***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: Abstract Monaghan , TP , Jacobson , BH , Sellers , JH , and Estrada , CA . Effects of energy beverage consumption on pistol aim ing steadiness in law enforcement officers . J Strength Cond Res 31(9 ) : 2557–2561 , 2017—The popularity of energy drinks (EDs)/shots ( ESs ) has grown steadily over the years result ing in billions of dollars of sales annually . Energy drink marketing focuses on the improved performance and alertness and a reduction in fatigue . Although caffeine comprises one of the ingredients , it is not fully known how the combination of the many remaining active ingredients affects physical performance . The purpose of this study was to investigate the effect of a commercially available ES on pistol aim ing steadiness .  Subjects ( N = 10 ) consisted of accredited police officers in the Midwest . A r and omized , blinded , crossover design was used to evaluate the pistol aim ing steadiness after the consumption of an ES or placebo .  Pistol aim ing steadiness was measured using a hole/stylus steadiness tester and laser attached to a training pistol before and 30 minutes after ES or placebo consumption . Analysis revealed that the ES significantly ( p ⩽ 0.05 ) impaired pistol steadiness , whereas the placebo yielded no significant difference in aim ing steadiness . Based on these results , it was concluded that the consumption of an ES could compromise aim ing accuracy and shot placement , thereby jeopardizing the health and welfare of law enforcement personnel INTRODUCTION Previous research has identified acute caffeine ingestion as an effective aid in counteracting the decline in vigilance experienced during sentry duty and sustained operations . However , further research is needed to clarify caffeine 's effects under various stressors and additional operational conditions . The purpose of the present study was to examine the effect of caffeine on target detection and rifle marksmanship during simulated combat operations . METHODS There were 12 reservists who ingested 5 mg x kg(-1 ) body mass of caffeine ( C ) or placebo ( P ) 1 h before beginning a 2.5-h loaded march and 1.0-h s and bag wall construction task . Following exercise , participants were given a re-dose of 2.5 mg x kg(-1 ) body mass of C or P. An hour after ingestion , participants commenced a 2.5-h shooting session on a small arms simulator , which included friend-foe discrimination ( FF ) and vigilance ( VIG ) tasks . Marksmanship performance measures included engagement time ( ET ) , the number of shots fired ( NS ) , accuracy , and precision . RESULTS C ingestion ( initial and /or redose ) did not affect shooting performance during the FF task . ET and NS improved during the VIG task with C ingestion ( mean + /- SD of 2.82 + /- 0.27 s and 29.2 + /- 1.9 shots out of 30 targets , respectively ) compared with the P trial ( 3.00 + /- 0.26 s and 28.0 + /- 3.0 shots ; p < 0.05 ) . CONCLUSION Caffeine ingestion improves target detection and engagement speed during vigilance situations , but is not effective during more complex operations requiring higher levels of cognitive processing and fine motor control and coordination Rationale Various occupational groups are required to maintain optimal physical and cognitive function during overnight periods of wakefulness , often with less than optimal sleep . Strategies are required to help mitigate the impairments in cognitive function to help sustain workplace safety and productivity . Objectives To test the effectiveness of repeated 200 mg doses of caffeine on cognitive function and live-fire marksmanship with soldiers during three successive nights of sustained wakefulness followed by 4-h afternoon sleep periods . Methods Twenty Special Forces personnel ( 28.6 ± 4.7 years , 177.6 ± 7.5 cm and 81.2 ± 8.0 kg ) were r and omly assigned to receive four 200-mg doses of caffeine ( n = 10 ) or placebo ( n = 10 ) during the late evening and early morning hours during three successive days . An afternoon 4-h sleep period followed . The psychomotor ( PVT ) and field ( FVT ) vigilance , logical reasoning ( LRT ) tests and a vigilance monitor assessed cognitive function throughout the study . Live-fire marksmanship requiring friend – foe discrimination was assessed . Results Caffeine maintained speed on the PVT ( p < 0.02 ) , improved detection of events during FVT ( p < 0.001 ) , increased number of correct responses to stimuli as assessed by the vigilance monitor ( p < 0.001 ) and increased response speed