A comparison of the metabolic effects of sustained strenuous activity in polar environments on men and women

Abstract

This study investigates differences in pre-to post-expedition energy expenditure, substrate utilisation and body composition, between the all-male Spear17 (SP-17) and all-female Ice Maiden (IM) transantarctic expeditions (IM: N = 6, 61 days, 1700 km; SP-17: N = 5, 67 days, 1750 km). Energy expenditure and substrate utilisation were measured by a standardised 36 h calorimetry protocol; body composition was determined using air displacement plethysmography. Energy balance calculation were used to assess the physical challenge. There was difference in the daily energy expenditure (IM: 4,939 kcal day −1 ; SP-17: 6,461 kcal day −1 , p = 0.004); differences related to physical activity were small, but statistically significant (IM = 2,282 kcal day −1 ; SP-17 = 3,174 kcal day −1 ; p = 0.004). Bodyweight loss was modest (IM = 7.8%, SP-17 = 6.5%; p > 0.05) as was fat loss (IM = 30.4%, SP-17 = 40.4%; p > 0.05). Lean tissue weight change was statistically significant (IM = − 2.5%, SP-17 = + 1.0%; p = 0.05). No difference was found in resting or sleeping energy expenditure, normalised to lean tissue weight (p > 0.05); nor in energy expenditure when exercising at 80, 100 and 120 steps min −1 , normalised to body weight (p > 0.05). Similarly, no difference was found in the change in normalised substrate utilisation for any of the activities (p > 0.05). Analysis suggested that higher daily energy expenditures for the men in Spear-17 was the result of higher physical demands resulting in a reduced demand for energy to thermoregulate compared to the women in Ice Maiden. The lack of differences between men and women in the change in energy expenditure and substrate utilisation, suggests no sex difference in response to exposure to extreme environments. There is an increasing involvement of women in extreme activities often in adverse environmental conditions that are characterised by a deficit in Energy Availability (EA), the difference between the calorific intake and the energy expended. These activities, which include extreme sports 1 , expeditionary travel and military combat training 2 , have traditionally been undertaken by men with the result that the majority of the research looking at physiological adaptation and responses, particularly during expeditionary travel in polar regions and to altitude,

Reindeer herders from subarctic Finland exhibit high total energy expenditure and low energy intake during the autumn herd roundup

“…Recent work has greatly expanded our understanding of variation in human TEE. However, TEE measurements among highly active populations living in a cold climate are few (Snodgrass, Leonard, Tarskaia, & Schoeller, 2006) or limited to expeditionary settings (Hattersley et al, 2020; Ocobock, 2016a, 2016b; Ocobock, 2017). The present study addresses this gap with TEE measurements and dietary intake among reindeer herders from sub‐Arctic Finland.…”

Sex differences and shifts in body composition, physical activity, and total energy expenditure across a 3‐month expedition

“…However, it is important to note that while the average error for the flex-HR method is relatively small, it can overestimate individual TEE up to 17% particularly at higher levels of energy expenditure (i.e., >3000 kcal day À1 ) (Leonard, 2003;Ocobock, 2016b). If our flex-HR estimates were inflated for higher values, it would suggest that TEE on average across the whole group would be slightly lower than seen in other shorterterm expedition settings, though still higher than the constrained level ~2500 kcal day À1 (Hattersley et al, 2020;Pontzer et al, 2016). Post-hoc analysis suggests that this overestimation does not seem to impact the patterns of difference between male and female TEE observed in this data set.…”

“…In addition, while it is well understood that males and females have differential basal metabolic rates largely due to relatively greater body and fat-free mass in males (Johnstone et al, 2005;Manini, 2010;Ocobock, 2020), it is less known how total energy expenditure may differ by sex during and after acclimatization. Beyond basic differences in body composition and basal metabolic rate, some previous research suggests that there are potential differences in how males and females respond to extreme physiological demands, for example, such as males having higher dependency on carbohydrate utilization and increases in the heart's stroke volume in expedition settings thus increasing energy expenditure during demanding activities (Braun et al, 2000;Hattersley et al, 2020;Pettit et al, 1999). However, when taken together, these findings do not yet show a conclusive pattern.…”

“…Backcountry expedition settings are a good model for understanding such shorter-term acclimatization processes since individuals are exposed to an energetically demanding environment for a set period of time, have constrained access to resources, and often engage in intensive physical activity. Energy expenditure has been shown to increase when individuals are first introduced to these settings, (Hattersley et al, 2020;Ocobock, 2016a;Pulfrey & Jones, 1996;Westerterp et al, 1992), though once acclimatized, bodies can potentially rebound from the increased energetic demands and return to their original baseline status. However, questions remain regarding differences in acclimatization, particularly when considering over a longer period of time beyond the first couple weeks and into several months.…”

“…Research has demonstrated notable changes in individual energy status and expenditure when individuals are on expeditions. Intensive backcountry expeditions are marked by increases in individuals' energy expenditure reaching up to well over 4000 kcal day À1 (Hattersley et al, 2020;Ocobock, 2016b;Pulfrey & Jones, 1996). Compared to adapted groups, sojourners to these challenging and physically intensive settings must acclimate to the dual burdens of everyday activity as well as novel and potentially harsh environmental stressors which may explain the initial increased energy expenditure (Frisancho, 2013;Moore et al, 1998).…”