Environmental conditions may be predictably extreme and severe, such as those in deserts, polar, alpine regions and deep ocean. However, even in normal habitat conditions, individuals may be exposed to transitory, sometime life-threatening, extreme conditions, due to their daily job activities. One such example, are the Advanced Chemical and Biological Reconnaissance Team from the Army Special Forces (ACBRT). Indeed militaries in the ACBRT are exposed to extreme working conditions, due, not only to the dangerous nature of the job (permissive, uncertain, and hostile environments), but also to the characteristic military wearable, which ultimately leads to a dangerous rise in all vital physiological parameters, within short time, sometimes in hot climates up to 45°C. Thus, real-time physiological status monitoring of these soldiers, is very important, to ensure individual and squad performance readiness. Herein, we present the preliminary evaluation of a ACBRT, during a simulation exercise (n=3). Heart rate (HR) and O2 consumption were recorded simultaneously. Heart Rate Variability was analyzed using the traditional Fast Fourier Transform (FFT). Briefly, the results show some interesting differences in the Low Frequency band (LF) profile, which varies according to the different roles. A clear sustained increase of LF can be seen in the Dirty Man (military responsible for collecting the samples), while the LF from the Clean Man (responsible for storing the samples, with no significant physical activity involved), has marked increase during the mission, with a marked decrease towards the end. On the other hand the High Frequency band (HF; parasympathetic Nervous System), revealed a similar profile amongst all the individuals throughout the mission, with a slight decrease in the beginning of the mission, followed by a steep increase half way through the mission. These changes were correlated with O2 consumption levels, indicative of a shift in the sympatho-vagal balance, towards a more pronounced sympathetic activity. Our results, even though not quite significant, considering the sample size, are a clear indicative of the possible usage of HRV, as a predictive tool for both physical and mental performance assessment, including team readiness for the mission ahead.