Histamine, mast cell tryptase and post-exercise hypotension in healthy and collapsed marathon runners.

PURPOSE: Heat stress exacerbates post-exercise hypotension (PEH) and cardiovascular disturbances from elevated body temperature may contribute to exertion-related incapacity. Mast cell degranulation and muscle mass are possible modifiers, though these hypotheses lack practical evidence. This study had three aims: (1) to characterise pre-post-responses in histamine and mast cell tryptase (MCT), (2) to investigate relationships between whole body muscle mass (WBMM) and changes in blood pressure post-marathon, (3) to identify any differences in incapacitated runners. METHODS: 24 recreational runners were recruited and successfully completed the 2019 Brighton Marathon (COMPLETION). WBMM was measured at baseline. A further eight participants were recruited from incapacitated runners (COLLAPSE). Histamine, MCT, blood pressure, heart rate, body temperature and echocardiographic measures were taken before and after exercise (COMPLETION) and upon incapacitation (COLLAPSE). RESULTS: In completion, MCT increased by nearly 50% from baseline (p = 0.0049), whereas histamine and body temperature did not vary (p > 0.946). Systolic (SBP), diastolic (DBP) and mean (MAP) arterial blood pressures and systemic vascular resistance (SVR) declined (p < 0.019). WBMM negatively correlated with Δ SBP (r = - 0.43, p = 0.046). For collapse versus completion, there were significant elevations in MCT (1.77 ± 0.25 µg/L vs 1.18 ± 0.43 µg/L, p = 0.001) and body temperature (39.8 ± 1.3 °C vs 36.2 ± 0.8 °C, p < 0.0001) with a non-significant rise in histamine (9.6 ± 17.9 µg/L vs 13.7 ± 33.9 µg/L, p = 0.107) and significantly lower MAP, DBP and SVR (p < 0.033). CONCLUSION: These data support the hypothesis that mast cell degranulation is a vasodilatory mechanism underlying PEH and exercise associated collapse. The magnitude of PEH is inversely proportional to the muscle mass and enhanced by concomitant body heating.

Risk of heat illness in men and women: A systematic review and meta-analysis.

BACKGROUND: Heat illness (HI) is a growing global concern; its incidence has risen dramatically across the world in recent years. The individual factors whereby elevated core temperature produces HI are not well-understood. Given known physiological differences between men and women pertaining to temperature regulation, we hypothesized that women would be at increased risk of HI than men. OBJECTIVES: We aimed to determine the relative risk of HI in women compared with men through an exhaustive literature review and meta-analysis. METHODS: We search PubMed and Ovid Medline databases from inception to Apr 2017. Search terms included all permutations of sex and heat illness (including heatstroke and exertional heat illness) with no language restrictions. We included adult or adolescent human data reporting comparable male and female HI rates. One reviewer identified and screened titles and abstracts. Two independent reviewers applied eligibility criteria. Disagreements were resolved with a third reviewer. RESULTS: Of 5888 articles identified by searches, 36 were included in the systematic review and 22 in the meta-analysis. The mean (standard deviation) quality score was 3.31(1.25)/5. Overall the rate among women was consistently lower than men across the lifespan. The male: female pooled IRR was 2.28 (p < 0.001, 95% CI: 1.66-3.16). There was modest heterogeneity (between-studies variance (τ2) = 0.02). The rates did not differ significantly when corrected for severity or occupation. DISCUSSION: The rate of HI was significantly increased in men compared with women. Risk for HI might be conferred by psychological and behavioral factors rather than physiological ones. Further research is required to delineate which groups are at greatest risk, leading to the development of mitigation strategies against HI. OTHER: No funding was received. The authors acknowledge the support of the UK Women in Ground Close Combat Review. The Study was registered with PROSPREO CRD42017064739.

Heart rate variability and plasma nephrines in the evaluation of heat acclimatisation status.

