John Castellani

United States Army Research Institute of Environmental Medicine · Thermal and Mountain Medicine Division

Wet clothing is less insulative than dry clothing and consequently increases heat loss in cold air. Tactical necessity can render removal of wet clothing impossible and/or require Warfighters to remain static to avoid detection, limiting heat production and posing a threat of hypothermia (core temperature <35 °C). This study aimed to characterize b...

Effective execution of military missions in cold environments requires highly trained, well-equipped, and operationally ready service members. Understanding the metabolic energetic demands of performing physical work in extreme cold conditions is critical for individual medical readiness of service members. In this narrative review, we describe 1)...

Cocoa-derived flavanols (CDF) may act as prebiotics. However, evidence is inconsistent, and the duration and dose of CDF intake needed to elicit any prebiotic effect are undefined. This randomized, double-blind, crossover study determined the effects of short-term, high-dose dietary supplementation with CDF versus matched placebo on gut microbiota...

Introduction The present study determined the (1) day-to-day reliability of basal heart rate (HR) and HR variability (HRV) measured by the Equivital eq02+ LifeMonitor and (2) agreement of ultra short-term HRV compared with short-term HRV. Methods Twenty-three active-duty US Army Soldiers (5 females, 18 males) completed two experimental visits sepa...

Background: Habituation is a pattern of cold acclimatization characterized by attenuated cold defense responses, including a reduction in peripheral vasoconstriction and subsequent increase in skin temperature (T Sk ) as well as a decrease in shivering thermogenesis. Habituation is achieved through repeated reductions in T Sk , rather than deep bod...

Purpose Cold-induced vasodilation (CIVD) is an oscillatory rise in blood flow to glabrous skin that occurs in cold-exposed extremities. Dietary flavanols increase bioavailable nitric oxide, a proposed mediator of CIVD through active vasodilation and/or withdrawal of sympathetic vascular smooth muscle tone. However, no studies have examined the effe...

Introduction: Freezing cold injuries (FCI) are a common risk in extreme cold weather operations. Although the risks have long been recognised, injury occurrences tend to be sparse and geographically distributed, with relatively few cases to study in a systematic way. The first challenge to improve FCI medical management is to develop a common nomen...

This paper defines functional cold exposure zones that illustrate whether a person is at risk of developing physical performance loss or cold weather injuries. Individual variation in body characteristics, activity level, clothing and protective equipment all contribute to variation in the effective exposure. Nevertheless, with the right education,...

For decades, the Wind Chill Temperature Index (WCT) and its various iterations have been used to assess the risk of frostbite on unclothed body parts. This paper presents an innovative knowledge-based Cold Weather Ensemble Decision Aid (CoWEDA) that can be used to guide the selection of the most appropriate cold weather ensemble(s) relative to anti...

Introduction: this study describes the development of a female finite element thermoregulatory model (FETM) METHOD: the female body model was developed from medical image datasets of a median U.S. female and was constructed to be anatomically correct. The body model preserves the geometric shapes of 13 organs and tissues, including skin, muscles,...

Human tolerance to cold environments is extremely limited and responses between individuals is highly variable. Such physiological and morphological predispositions place them at high risk of developing cold weather injuries [CWI; including hypothermia and/or non-freezing (NFCI) and freezing cold injuries (FCI)]. The present manuscript highlights c...

Cold-induced vasodilation (CIVD) is a cyclical rise in blood flow to glabrous skin that occurs during cold exposure of the extremities. Nitric oxide (NO) is a proposed mediator of the CIVD response through active vasodilation and/or withdrawal of sympathetic vascular smooth muscle tone. Dietary flavanols augment bioavailable NO by upregulating NO s...

Cold injury can result from exercising at low temperatures and can impair exercise performance or cause lifelong debility or death. This consensus statement provides up-to-date information on the pathogenesis, nature, impacts, prevention, and treatment of the most common cold injuries.

This paper outlines the development of a finite element human thermoregulatory model using an anatomically and geometrically correct human body model. The finite element body model was constructed from digital Phantoms and is anatomically realistic, including 13 organs and tissues: skin, muscles, fat, bones, heart, lungs, brain, bladder, intestines...

