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The emergence of the novel severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) rapidly evolved into a worldwide pandemic of Coronavirus Disease 2019 (COVID-19). The pandemic had a major operational impact upon the US military, requiring interventions to mitigate transmission risk resulting in DoD-wide disruption of daily operations, restriction of movement, and delays in training. Development of a rapid mobile COVID-19 testing strategy was pursued as a means to allow service members to complete critical missions in select settings. In this report, we describe the first of its kind mobile medical laboratory (MML) that allowed for testing of approximately 4,000 soldiers of the 1/34th Armored Brigade Combat Team (1/34th ABCT), 34th Infantry Division, prior to deployment for validation exercises to the National Training Center, Fort Irwin, CA. We describe the utilizing of the MML, COVID-19 testing workflow, clinical symptom data/cycle threshold (Ct) data from positive patients, and outcomes from this testing mission.

Acute mountain sickness (AMS) commonly occurs at altitudes exceeding 2000-2500 m and usually resolves after acclimatization induced by a few days of chronic residence at the same altitude. Increased ventilation and diuresis may contribute to the reduction in AMS with altitude acclimatization. The aim of the present study was to examine the effects of intermittent altitude exposures (IAE), in combination with rest and exercise training, on the incidence and severity of AMS, resting ventilation and 24-h urine volume at 4300 m. Six lowlanders (age, 23 +/- 2 years; body weight, 77 +/- 6 kg; values are means +/- S.E.M.) completed an Environmental Symptoms Questionnaire (ESQ) and Lake Louise AMS Scoring System (LLS), a resting end-tidal partial pressure of CO2 ( PETCO2) test and a 24-h urine volume collection at sea level (SL) and during a 30 h exposure to 4300 m altitude-equivalent (barometric pressure=446 mmHg) once before (PreIAE) and once after (PostIAE) a 3-week period of IAE (4 h.day(-1), 5 days.week(-1), 4300 m). The previously validated factor score, AMS cerebral score, was calculated from the ESQ and the self-report score was calculated from the LLS at 24 h of altitude exposure to assess the incidence and severity of AMS. During each IAE, three subjects cycled for 45-60 min.day(-1) at 60-70% of maximal O2 uptake (VO2 max) and three subjects rested. Cycle training during each IAE did not affect any of the measured variables, so data from all six subjects were combined. The results showed that the incidence of AMS (%), determined from both the ESQ and LLS, increased (P

A cold strain index (CSI) based on rectal (Tre) and mean skin temperatures ([Formula: see text] sk) using data from seminude resting subjects has been proposed (Moran DS, Castellani JW, O'Brien C, Young AJ, and Pandolf KB. Am J Physiol Regulatory Integrative Comp Physiol 277: R556–R564, 1999). The current study determined whether CSI could provide meaningful data for clothed subjects exercising in the cold with compromised insulation. Ten men exercised in cold-wet conditions (CW) for 6 h before (D0) and after 3 days of exhaustive exercise (D3). Each hour of CW consisted of 10 min of standing in rain (5.4 cm/h, 5°C air) followed by 45 min of walking (1.34 m/s, 5.4 m/s wind, 5°C air). The change in Tre across time was greater ( P < 0.05) on D3 than on D0, and the change in [Formula: see text] sk was less ( P < 0.05) on D3 than on D0. Although CSI increased across time, the index at the end of both trials (D3 = 4.6 ± 0.6; D0 = 4.2 ± 0.8) was similar ( P > 0.05). Thus, while [Formula: see text] sk was 1.3°C higher ( P < 0.05) and Tre was 0.3°C lower ( P < 0.05) on D3 than on D0, CSI did not discriminate the greater heat loss that occurred on D3. These findings indicate that when vasoconstrictor responses to cold are altered, such as after exhaustive exercise, CSI does not adequately quantify the different physiological strain between treatments. CSI may be useful for indicating increased strain across time, but its utility as a marker of strain between different treatments or studies is uncertain because no independent measure of strain has been used to determine to what extent CSI is a valid and reliable measure of strain.