PURPOSE: Heat adaptation (HA) is critical to performance and health in a hot environment. Transition from short-term heat acclimatisation (STHA) to long-term heat acclimatisation (LTHA) is characterised by decreased autonomic disturbance and increased protection from thermal injury. A standard heat tolerance test (HTT) is recommended for validating exercise performance status, but any role in distinguishing STHA from LTHA is unreported. The aims of this study were to (1) define performance status by serial HTT during structured natural HA, (2) evaluate surrogate markers of autonomic activation, including heart rate variability (HRV), in relation to HA status. METHODS: Participants (n = 13) were assessed by HTT (60-min block-stepping, 50% VO2peak) during STHA (Day 2, 6 and 9) and LTHA (Day 23). Core temperature (Tc) and heart rate (HR) were measured every 5 min. Sampling for HRV indices (RMSSD, LF:HF) and sympathoadrenal blood measures (cortisol, nephrines) was undertaken before and after (POST) each HTT. RESULTS: Significant (P < 0.05) interactions existed for Tc, logLF:HF, cortisol and nephrines (two-way ANOVA; HTT by Day). Relative to LTHA, POST results differed significantly for Tc (Day 2, 6 and 9), HR (Day 2), logRMSSD (Day 2 and Day 6), logLF:HF (Day 2 and Day 6), cortisol (Day 2) and nephrines (Day 2 and Day 9). POST differences in HRV (Day 6 vs. 23) were + 9.9% (logRMSSD) and - 18.6% (logLF:HF). CONCLUSIONS: Early reductions in HR and cortisol characterised STHA, whereas LTHA showed diminished excitability by Tc, HRV and nephrine measures. Measurement of HRV may have potential to aid real-time assessment of readiness for activity in the heat.

Reproductive dysfunction and associated pathology in women undergoing military training.

INTRODUCTION: Evidence from civilian athletes raises the question of whether reproductive dysfunction may be seen in female soldiers as a result of military training. Such reproductive dysfunction consists of impaired ovulation with or without long-term subfertility. METHODS: A critical review of pertinent evidence following an extensive literature search. RESULTS: The evidence points towards reduced energy availability as the most likely explanation for exercise-induced reproductive dysfunction. Evidence also suggests that reproductive dysfunction is mediated by activation of the hypothalamic-pituitary-adrenal axis and suppression of the hypothalamic-pituitary-gonadal axis, with elevated ghrelin and reduced leptin likely to play an important role. The observed reproductive dysfunction exists as part of a female athletic triad, together with osteopenia and disordered eating. If this phenomenon was shown to exist with UK military training, this would be of significant concern. We hypothesise that the nature of military training and possibly field exercises may contribute to greater risk of reproductive dysfunction among female military trainees compared with exercising civilian controls. We discuss the features of military training and its participants, such as energy availability, age at recruitment, body phenotype, type of physical training, psychogenic stressors, altered sleep pattern and elemental exposure as contributors to reproductive dysfunction. CONCLUSIONS: We identify lines of future research to more fully characterise reproductive dysfunction in military women and suggest possible interventions that, if indicated, could improve their future well-being.

The Reliability of a Pre-Loaded Treadmill Time-Trial in Moderate Normobaric Hypoxia.

The purpose of this study was to assess the reliability of a pre-loaded 1 500-m treadmill time trial, conducted in moderate normobaric hypoxia. 8 trained runners/triathletes (24±3 years, 73.2±8.1 kg, 182.5±6.5 cm, altitude specific V˙O2max: 52.9±5.5 ml·kg(-1)·min(-1)) completed 3 trials (the first as a familiarisation), involving 2, 15-min running bouts at 45% and 65% V˙O2max, respectively, and a 1 500-m time trial in moderate normobaric hypoxia equivalent to a simulated altitude of 2 500 m (FiO2~15%). Heart rate, arterial oxygen saturation, skeletal muscle and cerebral tissue oxygenation (StO2), expired gas ( V˙O2 and V˙CO2), and ratings of perceived exertion were monitored. Running performance (Trial 1: 352.7±40; Trial 2: 353.9±38.2 s) demonstrated a low CV (0.9%) and high ICC (1). All physiological variables demonstrated a global CV≤4.2%, and ICC≥0.87, with the exception of muscle (CV 10.4%; ICC 0.70) and cerebral (CV 4.1%; ICC 0.82) StO2. These data demonstrate good reliability of the majority of physiological variables and indicate that a pre-loaded 1 500-m time trial conducted in moderate normobaric hypoxia is a highly reliable test of performance.

