Reaction Time in Service Members with Mild Traumatic Brain Injury: Psychometric Evaluation of the Patrol Exertion Task

Context: Persistent mild traumatic brain injury (mTBI) symptoms can reduce a service member’s ability to perform their duties safely, making functional mTBI assessment a necessary part of rehabilitation. The Patrol Exertion Task (PET), a subtask within the Complex Assessment of Military Performance (CAMP), challenges physical, visual, and cognitive function in active duty service members (SM) with persistent mTBI symptoms. The measures collected during this assessment are designed to detect subtle impairments observable only during demanding cognitive and motor tasks, with the intent to inform return-to-duty (RTD) decisions. Because no standardized assessment currently exists to evaluate RTD readiness, it is imperative to develop and validate tools that inform clinical decisions.Objective: To validate the reaction time (RT) component of the PET through three aims: (1) examine test-retest reliability in a healthy control (HC) population, (2) evaluate group differences between HCs and SMs with persistent mTBI symptoms, and (3) assess pre- to post-intervention changes in the mTBI population.Methods: 132 participants (63 HC; 69 mTBI) completed at least one CAMP test session, during which self-report symptom data and PET performance were recorded. The PET required participants to engage in a 10-minute simulated foot patrol while continuously stepping, monitoring a virtual scene for markers of interest, and responding to auditory cues by pressing a switch on a non-firing simulated weapon. Heart Rate (HR) was recorded via a Polar H10 monitor, and RT was recorded using a dedicated Raspberry Pi device. Main Outcomes: RT was measured using 12 responses to auditory cues throughout the patrol. RPE (Borg 6-20) and HR (bpm) were recorded before and after the PET to assess changes in exertion.Results: Patrol RT demonstrated good reliability comparable to established military cognitive batteries such as ANAM and ImPACT. The PET also demonstrated preliminary known-groups validity, with the early phase most informative. The mTBI group was significantly slower than the HC group, potentially reflecting impaired initial cognitive engagement before compensatory strategies emerged. The PET also demonstrated responsiveness, detecting significant pre- to post-intervention improvement in Patrol RT.Conclusions: The PET’s RT component is reliable, sensitive to group differences, and responsive to clinically prescribed interventions.