***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: To investigate the effects of simultaneous explosive-strength and endurance training on physical performance characteristics , 10 experimental ( E ) and 8 control ( C ) endurance athletes trained for 9 wk . The total training volume was kept the same in both groups , but 32 % of training in E and 3 % in C was replaced by explosive-type strength training . A 5-km time trial ( 5 K ) , running economy ( RE ) , maximal 20-m speed ( V20 m ) , and 5-jump ( 5J ) tests were measured on a track . Maximal anaerobic ( MART ) and aerobic treadmill running tests were used to determine maximal velocity in the MART ( VMART ) and maximal oxygen uptake ( VO2 max ) . The 5 K time , RE , and VMART improved ( P < 0.05 ) in E , but no changes were observed in C. V20 m and 5J increased in E ( P < 0.01 ) and decreased in C ( P < 0.05 ) . VO2 max increased in C ( P < 0.05 ) , but no changes were observed in E. In the pooled data , the changes in the 5 K velocity during 9 wk of training correlated ( P < 0.05 ) with the changes in RE [ O2 uptake ( r = -0.54 ) ] and VMART ( r = 0.55 ) . In conclusion , the present simultaneous explosive-strength and endurance training improved the 5 K time in well-trained endurance athletes without changes in their VO2 max . This improvement was due to improved neuromuscular characteristics that were transferred into improved VMART and running economy Evidence -based practice involves the use of evidence from systematic review s and r and omised controlled trials , but the extent of this evidence in physiotherapy has not previously been surveyed . The aim of this survey is to describe the quantity and quality of r and omised controlled trials and the quantity of systematic review s relevant to physiotherapy . The Physiotherapy Evidence Data base ( PEDro ) was search ed . The quality of trials was assessed with the PEDro scale . The search identified a total of 2,376 r and omised controlled trials and 332 systematic review s. The first trial was published in 1955 and the first review was published in 1982 . Since that time , the number of trials and review s has grown exponentially . The mean PEDro quality score has increased from 2.8 in trials published between 1955 and 1959 to 5.0 for trials published between 1995 and 1999 . There is a substantial body of evidence about the effects of physiotherapy . However , there remains scope for improvements in the quality of the conduct and reporting of clinical trials At present , it is unclear how caffeine induced alterations in neuromuscular function might affect force production and EMG signal characteristics during isometric exercise . These data suggest that acute caffeine ingestion ( 7 mg/kg ) has no significant effect on force production during a maximal isometric h and grip contraction or endurance during a sustained submaximal contraction . Further , maximal motor unit activation , the relationship between submaximal motor unit activation and subsequent force production , and frequency content of the EMG signal were not significantly altered following caffeine ingestion . These results indicate that although caffeine may be a potential ergogenic aid for some activities , its ingestion may not improve performance in activities requiring strength and /or short-term endurance We hypothesized that if reduced spinal excitability contributes to central activation failure , then a caffeine-induced increase in spinal excitability would enhance postfatigue maximal voluntary activation and maximal voluntary contraction ( MVC ) .  Ten male volunteer subjects attended two laboratory sessions separated by at least 1 week . Contractile and electrical properties were assessed before , and 1 h after oral administration of caffeine ( 6 mg/kg ) or placebo ( all- purpose flour ) , and again following a fatigue protocol . The slope of the H reflex recruitment curve , normalized to that of the M wave ( Hslp/Mslp ) , was used to estimate spinal excitability . Maximal voluntary activation was assessed using maximal EMG ( EMGmax ) and twitch interpolation . Postfatigue , MVC torque declined ( P<0.05 ) to 75.2±12.7 and 70.2±9.3 % of the prefatigue values in the placebo ( PL ) and caffeine ( CF ) trials , respectively , and remained depressed throughout the recovery period . This was accompanied by a decline in % activation ( P<0.05 ) from 99.6±0.3 % ( PL ) and 99.8±0.3 % ( CF ) to 94.8±3.5 % ( PL ) and 95.3±5.0 % ( CF ) , indicating the presence of central activation failure . Caffeine offset the decline in Hslp/Mslp observed in the placebo trial ( P<0.05 ) , but it did not prevent the decline in maximal voluntary activation or MVC torque . Furthermore , although the decline in spinal excitability was correlated to the decline in EMGmax ( r=0.55 , P<0.05 ) it was not correlated with the decline in % activation or MVC torque . Thus a fatigue-induced decline in spinal excitability did not limit maximal activation This double-blind , repeated- measures study examined the effects of caffeine on  neuromuscular function .  