Impact of the occupational environment of a submerged submarine on cardiometabolic health of Royal Navy submariners.

OBJECTIVE: To determine the effect of prolonged exposure to a submarine environment on biomarkers of cardiometabolic risk in Royal Navy (RN) submariners. METHODS: Serum lipids (cholesterol (C), triglyceride (TG), low-density lipoprotein cholesterol, high-density lipoprotein cholesterol (HDL-C), non-HDL-C), glucose, insulin and anthropometrics were compared within three RN submarine crews before and after submerged patrols of 12 or 6 weeks, and with a crew that remained ashore (SUB-HOME). Dietary intake and activity patterns were self-reported during each patrol. Differences were assessed in crew characteristics using one-way analysis of variance and in serum lipids using paired t-tests. RESULTS: Postpatrol, the mean body weight of submerged crews decreased (-1.4±4.2 kg, p=0.0001), but increased in SUB-HOME (1.9±1.8 kg, p=0.0001). Modest improvements in serum lipids (mean individual change (mmol/L); C=-0.3±0.7, p=0.0001; TG=-0.3±0.7, p=0.0001; HDL-C=-0.1±0.3, p=0.0001; non-HDL-C=-0.2±0.6, p=0.012), glucose (-0.2±0.5, p=0.0001) and insulin (-1.5±4.6 mU/L, p=0.001) were observed in submerged crews. Changes in serum lipids were positively associated with changes in body weight within crews combined. Energy intake was maintained during submerged patrols but was lower compared with non-submerged (11 139±2792 vs. 9617±2466 kJ, p=0.001; 11 062±2775 vs. 9632±2682 kJ, p=0.003). CONCLUSIONS: The environment of a submerged submarine produced no adverse effects on serum biomarkers of cardiometabolic risk in crew. Conversely, modest improvements in these biomarkers were associated with a decrease in body weight.

Serum 25-hydroxyvitamin D fluctuations in military personnel during 6-month summer operational deployments in Afghanistan.

Soldier operational performance is determined by their fitness, nutritional status, quality of rest/recovery, and remaining injury/illness free. Understanding large fluctuations in nutritional status during operations is critical to safeguarding health and well-being. There are limited data world-wide describing the effect of extreme climate change on nutrient profiles. This study investigated the effect of hot-dry deployments on vitamin D status (assessed from 25-hydroxyvitamin D (25(OH)D) concentration) of young, male, military volunteers. Two data sets are presented (pilot study, n 37; main study, n 98), examining serum 25(OH)D concentrations before and during 6-month summer operational deployments to Afghanistan (March to October/November). Body mass, percentage of body fat, dietary intake and serum 25(OH)D concentrations were measured. In addition, parathyroid hormone (PTH), adjusted Ca and albumin concentrations were measured in the main study to better understand 25(OH)D fluctuations. Body mass and fat mass (FM) losses were greater for early (pre- to mid-) deployment compared with late (mid- to post-) deployment (P<0·05). Dietary intake was well-maintained despite high rates of energy expenditure. A pronounced increase in 25(OH)D was observed between pre- (March) and mid-deployment (June) (pilot study: 51 (sd 20) v. 212 (sd 85) nmol/l, P<0·05; main study: 55 (sd 22) v. 167 (sd 71) nmol/l, P<0·05) and remained elevated post-deployment (October/November). In contrast, PTH was highest pre-deployment, decreasing thereafter (main study: 4·45 (sd 2·20) v. 3·79 (sd 1·50) pmol/l, P<0·05). The typical seasonal cycling of vitamin D appeared exaggerated in this active male population undertaking an arduous summer deployment. Further research is warranted, where such large seasonal vitamin D fluctuations may be detrimental to bone health in the longer-term.

Environmental interventions to promote healthier eating and physical activity behaviours in institutions: a systematic review.

OBJECTIVE: The present review evaluated the effectiveness of environmental-based interventions aimed at improving the dietary and physical activity behaviours and body composition indices of adults in institutions. DESIGN: A systematic review was conducted. Electronic databases (MEDLINE, Embase, PsycINFO, CINAHL, The Cochrane Library, Web of Science, ProQuest Dissertation and Theses, Scopus and Athena) were searched for relevant articles published between database inception and October 2017. Searching, selecting and reporting were undertaken according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. SETTING: Military establishments and maritime workplaces.ParticipantsAdults in institutions, aged 18-45 years. RESULTS: A total of 27842 articles were screened for eligibility, nine studies (reported in eleven articles) were included in the review. Five studies used multilevel strategies and four used environmental strategies only. Duration of follow-up ranged from 3 weeks to 10 years. Eight of the studies reported significant positive effects on dietary behaviours, but effect sizes varied. The study that targeted physical activity had no effect on activity levels but did have a significant positive effect on physical fitness. No evidence was identified that the studies resulted in improvements in body composition indices. CONCLUSIONS: The evidence base appears to be in favour of implementing environmental interventions in institutions to improve the dietary behaviours of adults. However, due to the small number of studies included in the review, and the variable methodological quality of the studies and intervention reporting, further well-designed evaluation studies are required.

