***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: Clinical practice involves measuring quantities for a variety of purpose s , such as aiding diagnosis , predicting future patient outcomes , and serving as endpoints in studies or r and omized trials . Measurements are almost always prone to various sorts of errors , which cause the measured value to differ from the true value ; accordingly , studies investigating measurement error frequently appear in this and other journals . The importance of measurement error depends upon the context in which the measurements in question are to be used . For example , a certain degree of measurement error may be acceptable if measurements are to be used as an outcome in a comparative study such as a clinical trial , but the same measurement errors may be unacceptably large to make measurements usable in individual patient management , such as screening or risk prediction . In the past 20 years many papers have been published advocating how studies of measurement error should be analyzed , with a paper by Bl and and Altman1 being one of the most cited and well known examples . There has been much controversy concerning the choice of parameter to be estimated and reported , and consequently confusion surrounding the meaning and interpretation of results from studies investigating measurement error . In this paper we first distinguish between the general concepts of agreement and reliability to aid research ers in considering which are relevant for their particular application . We then review the statistical methods that can be used to investigate and quantify agreement and reliability , dealing separately with the different types of measurement error study , while emphasizing the largely common techniques that should be used for data analysis . We reiterate that the judgment of whether agreement or reliability are acceptable must be related to the clinical application , and can not be proven by a statistical test . We highlight the fact that reliability depends on the population in which measurements are made , and not just on the measurement errors of the measurement method . We discuss the advantages of method comparison studies making at least two measurements with each measurement method on each subject . A key advantage is that the cause of a correlation between paired differences and means in the so-called Bl and –Altman plot can be determined , in contrast to when only a single measurement is made with each method . Throughout the paper , we try to emphasize that calculated values of agreement and reliability from measurement error studies are estimates of parameters , and as such we should report such estimates with CIs to indicate the uncertainty with which they have been estimated . We restrict our attention to measurements of a continuous quantity ; alternative methods are required for categorical data 2 The interaction between fascicle and tendinous tissues ( TT ) in short-contact drop jumps ( DJ ) with three different drop heights [ low ( Low ) , optimal ( OP ) , and high ( High ) ] was examined with 11 subjects . The ground reaction force ( F(z ) ) and  ankle and knee joint angles  were measured together with real-time ultrasonography ( fascicle length ) and electromyographic activities of the medial gastrocnemius ( MG ) and vastus lateralis ( VL ) muscles during the movement . With increasing drop height , the braking force and flight time increased from Low to OP ( P < 0.05 ) . In High , the braking force increased but the flight time decreased compared with OP ( P < 0.05 ) . During contact of Low and OP conditions , the length of muscle-tendon unit and TT underwent lengthening before shortening in both MG and VL muscles . However , the two muscles differed in the fascicle behaviors . The MG fascicles behaved isometrically or shortened , and the VL fascicles underwent lengthening before shortening during contact . In High , the TT lengthening in both muscles decreased compared with OP ( P < 0.05 ) . The rapid stretch occurred in the MG fascicles but not in VL fascicles during the braking phase . The elastic recoil ratio decreased in both muscles with increasing the intensity during DJ . These findings demonstrated that TT underwent lengthening before shortening during DJ . However , the efficacy of elastic recoil decreased with increasing the drop intensity . The effective catapult action in TT can be limited by the drop intensity . In addition , the measured muscles behaved differently during DJ , providing evidence that each muscle may have a specific means of fascicle-TT interaction The present study was design ed to examine fascicle-tendon interaction in the synergistic medial gastrocnemius ( MG ) and soleus ( Sol ) muscles during drop jumps ( DJ )  performed from different drop heights ( DH ) . Eight subjects performed unilateral DJ with maximal rebounds on a sledge apparatus from different DH . During the exercises , fascicle lengths ( using ultrasonography ) and  electromyographic activities  were recorded . The results showed that the fascicles of the MG and Sol muscles behaved differently during the contact phase , but