Habituation is an adaptation seen in many organisms, defined by a reduction in the response to repeated stimuli. Evolutionarily, habituation is thought to benefit the organism by allowing conservation of metabolic resources otherwise spent on sub-lethal provocations including repeated cold exposure. Hypermetabolic and/or insulative adaptations may...

This paper describes a Cold Weather Ensemble Decision Aid (CoWEDA) that provides guidance for cold weather injury prevention, mission planning, and clothing selection. CoWEDA incorporates current science from the disciplines of physiology, meteorology, clothing, and computer modeling. The thermal performance of a cold weather ensemble is defined by...

Frostbite can occur during cold-weather operations when the temperature is <0°C (<32°F). When skin temperature is =-4°C (=25°F), ice crystals form in the blood, causing mechanical damage, inflammation, thrombosis, and cellular death. Lower temperatures, higher wind speeds, and moisture exacerbate the process. The frozen part or area should not be r...

Runners compete and train in diverse cold-weather environments that may impact performance and cause cold injuries. This article provides an overview of cold-weather effects on running performance. It also presents the cold-weather injuries likely to occur in runners as well as provides risk management guidance to mitigate susceptibility to cold-we...

New findings: What is the topic of this review? This review presents an update and synthesis of normal mechanisms of human cutaneous vasoconstriction in response to cold stress. It then discusses conditions in which cutaneous vasoconstrictor responses are excessive or insufficient and cases in which cold-induced vasoconstrictor responses become co...

A state-of-the-art decision aid, the Cold Weather Ensemble Decision Aid (CoWEDA), has been developed to optimize readiness for cold weather operations, prevent cold injury, and provide guidance for mission planning and clothing selection. CoWEDA is an interactive decision aid that supplements information found in Army Technical Bulletin – Medical 5...

Reduced dexterity (DEX) is a problem in cold weather with a need for countermeasures that increase hand (Thand) and finger (Tfing) temperatures and improve DEX. The purpose of the study was to determine whether heat applied to the forearm (ARM), face (FACE) or both (COMB) at the beginning of cold exposure (COLD; 0.5°C, 120-min) or after Tfing fell...

Table S1: Plasma metabolome before (PRE) and after (POST) a 4‐d, 51‐km cross‐country ski march.

Background: Cardiovascular (CV) and thermal responses to metabolically demanding multi-day military operations in extreme cold-weather environments are not well described. Characterization of these operations will provide greater insights into possible performance capabilities and cold injury risk. Methods: Soldiers from two cold-weather field t...

Military training studies provide unique insight into metabolic responses to extreme physiologic stress induced by multiple stressor environments, and the impacts of nutrition in mediating these responses. Advances in metabolomics have provided new approaches for extending current understanding of factors modulating dynamic metabolic responses in t...

Dietary intake and acute physiologic stress may modulate health in part by influencing interactions between the gut microbiome and host, but these relationships remain poorly characterized. This study explored relationships between gut microbiota composition and activity, and diet, gastrointestinal permeability and inflammation in Soldiers particip...

The magnitude, temporal dynamics, and physiologic effects of intestinal microbiome responses to physiologic stress are poorly characterized. This study used a systems biology approach and multiple-stressor military training environment to determine the effects of physiologic stress on intestinal microbiota composition and metabolic activity, and in...

Nonfreezing cold-induced injury (NFCI) is a clinical syndrome that results from the damage caused to tissues exposed to cold temperatures at or above freezing point (0° to 15° C [32° to 59° F). NFCI does not involve tissue freezing, which distinguishes it both clinically and pathologically from frostbite. 45 The earliest descriptions of this syndro...

Load carriage (LC) exercise may exacerbate inflammation during training. Nutritional supplementation may mitigate this response by sparing endogenous carbohydrate stores, enhancing glycogen repletion, and attenuating negative energy balance. Two studies were conducted to assess inflammatory responses to acute LC and training, with or without nutrit...

Hyperthermia is suspected of accentuating skeletal muscle injury from novel exercise, but this has not been well studied. This study examined if high muscle temperatures alters skeletal muscle injury induced by eccentric exercise (ECC). Eight volunteers (age, 22.5 ± 4.1 year; height, 169.5 ± 10.8 cm; body mass, 76.2 ± 12.6 kg), serving as their own...

