***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: 1 . The objectives of this study were to ( 1 ) quantify experimentally in vivo changes in pennation angle , fibre length and muscle thickness in the triceps surae complex in man in response to changes in ankle position and isometric plantarflexion moment and ( 2 ) compare changes in the above muscle architectural characteristics occurring in the transition from rest to a given isometric plantarflexion intensity with the estimations of a planimetric muscle model assuming constant thickness and straight muscle fibres . 2 . The gastrocnemius medialis ( GM ) , gastrocnemius lateralis ( GL ) and soleus ( SOL ) muscles of six males were scanned with ultrasonography at different sites along and across the muscle belly at rest and during maximum voluntary contraction ( MVC ) trials at ankle angles of -15 deg ( dorsiflexed direction ) , 0 deg ( neutral position ) , + 15 deg ( plantarflexed direction ) and + 30 deg . Additional images were taken at 80 , 60 , 40 and 20 % of MVC at an ankle angle of 0 deg . 3 . In all three muscles and all scanned sites , as ankle angle increased from -15 to + 30 deg , pennation increased ( by 6 - 12 deg , 39 - 67 % , P < 0.01 at rest and 9 - 16 deg , 29 - 43 % , P < 0.01 during MVC ) and fibre length decreased ( by 15 - 28 mm , 32 - 34 % , P < 0.01 at rest and 8 - 10 mm , 27 - 30 % , P < 0.05 during MVC ) . Thickness in GL and SOL increased during MVC compared with rest ( by 5 - 7 mm , 36 - 47 % , P < 0.01 in GL and 6 - 7 mm , 38 - 47 % , P < 0.01 in SOL ) while thickness of GM did not differ ( P > 0.05 ) between rest and MVC . 4 . At any given ankle angle the model underestimated changes in GL and SOL occurring in the transition from rest to MVC in pennation angle ( by 9 - 12 deg , 24 - 38 % , P < 0.01 in GL and 9 - 14 deg , 25 - 28 % , P < 0.01 in SOL ) and fibre length ( by 6 - 15 mm , 22 - 39 % , P < 0.01 in GL and 6 - 8 mm , 23 - 24 % , P < 0.01 in SOL ) . 5 . The findings of the study indicate that the mechanical output of muscle as estimated by the model used may be unrealistic due to errors in estimating the changes in muscle architecture during contraction compared with rest PURPOSE The purpose of the study was to investigate the effect of 4 and 8 wk of electromyostimulation ( EMS ) training on both muscular and neural adaptations of the knee extensor muscles . METHODS Twenty males were divided into the electrostimulated group ( EG , N = 12 ) and the control group ( CG , N = 8) . The training program consisted of 32 sessions of isometric EMS over an 8-wk period . All subjects were tested at baseline ( B ) and retested after 4 ( WK4 ) and 8 ( WK8 ) wk of EMS training . The EMG activity and muscle activation obtained under maximal voluntary contractions ( MVC ) was used to assess neural adaptations . Torque and EMG responses obtained under electrically evoked contractions , muscle anatomical cross-sectional area ( ACSA ) , and vastus lateralis ( VL ) pennation angle , both measured by ultrasonography imaging , were examined to analyze muscular changes . RESULTS At WK8 , knee extensor MVC significantly increased by 27 % ( P < 0.001 ) and was accompanied by an increase in muscle activation ( + 6 % , P < 0.01 ) , quadriceps muscle ACSA ( + 6 % , P < 0.001 ) , and VL pennation angle ( + 14 % , P < 0.001 ) . A significant increase in normalized EMG activity of both VL and vastus medialis ( VM ) muscles ( + 69 and + 39 % , respectively , P < 0.001 ) but not of rectus femoris ( RF ) muscle was also found at WK8 . The ACSA of the VL , VM , and vastus intermedius muscles significantly increased at WK8 ( 5 - 8 % , P < 0.001 ) but not at WK4 , whereas no changes occurred in the RF muscle . CONCLUSION We concluded that the voluntary torque gains obtained after EMS training could be attributed to both muscular and neural adaptations . Both changes selectively involved the monoarticular vastii muscles Abstract .There are a number of similarities between chronic exertional compartment syndrome ( CECS ) and the effects of high force eccentric contractions in healthy controls . We hypothesised that CECS patients would be particularly susceptible to pain , fatigue and swelling after eccentric exercise . Ten CECS patients [ aged 30.3 ( 8.0 ) years , mean ( SD ) ] , 7 males ) and 14 healthy controls [ aged 32.3 ( 9.0 ) years , 7 males ] performed 40 maximal eccentric contractions of the anterior tibial muscles at an angular velocity of 90o s–1 . Maximal voluntary isometric contractions ( MVC ) , force generated by electrical stimulation at 10 Hz and 50 Hz and muscle thickness ( measured by real-time ultrasound scanning ) were measured before exercise and for 10 min afterwards . Ratings of pain and tenderness were made before exercise , then 24 h and 48 h later . The two groups were comparable for initial isometric strength and muscle size . MVC force immediately after exercise fell to 90 (2.5)% [ mean ( SEM ) ] in patients and 86.5 (2.4)% in controls ( P<0.0005 for both groups ) and had not recovered after 10 min . Preferential loss of force at the low stimulation frequency occurred in both groups to a similar extent ( 20 % , P<0.0005 ) and continued to decline over 10 min of recovery . There was no significant change in muscle thickness in either group . Only mild pain and tenderness were reported by the controls . The patients showed great individual variation but their mean pain scores were significantly higher during dorsiflexion and palpation ( P<0.05 ) 24 h after exercise . After 48 h the patients reported more pain during dorsiflexion ( P=0.005 ) , plantarflexion ( P<0.05 ) and palpation ( P<0.05 ) . These results suggest that some , but not all , CECS patients may be more