***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: PURPOSE The purpose of this study was to determine whether ballistic resistance training would increase the vertical jump ( VJ ) performance of already highly trained jump athletes . METHODS Sixteen male volleyball players from a NCAA Division I team participated in the study . A Vertec was used to measure st and ing vertical jump and reach ( SJR ) and jump and reach from a three-step approach ( AJR ) . Several types of vertical jump tests were also performed on a Plyometric Power System and a forceplate to measure force , velocity , and power production during vertical jumping . The subjects completed the tests and were then r and omly divided into two groups , control and treatment . All subjects completed the usual preseason volleyball on-court training combined with a resistance training program . In addition , the treatment group completed 8 wk of squat jump training while the control group completed squat and leg press exercises at a 6RM load . Both groups were retested at the completion of the training period . RESULTS The treatment group produced a significant increase in both SJR and AJR of 5.9+/-3.1 % and 6.3+/-5.1 % . respectively . These increases were significantly greater than the pre- to postchanges produced by the control group , which were not significant for either jump . Analysis of the data from the various other jump tests suggested increased overall force output during jumping , and in particular increased rate of force development were the main contributors to the increased jump height . CONCLUSIONS These results lend support to the effectiveness of ballistic resistance training for improving vertical jump performance in elite jump athletes The purpose of this study was to compare the effects of combined strength and plyometric training with strength training alone on power-related measurements in professional soccer players . Subjects in the intervention team were r and omly divided into 2 groups . Group ST ( n = 6 ) performed heavy strength training twice a week for 7 weeks in addition to 6 to 8 soccer sessions a week . Group ST+P ( n = 8) performed a plyometric training program in addition to the same training as the ST group . The control group ( n = 7 ) performed 6 to 8 soccer sessions a week . Pretests and posttests were 1 repetition maximum ( 1RM ) half squat , countermovement jump ( CMJ ) , squat jump ( SJ ) , 4-bounce test ( 4BT ) , peak power in half squat with 20 kg , 35 kg , and 50 kg ( PP20 , PP35 , and PP50 , respectively ) , sprint acceleration , peak sprint velocity , and total time on 40-m sprint . There were no significant differences between the ST+P group and ST group . Thus , the groups were pooled into 1 intervention group . The intervention group significantly improved in all measurements except CMJ , while the control group showed significant improvements only in PP20 . There was a significant difference in relative improvement between the intervention group and control group in 1RM half squat , 4BT , and SJ . However , a significant difference between groups was not observed in PP20 , PP35 , sprint acceleration , peak sprinting velocity , and total time on 40-m sprint . The results suggest that there are no significant performance-enhancing effects of combining strength and plyometric training in professional soccer players concurrently performing 6 to 8 soccer sessions a week compared to strength training alone . However , heavy strength training leads to significant gains in strength and power-related measurements in professional soccer players 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 The present study investigates the effects of power training on mechanical efficiency ( ME ) in jumping . Twenty-three subjects , including ten controls , volunteered for the study . The experimental group trained twice a week for 15 weeks performing various jumping exercises such as drop jumps , hurdle jumps , hopping and bouncing . In the maximal jumping test , the take-off velocity increased from 2.56 ( 0.24 ) m·s−1 to 2.77 ( 0.18 ) m·s−1 ( P<0.05 ) . In the submaximal jumping of 50 % of the maximum , energy expenditure decreased from 660 ( 110 ) to 502 ( 68 ) J·kg−1·min−1 ( P<0.001 ) while , simultaneously , ME increased from 37.2 (8.4)% to 47.4 (8.2)% ( P<0.001 ) . Some muscle enzyme activities of the gastrocnemius muscle increased during the training period : citrate synthase from 35 ( 8) to 39 ( 7 ) μmol·g−1 dry mass·min−1 ( P<0.05 ) and β-hydroxyacyl CoA dehydrogenase from 21 ( 4 ) to 23 ( 5 ) μmol·g−1 dry mass·min−1 ( P<0.05 ) , whereas no significant changes were observed in phosphofructokinase and lactate dehydrogenase . In the control group , no changes in ME or in enzyme activities were observed . In conclusion , the enhanced performance capability of 8 % in maximal jumping as a result of power training was characterized by decreased energy expenditure of 24 % . Thus , the increased neuromuscular performance , joint control strategy , and intermuscular coordination ( primary factors ) , together with improved aerobic capacity ( secondary factor ) , may result in reduced oxygen dem and s and increased ME 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 This study was performed to determine which of three theoretically optimal resistance training modalities result ed in the greatest enhancement in the performance of a series of dynamic athletic activities . The three training modalities included 1 ) traditional weight training , 2 ) plyometric training , and 3 ) explosive weight training at the load that maximized mechanical power output .  