***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: Chelly , MS , Ghenem , MA , Abid , K , Hermassi , S , Tabka , Z , and Shephard , RJ . Effects of in-season short-term plyometric training program on leg power , jump- and sprint performance of soccer players . J Strength Cond Res 24(10 ) : 2670 - 2676 , 2010-Our hypothesis was that the addition of an 8-week lower limb plyometric training program ( hurdle and depth jumping ) to normal in-season conditioning would enhance measures of competitive potential ( peak power output [ PP ] , jump force , jump height , and lower limb muscle volume ) in junior soccer players . The subjects ( 23 men , age 19 ± 0.7 years , body mass 70.5 ± 4.7 kg , height 1.75 ± 0.06 m , body fat 14.7 ± 2.6 % ) were r and omly assigned to a  control ( normal training ) group  ( Gc ; n = 11 ) and an  experimental group  ( Gex , n = 12 ) that also performed biweekly plyometric training . A force-velocity ergometer test determined PP . Characteristics of the squat jump ( SJ ) and the countermovement jump ( CMJ ) ( jump height , maximal force and velocity before take-off , and average power ) were determined by force platform . Video-camera kinematic analyses over a 40-m sprint yielded running velocities for the first step ( VS ) , the first 5 m ( V5 m ) and between 35 and 40 m ( Vmax ) . Leg muscle volume was estimated using a st and ard anthropometric kit . Gex showed gains relative to controls in PP ( p < 0.01 ) ; SJ ( height p < 0.01 ; velocity p < 0.001 ) , CMJ ( height p < 0.001 ; velocity p < 0.001 , average power p < 0.01 ) and all sprint velocities ( p < 0.001 for V5 m and Vmax , p < 0.01 for VS ) . There was also a significant increase ( p < 0.05 ) in thigh muscle volume , but leg muscle volume and mean thigh cross-sectional area remain unchanged . We conclude that biweekly plyometric training of junior soccer players ( including adapted hurdle and depth jumps ) improved important components of athletic performance relative to st and ard in-season training . Accordingly , such exercises are highly recommended as part of an annual soccer training program Thomas , K , French , D , and Hayes , PR . The effect of two plyometric training techniques on muscular power and agility in youth soccer players . J Strength Cond Res 23(1 ) : 332 - 335 , 2009-The aim of this study was to compare the effects of two plyometric training techniques on power and agility in youth soccer players . Twelve males from a semiprofessional football club 's academy ( age = 17.3 ± 0.4 years , stature = 177.9 ± 5.1 cm , mass = 68.7 ± 5.6 kg ) were r and omly assigned to 6 weeks of depth jump ( DJ ) or countermovement jump ( CMJ ) training twice weekly . Participants in the DJ group performed drop jumps with instructions to minimize ground-contact time while maximizing height . Participants in the CMJ group performed jumps from a st and ing start position with instructions to gain maximum jump height . Posttraining , both groups experienced improvements in vertical jump height ( p < 0.05 ) and agility time ( p < 0.05 ) and no change in sprint performance ( p > 0.05 ) . There were no differences between the treatment groups ( p > 0.05 ) . The study concludes that both DJ and CMJ plyometrics are worthwhile training activities for improving power and agility in youth soccer players Meylan , C and Malatesta D. Effects of in-season plyometric training within soccer practice on explosive actions of young players . J Strength Cond Res 23(9 ) : 2605 - 2613 , 2009-In soccer , explosive actions such as jumping , sprinting , and changes of direction are essential to optimal performance not only in adults , but also in children 's games . The purpose of the present investigation was to determine the influence of a short-term plyometric training within regular soccer practice on explosive actions of early pubertal soccer players during the in-season . Fourteen children ( 13.3 ± 0.6 years ) were selected as the training group ( TG ) and 11 children ( 13.1 ± 0.6 years ) were defined as the control group ( CG ) . All children were playing in the same league and trained twice per week for 90 minutes with the same soccer drills . The TG followed an 8-week plyometric program ( i.e. , jumping , hurdling , bouncing , skipping , and footwork ) implemented as a substitute for some soccer drills to obtain the same session duration as CG . At baseline and after training , explosive actions were assessed with the following 6 tests : 10-meter sprint , agility test , 3 vertical jump tests ( squat jump [ SJ ] , countermovement jump [ CMJ ] , contact test [ CT ] and multiple 5 bounds test [ MB5 ] ) . Plyometric training was associated with significant decreases in 10-m sprint time ( −2.1 % ) and agility test time ( −9.6 % ) and significant increases in jump height for the CMJ ( + 7.9 % ) and CT ( + 10.9 % ) . No significant changes in explosive actions after the 8-week period were recorded for the CG . The current study demonstrated that a plyometric program within regular soccer practice improved explosive actions of young players compared to conventional soccer training only . Therefore , the short-term plyometric program had a beneficial impact on explosive actions , such as sprinting , change of direction , and jumping , which are important determinants of match-winning actions