Heat injury risk of simulated march and urban patrol infantry tasks

PURPOSE: To determine the thermal safety of soldiers undertaking 10 km march and simulated urban patrolling tasks in cool to moderately hot environments.\ud \ud METHODS: 144 trained infantry soldiers and 28 infantry trainees performed the march in thermal conditions that ranged from 11.8°C to 25.0°C WBGToutdoors. 173 trained infantry soldiers and 28 infantry trainees performed the simulated urban patrol in thermal conditions that ranged from 6.1°C to 26.8°C WBGToutdoors. All participants were acclimated to the test environment. The march was conducted at a velocity of 6 km.hr-1 (10 min rest after 50 min) in camouflage clothing while carrying a total weight of 45 kg. The simulated urban patrol involved repeated 22 m sprints (7 s sprint, 7 s recovery) to volitional fatigue or a maximum total test time of 12 min. Each sprint was initiated from a kneeling position. The soldiers wore/carried equipment totalling 20.6 kg, including ballistic vest and helmet, during the simulated urban patrol task. Environmental conditions were measured using a QuestTemp° 36 Thermal Environment Monitor and core temperature was measured using HQInc CorTemp radio telemetered thermal pills.\ud \ud RESULTS: Core temperature increase to 38.35 + 0.50 °C (mean + SD) (95% CI: 38.31 to 38.39 °C) during the march and to 38.20 + 0.51 °C (95% CI: 38.16 to 38.24 °C) during the simulated urban rushing task. Three (2%) and four (2%) of the participants in the respective tasks exceeded the pre-determined core temperature safety cut-off of 39.5 °C and were excluded from further participation. None of the soldiers experienced any signs or symptoms of heat illness during the tasks. \ud \ud CONCLUSION: The conduct of these simulated tasks in the cool to moderately hot conditions described did not result in heat injury and is likely to be safe so long as standard heat management practices are followed. Supported by the Australian Defence Force