Eleven male volunteers [ 22.3 + /- 2.4 ( SD ) yr ] came to the laboratory for control , placebo , and caffeine ( 6 mg/kg dose ) trials . Each trial consisted of 10 x 1-ms stimulation of the tibial nerve to elicit maximal H reflexes of the soleus , four attempts at a maximal voluntary contraction ( MVC ) of the right knee extensors , six brief submaximal contractions , and a 50 % MVC held to fatigue . Isometric force and surface electromyographic signals were recorded continuously . The degree of maximal voluntary activation was assessed with the twitch-interpolation technique . Single-unit recordings were made with tungsten microelectrodes during the submaximal contractions . Voluntary activation at MVC increased by 3.50 + /- 1.01 ( SE ) % ( P < 0 . 01 ) , but there was no change in H-reflex amplitude , suggesting that caffeine increases maximal voluntary activation at a supraspinal level . Neither the force-EMG relationship nor motor unit firing rates were altered by caffeine . Subjects were able to hold a 50 % MVC for an average of 66.1 s in the absence of caffeine . Time to fatigue ( T(lim ) ) increased by 25.80 + /- 16.06 % after caffeine administration ( P < 0.05 ) . There was no significant change in T(lim ) from pretest to posttest in the control or placebo trials . The increase in T(lim ) was associated with an attenuated decline in twitch amplitude , which would suggest that the mechanism is , at least in part , peripheral Hudson , GM , Green , JM , Bishop , PA , and Richardson , MT . Effects of caffeine and aspirin on light resistance training  performance , RPE , and pain perception . J Strength Cond Res 22(6 ) : 1950 - 1957 , 2008-This study compared independent effects of caffeine and aspirin on muscular endurance ( repetitions ) , heart rate ( HR ) , perceived exertion ( RPE ) , and perceived pain index ( PPI ) during light resistance training bouts performed to volitional failure . It was hypothesized that the hypoalgesic properties of these ergogenic aids would decrease pain perception and potentially result in enhanced performance . College-aged men ( n = 15 ) participated in a within-subjects , double-blind study with three independent , counterbalanced sessions wherein aspirin ( 10 mg·kg−1 ) , caffeine ( 6 mg·kg−1 ) , or matched placebo were ingested 1 hour before exercise , and  RPE , HR , PPI , and repetitions  ( per set and total per exercise ) were recorded at 100 % of individual , predetermined , 12-repetition maximum for leg extensions ( LE ) and seated arm curls ( AC ) . Repeated- measures analyses of variance were used for between-trial comparisons . Caffeine result ed in significantly greater ( p < 0.05 ) HR ( LE and AC ) , total repetitions ( LE ) , and repetitions in set 1 ( LE and AC ) compared with aspirin and placebo . Aspirin result ed in significantly higher PPI in set 1 ( LE ) . In LE , 47 % of participants ' performance exceeded the predetermined effect size ( ≥ 5 repetitions ) for total repetitions , with 53 % exceeding the effect size ( ≥ 2 repetitions ) for repetitions in set 1 with caffeine ( vs. placebo ) . In AC , 53 % ( total repetitions ) and 47 % ( set 1 repetitions ) of participants exceeded effect sizes with caffeine ( vs. placebo ) , with only 13 % experiencing decrements in performance ( total repetitions ) . Aspirin also produced a higher PPI and RPE overall and in set 1 ( vs. placebo ) . This study demonstrates that caffeine significantly enhanced resistance training performance in LE and AC , whereas aspirin did not . Athletes may improve their resistance training performance by acute ingestion of caffeine . As with most ergogenic aids , our analyses indicate that individual responses vary greatly The purpose of this study was to determine the effect of two doses of caffeine on peak torque and muscle endurance in the knee extensors and flexors . Twenty males and 16 females were r and omly assigned to one of three groups : 600 mg caffeine , 300 mg caffeine , or a control receiving a placebo .  