Modeling analysis of women litter bearers during heat stress

Background: The majority of military physiological studies have been conduc ted on men. Consequently most physiological modeling is based on male perfo rmance. This study obtained data on women performing military tasks under h ot-dry field conditions. Results for rectal temperature (Trf) and heart rat e (HR) were compared with values generated by the SCENARIO physiological mo del. Methods: Three skin surface temperatures, T-re, and HR were collected while four female subjects participated in walking or two-person litter car riage (68 kg load) in regular battledress and with full chemical protection at Yuma Proving Ground, AZ. Metabolic rates were measured prior to the tes t days. Meteorological data were also recorded. Results: Overall, the poten tial for thermal stress decreased over the four test days, with air tempera ture dropping from 39.4 degrees to 35.5 degrees C. Whole body metabolic val ues were 364 W (walking), 91 W (standing), and 492 W (litter carriage). End urance times (160 min maximum) for walking were 140 min in Mission Oriented Protective Posture (MOPP)-0 and 29 min in MOPP-4. For litter carriage, the average times were 59 min in MOPP-0 and 43 min in MOPP-Q. A comparison of root mean squared deviation (RMSD) to the mean standard deviation for Tre d emonstrated a good fit between the model and mean observed values for the M OPP-0 condition. Observed HRs were greater than predicted by the model. Con clusions: The modeling results support a conclusion that factors other than heat stress limited litter carriage in MOPP-0. Analysis of calculated valu es for Tre using RMSD supports an assumption that the male-based SCENARIO m ay be applicable to females.