fphys-12-687605 June 2, 2021 Time: 16:57 # 1 BRIEF RESEARCH REPORT published: 26 May 2021 doi: 10.3389/fphys.2021.687605 The Assessment of Daily Energy Expenditure of Commercial Saturation Divers Using Doubly Labelled Water Sanjoy K. Deb1,2*, Eimear Dolan3, Catherine Hambly4, John R. Speakman4,5, Olav Eftedal6, Mohammed Gulrez Zariwala1 and Ingrid Eftedal2,7 1 Centre for Nutraceuticals, School of Life Sciences, University of Westminster, London, United Kingdom, 2 Department of Circulation and Medical Imaging, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Trondheim, Norway, 3 Applied Physiology and Nutrition Research Group, University of São Paulo, São Paulo, Brazil, 4 Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, United Kingdom, 5 Centre of Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, China, 6 Equinor ASA, Stavanger, Norway, 7 Faculty of Nursing and Health Sciences, Nord University, Bodø, Norway Commercial saturation divers are exposed to unique environmental conditions and Edited by: are required to conduct work activity underwater. Consequently, divers’ physiological Costantino Balestra, Haute École Bruxelles-Brabant status is shown to be perturbed and therefore, appropriate strategies and guidance are (HE2B), Belgium required to manage the stress and adaptive response. This study aimed to evaluate Reviewed by: the daily energy expenditure (DEE) of commercial saturation divers during a 21-day Jacek Kot, Medical University of Gdansk,´ Poland diving operation in the North Sea. Ten saturation divers were recruited during a diving Pasquale Longobardi, operation with a living depth of 72 metres seawater (msw) and a maximum working Hyperbaric Center of Ravenna, Italy dive depth of 81 msw. Doubly labelled water (DLW) was used to calculate DEE during *Correspondence: a 10-day measurement period. Energy intake was also recorded during this period by Sanjoy K. Deb [email protected] maintaining a dietary log. The mean DEE calculated was 3030.9 ± 513.0 kcal/day, which was significantly greater than the mean energy intake (1875.3 ± 487.4 kcal; p = 0.005). Specialty section: This article was submitted to There was also a strong positive correction correlation between DEE and total time spent Environmental, Aviation and Space performing underwater work (r = 0.7, p = 0.026). The results suggested saturation divers Physiology, were in a negative energy balance during the measurement period with an intraindividual a section of the journal Frontiers in Physiology variability in the energy cost present that may be influenced by time spent underwater. Received: 29 March 2021 Keywords: saturation diving, extreme environment, hyperbaric, energy expenditure, doubly labelled water Accepted: 03 May 2021 Published: 26 May 2021 Citation: INTRODUCTION Deb SK, Dolan E, Hambly C, Speakman JR, Eftedal O, Saturation diving is an extreme environmental occupation, with extended exposure to a confined, Zariwala MG and Eftedal I (2021) The hyperbaric, hyperoxic environment to allow subsea activity for prolonged periods. The hyperbaric Assessment of Daily Energy Expenditure of Commercial Saturation environment places unique demands on the human body that challenges the physiological, Divers Using Doubly Labelled Water. cognitive, and physical functions of professional saturation divers. These challenges may cause Front. Physiol. 12:687605. immunosuppression, reduce body mass, and alter the gut microbiome environment (Brubakk doi: 10.3389/fphys.2021.687605 et al., 2014; Yuan et al., 2019). Although longitudinal studies to assess the chronic health-related Frontiers in Physiology| www.frontiersin.org 1 May 2021| Volume 12| Article 687605 fphys-12-687605 June 2, 2021 Time: 16:57 # 2 Deb et al. Energy Expenditure of Saturation Divers implications of saturation diving is sparse, purported long- weight was also recorded to the nearest 0.1 kg (SECA, term consequences include reduced musculoskeletal health and Birmingham, United Kingdom). The Norwegian Regional impaired cognition (Ross et al., 2007; Brubakk et al., 2014). Committee approved the study protocol for Medical and Health Given the potential health-related consequences of prolonged Research Ethics (REK; approval number: 2018/1184). The exposure to this environmental stressor, there is a clear need participants provided their written informed consent before to develop strategies to support acclimatisation, adaptation, volunteering for the study. and management of physiological perturbations that these unique environmental conditions bring. Appropriate and Saturation Dive Operation targeted nutritional interventions represent some such potential Diving operations took place in October–November 2019, off mitigation approach and