***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: Contractile force is transmitted to the skeleton through tendons and aponeuroses , and , although it is appreciated that the mechanocharacteristics of these tissues play an important role for movement performance with respect to energy storage , the association between tendon mechanical properties and the contractile muscle output during high-force movement tasks remains elusive . The purpose of the study was to investigate the relation between the mechanical properties of the connective tissue and muscle performance in maximal isometric and dynamic muscle actions . Sixteen trained men participated in the study . The mechanical properties of the vastus lateralis tendon-aponeurosis complex were assessed by ultrasonography .  Maximal isometric knee extensor force and rate of torque development ( RTD ) were determined . Dynamic performance was assessed by maximal squat jumps and countermovement jumps on a force plate . From the vertical ground reaction force , maximal jump height , jump power , and force-/velocity-related determinants of jump performance were obtained . RTD was positively related to the stiffness of the tendinous structures ( r = 0.55 , P < 0.05 ) , indicating that tendon mechanical properties may account for up to 30 % of the variance in RTD . A correlation was observed between stiffness and maximal jump height in squat jumps and countermovement jumps ( r = 0.64 , P < 0.05 and r = 0.55 , P < 0.05 ) . Power , force , and velocity parameters obtained during the jumps were significantly correlated to tendon stiffness . These data indicate that muscle output in high-force isometric and dynamic muscle actions is positively related to the stiffness of the tendinous structures , possibly by means of a more effective force transmission from the contractile elements to the bone This study investigated the influence of tendon elongation ( TE ) on postcontraction doublet ( PCD ) torque in the assessment of activation in the plantar flexors of nine elderly men ( EM , age 73.7 + /- 3.6 yr ) and nine young men ( YM , age 24.7 + /- 4.7 yr ) .  Plantar flexion maximal voluntary contractions ( MVC ) and activation  were assessed at ankle joint angles of -20 degrees ( dorsiflexion ) , 0 degrees , and 20 degrees ( plantar flexion ) . Across the ankle joint angles tested , compared with YM , the EM had a 36 - 49 % lower plantar flexion MVC ( P < 0.01 ) , TE was greater by 25 - 31 % ( P < 0.01 ) , and electromechanical delay was 65 - 108 % greater ( P < 0.01 ) . Activation ( PCD torque to interpolated doublet torque ) was 15 % lower in EM compared with YM at -20 degrees ( P < 0.05 ) , but no different at 0 and 20 degrees . In the EM , PCD torque relative to MVC torque was significantly lower at 20 degrees compared with 0 degrees ( P < 0.05 ) . Electromechanical delay was positively correlated with TE ( R(2 ) = 0.489 , P < 0.01 ) . In conclusion , this investigation demonstrates that , although a negative association exists between TE and PCD torque , the consequence of a greater TE on the estimation of activation in EM is negligible . This is due to a greater influence of ankle joint angle on the occlusion of a superimposed doublet , which counteracts the lesser influence of joint angle on TE and PCD torque . However , a greater TE in EM was found to significantly increase electromechanical delay , which is expected to influence the time needed for postural readjustments The purpose of this study was to determine if changes in triceps-surae tendon stiffness ( TST K ) could affect running economy ( RE ) in highly trained distance runners . The intent was to induce increased TST K in a subgroup of runners by an added isometric training program . If TST K is a primary determinant of RE , then the energy cost of running ( EC ) should decrease in the trained subjects . EC was measured via open-circuit spirometry in 12 highly trained male distance runners , and TST K was measured using ultrasonography and dynamometry . Runners were r and omly assigned to either a training or control group . The training group performed 4 × 20 s isometric contractions at 80 % of maximum voluntary plantarflexion moment three times per week for 8 weeks . All subjects ( mean $ $ \dot{V}{\text{O } } _ { 2 } { \max } $ $ = 67.4 ± 4.6 ml kg−1 min−1 ) continued their usual training for running . TST K was measured every 2 weeks . EC was measured in both training and control groups before and after the 8 weeks at three submaximal velocities , corresponding to 75 , 85 and 95 % of the speed at lactate threshold ( sLT ) . Isometric training did neither result in a mean increase in TST K ( 0.9 ± 25.8 % ) nor a mean improvement in RE ( 0.1 ± 3.6 % ) ; however , there was a significant relationship ( r2 = 0.43 , p = 0.02 ) between the change in TST K and change in EC , regardless of the assigned group . It was concluded that TST K and EC are somewhat labile and change together The aims of this study were to determine the effects of plyometric training on both active and passive parts of the series elastic component ( SEC ) stiffness , and on geometrical parameters [ i.e. , muscle architecture , muscle and tendon cross-sectional area ( CSA ) ] of the plantarflexors muscle – tendon complex to assess possible specific adaptations of the elastic properties . Nineteen subjects were r and omly divided into a trained group and a control group . Active and passive components of the SEC stiffness  were determined using a fast stretch during submaximal voluntary isometric plantarflexor activity .  