Effect of caffeine on target detection and rifle marksmanship

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 14degreesC) 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.