This study examined the hypothesis that several days of exhaustive exercise would impair thermoregulatory effector responses to cold exposure, leading to an accentuated core temperature reduction compared with exposure of the same individual to cold in a rested condition. Thirteen men (10 experimental and 3 control) performed a cold-wet walk (CW) for up to 6 h (6 rest-work cycles, each 1 h in duration) in 5°C air on three occasions. One cycle of CW consisted of 10 min of standing in the rain (5.4 cm/h) followed by 45 min of walking (1.34 m/s, 5.4 m/s wind). Clothing was water saturated at the start of each walking period (0.75 clo vs. 1.1 clo when dry). The initial CW trial ( day 0) was performed (afternoon) with subjects rested before initiation of exercise-cold exposure. During the next 7 days, exhaustive exercise (aerobic, anaerobic, resistive) was performed for 4 h each morning. Two subsequent CW trials were performed on the afternoon of days 3 and 7, ∼2.5 h after cessation of fatiguing exercise. For controls, no exhaustive exercise was performed on any day. Thermoregulatory responses and body temperature during CW were not different on days 0, 3, and 7 in the controls. In the experimental group, mean skin temperature was higher ( P< 0.05) during CW on days 3 and 7 than on day 0. Rectal temperature was lower ( P < 0.05) and the change in rectal temperature was greater ( P < 0.05) during the 6th h of CW on day 3. Metabolic heat production during CW was similar among trials. Warmer skin temperatures during CW after days 3 and 7indicate that vasoconstrictor responses to cold, but not shivering responses, are impaired after multiple days of severe physical exertion. These findings suggest that susceptibility to hypothermia is increased by exertional fatigue.

Survivors awaiting rescue aboard a disabled submarine (DISSUB) lacking power and/or environmental control would potentially be exposed to cold and reduced O2 and elevated CO2 levels. We hypothesized that elevated CO2 levels would lead to hormone changes that would mitigate cold and hypoxia-induced body fluid losses.Blood was drawn from seven men on three mornings: baseline (21% O2, 0.05% CO2), after 4 d of low O2, cold, and high CO2 (T101; 4 degrees C, 16.75% O2, 2.5% CO2), and following acute withdrawal of cold and high CO2 (T173, 16.75% O2, 0.05% CO2). Total body water (TBW) was measured using deuterium oxide dilution at baseline and at T148. Hormone analyses included atrial natriuretic peptide (ANP), aldosterone (ALDO), and plasma renin activity (PRA).TBW decreased by 0.4 +/- 0.4 L. Water turnover was 3.0 +/- 0.5 L x d(-1). ANP (pg x ml(-1)) was lower (p0.05) at T101 (3.46 +/- 1.17) and T173 (4.97 +/- 2.28) vs. baseline (8.19 +/- 3.40). PRA (pg x ml(-1)) was higher (p0.05) at T101 (10.43 +/- 4.90) and T173 (14.23 +/- 4.48) vs. baseline (6.81 +/- 3.43). ALDO, serum osmolality, and electrolytes were not different across time. Urine flow was lower at T101 and T173 vs. baseline, and urine osmotic clearance was lower at T173 vs. baseline. Free water clearance did not change across time.These data indicate that the combination of cold, low O2, and high CO2 for 5-7 d did not change total body water and hormone changes and urinary measures across the DISSUB were consistent with fluid retention.

Chronic altitude residence improves muscular performance at altitude, but the effect of intermittent altitude exposures (IAE) on muscular performance at altitude has not been defined. The purpose of this study was to determine the effects of 3 wk of IAE, in combination with rest and cycle training, on muscular performance at altitude. Six lowlanders (23 ± 2 yr, 77 ± 6 kg; means ± SE) completed a cycle time trial and adductor pollicis endurance test at sea level and during a 30-h acute exposure to 4,300 m altitude equivalent (barometric pressure = 446 mmHg) once before (pre-IAE) and once after (post-IAE) a 3-wk period of IAE (4 h/day, 5 days/wk, 4,300 m). During each IAE, three subjects cycled for 45–60 min/day at 60%-70% of maximal O2 uptake and three subjects rested. Cycle training during each IAE did not appear to affect muscular performance at altitude. Thus data from all six subjects were combined. Three weeks of IAE resulted in 1) a 21 ± 6% improvement ( P < 0.05) in cycle time-trial performance (min) from pre-IAE (32.8 ± 3.7) to post-IAE (24.8 ± 1.2), 2) a 63 ± 26% improvement ( P < 0.05) in adductor pollicis endurance (min) from pre-IAE (9.2 ± 2.8) to post-IAE (14.8 ± 4.2), and 3) a 10 ± 4% increase ( P < 0.05) in resting arterial O2 saturation (%) from pre-IAE (82 ± 2) to post-IAE (90 ± 1). These improvements in muscular performance after IAE correlated strongly with increases in resting arterial O2 saturation and were comparable to those reported previously after chronic altitude residence. IAE may therefore be used as an alternative to chronic altitude residence to facilitate improvements in muscular performance in athletes, soldiers, mountaineers, shift workers, and others that are deployed to altitude.