Incidence of acute mountain sickness in UK Military Personnel on Mount Kenya.

BACKGROUND: Acute mountain sickness (AMS) is a common problem of trekkers to high altitude. The UK military train at high altitude through adventurous training (AT) or as exercising troops. The ascent of Point Lenana at 4985 m on Mount Kenya is frequently attempted on AT. This study sought to establish the incidence of AMS within this population, to aid future planning for military activities at altitude. METHODS: A voluntary questionnaire was distributed to all British Army Training Unit Kenya based expeditions attempting to ascend Mount Kenya during the period from February to April 2014. The questionnaire included twice daily Lake Louise and Borg (perceived exertion scale) self-scoring. All expeditions were planned around a 5-day schedule, which included reserve time for acclimatisation, illness and inclement weather. RESULTS: Data were collected on 47 participants, 70% of whom reached the summit of Point Lenana. 62% (29/47) self-reported AMS (defined as Lake Louise score (LLS) ≥3) on at least one occasion during the ascent, and 34% (10/29) suffered severe AMS (LLS ≥6). Those who attempted the climb within 2 weeks of arrival in Kenya had a higher incidence of AMS (12/15 (80%) vs 17/32 (53%), p=0.077). Participants recording a high Borg score were significantly more likely to develop AMS (16/18 vs 9/21, p=0.003). CONCLUSIONS: This represents the first informative dataset for Mount Kenya ascents and altitude. The incidence of AMS during AT on Mount Kenya using this ascent profile is high. Adapting the current ascent profile, planning the ascent after time in country and reducing perceived exertion during the trek may reduce the incidence of AMS.

Risk factors for heat illness among British soldiers in the hot Collective Training Environment.

BACKGROUND: Heat illness is a preventable disorder in military populations. Measures that protect vulnerable individuals and contribute to effective Immediate Treatment may reduce the impact of heat illness, but depend upon adequate understanding and awareness among Commanders and their troops. OBJECTIVE: To assess risk factors for heat illness in British soldiers deployed to the hot Collective Training Environment (CTE) and to explore awareness of Immediate Treatment responses. METHODS: An anonymous questionnaire was distributed to British soldiers deployed in the hot CTEs of Kenya and Canada. Responses were analysed to determine the prevalence of individual (Intrinsic) and Command-practice (Extrinsic) risk factors for heat illness and the self-reported awareness of key Immediate Treatment priorities (recognition, first aid and casualty evacuation). RESULTS: The prevalence of Intrinsic risk factors was relatively low in comparison with Extrinsic risk factors. The majority of respondents were aware of key Immediate Treatment responses. The most frequently reported factors in each domain were increased risk by body composition scoring, inadequate time for heat acclimatisation and insufficient briefing about casualty evacuation. CONCLUSIONS: Novel data on the distribution and scale of risk factors for heat illness are presented. A collective approach to risk reduction by the accumulation of 'marginal gains' is proposed for the UK military. This should focus on limiting Intrinsic risk factors before deployment, reducing Extrinsic factors during training and promoting timely Immediate Treatment responses within the hot CTE.

Copeptin and arginine vasopressin at high altitude: relationship to plasma osmolality and perceived exertion.