the whole muscle-tendon unit and its tendinous tissue lengthened before shortening in both muscles . The Sol fascicles also lengthened before shortening during the ground contact in all conditions . During the braking phase , the Sol activation increased with increasing DH . However , the amplitude of Sol fascicle lengthening was not dependent on DH during the same phase . In the MG muscle , the fascicles primarily shortened during the braking phase in the lower DH condition . However , in the higher DH conditions , the MG fascicles either behaved isometrically or were lengthened during the braking phase . These results suggest that the fascicles of synergistic muscles ( MG and Sol ) can behave differently during DJ and that , with increasing DH , there may be specific length change patterns of the fascicles of MG but not of Sol Plantar flexor series elasticity can be used to dissociate muscle-fascicle and muscle-tendon behavior and thus afferent feedback during human walking . We used electromyography ( EMG ) and high-speed ultrasonography concomitantly to monitor muscle activity and muscle fascicle behavior in 19 healthy volunteers as they walked across a platform . On r and om trials , the platform was dropped ( 8 cm , 0.9 g acceleration ) or held at a small inclination ( up to + /-3 degrees in the parasagittal plane ) with respect to level ground . Dropping the platform in the mid and late phases of stance produced a depression in the soleus muscle activity with an onset latency of about 50 ms . The reduction in ground reaction force also unloaded the plantar flexor muscles . The soleus muscle fascicles shortened with a minimum delay of 14 ms . Small variations in platform inclination produced significant changes in triceps surae muscle activity ; EMG increased when stepping on an inclined surface and decreased when stepping on a declined surface . This sensory modulation of the locomotor output was concomitant with changes in triceps surae muscle fascicle and gastrocnemius tendon length . Assuming that afferent activity correlates to these mechanical changes , our results indicate that within-step sensory feedback from the plantar flexor muscles automatically adjusts muscle activity to compensate for small ground irregularities . The delayed onset of muscle fascicle movement after dropping the platform indicates that at least the initial part of the soleus depression is more likely mediated by a decrease in force feedback than length-sensitive feedback , indicating that force feedback contributes to the locomotor activity in human walking Fascicle curvature of human medial gastrocnemius muscle ( MG ) was determined in vivo by ultrasonography during  isometric contractions  at three ( distal , central , and proximal ) locations ( n = 7 ) and at three ankle angles ( n = 7 ) . The curvature significantly ( P < 0.05 ) increased from rest to maximum voluntary contraction ( MVC ) ( 0.4 - 5.2 m(-1 ) ) . In addition , the curvature at MVC became larger in the order dorsiflexed , neutral , plantar flexed ( P < 0.05 ) . Thus both contraction levels and muscle length affected the curvature . Intramuscular differences in neither the curvature nor the fascicle length were found . The direction of curving was consistent along the muscle : fascicles were concave in the proximal side . Fascicle length estimated from the pennation angle and muscle thickness , under the assumption that the fascicle was straight , was underestimated by ~6 % . In addition , the curvature was significantly correlated to pennation angle and muscle thickness . These findings are particularly important for underst and ing the mechanical functions of human skeletal muscle in vivo Architectural properties of the triceps surae muscles were determined in vivo for six men . The ankle was positioned at 15 degrees dorsiflexion ( -15 degrees ) and 0 , 15 , and 30 degrees plantar flexion , with the knee set at 0 , 45 , and 90 degrees . At each position , longitudinal ultrasonic images of the medial ( MG ) and lateral ( LG ) gastrocnemius and soleus ( Sol ) muscles were obtained while the subject was relaxed ( passive ) and performed maximal isometric plantar flexion ( active ) , from which fascicle lengths and angles with respect to the aponeuroses were determined . In the passive condition , fascicle lengths changed from 59 , 65 , and 43 mm ( knee , 0 degrees ; ankle , -15 degrees ) to 32 , 41 , and 30 mm ( knee , 90 degrees ankle , 30 degrees ) for MG , LG , and Sol , respectively . Fascicle shortening by contraction was more pronounced at longer fascicle lengths . MG had greatest fascicle angles , ranging from 22 to 67 degrees , and was in a very disadvantageous condition when the knee was flexed at 90 degrees , irrespective of ankle positions . Different lengths and angles of fascicles , and their changes by contraction , might be related to differences in force-producing capabilities of the muscles and elastic characteristics of tendons and aponeuroses Abstract Purpose The present study examined the effects of repetitive hopping training on muscle activation profiles and fascicle – tendon interaction in the elderly . Methods 