UNLABELLED PURPOSE; This study examined the effects of short-term (3.5 d) sustained military operations (SUSOPS) on thermoregulatory responses to cold stress. METHODS Ten men (22.8 +/- 1.4 yr) were assessed during a cold-air test (CAT) after a control week (control) and again after an 84-h SUSOPS (sleep = 2 h.d (-1), energy intake = approximately 1650 kcal.d(-1), and energy expenditure = approximately 4500 kcal.d(-1). CAT consisted of a resting subject (seminude) being exposed to an ambient temperature ramp from 25 degrees C to 10 degrees C during the initial 30 min of CAT, with the ambient temperature then remaining at 10 degrees C for an additional 150 min. RESULTS SUSOPS decreased (P< 0.05) body weight, % body fat, and fat-free mass by 3.9 kg, 1.6%, and 1.8 kg, respectively. During CAT, rectal temperature decreased to a greater extent (P< 0.05) after SUSOPS (0.52 +/- 0.09 degrees C) versus control (0.45 +/- 0.12 degrees C). Metabolic heat production was lower (P< 0.05) after SUSOPS at min 30 (55.4 +/- 3.3 W.m (-2)) versus control (66.9 +/- 4.4 W.m(-2)). Examination of the mean body temperature-metabolic heat production relationship indicated that the threshold for shivering was lower (P< 0.05) after SUSOPS (34.8 +/- 0.2 degrees C) versus control (35.8 +/- 0.2 degrees C). Mean weighted skin temperatures ( degrees C) were lower during the initial 1.5 h of CAT in SUSOPS versus control. Heat debt was similar between trials. CONCLUSION These results indicate that sustained (84-h) military operations leads to greater declines in core temperature, due to either a lag in the initial shivering response or heat redistribution secondary to an insulative acclimation.

After several days of exhaustive exercise in mild-warm environments, cutaneous vasoconstrictor responses to cold exposure are less effective in conserving body heat than in the rested condition. Hypothalamic-pituitary-adrenal and hypothalamic-pituitary-thyroid axes hormones could mediate this response since they may affect vasoconstriction. The effects of exertional fatigue on pituitary-adrenal hormones and thyroid hormone responses to exercise-cold stress are unknown.We hypothesized that 7 consecutive days of exercise would decrease adrenocorticotropin (ACTH) and cortisol, while elevating thyroid stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) and that these hormones would be related to a blunted vasoconstrictor response to cold.Nine male volunteers walked, completely wetted, for up to 6 h in 5 degrees C air, when rested (day 0, control) and after 7 consecutive days (day 7) of exhaustive exercise (4 h each day of mixed aerobic and anaerobic activities in thermoneutral conditions). Blood was sampled on day 0 and day 7 at baseline (0700 hours), and before and immediately after cold exposure.At 0700 hours, ACTH and cortisol were elevated (p0.05) after 7 d of exercise, compared with control conditions. Following exercise-cold exposure, cortisol, T3, and T4 increased (p0.05) similarly on both day 0 and day 7. ACTH and TSH did not increase as a result of exercise-cold exposure on either day.These data indicate that 7 d of exercise elevates basal (0700 hours) pituitary-adrenal stress hormones (ACTH, cortisol). However, 7 d of exercise did not modify adrenal or thyroid hormone responses, relative to the day 0 cold exposure, suggesting that they are not responsible for the blunted vasoconstriction during exercise-cold exposure following 7 consecutive days of exercise.