PURPOSE: A diuresis is a key part of acclimatisation to high altitude (HA). Arginine vasopressin (AVP) is a hormone involved in salt and water balance and may potentially have a role in the development of altitude illness. ProAVP (copeptin) is more stable than AVP and is assayed by a straightforward, automated method. We investigated the relationship of AVP to copeptin and the copeptin response to exercise and altitude illness in a large cohort during a field study at HA. METHODS: 48 subjects took part in a 10-day trek at HA. Venous blood samples were taken at 3,833, 4,450 and 5,129 m post-trek (exercise) and the following day at rest. Daily recordings of symptoms of altitude illness, oxygen saturations and perceived exertion were carried out. RESULTS: AVP and copeptin levels increased with exercise and correlated closely (ρ 0.621 p < 0.001), this was strongest in the stressed state when AVP secretion was highest, at 5,129 m post-exercise (ρ 0.834 p < 0.001). On two-way ANOVA, both altitude (F = 3.5; p = 0.015) and exercise (F = 10.2; p = 0.002) influenced copeptin levels (interaction F = 2.2; p = 0.08). AVP levels were influenced by exercise (F = 14.4; p = 0.0002) but not altitude (F = 2.0; p = 0.12) with no overall group interactions (F = 1.92.6; p = 0.06). There was no association between copeptin or arginine vasopressin and altitude illness. Copeptin correlated with the Borg RPE score and was significantly higher in the group with a Borg score ≥15 (7.9 vs. 3.7 p < 0.001). CONCLUSION: We have shown that arginine vasopressin and copeptin levels correlate and are suppressed below 5,129 m. Furthermore, we have demonstrated that exertion, rather than altitude illness or increasing osmolality, is the stimulus for increases in copeptin.

Assessment of salivary cortisol dynamics in an infantry training exercise: a pilot study.

INTRODUCTION: Measuring cortisol during military training offers insights into physiological responses to stress. We attempted precisely timed, cortisol awakening response (CAR) and pre-sleep cortisol (PSC), and diurnal slope (peak morning minus evening cortisol), during a British Army exercise. We aimed to understand cortisol dynamics and evaluate the feasibility of CAR and PSC in this environment. METHOD: Setting: high-intensity, 10-day infantry exercise. Participants: regular infantry soldiers exercising (EX, n=25) or headquarters-based (HQ, n=6). Participants undertook PSC and WAKE and WAKE+30 min samples after 1-2 days, 5-6 days and 9-10 days. Wrist-worn GENEActiv accelerometers were used to assess sleep duration in EX only. Samples taken ±15 min from prespecified time points were deemed adherent. Validated questionnaires were used to measure resilience and perceived stress. Cortisol and cortisone were measured simultaneously by liquid chromatography tandem mass spectrometry. RESULTS: From adherent participants' samples, CAR was positive and tended to decrease as the exercise progressed. From all available data, HQ demonstrated greater diurnal slope than EX (F=7.68, p=0.02), reflecting higher morning cortisol (F=4.72, p=0.038) and lower PSC (p=0.04). No differences were seen in cortisol:cortisone ratio. 26.1% of CAR samples were adherent, with moderately strong associations between adherence and stress (r=0.41, p=0.009) but no association between adherence and day of exercise (χ2=0.27, p=0.8), sleep duration (r=-0.112, p=0.43) or resilience (r=-0.79, p=0.75). Test-retest reliability ratings for CAR were Cronbach's α of 0.48, -11.7 and 0.34 for the beginning, middle and end of the exercise, respectively. CONCLUSIONS: We observed a reduction in morning cortisol and decreased diurnal slope during a high-intensity military exercise, compared with the HQ comparator cohort in whom diurnal slope was preserved. A carefully timed CAR was not feasible in this setting.

Sex, gender or occupational psychology: what matters most to preventing heat-related illnesses and improving outcomes for women in ground close combat?

Since the advent of women in ground close combat (WGCC) roles, the impact on women of the attendant risk of heat stress and heat illness has been considered. Much emphasis has been placed on sex differences in thermal physiology. This article considers the application of evidence of sex-associated thermoregulatory variation to the occupational and environmental setting of WGCC, and weighs the relative importance of physiological differences arising from biological sex, and behaviour associated with gender normatives. Quantifying the risk of heat illness to WGCC should draw on data from their real-world occupational context.

Risk factors for reflex syncope in the British Army.