during the LRT ( p < 0.001 ) throughout the three overnight testing periods . Live-fire marksmanship was not altered by caffeine . Conclusions A total daily dose of 800 mg caffeine during successive overnight periods of wakefulness is an effective strategy to maintain cognitive function when optimal sleep periods during the day are not available Thirteen healthy and rifle-trained male military reservists performed shooting sessions on two separate occasions 1 h following the ingestion of placebo or 300 mg of caffeine . Shooting included both friend – foe ( FF ) and vigilance ( VIG ) tasks , and were performed in the following order : two FF sequences ( 4 min each ) , four VIG sequences ( 30 min each ) , and two additional FF sequences . The shooting sessions lasted approximately 2.5 h under outdoor conditions ( air temperature range from − 3 to 14 ° C ) and were held 48 h apart in a counter-balanced order . Performance measures during the shooting session included engagement time , friend – foe discrimination , and marksmanship accuracy and precision . Assessment s of thermal comfort , tiredness , and debilitating symptoms preceded and followed the shooting session , while a self- assessment on performance was administered post-shooting only . Blood was sample d immediately prior to the beginning of the shooting session and was used to determine plasma caffeine , cortisol , and testosterone levels . Engagement times were faster and certain measures of accuracy and precision were impaired during the later FF and VIG sequences . However , caffeine ingestion had no affect upon any of the marksmanship measures , although it did alleviate cold stress and tiredness . That caffeine ingestion did not affect target detection and rifle marksmanship is a finding that differs from other studies , and is explained by a beneficial arousal caused by the mild level of cold stress experienced by the participants BACKGROUND Ingestion of a combination of 5 mg x kg(-1 ) caffeine ( C ) , and 1 mg x kg(-1 ) ephedrine ( E ) was reported to have an ergogenic effect on high intensity aerobic exercise performance , but 25 % of the subjects experienced vomiting and nausea while engaging in hard exercise after the treatment . The present study was undertaken to investigate whether reduced levels of C+E would alleviate the problem and maintain the ergogenic effect . METHODS Twelve healthy untrained male subjects completed four r and omized and double-blind , cycle ergometer trials  to exhaustion at a power output equivalent to approximately 85 % Vo2peak 1.5 - 2 hours after ingesting a placebo ( P ) or a mixture of C+E in the following doses : 5 mg x kg(-1 ) of C plus 0.8 mg x kg(-1 ) of E ( CLE ) ; 4 mg x kg(-1 ) of C plus 1 mg x kg(-1 ) of E ( LCE ) ; or 4 mg x kg of C plus 0.8 mg x kg(-1 ) of E ( LCLE ) . Trials were separated by 1 wk . Venous blood sample s were obtained and analyzed for caffeine and ephedrine levels 1.5 h post-drug ingestion . Vo2 , Vco2 , VE , and RQ were measured every minute throughout the exhaustion ride . Heart rate and perceived exertion ( RPE ) were also recorded every 5 min and at the end of the exercise session . RESULTS Plasma levels of C and E immediately before the exhaustion ride were ( mean + /- SD ) : 38.7+/-5.2 micromol x L(-1 ) C , 1.285+/-0.275 micromol x L(-1 ) E in the CLE trial ; 33.2+/-5.8 micromol x L(-1 ) C , 1.462+/-0.283 micromol x L(-1 ) E in the LCE trial ; 33.0+/-2.9 micromol x L(-1 ) C , 1.229+/-0.202 micromol x L(-1 ) E in the LCLE trial . The times to exhaustion for the treatment trials ( CLE = 27.5+/-12.4 min , LCE = 27.6+/-10.9 min , LCLE = 28.2+/-9.3 min ) were similar and were significantly greater than placebo ( p = 17.0+/-3.0 min ) . The drugs did not affect Vo2 , Vco2 , or VE . Heart rates were significantly higher for the drug trials while RPE was lower compared with P. No incidents of nausea or vomiting occurred with the lowest dose of the C+E , LCLE . CONCLUSIONS A lower dose of C+E result ed in an ergogenic effect similar in magnitude to that reported previously with a higher dose , and with a reduced incidence of negative side effects BACKGROUND Current military missions occasionally require combat readiness of soldiers who might be experiencing a sustained period of activity without sleep . Strategies to overcome the debilitating effects of sleep deprivation include the ingestion of caffeine . Unknown is the efficacy of caffeine use on specific elements of target detection and marksmanship following a modest period of sustained wakefulness . METHODS