***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: Functional performance of lower limb muscles and contractile properties of chemically skinned single muscle fibers were evaluated before and after 8 wk of maximal effort stretch-shortening cycle ( SSC ) exercise training . Muscle biopsies were obtained from the vastus lateralis of eight men before and after the training period . Fibers were evaluated regarding their mechanical properties and subsequently classified according to their myosin heavy chain content ( SDS-PAGE ) . After training , maximal leg extensor muscle force and vertical jump performance were improved 12 % ( P<0.01 ) and 13 % ( P<0.001 ) , respectively . Single-fiber cross-sectional area increased 23 % in type I ( P<0.01 ) , 22 % in type IIa ( P<0.001 ) , and 30 % in type IIa/IIx fibers ( P<0.001 ) . Peak force increased 19 % in type I ( P<0.01 ) , 15 % in type IIa ( P<0.001 ) , and 16 % in type IIa/IIx fibers ( P<0.001 ) . When peak force was normalized with cross-sectional area , no changes were found for any fiber type . Maximal shortening velocity was increased 18 , 29 , and 22 % in type I , IIa , and hybrid IIa/IIx fibers , respectively ( P<0.001 ) . Peak power was enhanced in all fiber types , and normalized peak power improved 9 % in type IIa fibers ( P<0.05 ) . Fiber tension on passive stretch increased in IIa/IIx fibers only ( P<0.05 ) . In conclusion , short-term SSC exercise training enhanced single-fiber contraction performance via force and contraction velocity in type I , IIa , and IIa/IIx fibers . These results suggest that SSC exercises are an effective training approach to improve fiber force , contraction velocity , and therefore power This study compared the magnitude of muscle damage induced when consecutive drop jumps ( DJs ) were performed on s and vs. firm ( wood ) surfaces from a height of 0.6 m. Eight subjects performed DJs on a s and surface at a depth of 0.2 m ( S condition ) , and 8 other subjects performed DJs on a wood surface ( F condition ) . Each set consisted of 20 DJs with an interval of 10 seconds between jumps . Subjects performed 5 sets of DJs with 2 minutes between sets . Maximal isometric force , muscle soreness , and plasma cre-atine kinase ( CK ) activity were measured immediately before and immediately after the DJ exercise as well as 1 , 24 , 48 , 72 , and 96 hours after the DJ exercise . All measures changed significantly ( p < 0.05 ) after exercise for both conditions ; however , significantly ( p < 0.05 ) smaller changes in these measures were evident for the S condition than for the F condition . These results show that DJs on a s and surface induce less muscle damage than on a firm surface . Training on s and may improve aerobic capacity or strength with a low risk of muscle damage The ability to generate lower body explosive power is considered an important factor in many athletic activities . Thirty-one men and women , recreationally trained volunteers , were r and omly assigned to 3 different groups ( control , n = 10 ; VertiMax , n = 11 ; and depth jump , n = 10 ) . A Vertec measuring device was used to test vertical jump height pre- and post-training . All subjects trained twice weekly for 6 weeks , performing approximately 140 jumps . The VertiMax group increased elastic resistance and decreased volume each week , while the depth jump group increased both box height and volume each week . The depth jump group significantly increased their vertical jump height ( pre : 20.5 ± 3.98 ; post : 22.65 ± 4.09 ) , while the VertiMax ( pre : 22.18 ± 4.31 ; post : 23.36 ± 4.06 ) and control groups ( pre : 15.65 ± 4.51 ; post : 15.85 ± 4.17 ) did not change . These findings suggest that , within the volume and intensity constraints of this study , depth jump training twice weekly for 6 weeks is more beneficial than VertiMax jump training for increasing vertical jump height . Strength professionals should focus on depth jump exercises in the short term over commercially available devices to improve vertical jump performance Sáez Sáez de villarreal , E , Izquierdo , M , and Gonzalez-Badillo , JJ . Enhancing jump performance after combined vs. maximal power , heavy-resistance , and plyometric training alone . J Strength Cond Res 25(12 ) : 3274–3281 , 2011—The purpose of this study was to examine the effects of 5 different stimuli on jumping ability and power production after 7 weeks of training . Sixty-five ( 47 men and 18 women ) physical education students were r and omly assigned to 5 experimental groups that performed : combination of all training methods ( A ) ; heavy-resistance training using full-squat exercise ( i.e. , 56–85 % of 1 RM for 3–6 repetitions ) ( B ) ; power-oriented strength training using a parallel-squat exercise ( i.e. , 100–130 % of load that maximizes power output for 2–6 repetitions ) ( C ) ; power-oriented strength training using a loaded countermovement jumping ( i.e. , 70–100 % of load that maximizes power output for 2–5 repetitions ; countermovement jump [ CMJ ] ) ( D ) ; and plyometric jumping ( E ) . The CMJ ( cm ) , loaded CMJ ( cm ) , maximum rate of force development ( RFDmax ) during early concentric phase of loaded CMJ ( N·s−1 ) and power output during early concentric phase of loaded CMJ ( watts ) were measured before and after 7 weeks of training . Significant improvements in CMJ ( from 7.8 to 13.2 % ) were observed in all groups . Significantly greater increases in power output during loaded jumps were observed in A ( 10–13 % ) and D ( 8–12 % ) groups compared with in the other groups . Significant increases in RFDmax were observed in A ( 20–30 % ) , C ( 18–26 % ) , and D ( 20–26 % ) groups . The results of this study provide evidence to suggest that if training program is design ed and implemented correctly , both traditional slow velocity training and faster power-oriented strength training alone , or in combination with plyometric training , would provide a positive training stimulus to enhance jumping performance The purpose of this study was to compare the effects of l and - vs. aquatic based plyometric training programs on the drop jump , repeated jump performance and muscle damage .  