INTRODUCTION: Reflex syncope in the UK Armed Forces is reportedly higher than comparable militaries and civilian populations and is significantly more common in soldiers who take part in State Ceremonial and Public Duties (SCPD) compared with other British Army service personnel (SP). This study aimed to investigate individual susceptibility factors for syncope in soldiers who regularly take part in SCPD. METHODS: A retrospective cohort study was performed in 200 soldiers who perform SCPD. A questionnaire was undertaken reviewing soldiers' medical history and circumstances of any fainting episodes. A consented review of participants' electronic primary healthcare medical record was also performed. Participants were divided into two groups (syncope, n=80; control, n=120) based on whether they had previously fainted. RESULTS: In the syncope group orthostasis (61%) and heat (35%) were the most common precipitating factors. The most common interventions used by soldiers were to maintain hydration (59%) and purposeful movements (predominantly 'toe wiggling'; 55%). 30% of participants who had previously fainted did not seek definitive medical attention. A history of migraines/headaches was found to increase the risk of reflex syncope (OR 8.880, 1.214-218.8), while a history of antihistamine prescription (OR 0.07144, 0.003671-0.4236), non-white ethnicity (OR 0.03401, 0.0007419-0.3972) and male sex (OR 0.2640, 0.08891-0.6915) were protective. CONCLUSION: This is the first study, in the British Army, to describe, categorise and establish potential risk factors for reflex syncope. Orthostatic-mediated reflex syncope is the most common cause in soldiers who regularly perform SCPD and this is further exacerbated by heat exposure. Soldiers do not use evidence-based methods to avoid reflex syncope. These data could be used to target interventions for SP who have previously fainted or to prevent fainting during SCPD.

Neurobiomarker and body temperature responses to recreational marathon running.

OBJECTIVES: To assess how biomarkers indicating central nervous system insult (neurobiomarkers) vary in peripheral blood with exertional-heat stress from prolonged endurance exercise. DESIGN: Observational study of changes in neuron specific enolase (NSE), S100 calcium-binding protein B (S100ß), Glial Fibrillary Acid Protein (GFAP) and Ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCHL1) at Brighton Marathon 2022. METHODS: In 38 marathoners with in-race core temperature (Tc) monitoring, exposure (High, Intermediate or Low) was classified by cumulative hyperthermia - calculated as area under curve of Time × Tc > 38 °C - and also by running duration (finishing time). Blood was sampled for neurobiomarkers, cortisol and fluid-regulatory stress surrogates, including copeptin and creatinine (at rested baseline; within 30 min of finishing; and at 24 h). RESULTS: Finishing in 236 ±â€¯40 min, runners showed stable GFAP and UCH-L1 across the marathon and next-day. Significant (P < 0.05) increases from baseline were shown post-marathon and at 24 h for S100ß (8.52 [3.65, 22.95] vs 39.0 [26.48, 52.33] vs 80.3 [49.1, 99.7] ng·L-1) and post-marathon only for NSE (3.73 [3.30, 4.32] vs 4.85 [4.45, 5.80] µg·L-1, P < 0.0001). Whilst differential response to hyperthermia was observed for cortisol, copeptin and creatinine, neurobiomarker responses did not vary. Post-marathon, only NSE differed by exercise duration (High vs Low, 5.81 ±â€¯1.77 vs. 4.69 ±â€¯0.73 µg·L-1, adjusted P = 0.0358). CONCLUSIONS: Successful marathon performance did not associate with evidence for substantial neuronal insult. To account for variation in neurobiomarkers with prolonged endurance exercise, factors additional to hyperthermia, such as exercise duration and intensity, should be further investigated.

The cortisol response to hypobaric hypoxia at rest and post-exercise.