in soccer performance BACKGROUND AND PURPOSE Assessment of the quality of r and omized controlled trials ( RCTs ) is common practice in systematic review s. However , the reliability of data obtained with most quality assessment scales has not been established . This report describes 2 studies design ed to investigate the reliability of data obtained with the Physiotherapy Evidence Data base ( PEDro ) scale developed to rate the quality of RCTs evaluating physical therapist interventions . METHOD In the first study , 11 raters independently rated 25 RCTs r and omly selected from the PEDro data base . In the second study , 2 raters rated 120 RCTs r and omly selected from the PEDro data base , and disagreements were resolved by a third rater ; this generated a set of individual rater and consensus ratings . The process was repeated by independent raters to create a second set of individual and consensus ratings . Reliability of ratings of PEDro scale items was calculated using multirater kappas , and reliability of the total ( summed ) score was calculated using intraclass correlation coefficients ( ICC [ 1,1 ] ) . RESULTS The kappa value for each of the 11 items ranged from.36 to.80 for individual assessors and from.50 to.79 for consensus ratings generated by groups of 2 or 3 raters . The ICC for the total score was.56 ( 95 % confidence interval=.47-.65 ) for ratings by individuals , and the ICC for consensus ratings was.68 ( 95 % confidence interval=.57-.76 ) . DISCUSSION AND CONCLUSION The reliability of ratings of PEDro scale items varied from " fair " to " substantial , " and the reliability of the total PEDro score was " fair " to " good . 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 Abstract Michailidis , Y , Fatouros , IG , Primpa , E , Michailidis , C , Avloniti , A , Chatzinikolaou , A , Barbero-Álvarez , JC , Tsoukas , D , Douroudos , II , Draganidis , D , Leontsini , D , Margonis , K , Berberidou , F , and Kambas , A. Plyometrics ' trainability in preadolescent soccer athletes . J Strength Cond Res 27(1 ) : 38–49 , 2013—Plyometric training ( PT ) is a widely used method to improve muscle ability to generate explosive power . This study aim ed to determine whether preadolescent boys exhibit plyometric trainability or not . Forty-five children were r and omly assigned to either a control ( CG , N = 21 , 10.6 ± 0.5 years ; participated only in regular soccer practice ) or a plyometric training group ( PTG , N = 24 , 10.6 ± 0.6 years ; participated in regular soccer practice plus a plyometric exercise protocol ) . Both groups trained for 12 weeks during the in-season period . The PT exercises ( forward hopping , lateral hopping , shuffles , skipping , ladder drills , skipping , box jumps , low-intensity depth jumps ) were performed twice a week . Preadolescence was verified by measuring Tanner stages , bone age , and serum testosterone . Speed ( 0–10 , 10–20 , 20–30 m ) , leg muscle power ( static jumping , countermovement jumping , depth jumping [ DJ ] , st and ing long jump [ SLJ ] , multiple 5-bound hopping [ MB5 ] ) , leg strength ( 10 repetition maximum ) , anaerobic power ( Wingate testing ) , and soccer-specific performance ( agility , kicking distance ) were measured at baseline , midtraining , and posttraining . The CG caused only a modest ( 1.2–1.8 % ) increase in speed posttraining . The PTG induced a marked ( p < 0.05 ) improvement in all speed tests ( 1.9–3.1 % at midtraining and 3–5 % at posttraining ) and vertical jump tests ( 10–18.5 % at midtraining and 16–23 % at posttraining ) , SLJ ( 2.6 % at midtraining and 4.2 % at posttraining ) , MB5 ( 14.6 % at midtraining and 23 % at posttraining ) , leg strength ( 15 % at midtraining and 28 % at posttraining ) , agility ( 5 % at midtraining and 23 % at posttraining ) , and kicking distance ( 13.6 % at midtraining and 22.5 % at posttraining ) . Anaerobic power remained unaffected in both groups . These data indicate that ( a ) prepubertal boys exhibit considerable plyometric trainability , and ( b ) when soccer practice is supplemented with a PT protocol , it leads to greater performance gains Buchheit , M , Mendez-Villanueva , A , Delhomel , G , Brughelli , M , and Ahmaidi , S. Improving repeated sprint ability in young elite soccer players :  repeated shuttle sprints vs. explosive strength training . J Strength Cond Res 24(10 ) : 2715 - 2722 , 2010-To compare the effects of explosive strength ( ExpS ) vs. repeated shuttle sprint ( RS ) training on repeated sprint ability ( RSA ) in young elite soccer players , 15 elite male adolescents ( 14.5 ± 0.5 years ) performed , in addition to their soccer training program , RS ( n = 7 ) or ExpS ( n = 8) training once a week for a total of 10 weeks . RS training consisted of 2 - 3 sets of 5 - 6 × 15- to 20-m repeated shuttle sprints interspersed with 14 seconds of passive or 23 seconds of active recovery ( ≈2 m·s−1 ) ; ExpS training consisted of 4 - 6 series of 4 - 6 exercises ( e.g. , maximal unilateral countermovement jumps ( CMJs ) , calf and squat plyometric jumps , and short sprints ) . Before and after training , performance was assessed by 10 and 30 m 
    Output:
    
Athletic performance consisting of kicking distance , speed , jumping ability , and agility significantly improved because of plyometric training interventions .