There were 20 subjects ( mean + /- SD of 26.7 + /- 7.2 yr of age , 179 + /- 6 cm in height , and 84.5 + /- 10.8 kg in weight ) who participated in double-blind caffeine and placebo  trials where each trial involved a 24-h control period ( with sleep ) followed by 22 h of mixed mental and physical activity with no sleep . At the end of this period , subjects engaged in a 1-h rifle-shooting task . Subjects ingested 400 , 100 , and 100 mg of caffeine or placebo at 7.5 , 3 , and 0 h , respectively , prior to shooting . Measures of shooting performance included target engagement time ( between target appearance and firing ) , friend-foe discrimination , accuracy , and precision . RESULTS Most measures of performance were de grade d in the placebo sleep-deprived condition , but only the target engagement time and the number of shots fired were restored by caffeine ingestion . CONCLUSIONS These findings concur with other research involving different periods of sleep deprivation , and indicate that the cognitive component of the shooting task ( i.e. , target detection ) can benefit from caffeine whereas the psychomotor component ( marksmanship ) does not . It appears that once the target is detected , the subject is sufficiently aroused to engage the target regardless of the subject 's level of alertness prior to detection Abstract Controversy surrounds the influence that caffeine has on accuracy and cognitive performance in precision activities such as shooting and archery . The aim of this study was to assess the effects of two doses of caffeine on shooting performance , reaction time , and target tracking times in the sport of clay target shooting . A r and omized , double-blind , placebo-controlled design was undertaken by seven elite male shooters from the double-trap discipline . Three intervention trials ( 2 mg caffeine · kg−1 body mass ( BM ) ; 4 mg caffeine · kg−1 BM ; placebo ) were undertaken , in which shooters completed four rounds per trial of 50 targets per round . Performance accuracy ( score ) and digital video footage ( for determination of reaction time and target tracking times ) were gathered during competition . Data were analysed using repeated- measures analysis of variance . No differences in shooting accuracy , reaction time or target tracking times among the three intervention trials or across the four rounds within each intervention were observed ( P > 0.05 ) . The results indicate that ingestion of ≤4 mg caffeine · kg−1 BM does not provide performance benefits to elite performers of clay target shooting in the double-trap discipline PURPOSE Navy SEALs ( sea , air , l and ) are elite special warfare units that conduct unconventional warfare primarily in marine environments . Marksmanship accuracy and sighting time were quantified with 62 male trainees during Navy SEAL Hell Week , which involves the combined stress of sleep loss , operational combat scenarios , and cold-wet environmental conditions .  Caffeine was administered to minimize deficits due to sleep deprivation . METHODS Volunteers dry-fired a disabled rifle equipped with a laser-based marksmanship simulator system to measure shooting speed and accuracy . The target was a 2.3-cm diameter circle at a distance of 5 m , simulating a 46 cm target at a distance of 50 m. Marksmanship was assessed prior to training , and at 73 and 80 h into Hell Week . Volunteers were r and omly assigned to 1 of 4 treatments : 100 , 200 , or 300 mg of caffeine or a placebo . Dosing occurred 72 h after training commenced . RESULTS The combined effects of almost 73 h of total sleep deprivation and operational and environmental stress de grade d all marksmanship accuracy measures ( p < 0.05 ) as shown by the 37.5 % increase in percent of targets missed , 38 % increase in distance from center of mass of the target , and the 235 % increase in shot group tightness . Sighting time increased by 53 % or  
    Output:
    
Caffeine consistently improved marksman reaction time but did not improve marksmanship accuracy .
However , there is some evidence that caffeine attenuates performance decrements in marksman accuracy caused by stress and fatigue if optimal dosing strategies are employed .
Dosing strategies timed according to hours of wakefulness and time before testing could prevent performance deterioration .
Doses of 100–200 mg every 2 hours may effectively improve accuracy during extended duty ; however , further research is needed .
Caffeine consistently improved marksman reaction time but did not improve marksmanship accuracy