MSDs . The most frequent disorder was rotator cuff syndrome followed by carpal tunnel syndrome and lateral epicondylitis . The prevalence of MSDs increased with age and varied widely across economic sectors and occupations . More than half of the workers were exposed to at least 2 risk factors of MSDs . Exposure varied according to industrial activity and occupation . According to the criteria document , a high percentage of MSD cases could be classified as probably work related ( 95 % in men and 89 % in women age < 50 , and 87 % in men and 69 % in women age > 50 ) . CONCLUSION Nonspecific upper-limb symptoms and specific upper-limb MSDs are common in the working population . These results show the need to implement prevention programs in most sectors to reduce the prevalence of MSDs BACKGROUND Scapulothoracic muscle activity is believed to be important for normal scapulothoracic motion . In particular , the trapezius and serratus anterior muscles are believed to play an important role in the production and control of scapulothoracic motion . The aim of this study was to determine the effects of different levels of muscle activity ( active versus passive arm elevation ) on three-dimensional scapulothoracic motion . METHODS Twenty subjects without a history of shoulder pathology participated in this study . Three-dimensional scapulothoracic motion was determined from electromagnetic sensors attached to the scapula , thorax and humerus during active and passive arm elevation . Muscle activity was recorded from surface electrodes over the upper and lower trapezius , serratus anterior , anterior and posterior deltoid , and infraspinatus muscles . Differences in scapulothoracic motion were calculated between active and passive arm elevation conditions . FINDINGS Scapular motion was observed during the trials of passive arm elevation ; however , there was more upward rotation of the scapula , external rotation of the scapula , clavicular retraction , and clavicular elevation under the condition of active arm elevation . This was most pronounced for scapular upward rotation through the mid-range ( 90 - 120 degrees ) of arm elevation . INTERPRETATION The upper and lower trapezius and serratus anterior muscles have an important role in producing upward rotation of the scapula especially throughout the mid-range of arm elevation . Additionally , it appears that capsuloligamentous and passive muscle tension contribute to scapulothoracic motion during arm elevation . Assessment of the upper and lower trapezius and serratus anterior muscles and upward rotation of the scapula should be part of any shoulder examination OBJECTIVES To estimate the national prevalence and incidence of adults consulting for a shoulder condition and to investigate patterns of diagnosis , treatment , consultation and referral 3 yr after initial presentation . METHODS Prevalence and incidence rates were estimated for 658469 patients aged 18 and over in the year 2000 using a primary care data base , the IMS Disease Analyzer-Mediplus UK . A cohort of 9215 incident cases was followed-up prospect ively for 3 yr beyond the initial consultation . RESULTS The annual prevalence and incidence of people consulting for a shoulder condition  was 2.36 % [ 95 % confidence interval ( CI ) 2.32 - 2.40 % ] and 1.47 % ( 95 % CI 1.44 - 1.50 % ) , respectively . Prevalence increased linearly with age whilst incidence peaked at around 50 yr then remained static at around 2 % . Around half of the incident cases consulted once only , while 13.6 % were still consulting with a shoulder problem during the third year of follow-up . During the 3 yr following initial presentation , 22.4 % of patients were referred to secondary care , 30.8 % were prescribed non-steroidal anti-inflammatory drugs and 10.6 % were given an injection by their general practitioner ( GP ) . GPs tended to use a limited number of generalized codes when recording a diagnosis ; just five of 426 possible Read codes relating to shoulder conditions accounted for 74.6 % of the diagnoses of new cases recorded by GPs . CONCLUSIONS The prevalence of people consulting for shoulder problems in primary care is substantially lower than community-based estimates of shoulder pain . Most referrals occur within 3 months of initial presentation , but only a minority of patients are referred to orthopaedic specialists or rheumatologists . GPs may lack confidence in applying precise diagnoses to shoulder conditions Properly conducted r and omised trials can aid clinical decision-making by providing unbiased estimates of the average size of treatment effects . This paper , the first of two , discusses how readers of clinical trials can extract simple estimates of treatment effect size from trial reports when trial outcomes are measured on a continuous scale . When making decisions about therapy for individual patients , these estimates can be modified on the basis of patient characteristics . Modified estimates of treatment effect size can be used to determine if the effect of treatment is likely to be large enough to be " clinical ly worthwhile " . This approach optimises clinical decision-making by combining unbiased estimates of the size of treatment effect from clinical trials with clinical intuition and patient preferences BACKGROUND Muscle imbalance between serratus anterior ( SA ) , upper trapezius ( UA ) , middle trapezius ( MT ) , and lower trapezius ( LT ) muscles has been observed in subjects with subacromial impingement syndrome ( SAIS ) . OBJECTIVE ( 1 ) To investigate the effect of electromyography ( EMG ) biofeedback training on muscle balance ratios and scapular kinematics in healthy adults and subjects with SAIS . ( 2 ) To investigate whether the effects of EMG biofeedback on muscle balance ratios are different between groups . DESIGN Twelve healthy adults and 13 subjects with SAIS were recruited in this study .  