Sixty-five male students were r and omly assigned to one of 3 groups : aquatic plyometric training group ( APT ) , plyometric training group ( PT ) and control group ( CG ) . Both experimental groups trained twice a week for 10 weeks performing the same number of sets and total jumps . The following variables were measured prior to , halfway through and after the training programs : creatine kinase ( CK ) concentration , maximal height during a drop jump from the height of 30 ( DJ30 ) and 50 cm ( DJ50 ) , and mean height during a repeated vertical jump test ( RJ ) . The training program result ed in a significant increase ( P<0.01 - 0.001 ) in RJ , DJ30 , and DJ50 for PT , whereas neither APT nor CG reached any significant improvement APT showed likely/possibly improvements on DJ30 and DJ50 , respectively . Greater intra-group Effect Size in CK was found for PT when compared to APT . In conclusion , although APT seems to be a safe alternative method for reducing the stress produced on the musculoskeletal system by plyometric training , PT produced greater gains on reactive jumps performance than APT 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 Objective : The lower impact on the musculoskeletal system induced by plyometric exercise on s and compared to a firm surface might be useful to reduce the stress of intensified training periods or during rehabilitation from injury . The aim of this study was to compare the effects of plyometric training on s and versus a grass surface on muscle soreness , vertical jump height and sprinting ability . Design : Parallel two-group , r and omised , longitudinal ( pretest−post-test ) study . Methods : After r and om allocation , 18 soccer players completed 4 weeks of plyometric training on grass ( grass group ) and 19 players on s and ( s and group ) . Before and after plyometric training , 10 m and 20 m sprint time , squat jump ( SJ ) , countermovement jump ( CMJ ) , and eccentric utilization ratio ( CMJ/SJ ) were determined . Muscle soreness was measured using a Likert scale . Results : No training surface × time interactions were found for sprint time ( p>0.87 ) , whereas a trend was found for SJ ( p = 0.08 ) , with both groups showing similar improvements ( p<0.001 ) . On the other h and , the grass group improved their CMJ ( p = 0.033 ) and CMJ/SJ ( p = 0.005 ) significantly ( p<0.001 ) more than players in the s and group . In contrast , players in the s and group experienced less muscle soreness than those in the grass group ( p<0.001 ) . Conclusions : Plyometric training on s and improved both jumping and sprinting ability and induced less muscle soreness . A grass surface seems to be superior in enhancing CMJ performance while the s and surface showed a greater improvement in SJ . Therefore , plyometric training on different surfaces may be associated with different training-induced effects on some neuromuscular factors related to the efficiency of the stretch-shortening cycle The purpose of this study was to compare symptoms of exercise-induced muscle damage after an initial and repeated bout of  plyometric exercise in men and boys . Ten boys ( 9 - 10 yr ) and 10 men ( 20 - 29 yr ) completed two bouts of eight sets of 10 plyometric jumps , 2 wk apart . Perceived soreness ( 0 - 10 , visual analog scale ) , isometric strength of the quadriceps at six knee flexion angles , and countermovement jump and squat jump height were assessed before and at 30 min , 24 h , 48 h , and 72 h after each bout . All variables followed the expected patterns of change in men , with soreness peaking at 24 - 48 h ( 5.8 + /- 1.7 ) and decrements in muscle function peaking at 30 min after the first bout ( 73 - 85 % of baseline scores ) . Symptoms remained for 72 h after the first bout in men . In boys , symptoms were much less severe and peaked at 30 min ( visual analog scale = 2.1 + /- 1.8 , functional decrements 87 - 92 % of baseline ) and , with the exception of soreness , returned to baseline after 24 h. After the second bout of plyometric exercise , the level of soreness and decrements in countermovement jump , squat jump , and isometric strength were lower , although the effect was stronger in men , in all cases . The results of this study suggest that although children may experience symptoms of muscle damage after intensive plyometric exercise , they are much less severe . A prior bout of plyometric exercise also appears to provide children with some protection from soreness after a subsequent bout of plyometric exercise . Explanations for milder symptoms of exercise-induced muscle damage in children include greater flexibility leading to less overextension of sarcomeres during eccentric exercise , fewer fast-twitch muscle fibers , and greater and perhaps more varied habitual physical activity patterns In the literature , it is well established that subjects are able to jump higher in a countermovement jump ( CMJ ) than in a squat jump ( SJ ) . The purpose of this study was to estimate the relative contribution of the time available for force development and the storage and reutilization of elastic energy to the enhancement of performance in CMJ compared with SJ .  Six male volleyball players performed CMJ and SJ .  Kinematics , kinetics , and muscle electrical activity ( EMG )  from six muscles of the lower extremity were monitored . It was found that even when the body position at the start of push-off was the same in SJ as in CMJ , jump height was on average 3.4 cm greater in CMJ . The possibility that nonoptimal coordination in SJ explained the difference in jump height was ruled out : there were no signs of movement disintegration in SJ , and toe-off position was the same in SJ as in CMJ . The greater jump height in CMJ was attributed to the fact that the countermovement allowed the subjects to attain greater joint moments at the start of push-off . As a consequence , joint moments were greater over the first part of the range of joint extension in CM 
    Output:
    
Traditional , assisted and resisted plyometric methods are effective training modalities for augmenting vertical jump performance in healthy adults .
Resisted and assisted plyometric methods are equally effective as the traditional plyometric method in improving vertical jumping ability in healthy adults