Simulation of thermal-work strain of dismounted Marines wearing different body armor protection levels in a jungle environment
DOI:
https://doi.org/10.12922/jshp.v6i1.134Keywords:
thermal-work strain, metabolic rate, modeling, thermal performanceAbstract
Dismounted warfighters often experience thermal-work strain when performing missions in hot and humid jungle environments. Under these conditions, the survivability benefits provided by increased body armor protection levels (BAPL) must be carefully balanced with their associated thermal and metabolic burdens and avoid thermal injury. PURPOSE: Model the effects of increased BAPL on the thermal-work strain of U.S. Marines engaged in dismounted training activities at Camp Gonsalves, Okinawa, Japan (June, 2013). METHODS: Core temperature (TC), heart rate (HR), and accelerometry data were collected over 3 days (5-9 hr/day) from U.S. Marines (N = 11, age = 21 ± 2 yr, ht = 172 ± 4 cm, wt = 78.2 ± 1.9 kg, x̅ ± SD) using chest-worn physiological monitors and ingested thermometer pills. Metabolic rates, estimated from accelerometry data by matching modeled to observed TC values using a thermoregulatory model, used to predict the physiological effects of increased BAPL under jungle conditions (air temperature = 28.3 ± 0.8 ºC, relative humidity = 91 ± 7 %). RESULTS: Root mean square error between observed and modeled TC was 0.24 ± 0.09 ºC for BAPL 0, indicating reasonable metabolic rate estimations. Mean daily increases in TC were 0.3 ± 0.4 ºC, 0.7 ± 0.4 ºC, 2.8 ± 0.9 ºC, and 3.2 ± 0.9 ºC for observed data and data modeled with BAPL 0, 3, and 5 respectively. Modeling BAPL 0 with either increased load or reduced vapor permeability resulted in TC increases of 2.9 ± 0.8 ºC and 1.4 ± 0.6 ºC respectively. Differences between BAPL resulted in Modeled TC values > 39.5 ºC at 238 ± 65 minutes and 188 ± 42 hrs for BAPL 3 and 5. CONCLUSION: Predictive modeling indicates that the risk of thermal-work strain is severe given jungle conditions and increased BAPL. The mass of BAPL ensembles contributes more to thermal-work strain than reductions in ensemble permeability and evaporative heat loss.References
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