The study by Amitabh et al (1) in this issue, on adaptive changes in body composition and fitness in Indian soldiers exposed to extreme environments, is an important step in understanding how to manage performance, health and well being in harsh conditions. It is always challenging to accurately measure physiological adaptations in extreme environments, and the authors have done well. The critical considerations in these assessments are: (i) the duration of exposure or acclimatization to the extreme environment, (ii) whether the measurements were longitudinal, (iii) whether the measurements were made under controlled laboratory conditions or in real environment, (iv) whether the housing and nutritional care of the subjects was optimal during the adaptation period, (v) whether there was targeted physical activity or training of the participants, and (vi) whether an assessment of psychological factors affecting the subjects motivation was available. In this study, (1) the assessment of adaptation to high altitude (HA) was made after a period of 3-6 months, and for the hot desert (HD), was made after a period of 1 month. The measurements were crosssectional and not longitudinal, which is a weakness the authors acknowledge. The actual measurement of fitness was made under laboratory conditions, which is reasonable, but for a complete analysis, it is necessary to have measurements of fitness under the actual extreme conditions (challenging as those are), since performance must be considered under conditions that could affect mission success. Some critical elements of information in this study have also to be considered before comment on the actual findings. On the one hand, the subjects appear to have been a homogenous group of lowlanders in terms of their age, were non smokers in the majority, and reported similar food intakes. They also did not report any change in their body weight over the duration of the acclimatization to the respective extreme environments. On the other hand, their physical activity was not similar, and was restricted by the environmental conditions in both HA and HD. For comparisons, the assumption was that the control subjects represented the condition of the HA or HD subjects prior to their acclimation.