1.
Caffeine restores engagement speed but not shooting precision following 22 h of active wakefulness.
Tikuisis, P, Keefe, AA, McLellan, TM, Kamimori, G
Aviation, space, and environmental medicine. 2004;(9):771-6
Abstract
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 degraded 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.
2.
Effect of caffeine on target detection and rifle marksmanship.
Gillingham, R, Keefe, AA, Keillor, J, Tikuisis, P
Ergonomics. 2003;(15):1513-30
Abstract
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 degrees 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. Assessments 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 sampled 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.