are believed to play a vital role in the west coast of Norway and were conducted per the NORSOK managing a saturation divers physiology, health and wellness U-100 requirements (Standards Norway, 2014). All participants (Deb et al., 2016). For example, oral antioxidant supplementation were part of the same diving operation; therefore, they were has been reported to reduce hepatic oxidative damage during exposed to similar dive conditions with a living depth of saturation diving (Ikeda et al., 2004). Furthermore, commercial 72 metres seawater (msw) resulting in a maximum working depth saturation diving results in changes to the gut microbiome of 81 msw. In the chamber the oxygen pressure was maintained by reducing Bifidobacterium and short-chain fatty acid (Yuan at 380 mbar and this increased to 756 mbar during the bell run. et al., 2019), both of which can also be modulated by nutritional The temperature was adjusted to maintain the thermal comfort of intervention (Ojeda et al., 2016). Despite emerging research divers and typically maintained between 28 and 30◦C. The dive highlighting the importance of nutrition for saturation divers’ operation was up to 18 days, with divers spending 14 days in a health, there remains a gap in knowledge on this occupation’s saturation at the living depth of 72 msw followed by a 3–4 days unique dietary needs (Deb et al., 2016). decompression period. The divers organised into 4 teams of 3 and Energy requirements are a fundamental component of working in overlapping 12 h shift patterns with a new 3-man shift dietary guidelines, as it provides a quantitative assessment of starting every 6 h throughout a 24-h cycle. The divers had 12 h physiological and behavioural energy cost of an individual within off between each shift. The dive teams worked in rotation; for their environment (Speakman, 1999). Commercial saturation every third shift, the divers provided support from the diving bell divers self-reported their daily activity within the chamber’s and did not perform any activities underwater. For the purposes confinement to be low (Dolan et al., 2016), with the main activity of this study, an underwater excursion was defined the duration (and therefore activity-related energy expenditure) occurring of a wet bell run during shifts where the divers undertook during underwater excursions. This underwater activity’s energy activity in the water, as one diver would remain dry in the bell requirements are unknown; although, reports suggest that this throughout any given shift. Each diver completed 7.4 ± 1.7 can vary between diving operations depending on the tasks underwater excursions on average during this operation, with performed (Gernhardt and Lambertsen, 2002; Dolan et al., an average underwater working period of 193.1 ± 25.9 min per 2016). Taken together, the changes in daily physical activity excursion. The total time that a diver spent in water during this in the chamber, the atmospheric conditions and the energy saturation operation was 1066.8 ± 417.9 min across the 21-day cost of underwater activity may all theoretically influence daily saturation dive. It was not possible to measure the underwater energy expenditure (DEE) during commercial saturation diving. excursion’s intensity, but the divers subjectively reported that However, to date, an accurate assessment of DEE during the the underwater excursions were approximately half the length of real-life offshore work environment has not been undertaken. the typical 5.30 h underwater working period, and the workload Establishing the energy requirements of saturation diving is was perceived as “light.” Examples of work performed during essential to formulate appropriate nutritional guidelines to underwater excursions during this operation include: Installation support occupational divers’ health and well-being (Deb et al., of blind flange plugs, pipe support installation, seal replacements, 2016). Therefore, the purpose of this study was to determine bell mouth installation, and inspection works. the average DEE of occupational saturation divers who are undertaking a 21-day commercial dive in the North Sea using the gold standard energy assessment technique of doubly Measurement of Daily Energy labelled water (DLW). Expenditure The DLW stable isotope technique was used to measure energy expenditure. This is the gold-standard method that METHODS provides a safe and non-invasive procedure to determine energy expenditure (Westerterp, 2017). Participants completed a 10-day Participants and Saturation Dive sampling period commencing 3 days after they were compressed Ten operational and medically certified divers were to hyperbaric pressure equivalent to 72 msw. A second-morning recruited with