***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: CONTEXT Nondystrophic myotonias ( NDMs ) are rare diseases caused by mutations in skeletal muscle ion channels . Patients experience delayed muscle relaxation causing functionally limiting stiffness and pain . Mexiletine-induced sodium channel blockade reduced myotonia in small studies ; however , as is common in rare diseases , larger studies of safety and efficacy have not previously been considered feasible . OBJECTIVE To determine the effects of mexiletine for symptoms and signs of myotonia in patients with NDMs . DESIGN , SETTING , AND PARTICIPANTS A r and omized , double-blind , placebo-controlled 2-period crossover study at 7 neuromuscular referral centers in 4 countries of 59 patients with NDMs conducted between December 23 , 2008 , and March 30 , 2011 , as part of the National Institutes of Health-funded Rare Disease Clinical Research Network . INTERVENTION Oral 200-mg mexiletine or placebo capsules 3 times daily for 4 weeks , followed by the opposite intervention for 4 weeks , with 1-week washout in between . MAIN OUTCOME MEASURES Patient-reported severity score of stiffness recorded on an interactive voice response ( IVR ) diary ( scale of 1 = minimal to 9 = worst ever experienced ) . Secondary end points included IVR-reported changes in pain , weakness , and tiredness ; clinical myotonia assessment ; quantitative measure of h and grip myotonia ; and Individualized Neuromuscular Quality of Life summary quality of life score ( INQOL-QOL , percentage of maximal detrimental impact ) . RESULTS Mexiletine significantly improved patient-reported severity score stiffness on the IVR diary . Because of a statistically significant interaction between treatment and period for this outcome , primary end point is presented by period ( period 1 means were 2.53 for mexiletine and 4.21 for placebo ; difference , -1.68 ; 95 % CI , -2.66 to -0.706 ; P < .001 ; period 2 means were 1.60 for mexiletine and 5.27 for placebo ; difference , -3.68 ; 95 % CI , -3.85 to -0.139 ; P = .04 ) . Mexiletine improved the INQOL-QOL score ( mexiletine , 14.0 vs placebo , 16.7 ; difference , -2.69 ; 95 % CI , -4.07 to -1.30 ; P < .001 ) and decreased h and grip myotonia on clinical examination ( mexiletine , 0.164 seconds vs placebo , 0.494 seconds ; difference , -0.330 ; 95 % CI , -0.633 to -0.142 ; P < .001 ) . The most common adverse effect was gastrointestinal ( 9 mexiletine and 1 placebo ) . Two participants experienced transient cardiac effects that did not require stopping the study ( 1 in each group ) . One serious adverse event was determined to be not study related . CONCLUSION In this preliminary study of patients with NDMs , the use of mexiletine compared with placebo result ed in improved patient-reported stiffness over 4 weeks of treatment , despite some concern about the maintenance of blinding . TRIAL REGISTRATION clinical trials.gov Identifier : NCT00832000 Background Myotonic dystrophy type 1 ( DM1 ) is a multisystem disorder that demonstrates variable symptoms and rates of progression . Muscle weakness is considered one of the main problems with a clinical picture that is characterized by distal weakness of the limbs progressing to proximal weakness . The main objective of this study was to characterize the maximal strength of ankle eversion and dorsiflexion in DM1 patients .  Manual and h and held dynamometer ( HHD ) muscle testing were also compared . Methods The maximal strength of 22 patients from Quebec ( mean age = 41,1 ± 13,8 ) and 24 from Lyon ( mean age = 41,6 ± 10,2 ) were compared to 16 matched controls . Results With the use of HHD , an excellent reproducibility of the torque measurements was obtained for both centers in eversion ( R2 = 0,94/Quebec ; 0,89/Lyon ) and dorsiflexion ( R2 = 0,96/Quebec ; 0,90/Lyon ) . The differences between 3 groups of DM1 ( mild , moderate , severe ) and between them and controls were all statistically significant ( p < 0,001 ) . No statistical differences between sites were observed ( p > 0.05 ) . The degree of muscle strength decline in dorsiflexion ( eversion ) were 60 % ( 47 % ) , 77 % ( 71 % ) , and 87 % ( 83 % ) for DM1 with mild , moderate , and severe impairments , respectively . The smallest mean difference between all DM1 patients taking together was 2.3 Nm , a difference about twice than the st and ard error of measurement . There was a strong relationship between eversion and dorsiflexion strength profiles ( R2 = 0,87;Quebec/0,80;Lyon ) . Using a 10-point scale , manual muscle testing could not discriminate between the 3 groups of DM1 patients . Conclusions The HHD protocol showed discriminative properties suitable for multicentre therapeutic trial . The present results confirmed the capacity of quantitative muscle testing to discriminate between healthy and DM1 patients with different levels of impairments . This study is a preliminary step for the implementation of a valid , reliable and responsive clinical outcome for the measurement of muscle impairments with this population OBJECTIVE To revise the content of the Functional Index in myositis ( FI ) and to evaluate measurement properties of a revised FI . METHODS Previously performed FI ( n = 287 ) were analyzed for internal redundancy and consistency , and ceiling and floor effects . Content was evaluated and a preliminary revised FI was developed . To evaluate the construct validity of the preliminary revised FI , it was compared with isokinetic measurements of muscular strength and endurance , the Myositis Activities Profile , disease impact on general wellbeing , and creatine phosphokinase levels . Minor adjustments were made and the revised FI was investigated for interrater reliability and intrarater reliability over a 1-week period . After this , some minor , additional adjustments were made leading to the final version , FI-2 . RESULTS Five tasks were removed from the original FI due to ceiling effects . Performance pace and number of repetitions were modified for the remaining tasks . A moderate correlation ( r(s ) = 0.58 ) was found between the shoulder flexion task of the preliminary revised FI and isokinetic measurements of shoulder flexion endurance . Intraclass correlation coefficient ( ICC ) for interrater reliability of the revised FI varied from 0.86 - 0.99 with no systematic differences . ICC for intrarater reliability varied from 0.56 - 0.99 with systematic differences ( P < 0.05 ) between test and retest in 3 of the tasks . The sit-up task was excluded due to low intrarater reliability result ing in the final 7-item FI-2 . There was a good correlation between tasks on the right and left side suggesting that the FI-2 could be performed unilaterally . CONCLUSION The FI-2 is a valid and reliable outcome measure of impairment for patients with polymyositis or dermatomyositis . It is well tolerated and the unilateral FI-2 requires a maximum of 20 minutes to perform . Further evaluation of sensitivity to change and testing in healthy individuals needs to be conducted Background : Myotonic dystrophy type 1 is a slowly progressive multisystem disease in which skeletal muscle involvement is prominent . As novel physical and pharmacological treatments become available , it is crucial to be able to measure their efficacy accurately . Methods : 158 consecutive patients with myotonic dystrophy were assessed annually in a specialist muscle clinic . Strength was measured using both the Medical Research Council ( MRC ) scale and a h and -held dynamometer . Dynamometer readings were obtained from 108 normal subjects ( controls ) . Results : The movements showing the greatest rate of change in strength were ankle dorsiflexion and pinch grip . Both of these showed a decline of only 0.06 points/year on the MRC scale . Using a h and -held dynamometer , a change in strength of 1.18 kgN/year for women and 1.61 kgN/year for men was detected . Conclusions : The MRC scale is unsuitable for detecting the small changes in strength seen in a slowly progressive disease such as myotonic dystrophy . Dynamometry provides a simple alternative that can give meaningful data over the duration of a typical clinical trial Objective : This method ologic study investigates if the 2-minute walk test ( 2MWT ) can be a valid alternative to the 6-minute walk test ( 6MWT ) to describe walking capability in patients with neuromuscular diseases . Methods : Patients ( n = 115 ) with different neuromuscular diseases were invited to participate on 2 test days , each consisting of 1 2MWT and 1 6MWT separated by a minimum 30-minute period of rest . The order of the walk tests was r and omly assigned via sealed envelopes . A group of 38 healthy controls completed 1 6MWT . Results : The mean walking distance for the 2MWT was 142.8 meters and for the 6MWT 405.3 meters . The distance walked in the 2MWT  was highly correlated to the distance walked in the 6MWT ( r = 0.99 , p < 0.001 ) . There was a