Effect of physical, cognitive, and combined fatigue on military marksmanship performance and perceived workload

Simultaneous physical and cognitive demands challenge military operational capability under prolonged stress. While the independent effects of fatigue on performance are established, no study has systematically compared the effects of isolated and combined fatigue states on performance. This study examined the effect of physical, cognitive, and combined fatigue on military marksmanship performance. Participants (N = 24; M age = 22.04 + 3.22 years, male = 20) completed three study visits, with seven days between visits, encompassing a physical, cognitive, and combined fatigue protocol and common military marksmanship tasks. Results demonstrated significant differences in marksmanship accuracy (p < .001; partial η² = 0.57), discriminatory reaction time (p = .002; partial η² = 0.15), and marksmanship efficiency (p < .001; partial η² = 0.15-0.17). Posthoc decomposition confirmed that combined fatigue produced significantly greater decrements (Cohen's d = 0.78-1.12). Additionally, results revealed significant differences in self-reported mental and physical demand (p < .001), temporal demand (p = .014; partial η² = 0.17), and effort, frustration, and perceived exertion (p's < 0.001). These findings demonstrate the negative, compounding effect of combined fatigue on military marksmanship performance and highlight the need for comprehensive training programs, interventions, and countermeasures that address the challenges of real-world combat operations.