Page 57 - JSOM Fall 2021

Impact of a 10,000-m Cold-Water Swim

on Norwegian Naval Special Forces Recruits

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Jørgen Melau, EMT, CRNA *; Jonny Hisdal, PhD ; Paul A. Solberg, PhD 3

ABSTRACT
Background: Special Operation Forces (SOF) operate reg- In an interesting study from Jimenez et al., a decrease in core
ularly in extreme environmental conditions that may affect temperature, as well as cardiovascular and immunologi-
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tactical and physical performance. The main aims of the pres- cal changes, were reported in SOF operators. However, the
ent study were to elucidate the impact of a long cold-water knowledge of how exposure to swimming in cold water af-
swim on SOF recruits’ dexterity, performance, and reaction fects the performance of SOF operators is limited. As the SOF
time. Material and Methods: Eleven recruits from Norwe- operators must prepare to do missions after exiting from cold
gian Naval Special Operation Command (NORNAVSOC) water, it is crucial to understand how cold water influences
that were participating in a 10,000-m open water swim with their performance. A typical mission for a SOF operator could
a dry suit in 5°C cold water volunteered to participate in this be a long swim into a target, in which the mission transforms
study. The exercise was part of their training. Grip strength, to involve tasks such as climbing a ladder, using a weapon,
lower body power, and dexterity were measured before, im- clipping into a harness, and similar.
mediately after, and 24 hours after the swim. In addition, core
and skin temperatures were measured continuously during the The main aim of the present study was therefore to elucidate
swim and until 45 minutes after the swim. Results: After the the burden and impact of a long cold-water swim on the dex-
swim, moderate to large reductions in core temperature, lower terity, performance, and reaction time of SOF operators. The
body power, and reaction time were observed. Moreover, very impact on skin and core temperature, as well as biomarkers
large to extremely large reductions in skin temperature, grip for stress and muscle damage, were also measured.
strength, and dexterity were also observed. Conclusion: These
results demonstrate that exposure to a 10,000-m swim in 5°C
water using standard equipment led to a significant drop in the Methods
recruits’ temperature and performance. These findings could Design and Recruits
have a meaningful impact on the planning of training, opera- Eleven male recruits (age 23.9 ± 2.1 years, 83.3 ± 6.8 kg) from
tions, and gear used for SOF. NORNAVSOC that completed a 10,000-m swim in the open
sea during wintertime in Norway, as a part of their qualifica-
Keywords: stress hormones; body temperature; skin tempera- tion training program to become a SOF operator, volunteered
ture; military medicine; swimming; physical fitness; combat to participate in the study (Table 1).
swimmer; combat diver
Ethical Considerations
The study was approved by the Regional Committee for Med-
ical Health Research Ethics, Oslo, Norway (REK) reference
Introduction
number REK southeast C-35176, and by the data protection
Special Operation Forces (SOF) have an exceedingly phys- officer at Oslo University hospital (19/28581). Before provid-
ically and psychologically demanding occupation, which ing written informed consent, recruits received information
often include training and operations under stressful and about potential risks of participation and were particularly
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challenging environmental conditions. Due to climatic con- informed that a withdrawal from the research project would
ditions, the Norwegian Naval Special Operation Command not influence the selection process to become a SOF operator.
( NORNAVSOC) operators are regularly exposed to cold envi-
ronments in many of their operations and training, especially Timeline and Test Descriptions
during operations on, under, and from the sea. Water tempera- The recruits were familiarized with the tests 24 hours prior
ture during winter in the Nordic countries is regularly below to the swim. Pre-tests were performed early in the morning
5°C (41°F). Therefore, one of the possible stressors applied to (5 a.m.–6 a.m.) before entering the water. Immediately after
SOF operators, both in training and operations, is local cool- the swim, the first set of tests were performed (0 hours). The
ing and hypothermia. Following that, it is vital to investigate last set of tests were performed 24 hours after finishing the
the effects of cold weather and particularly cold water opera- swim. The recruits completed the swim with a Kevlar dry suit
tions among SOF personnel. (Ursuit, www.ursuit.com/en/ursuit-heavy-light1) with latex
*Correspondence to jorgen@melau.no
1 Jorgen Melau is a emergency medical technician and certified registered nurse anesthetist and a PhD candidate in temperature physiology, affili-
ated with Prehospital Division of Vestfold Hospital Trust, Department of Clinical Medicine at the University of Oslo and Department of Vascular
Surgery at Oslo University Hospital. He is a former officer in the Norwegian Navy. Dr Jonny Hisdal is a professor affiliated with the Department
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of Clinical Medicine at the University of Oslo and the Department of Vascular Surgery at Oslo University Hospital. Dr Paul A. Solberg is a
researcher affiliated with the Norwegian Olympic and Paralympics Committee and Confederation of Sports, in Oslo, Norway.
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