Effects Of Dual-tasking On Physiological Responses During A Simulated Military Patrol

Soldiers frequently carry heavy loads, such as body armor, equipment, and weapons, while on patrol, which increases the physiological demands of walking and can contribute to physical fatigue. Additionally, soldiers often perform cognitive tasks, like scanning for enemies, which may further increase physiological demands. Although dual-tasking (physical + cognitive) has been shown to elevate the physiological cost of activity, no studies have assessed this in a military-specific scenario involving load carriage. PURPOSE: To examine the impact of a dual-task (DT) versus a single-task (ST) patrol on physiological responses. METHODS: Nine adults (7 men, 2 women; 31.0 ± 10.5 yrs, 179.9 ± 6.6 cm, 80.5 ± 13.6 kg, 17.5 ± 4.7 % body fat, 53.1 ± 6.2 mL/kg/min) completed both conditions in a randomized order. Participants carried a 30 kg load (10 kg body armor, 15 kg assault pack, 5 kg dummy weapon) while walking on a treadmill (4.8kph, 0% incline) for 60 minutes. In the DT condition, participants also played a game, scanning a city shown on a screen in front of the treadmill. Participants pressed a button on the dummy weapon as fast as possible when an enemy character appeared but ignored friendlies. Respiratory parameters of oxygen consumption (VO2), heart rate (HR), respiratory rate (BrPM), tidal volume (TV), and ventilation were recorded throughout. Non-parametric ANOVAs were utilized, with results shown as median (interquartile range) and Cohen’s d. Α =0.05. RESULTS: The DT condition showed significantly higher relative VO2 (p = 0.04, DT = 22.3(4.1) ST = 21.7(3.4), d = -0.06) and BrPM (p < 0.001, DT = 40.0(7.8); ST = 37.2(9.7), d = -0.26), and lower TV (p < 0.001, DT = 1.3(0.3); ST = 1.4(0.3), d = 0.27). HR was greater in the ST than DT (p = 0.015, ST = 129.4(17.5); DT = 126.7(14.1), d = 0.13). There was no significant difference in ventilation (p = 0.11, DT = 51.6(10.4); ST = 51.3(11.5), d = -0.12) or absolute VO2 (p = 0.14, DT = 1.8(0.5); ST = 1.8(0.5), d = -0.08). CONCLUSIONS: DT marching led to statistically significant changes in respiratory parameters, though the effects were small to negligible at the group level. The addition of a cognitive task in this military context may not have a practically meaningful impact on soldiers' physiological responses over 60-minutes but should be analyzed over longer patrols.