Subjects with similar caffeine consumption history were used and all subjects abstained from caffeine usage for 24 hours prior to testing . Subjects were tested for maximal strength and endurance at 75 , 180 , and 300 degrees per second using a Cybex II Isokinetic Dynomometer interfaced with a Cybex Data Reduction Computer . After pretesting , each subject was given one of three solutions using a double-blind design . Following a one hour rest and absorption period , the subjects were again tested . Data were analyzed using a 3 x 2 repeated measures analysis of variance with a grouping factor at three levels ( 600 mg vs 300 mg vs 0 mg ) and a trial factor at two levels ( pre- vs posttest ) . The following variables were analyzed at all angular velocities : peak torque and subsequent joint angle , peak torque at 30 degrees , and peak torque at 70 degrees . At 300 degrees per second , the dependent variables were total torque for 15 repetitions , total torque for the first 3 repetitions , and total torque for the last 3 repetitions . The results indicated no significant changes from pre- to posttest . It was concluded that maximal strength and endurance was not affected by the two levels of caffeine used in this study and that caffeine may not be considered an ergogenic aid in strength output in subjects naive to resistance training PURPOSE It has been suggested that endurance training influences the running economy ( CR ) and the oxygen uptake ( .VO(2 ) ) kinetics in heavy exercise by accelerating the primary phase and attenuating the .VO(2 ) slow component . However , the effects of heavy weight training ( HWT ) in combination with endurance training remain unclear . The purpose of this study was to examine the influence of a concurrent HWT+endurance training on CR and the .VO(2 ) kinetics in endurance athletes . METHODS Fifteen triathletes were assigned to endurance+strength ( ES ) or endurance-only ( E ) training for 14 wk . The training program was similar , except ES performed two HWT sessions a week . Before and after the training period , the subjects performed 1 ) an incremental field running test for determination of .VO(2max ) and the velocity associated ( V(.VO2max ) ) , the second ventilatory threshold ( VT(2 ) ) ; 2 ) a 3000-m run at constant velocity , calculated to require 25 % of the difference between .VO(2max ) and VT(2 ) , to determine CR and the characteristics of the VO(2 ) kinetics ; 3 ) maximal hopping tests to determine maximal mechanical power and lower-limb stiffness ; 4 ) maximal concentric lower-limb strength measurements . RESULTS After the training period , maximal strength were increased ( P < 0.01 ) in ES but remained unchanged in E. Hopping power decreased in E ( P < 0.05 ) . After training , economy ( P < 0.05 ) and hopping power ( P < 0.001 ) were greater in ES than in E. .VO(2max ) , leg hopping stiffness and the .VO(2 ) kinetics were not significantly affected by training either in ES or E. CONCLUSION Additional HWT led to improved maximal strength and running economy with no significant effects on the .VO(2 ) kinetics pattern in heavy exercise This study investigated the effect of caffeine on physical performance in healthy citizens aged > or = 70 yr . The r and omized , double-blind , placebo-controlled , crossover study was conducted in 15 men and 15 women recruited by their general practitioner . Participants abstained from caffeine for 48 h and were r and omized to receive one capsule of placebo and then caffeine ( 6 mg/kg ) or caffeine and then placebo with 1 wk in between . One hour after intervention , we measured reaction and movement times , postural stability , walking speed , cycling at 65 % of expected maximal heart rate , perceived effort during cycling , maximal isometric arm flexion strength , and endurance . Analysis was by intention to treat , and P < 0.05 was regarded as significant . Caffeine increased cycling endurance by 25 % [ 95 % confidence interval ( CI ) 
    Output:
    
However , caffeine appears to improve MVC strength primarily in the knee extensors ( i.e. , by approximately 7 % , ES = 0.37 ) and not in other muscle groups such as the forearm or the knee flexors .
However , it appears caffeine improves muscular endurance only when it is assessed using open ( i.e. , by approximately 18 % , ES = 0.37 ) and not fixed end point tests .
Overall , caffeine ingestion improves MVC strength and muscular endurance .
The effect on strength appears exclusively in the knee extensors , and the effect on muscular endurance appears only detectable with open end point tests