susceptible to the pain associated with eccentric contractions that is thought to be the cause of damage and inflammation of connective tissue This study aim ed to investigate the accuracy of estimating the volume of limb muscles ( MV ) using ultrasonographic muscle thickness ( MT ) measurements . The MT and MV of each of elbow flexors and extensors , knee extensors and ankle plantar flexors were determined from a single ultrasonographic image and multiple magnetic resonance imaging ( MRI ) scans , respectively , in 27 healthy men ( 23–40 years of age ) who were allocated to validation ( n=14 ) and cross-validation groups ( n=13 ) . In the validation group , simple and multiple regression equations using MT and a set of MT and limb length , respectively , as independent variables were derived to estimate the  MV  measured by MRI . However , only the multiple regression equations were cross-vali date d , and so the prediction equations with r2 of 0.787–0.884 and the st and ard error of estimate of 22.1 cm3 ( 7.3 % ) for the elbow flexors to 198.5 cm3 ( 11.1 % ) for the knee extensors were developed using the pooled data . This approach did not induce significant systematic error in any muscle group , with no significant difference in the accuracy of estimating MV between muscle groups . In the multiple regression equations , the relative contribution of MT for predicting MV varied from 41.9 % for the knee extensors to 70.4 % for the elbow flexors . Thus , ultrasonographic MT measurement was a good predictor of MV when combined with limb length . For predicting MV , however , the unsuitability of a simple equation using MT only and the difference between muscle groups in the relative contribution of MT in multiple regression equations indicated a need for further research on the limb site selected and muscle analyzed for MT measurement The present study was performed to develop regression-based prediction equations for skeletal muscle ( SM ) mass by ultrasound and to investigate the validity of these equations in Japanese adults . Seventy-two Japanese men ( n=38 ) and women ( n=34 ) aged 18–61 years participated in this study and were r and omly separated into two groups : the model development group ( n=48 ) and the validation group ( n=24 ) . The total and regional SM mass were measured using magnetic resonance imaging ( MRI ) 1.5 T-scanners with spin-echo sequence . Contiguous transverse images ( about 150 slices ) with a slice thickness of 1 cm were obtained from the first cervical vertebra to the ankle joints . The volume of SM was calculated from the summation of digitized cross-sectional area . The SM volume was converted into mass units ( kg ) by an assumed SM density of 1.04 kg l−1 . The muscle thickness ( MTH ) was measured by B-mode ultrasound ( 5 MHz scanning head ) at nine sites on the anatomical SM belly . Strong correlations were observed between the site-matched SM mass ( total , arm , trunk body , thigh , and lower leg ) by MRI measurement and the MTH × height ( in m ) in the model development group ( r=0.83–0.96 in men , r=0.53–0.91 in women , P<0.05 ) . When the SM mass prediction equations were applied to the validation group , significant correlations were also observed between the MRI-measured and predicted SM mass ( P<0.05 ) . The predicted total SM mass for the validation group was 19.6 ( 6.5 ) kg and was not significantly different from the MRI-measured SM mass of 20.2 ( 6.5 ) kg . Bl and –Altman analysis did not indicate a bias in prediction of the total SM mass for the validation group ( r=0.00 , NS ) . These results suggested that ultrasound-derived prediction equations are a valid method to predict SM mass and an alternative to MRI measurement in healthy Japanese adults Abstract . This study aim ed to investigate the suitability of using ultrasonograph muscle thickness ( MT ) measurements to estimate the muscle volume ( MV ) of the quadriceps femoris as an alternative approach to magnetic resonance imaging ( MRI ) . The subjects were 46 men aged from 20 to 70 years who were r and omly allocated to either a validation or a cross-validation group . In the validation group , multiple and simple regression equations , which used a set of MT values determined at mid-thigh and thigh length ( l ) and the product of π , (MT/2)2 , and l [ π·(MT/2)2·l ] , respectively , as independent variables , were derived to estimate the MV measured by MRI . Because the two equations were cross-vali date d , the data from the two groups were pooled to generate the final prediction equations : MV (cm3)=(MT × 311.732)+(l × 53.346 ) –2058.529 as the multiple regression equation and MV (cm3)=[π·(MT/2)2·l] × 1.1176 + 663.040 as the simple regression equation . In the multiple regression equation , MT explained 75 % of the variation in the MV measured by MRI .  The r2 and the st and ard error of the estimate ( SEE ) of the equations were 0.824 and 175.6 cm3 ( 10.6 % ) , respectively , for the multiple regression equation and 0.829 and 173.7 cm3 ( 10.5 % ) , respectively , for the simple regression equation . Thus , the present results indicate that ultrasonograph MT measurements at mid-thigh are useful for estimating the MV of knee extensors . However , the observed SEE values suggest that the prediction equation obtained in this study may be limited to population studies rather than individual assessment s in longitudinal studies 
    Output:
    
Conclusion : There is a moderate amount of low-level evidence that real-time brightness-mode ultrasound has good reliability for measuring muscle size across a number of limb sites in healthy population s. There is limited evidence for the reliability of ultrasound measures of muscle size in clinical population