Sixty-four previously trained subjects were r and omly allocated to four groups that included the above three training modalities and a control group . The experimental groups trained for 10 wk performing either heavy squat lifts , depth jumps , or weighted squat jumps . All subjects were tested prior to training , after 5 wk of training and at the completion of the training period . The test items included 1 ) 30-m sprint , 2 ) vertical jumps performed with and without a countermovement , 3 ) maximal cycle test , 4 ) isokinetic leg extension test , and 5 ) a maximal isometric test . The experimental group which trained with the load that maximized mechanical power achieved the best overall results in enhancing dynamic athletic performance recording statistically significant ( P < 0.05 ) improvements on most test items and producing statistically superior results to the two other training modalities on the jumping and isokinetic tests OBJECTIVE : To test the feasibility of creating a valid and reliable checklist with the following features : appropriate for assessing both r and omised and non-r and omised studies ; provision of both an overall score for study quality and a profile of scores not only for the quality of reporting , internal validity ( bias and confounding ) and power , but also for external validity . DESIGN : A pilot version was first developed , based on epidemiological principles , review s , and existing checklists for r and omised studies . Face and content validity were assessed by three experienced review ers and reliability was determined using two raters assessing 10 r and omised and 10 non-r and omised studies . Using different raters , the checklist was revised and tested for internal consistency ( Kuder-Richardson 20 ) , test-retest and inter-rater reliability ( Spearman correlation coefficient and sign rank test ; kappa statistics ) , criterion validity , and respondent burden . MAIN RESULTS : The performance of the checklist improved considerably after revision of a pilot version . The Quality Index had high internal consistency ( KR-20 : 0.89 ) as did the subscales apart from external validity ( KR-20 : 0.54 ) . Test-retest ( r 0.88 ) and inter-rater ( r 0.75 ) reliability of the Quality Index were good . Reliability of the subscales varied from good ( bias ) to poor ( external validity ) . The Quality Index correlated highly with an existing , established instrument for assessing r and omised studies ( r 0.90 ) . There was little difference between its performance with non-r and omised and with r and omised studies . Raters took about 20 minutes to assess each paper ( range 10 to 45 minutes ) . CONCLUSIONS : This study has shown that it is feasible to develop a checklist that can be used to assess the method ological quality not only of r and omised controlled trials but also non-r and omised studies . It has also shown that it is possible to produce a checklist that provides a profile of the paper , alerting review ers to its particular method ological strengths and weaknesses . Further work is required to improve the checklist and the training of raters in the assessment of external validity The purpose of this study was to evaluate the effects of sprint training on muscle function and dynamic athletic performance and to compare them with the training effects induced by st and ard plyometric training .  Male physical education students were assigned r and omly to 1 of 3 groups : sprint group ( SG ; n = 30 ) , plyometric group ( PG ; n = 30 ) , or control group ( CG ; n = 33 ) . Maximal isometric squat strength , squat- and counter-movement jump ( SJ and CMJ ) height and power , drop jump performance from 30-cm height , and 3 athletic performance tests  ( st and ing long jump , 20-m sprint , and 20-yard shuttle run ) were measured prior to and after 10 weeks of training . Both experimental groups trained 3 days a week ; SG performed maximal sprints over distances of 10–50 m , whereas PG performed bounce-type hurdle jumps and drop jumps . Participants in the CG group maintained their daily physical activities for the duration of the study . Both SG and PG significantly improved drop jump performance ( 15.6 and 14.2 % ) , SJ and CMJ height ( ∼10 and 6 % ) , and st and ing long jump distance ( 3.2 and 2.8 % ) , whereas the respective effect sizes ( ES ) were moderate to high and ranged between 0.4 and 1.1 . In addition , SG also improved isometric squat strength ( 10 % ; ES = 0.4 ) and SJ and CMJ power ( 4 % ; ES = 0.4 , and 7 % ; ES = 0.4 ) , as well as sprint ( 3.1 % ; ES = 0.9 ) and agility ( 4.3 % ; ES = 1.1 ) performance . We conclude that short-term sprint training produces similar or even greater training effects in muscle function and athletic performance than does conventional plyometric training . This study provides support for the use of sprint training as an applicable training method of improving explosive performance of athletes in general Among sport conditioning coaches , there is considerable discussion regarding the efficiency of training methods that improve lower-body power .  Heavy resistance training combined with vertical jump ( VJ ) training is a well-established training method ; however , there is a lack of information about its combination with Olympic weightlifting 
    Output:
    
Change in VJ height was not different for OW versus plyometric training .
CONCLUSIONS OW is an effective training method to improve VJ height .
The similar effects observed for OW and plyometric training  on VJ height suggests that either of these methods would be beneficial when devising training programmes to improve VJ height