Energy expenditure, nutritional status, body composition and physical fitness of Royal Marines during a 6-month operational deployment in Afghanistan.

Understanding the nutritional demands on serving military personnel is critical to inform training schedules and dietary provision. Troops deployed to Afghanistan face austere living and working environments. Observations from the military and those reported in the British and US media indicated possible physical degradation of personnel deployed to Afghanistan. Therefore, the present study aimed to investigate the changes in body composition and nutritional status of military personnel deployed to Afghanistan and how these were related to physical fitness. In a cohort of British Royal Marines (n 249) deployed to Afghanistan for 6 months, body size and body composition were estimated from body mass, height, girth and skinfold measurements. Energy intake (EI) was estimated from food diaries and energy expenditure measured using the doubly labelled water method in a representative subgroup. Strength and aerobic fitness were assessed. The mean body mass of volunteers decreased over the first half of the deployment ( - 4·6 (sd 3·7) %), predominately reflecting fat loss. Body mass partially recovered (mean +2·2 (sd 2·9) %) between the mid- and post-deployment periods (P< 0·05). Daily EI (mean 10 590 (sd 3339) kJ) was significantly lower than the estimated daily energy expenditure (mean 15 167 (sd 1883) kJ) measured in a subgroup of volunteers. However, despite the body mass loss, aerobic fitness and strength were well maintained. Nutritional provision for British military personnel in Afghanistan appeared sufficient to maintain physical capability and micronutrient status, but providing appropriate nutrition in harsh operational environments must remain a priority.

Risk of Injury in Royal Air Force Training: Does Sex Really Matter?

INTRODUCTION: Musculoskeletal injuries are common during military and other occupational physical training programs. Employers have a duty of care to reduce employees' injury risk, where females tend to be at greater risk than males. However, quantification of principle co-factors influencing the sex-injury association, and their relative importance, remain poorly defined. Injury risk co-factors were investigated during Royal Air Force (RAF) recruit training to inform the strategic prioritization of mitigation strategies. MATERIAL AND METHODS: A cohort of 1,193 (males n = 990 (83%); females n = 203 (17%)) recruits, undertaking Phase-1 military training, were prospectively monitored for injury occurrence. The primary independent variable was sex, and potential confounders (fitness, smoking, anthropometric measures, education attainment) were assessed pre-training. Generalized linear models were used to assess associations between sex and injury. RESULTS: In total, 31% of recruits (28% males; 49% females) presented at least one injury during training. Females had a two-fold greater unadjusted risk of injury during training than males (RR = 1.77; 95% CI 1.49-2.10). After anthropometric, lifestyle and education measures were included in the model, the excess risk decreased by 34%, but the associations continued to be statistically significant. In contrast, when aerobic fitness was adjusted, an inverse association was identified; the injury risk was 40% lower in females compared with males (RR = 0.59; 95% CI: 0.42-0.83). CONCLUSIONS: Physical fitness was the most important confounder with respect to differences in males' and females' injury risk, rather than sex alone. Mitigation to reduce this risk should, therefore, focus upon physical training, complemented by healthy lifestyle interventions.

Rebreather Unit to Prolong Underwater Survival Time.