20 physically active elderly men were r and omly assigned for training ( TG ) and control groups ( CG ) . TG performed supervised bilateral short contact hopping training with progressively increasing training volume . Measurements were performed before the training period ( BEF ) as well as after 2 weeks ( 2 W ) and 11 weeks ( 11 W ) of training . During measurements , the gastrocnemius medialis – muscle ( GaM ) fascicle and its outer Achilles tendon length changes during hopping were examined by ultrasonography together with electromyographic ( EMG ) activities of calf muscles , kinematics , and kinetics . Results At 2 W , the ankle joint stiffness was increased by 21.0 ± 19.3 % and contact time decreased by 9.4 ± 7.8 % in TG . Thereafter , from 2–11 W the jumping height increased 56.2 ± 18.1 % in TG . Simultaneously , tendon forces increased 24.3 ± 19.0 % but tendon stiffness did not change . GaM fascicles shifted to shorter operating lengths after training without any changes in their length modifications during the contact phase of hopping . Normalized EMG amplitudes during hopping did not change with training . Conclusions The present study shows that 11 W of hopping training improves the performance of physically active elderly men . This improvement is achieved with shorter GaM operating lengths and , therefore , increased fascicle stiffness and improved tendon utilization after training . Based on these results , hopping training could be recommended for healthy fit elderly to retain and improve rapid force production capacity Purpose Hamstring strain injury is a frequent and serious injury in competitive and recreational sports . While Nordic hamstring ( NH ) eccentric strength training is an effective hamstring injury-prevention method , the protective mechanism of this exercise is not understood . Strength training increases muscle strength , but also alters muscle architecture and stiffness ; all three factors may be associated with reducing muscle injuries . The purpose of this study was to examine the effects of NH eccentric strength training on hamstring muscle architecture , stiffness , and strength . Methods Twenty healthy participants were r and omly assigned to an eccentric training group or control group . Control participants performed static stretching , while experimental participants performed static stretching and NH training for 6 weeks . Pre- and post-intervention measurements included : hamstring muscle architecture and stiffness using ultrasound imaging and elastography , and maximal hamstring strength measured on a dynamometer . Results The experimental group , but not the control group , increased volume ( 131.5 vs. 145.2 cm3 , p < 0.001 ) and physiological cross-sectional area ( 16.1 vs. 18.1 cm2 , p = 0.032 ) . There were no significant changes to muscle fascicle length , stiffness , or eccentric hamstring strength . Conclusions The NH intervention was an effective training method for muscle hypertrophy , but , contrary to common literature findings for other modes of eccentric training , did not increase fascicle length . The data suggest that the mechanism behind NH eccentric strength training mitigating hamstring injury risk could be increasing volume rather than increasing muscle length . Future research is , therefore , warranted to determine if muscle hypertrophy induced by NH training lowers future hamstring strain injury risk Six men performed a single ankle plantar flexion exercise in the supine position with the maximal effort with counter movement ( CM , plantar flexion preceded by dorsiflexion ) and without counter movement ( NoCM , plantar flexion only ) produced by a sliding table that controlled applied load to the ankle ( 40 % of the maximal voluntary force ) . The reaction force at the foot and ankle joint angle were measured using a force plate and a goniometer , respectively . From real-time ultrasonography of the gastrocnemius medialis muscle during the movement , the fascicle length was determined . The estimated peak force , average power , and work at the Achilles ' tendon during the plantar flexion phase in CM were significantly greater than those in NoCM . In CM , in the dorsiflexion phase , fascicle length initially increased with little electromyographic activity , then remained constant while the whole muscle-tendon unit lengthened , before decreasing in the final plantar flexion phase . In NoCM , fascicle length decreased throughout the movement and the fascicle length at the onset of movement was longer than that of the corresponding phase in CM . It was concluded that during CM muscle fibres optimally work almost isometrically , by leaving the task of storing and releasing elastic energy for enhancing exercise performance to the tendon Muscle imaging is a promising field of research to underst and the biological and bioelectrical characteristics of muscles through the observation of muscle architectural 
    Output:
    
B-mode ultrasound is a reliable method to quantify fascicle architecture during movement .
Additionally , computational approaches can provide a reliable and valid estimation of fascicle architecture