EMG  was used to record the activity of scapular muscles . The ratios ( UT/SA , UT/MT , and UT/LT ) during exercises with/without EMG biofeedback were calculated . Scapular kinematics were recorded before and after exercises with/without EMG biofeedback . RESULTS For the subjects with SAIS , muscle balance ratios were lower during forward flexion with EMG biofeedback than during exercise only ( UT/SA : 70.3 - 45.2 ; UT/LT : 124.8 - 94.6 ) . Additionally , similar results were found during side-lying external rotation ( UT/MT : 58.5 - 36.4 ) . For the scapular upward rotation and tipping in both groups , there were no significant differences with and without EMG biofeedback . CONCLUSION EMG biofeedback improved the scapular muscular balance during training exercises in both groups . Further clinical trials should investigate the long-term effects of EMG biofeedback OBJECTIVE To examine the influence of pain on activation in brief maximal and sustained submaximal isometric abduction in patients with rotator tendinosis of the shoulder . DESIGN R and omized , controlled experimental trial . PARTICIPANTS Ten patients with complaints of at least 3 months ' duration ( median range , 1 to 2 years ) and nine healthy controls . INTERVENTION Patients and controls were r and omized into subacromial local anesthetic injection on 2 different days . METHODS The uninvolved shoulder was tested first , elbow flexed 90 degrees , shoulder abducted 45 degrees . The protocol consisted of three brief maximal voluntary contractions ( MVCs ) , followed by a sustained submaximal contraction until exhaustion and three MVCs during a 20-minute recovery period . Electromyography ( EMG ) was obtained bilaterally from the supraspinatus , infraspinatus , upper trapezius , and middle deltoid muscles . Pain was scored on a visual analogue scale ( 0 to 100 ) . RESULTS Mean pain rating on MVC of the involved side of patients was reduced from 28 to 10 by subacromial injection . Mean MVC force improved from 163N to 184N ( 95 % confidence interval for the difference , 14 to 29N ) . The accompanying EMG amplitude during MVC increased significantly in three of the four muscles examined . Pain , force , and EMG of the uninvolved side and in controls were unaltered . Endurance time and EMG ( given as microV ) during the submaximal contraction were not influenced by pain . MVC did not fully recover during the postexhaustive period , while the corresponding EMG amplitudes were comparable to values in unfatigued muscle . CONCLUSION Pain reduced central motor drive during maximal efforts in the unfatigued state , but no additional reduction was seen after a sustained submaximal contraction A quantitative systematic review , or meta- analysis , uses statistical methods to combine the results of multiple studies . Meta-analyses have been done for systematic review s of therapeutic trials , diagnostic test evaluations , and epidemiologic studies . Although the statistical methods involved may at first appear to be mathematically complex , their purpose is simple : They are trying to answer four basic questions . Are the results of the different studies similar ? To the extent that they are similar , what is the best overall estimate ? How precise and robust is this estimate ? Finally , can dissimilarities be explained ? This article provides some guidance in underst and ing the key technical aspects of the quantitative approach to these questions . We have avoided using equations and statistical notations ; interested readers will find implementations of the described methods in the listed references . We focus here on the quantitative synthesis of reports of r and omized , controlled , therapeutic trials because far more meta-analyses on therapeutic studies than on other types of studies have been published . For practical reasons , we present a stepwise description of the tasks that are performed when statistical methods are used to combine data . These tasks are 1 ) deciding whether to combine data and defining what to combine , 2 ) evaluating the statistical heterogeneity of the data , 3 ) estimating a common effect , 4 ) exploring and explaining heterogeneity , 5 ) assessing the potential for bias , and 6 ) presenting the results . Deciding Whether To Combine Data and Defining What To Combine By the time one performs a quantitative synthesis , certain decisions should already have been made about the formulation of the question and the selection of included studies . These topics were discussed in two previous articles in this series [ 1 , 2 ] . Statistical tests can not compensate for lack of common sense , clinical acumen , and biological plausibility in the design of the protocol of a meta- analysis . Thus , a reader of a systematic review should always address these issues before evaluating the statistical methods that have been used and the results that have been generated . Combining poor- quality data , overly biased data , or data that do not make sense can easily produce unreliable results . The data to be combined in a meta- analysis are usually 
    Output:
    
Results There was limited evidence that serratus anterior has lower amplitude , delayed activation and earlier termination in SPS participants .
For the majority of muscles , regardless of task , load or arm position , significant differences were not demonstrated or results were contradictory .
Conclusions The underst and ing of SPS is changing and EMG appears unable to capture the complexities associated with this condition .