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Limitations 2. Cajigal Vargas J, Triantafilo Vladilo VS, Naranjo Orellana J. Im-
First, the present study had a small sample size, and some pact of hypothermic stress during Special Operations training of
small findings were not clear. However, this is due to the na- Chilean military forces. Mil Med. 2018;183(7–8):e193–e199.
ture of the training of NORNAVSOC recruits. Second, in- 3. Laurent CM, Green JM, Bishop PA, et al. A practical approach to
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the present study underwent heavy strain before starting this 5. Hamarsland H, Paulsen G, Solberg PA, et al. Depressed physical
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side normal ranges on some variables. Fourth, including more ing. Med Sci Sports Exerc. 2018;50(10):2076–2084.
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Acknowledgments Acta Physiol Scand. 1979;107(1):33–37.
The authors would like to thank the instructors and recruits 15. Chi C-F, Shih Y-C, Chen W-L. Effect of cold immersion on grip
who participated in the study and the NORNAVSOC Com- force, EMG, and thermal discomfort. Int J Ind Ergon. 2012;42(1):
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mand who gave permission and supported us in this study. 16. Cheung SS, Montie DL, White MD, Behm D. Changes in manual
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Disclosure degrees C water. Aviat Space Environ Med. 2003;74(9):990–993.
The authors have no conflicts of interest to declare. 17. DuCharme MB, Brajkovic D. Maintaining finger dexterity in the
cold: a comparison of passive, direct and indirect hand heating
methods. Defense Technical Information Center. https://apps
Funding .dtic.mil/dtic/tr/fulltext/u2/p012428.pdf. Accessed 22 April 2021.
This study was supported by the NORNAVSOC, Oslo Univer- 18. Imray C, Richards P, Greeves J, Castellani JW. Nonfreezing
sity Hospital, and Vestfold Hospital Trust. Parts of this study cold-induced injuries. BMJ Mil Health. 2011;157(1):79–84.
have been presented as a poster at the Special Operations 19. Vikmoen O, Teien HK, Raustøl M, et al. Sex differences in the
Medical Association 2020 Virtual Scientific Assembly. physiological response to a demanding military field exercise.
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20. Neubauer O, Konig D, Wagner KH. Recovery after an Ironman
Author Contributions triathlon: sustained inflammatory responses and muscular stress.
PAS and JM conceived the study concept. JH and PAS obtained Eur J Appl Physiol. 2008;104:417–426.
funding. PAS recruited participants. JM and PAS planned the 21. Nyborg C, Melau J, Bonnevie-Svendsen M, et al. Biochemical
study, collected the data, and analyzed the data. JM wrote markers after the Norseman Extreme Triathlon. Tauler P, ed.
the first draft, and all authors read and approved the final PLOS ONE. 2020;15(9):e0239158.
manuscript. 22. Pendergast DR, Tedesco M, Nawrocki DM, Fisher NM. Energet-
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