significant decrease in walking speed from the first to last minute in the 6MWT , both among patients and healthy controls , which was not evident in the 2MWT . Results were consistent across diagnoses and levels of disease severity . Conclusion : The 2MWT is a potential alternative to the 6MWT to describe walking capability among patients with neuromuscular diseases during clinical trials BACKGROUND / PURPOSE The six minute walk test is a widely accepted primary outcome parameter in most studies in Duchenne muscular dystrophy ( DMD ) . To compare information obtained by the six minute walk distance ( 6MWD ) test and the two minute walk distance ( 2MWD ) in patients with DMD , a cohort of 13 voluntary DMD boys did a repeated six minute walking test . METHODS Patients had to be ambulatory with a physical disability according to Levels 1 - 3 on the Vignos-Scale for lower extremity . Measurements were taken at one minute intervals . Reliability was measured by intraclass correlation . RESULTS Test-retest reliability for 6MWD and 2MWD in two different age classes was very good for both subgroups . Test-retest-reliability was lower in patients with more advanced disability in both tests . Walking speed remained completely stable from time points 1 - 6 minutes in the whole study patient collective , which indicates that physical exhaustion is not reached after six minutes even in more disabled patients . CONCLUSION Thus the 6MWD in DMD patients does not give additional information as compared to a 2MWD Objective To evaluate interrater reliability using 5 newly trained observers in the assessment of  pressure pain threshold ( PPT )  using a fixed-angle algometer . Methods The study design comprised 2 phases . Phase 1 : 5 undergraduate physical therapists were  trained  in algometry at a predefined angle , at a rate of 5 Newtons (N)/s , to the first dorsal interosseous muscle . Each observer then underwent a competency test of the application speed . The aim was to achieve repeated applications at 5 N/s without visual feedback from the algometer . Phase 2 : the 5 observers measured PPT of 13 healthy volunteers , at the first dorsal interosseous muscle . The sequence of observer measurements for each participant was r and omized . Mean PPT values for each observer were analyzed using repeated measures analysis of variance , intraclass correlation coefficient ( ICC2,1 ) , and st and ard error of measurement , with 95 % confidence intervals ( CIs ) . Results No significant differences between observers ' mean values were found ( P=0.094 ) , suggesting no bias . The ICC was 0.91 ( 95 % CI 0.82 , 0.97 ) . The st and ard error of measurement value was 6.27 N/cm2 ( 95 % CI 5.35 , 7.59 ) . Differences in PPT measurements of more than 17.39 N/cm2 ( 1.77 kg/cm2 ) are likely to exceed the magnitude of measurement error , and could be used to indicate true change . This margin of error is , however , somewhat larger than a previously proposed minimum clinical ly important difference in PPT of 14.71 N/cm2 ( 1.5 kg/cm2 ) . Discussion This study provides new evidence that trained observers can apply an algometer at a consistent rate and provide highly reliable measures of PPT in healthy humans , when PPT is calculated as the mean of 3 trials The purpose of this study was to estimate inter-examiner reliability of  head and neck algometry .  Pain perception thresholds were assessed with a mechanical pressure algometer in 21 healthy individuals . Thresholds were assessed at 13 symmetrical points on each side of the head and neck , at the deltoid muscle and at the median finger . The pressure range of the instrument proved insufficient to study the pain perception threshold on the finger , however . Two different examiners carried out one or two examinations in each subject during one day . The sequence of investigations was varied r and omly . The inter-examiner reliability was found to be good , with a mean intra-class correlation coefficient ( ICC ) of 0.75 . Intra-examiner reproducibility was excellent ( mean ICC = 0.84 ) . The mean inter-examiner coefficient of 
    Output:
    
Recent findings : No outcome measures or PROs have been vali date d in DM2 .
The most used PROs in DM2 were INQoL , SF-36 , MPQ , and BPI .
It is not clear whether it is better to use MMT or QMT to assess muscle strength .
The algometer seems to be a useful tool to assess myalgia .
No currently adopted tests or PROs seem effective to assess the mild myotonia of DM2 .