High altitude exposure normally leads to a marked natriuresis and diuresis. Acute mountain sickness is often associated with fluid retention, to which an elevated cortisol may contribute. Most investigators report a rise in resting cortisol with ascent, but little data exist regarding the cortisol response to a day trekking. We therefore measured salivary cortisol during ascent to > 5000 m in a cohort of between 42-45 subjects following a 6-h trek (samples taken between 15:30-16:30 h) and between 15-20 subjects at rest (morning samples taken between 08:00-09:00 h). Morning resting cortisol [nmol/l, mean±sd, (range)] was 5.5±2.9 (2.13-13.61) at 1300 m; 4.7±6.8 (1.4-27.02) at 3400 m, and significantly (p=0.002) rose between 4270 m [3.5±2.1 (1.4-8.34)] and 5150 m [14.5±30.3 (1.9-123.1)]. Post-exercise cortisol [nmol/l, mean±sd, (range)] dropped between 3400 m [7±6 (1.5-33.3)] and 4270 m [4.2±4.8 (1.4-29.5)] (p=0.001) followed by a significant rise in post-exercise cortisol between 4270 m [4.2±4.8 (1.4-29.5)] and 5 150 m [9.2±10.2 (1.4-61.3)] (p<0.001). There were no significant associations between severity of acute mountain sickness and cortisol levels. There was a significant though weak correlation between cortisol post-exercise at 5150 m and oxygen saturation at 5150 m (rho= - 0.451, p=0.004). In conclusion, this is the largest cohort to have their resting and post-exercise cortisol levels ascertained at high altitude. We confirm the previous findings of an elevated resting morning cortisol at > 5000 m, but present the novel finding that the cortisol response to a day trekking at HA appears suppressed at 4270 m.

Cardiac arrhythmias at high altitude.

Palpitations at high altitude have been experienced, but seldom recorded, for centuries. The hypoxia, sympathetic activation and alkalosis of altitude predispose to cardiac ischaemia and arrhythmia. Indeed, sudden cardiac death is responsible for 30% of all deaths during mountain sports at altitude. This article reviews the literature to date on the evidence for cardiac arrhythmias at altitude.

Endocrine aspects of high altitude acclimatization and acute mountain sickness.

The acute acclimatization to high altitude is underpinned by a diuresis (and to a lesser extent a natriuresis) that facilitates a reduction in plasma volume. This allows a haemoconcentration to occur that increases the oxygen carrying capacity of a given volume of blood, a vital effect in the presence of a reduced partial pressure of oxygen. This critical acclimatization process is orchestrated by the endocrine system. This review will present the key evidence regarding the changes in several important hormones that affect this process.

Energy at high altitude.

For the military doctor, an understanding of the metabolic effects of high altitude (HA) exposure is highly relevant. This review examines the acute metabolic challenge and subsequent changes in nutritional homeostasis that occur when troops deploy rapidly to HA. Key factors that impact on metabolism include the hypoxic-hypobaric environment, physical exercise and diet. Expected metabolic changes include augmentation of basal metabolic rate (BMR), decreased availability of oxygen in peripheral metabolic tissues, reduction in VO2 max, increased glucose dependency and lactate accumulation during exercise. The metabolic demands of exercise at HA are crucial. Equivalent activity requires greater effort and more energy than it does at sea level. Soldiers working at HA show high energy expenditure and this may exceed energy intake significantly. Energy intake at HA is affected adversely by reduced availability, reduced appetite and changes in endocrine parameters. Energy imbalance and loss of body water result in weight loss, which is extremely common at HA. Loss of fat predominates over loss of fat-free mass. This state resembles starvation and the preferential primary fuel source shifts from carbohydrate towards fat, reducing performance efficiency. However, these adverse effects can be mitigated by increasing energy intake in association with a high carbohydrate ration. Commanders must ensure that individuals are motivated, educated, strongly encouraged and empowered to meet their energy needs in order to maximise mission-effectiveness.

Does vitamin D supplementation prevent SARS-CoV-2 infection in military personnel? Review of the evidence.