INTRODUCTION: This study investigated whether the timing of activation affects the utility of an emergency underwater rebreather unit (RBU) when submerged in cold water. METHOD: On two successive occasions, 16 male UK Royal Marines were submerged in stirred water at 12.2°C for up to 78 s. The subjects were lowered (taking 18 s) into the water in a seated position and were instructed to take a large breath in, activate the unit, breath-hold for as long as possible, exhale into the unit, and breathe normally to and from the unit for the remainder of submersion. On one occasion the subjects were instructed to activate the RBU when the water reached chest height (Condition-1) and, on the other, prior to the feet entering the water (Condition-2). Measurements were made of the duration of breath-hold, rebreathing and submersion, exhaled oxygen and carbon dioxide concentrations, skin temperature, and heart rate. RESULTS: In 16 of the 32 submersions, the breath-hold was released before the subject became fully submerged and in 8 submersions the subject requested early withdrawal from the water. Mean (SD) breath-hold duration was 14.0 (13.8) s and the duration of rebreathing was 45.9 (21.9) s. The duration of breath-hold once completely submerged was longer in Condition-1 (9.1 s) than Condition-2 (4.1 s). CONCLUSIONS: The study indicates the RBU should be activated just before the mouth becomes submerged rather than before entering the water, and that the RBU will prolong underwater stay time, thereby increasing survival prospects. House CM, Shaw AM, Roiz de Sa DG. Rebreather unit to prolong underwater stay time, thereby increasing survival prospects.

Nutritional status and the gonadotrophic response to a polar expedition.

Polar expeditions have been associated with changes in the hypothalamic-pituitary-testicular axis consistent with central hypogonadism (i.e., decreased testosterone, luteinising hormone (LH), and follicle stimulating hormone (FSH)). These changes are typically associated with body mass loss. Our aim was to evaluate whether maintenance of body mass during a polar expedition could mitigate against the development of central hypogonadism. Male participants (n = 22) from a 42-day expedition (British Services Antarctic Expedition 2012) volunteered to take part in the study. Body mass, body composition, and strength data were recorded pre- and postexpedition in addition to assessment of serum testosterone, LH, FSH, thyroid hormones, insulin-like growth factor 1 (IGF-1), and trace elements. Energy provision and energy expenditure were assessed at mid- and end-expedition. Daily energy provision was 6335 ± 149 kcal·day(-1). Estimated energy expenditure midexpedition was 5783 ± 1690 kcal·day(-1). Body mass and percentage body fat did not change between pre- and postexpedition. Total testosterone (nmol·L(-1)) (14.0 ± 4.9 vs. 17.3 ± 4.0, p = 0.006), calculated free testosterone (pmol·L(-1)) (288 ± 82 vs. 350 ± 70, p = 0.003), and sex hormone binding globulin (nmol·L(-1)) (33 ± 12 vs. 36 ± 11, p = 0.023) concentrations increased. LH and FSH remained unchanged. Thyroid stimulating hormone (TSH; IU·L(-1)) (2.1 ± 0.8 vs. 4.1 ± 2.1, p < 0.001) and free triiodothyronine (FT3; IU·L(-1)) (5.4 ± 0.4 vs. 6.1 ± 0.8, p < 0.001) increased while free thyroxine, IGF-1, and trace elements remained unchanged. Hand-grip strength was reduced postexpedition but static lift strength was maintained. Maintenance of body mass and nutritional status appeared to negate the central hypogonadism previously reported from polar expeditions. The elevated TSH and free FT3 were consistent with a previously reported "polar T3 syndrome".

Fundamental differences in axial and appendicular bone density in stress fractured and uninjured Royal Marine recruits--a matched case-control study.

Stress fracture is a common overuse injury within military training, resulting in significant economic losses to the military worldwide. Studies to date have failed to fully identify the bone density and bone structural differences between stress fractured personnel and controls due to inadequate adjustment for key confounding factors; namely age, body size and physical fitness; and poor sample size. The aim of this study was to investigate bone differences between male Royal Marine recruits who suffered a stress fracture during the 32 weeks of training and uninjured control recruits, matched for age, body weight, height and aerobic fitness. A total of 1090 recruits were followed through training and 78 recruits suffered at least one stress fracture. Bone mineral density (BMD) was measured at the lumbar spine (LS), femoral neck (FN) and whole body (WB) using Dual X-ray Absorptiometry in 62 matched pairs; tibial bone parameters were measured using peripheral Quantitative Computer Tomography in 51 matched pairs. Serum C-terminal peptide concentration was measured as a marker of bone resorption at baseline, week-15 and week-32. ANCOVA was used to determine differences between stress fractured recruits and controls. BMD at the LS, WB and FN sites was consistently lower in the stress fracture group (P<0.001). Structural differences between the stress fracture recruits and controls were evident in all slices of the tibia, with the most prominent differences seen at the 38% tibial slice. There was a negative correlation between the bone cross-sectional area and BMD at the 38% tibial slice. There was no difference in serum CTx concentration between stress fracture recruits and matched controls at any stage of training. These results show evidence of fundamental differences in bone mass and structure in stress fracture recruits, and provide useful data on bone risk factor profiles for stress fracture within a healthy military population.