Geometrical parameters of the triceps surae muscles and the Achilles tendon were determined using ultrasonography . A significant increase in the passive component of the SEC stiffness was found ( p < 0.05 ) . In contrast , a significant decrease in the active part of the SEC stiffness was observed ( p < 0.05 ) . No significant changes in plantarflexor muscles CSA , architecture and Achilles tendon CSA were seen ( p > 0.05 ) . Thus , plyometric training led to specific adaptations within each part of the SEC . Theses adaptations could increase both the efficiency of the energy storage – recoil process and muscular tension transmission leading to an increase in jump performances Manipulating joint range of motion during squat training may have differential effects on adaptations to strength training with implication s for sports and rehabilitation . Consequently , the purpose of this study was to compare the effects of squat training with a short vs. a long range of motion . Male students ( n = 17 ) were r and omly assigned to 12 weeks of progressive squat training ( repetition matched , repetition maximum sets ) performed as either a ) deep squat ( 0–120 ° of knee flexion ) ; n = 8 ( DS ) or ( b ) shallow squat ( 0–60 of knee flexion ) ; n = 9 ( SS )  . Strength ( 1 RM and isometric strength ) , jump performance , muscle architecture and cross-sectional area ( CSA ) of the thigh muscles , as well as CSA and collagen synthesis in the patellar tendon , were assessed before and after the intervention . The DS group increased 1 RM in both the SS and DS with ~20 ± 3 % , while the SS group achieved a 36 ± 4 % increase in the SS , and 9 ± 2 % in the DS ( P < 0.05 ) . However , the main finding was that DS training result ed in superior increases in front thigh muscle CSA ( 4–7 % ) compared to SS training , whereas no differences were observed in patellar tendon CSA . In parallel with the larger increase in front thigh muscle CSA , a superior increase in isometric knee extension strength at 75 ° ( 6 ± 2 % ) and 105 ° ( 8 ± 1 % ) knee flexion , and squat-jump performance ( 15 ± 3 % ) were observed in the DS group compared to the SS group . Training deep squats elicited favourable adaptations on knee extensor muscle size and function compared to training shallow squats Objective To assess whether three-dimensional imaging of the Achilles tendon by ultrasonographic tissue characterisation ( UTC ) can differentiate between symptomatic and asymptomatic tendons . Design Case-control study . Setting Sports Medical Department of the Hague Medical Centre . Patients Twenty-six tendons from patients with chronic midportion Achilles tendinopathy were included . The “ matched ” control group consisted of 26 asymptomatic tendons . Interventions Symptomatic and asymptomatic tendons were scanned using the UTC procedure . One research er performed the ultrasonographic data collection . These blinded data were r and omised , and outcome measures were determined by two independent observers . Main outcome measurements The raw ultrasonographic images were analysed with a custom design ed algorithm that quantifies the three-dimensional stability of echo patterns , qua intensity and distribution over contiguous transverse images . This threedimensional stability was related to tendon structure in previous studies . UTC categorises four different echotypes that represent ( I ) highly stable ; ( II ) medium stable ; ( III ) highly variable and ( IV ) constantly low intensity and variable distribution . The percentages of echo-types were calculated , and the maximum tendon thickness was measured . Finally , the inter-observer reliability of UTC was determined . Results Symptomatic tendons showed less pixels in echo-types I and II than asymptomatic tendons ( 51.5 % vs 76.6 % , p<0.001 ) , thus less three-dimensional stability of the echo pattern . The mean maximum tendon thickness was 9.2 mm in the symptomatic group and 6.8 mm in the asymptomatic group ( p<0.001 ) . The Intraclass Correlation Coefficient ( ICC ) for the interobserver reliability of determining the echo-types I+II was 0.95 . The ICC for tendon thickness was 0.84 . Conclusion UTC can quantitatively evaluate tendon structure and thereby discriminate symptomatic and asymptomatic tendons . As such , UTC might be useful to monitor treatment protocol The aim of this study was to determine the effects of 14 wk of plyometric training on mechanical properties of the Achilles tendon .  Nineteen subjects were r and omly assigned to trained or  control group .  Cross-sectional area ( CSA ) , stiffness , and dissipation coefficient of the Achilles tendon were measured before and after the training period . In the trained group , a decrease in dissipation coefficient ( -35.0 % ; P<0.05 ) and an upward trend in stiffness ( + 24.1 % ) of the Achilles tendon was found , without any changes in Achilles tendon CSA ( P>0.05 ) . Plyometric training enhances the muscular tension transmission mainly through a reduction in energy dissipated by the tendon . The lack of changes in the Achilles tendon CSA indicates that changes in mechanical properties would mainly result from a qualitative change in tendinous tissues rather than from changes in the geometry of the Achilles tendon 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 purpose of this study was to investigate whether the mechanical properties of the Achilles tendon were correlated to muscle strength in the triceps surae in humans . Twenty-four men and twelve women exerted  maximal voluntary isometric plantar flexion ( MVIP ) torque . The elongation ( DeltaX ) and strain of the Achilles tendon  ( epsilon ) , the proximal part of which is the composite of the gastrocnemius tendon and the soleus aponeurosis , at MVIP were determined from the displacement of the distal myotendinous junction of the medial gastrocnemius using ultrasonography . The Achilles tendon force at MVIP ( F ) was calculated from the MVIP torque and the Achilles tendon moment arm . There were no significant differences in either the F-DeltaX or F-epsilon relationships between men and women . DeltaX and epsilon were 9.8 + /- 2.6 mm and 5.3 + /- 1.6 % , respectively , and were positively correlated to F ( r = 0.39 , P < 0.05 ; r = 0.39 , P < 0.05 ) , which meant that subjects with greater muscle strength could store more elastic energy in the tendon . The regression y-intercepts for the F 
    Output:
    
The subgroup analysis confirmed that stiffness adaptation significantly ( p<0.05 ) depends on loading intensity ( I2=0 % ) , but not on muscle contraction type .
Although not significantly different , SMD was higher for interventions with longer duration ( ≥12 weeks ) .
Conclusions The present meta- analysis provides elaborate statistical evidence that tendons are highly responsive to diverse loading regimens .
However , the data strongly suggests that loading magnitude in particular plays a key role for tendon adaptation in contrast to muscle contraction type .
Furthermore , intervention-induced changes in tendon stiffness seem to be more attributed to adaptations of the material rather than morphological properties