For most individuals residing in Northwestern Europe, maintaining replete vitamin D status throughout the year is unlikely without vitamin D supplementation and deficiency remains common. Military studies have investigated the association with vitamin D status, and subsequent supplementation, with the risk of stress fractures particularly during recruit training. The expression of nuclear vitamin D receptors and vitamin D metabolic enzymes in immune cells additionally provides a rationale for the potential role of vitamin D in maintaining immune homeostasis. One particular area of interest has been in the prevention of acute respiratory tract infections (ARTIs). The aims of this review were to consider the evidence of vitamin D supplementation in military populations in the prevention of ARTIs, including SARS-CoV-2 infection and consequent COVID-19 illness. The occupational/organisational importance of reducing transmission of SARS-CoV-2, especially where infected young adults may be asymptomatic, presymptomatic or paucisymptomatic, is also discussed.

The use of routine blood tests to assist the diagnosis of COVID-19 in symptomatic hospitalized patients.

INTRODUCTION: Specific patterns of blood test results are associated with COVID-19 infection. The aim of this study was to identify which blood tests could be used to assist in diagnosing COVID-19. METHOD: A retrospective review was performed on consecutive patients referred to hospital with a clinical suspicion of COVID-19 over a period of four weeks. The patient's clinical presentation and severe acute respiratory syndrome coronavirus 2 reverse-transcription polymerase chain reaction (SARS-CoV-2 RT-PCR) were recorded. The patients were divided by diagnosis into COVID (COVID-19 infection) or CONTROL (an alternate diagnosis). A retrospective review of consecutive patients over a further two-week period was used for the purposes of validation. RESULTS: Overall, 399 patients (53% COVID, 47% CONTROL) were analysed. White cell count, neutrophils and lymphocytes were significantly lower, while lactate dehydrogenase and ferritin were significantly higher, in the COVID group in comparison to CONTROL. Combining the white cell count, lymphocytes and ferritin results into a COVID Combined Blood Test (CCBT) had an area under the curve of 0.79. Using a threshold CCBT of -0.8 resulted in a sensitivity of 0.85 and a specificity of 0.63. Analysing this against a further retrospective review of 181 suspected COVID-19 patients, using the same CCBT threshold, resulted in a sensitivity of 0.73 and a specificity of 0.75. The sensitivity was comparable to the SARS-CoV-2 RT PCR. DISCUSSION: Mathematically combining the blood tests has the potential to assist clinical acumen allowing for rapid streaming and more accurate patient flow pending definitive diagnosis. This may be of particular use in low-resource settings.

Experience from the selection and nutritional preparation for Expedition ICE MAIDEN: the first successful all-female unassisted Antarctic traverse.

INTRODUCTION: Expedition ICE MAIDEN (Ex IM) was the first all-female unsupported crossing of Antarctica. We describe the prerequisite selection and training, comparing those who formed the final team with other participants, and discuss how the expedition diet was established. METHODS: All women serving in the British Army were invited to participate. Following initial assessments, successful women completed three training/selection ski expeditions. Between expeditions 1 and 2, participants completed 6 months rigorous UK-based training. Weight was measured before and after the 6 months UK-based training, expeditions 2 and 3, and body composition by skinfold before and after expedition 2. Participant feedback, body composition and weight changes were applied to modify the expedition diet and provide weight gain targets prior to Ex IM. RESULTS: Following 250 applications, 50 women were assessed and 22, 12 and seven women attended training expeditions 1, 2 and 3, respectively. The final team of six women lost more weight than other participants during UK-based training (mean (SD) change -1.3 (1.5) kg vs -0.5 (1.6) kg, respectively, p=0.046) and during training expedition 2 (-2.8 (0.8) kg vs -1.7 (0.4) kg, respectively, p=0.048), when they also gained more lean mass (+2.1 (0.8) kg vs +0.4 (0.7) kg, respectively, p=0.004). The Ex IM diet provided 5000 kCal/day, comprising approximately 45% carbohydrate, 45% fat and 10% protein. Median (range) weight change between expedition 3 and Ex IM was +8.7 (-1.9 to +14.3) kg. CONCLUSIONS: The selected Ex IM team demonstrated favourable training-associated body composition changes. Training-associated weight loss informed the expeditionary diet design.