Purpose: Determine if providing supplemental nutrition spares whole-body protein by attenuating the level of negative energy balance induced by military training, and to assess whether protein balance is differentially influenced by macronutrient source. Methods: Soldiers participating in 4-d arctic military training (AMT, 51 km ski march) rando...

Increased gastrointestinal permeability (GP) induced by prolonged physical stress may contribute to systemic inflammation by facilitating translocation of microbial compounds from the gut. Though undernutrition and macronutrient intake independently modulate GP, relationships between diet and GP during prolonged physical stress are not well charact...

Cold exposure in humans causes specific acute and chronic physiological responses. This paper will review both the acute and long-term physiological responses and external factors that impact these physiological responses. Acute physiological responses to cold exposure include cutaneous vasoconstriction and shivering thermogenesis which, respective...

Cold weather can have deleterious effects on health, tolerance, and performance. This paper will review the physiological responses and external factors that impact cold tolerance and physical performance. Tolerance is defined as the ability to withstand cold stress with minimal changes in physiological strain. Physiological and pathophysiological...

O'Brien, Catherine, John W. Castellani, and Stephen R. Muza. Acute hypobaric hypoxia effects on finger temperature during and after local cold exposure. High Alt Med Biol 16:244-250, 2015.-Mountain environments have combined stressors of lower ambient temperature and hypoxia. Cold alone can reduce finger temperature, resulting in discomfort, impair...

Rhabdomyolysis is often associated with novel physical exercise and exertional heat illness in warm temperatures. It is possible that accentuated hyperthermia might partially be responsible for these observations, but direct evidence is lacking. Previous research has not manipulated skeletal muscle temperature and evaluated its impact on muscle dam...

Physiological consequences of winter military operations are not well described. This study examined Norwegian soldiers (n = 21 males) participating in a physically demanding winter training program to evaluate whether short-term military training alters energy and whole-body protein balance, muscle damage, soreness, and performance. Energy expendi...

It has been proposed that microclimate cooling systems exploit the peripheral extremities because of more efficient heat transfer. The purpose of this study was to quantify, using a patented microclimate cooling technique, the heat transfer from the plantar surface of the foot for comparison to other commonly cooled body regions. A military boot wa...

Core temperature (CT) in combination with heart rate (HR) can be a good indicator of impending heat exhaustion for occupations involving exposure to heat, heavy workloads, and wearing protective clothing. However, continuously measuring CT in an ambulatory environment is difficult. To address this problem we developed a model to estimate the time c...

Small Unit Tactics (SUT) is a 64-day phase of the Special Forces Qualification Course designed to simulate real-world combat operations. Assessing the metabolic and physiological responses of such intense training allows greater insights into nutritional requirements of soldiers during combat. The purpose of this study was to examine energy balance...

Exercise (EX), prior to cold air exposure (CAE), increases heat flow (HF) and reduces insulation (I t ) to a greater extent compared to passive warming (HEAT). It is not known if this is due to an attenuated skin blood flow (SkBF) response and/or changes in superficial shell and muscle I t . We hypothesized that skin vasoconstriction and insulation...

Modern international military deployments in austere environments (i.e., Iraq and Afghanistan) place considerable physiological demands on soldiers. Significant physiological challenges exist: maintenance of physical fitness and body composition, rigors of external load carriage, environmental extremes (heat, cold, and altitude), medical illnesses,...

Olympic athletes compete and train in diverse cold-weather environments, generally without adverse effects. However, the nature of some sports may increase the risk of cold injuries. This paper provides guidance to enable competition organisers and officials, coaches and athletes to avoid cold-weather injuries. This paper will (1) define potential...

It is unknown whether hypohydration (HYPO) or hypobaric hypoxia alter skin blood flow (SkBF) responses to local heating. We hypothesized that HYPO (4% of body weight) and acute altitude (ALT, 3,048 m) would decrease forearm SkBF responses to local heating and that ALT‐HYPO together would result in a further decline. Four healthy young men (23 ± 6 y...

Small teams of emergency workers/military can often find themselves engaged in critical, high exertion work conducted under challenging environmental conditions. These types of conditions present thermal work strain challenges which unmitigated can lead to collapse (heat exhaustion) or even death from heat stroke. Physiological measurement of these...

When people dress for cold weather, the face often remains exposed. Facial cooling can decrease finger blood flow, reducing finger temperature (T f). This study examined whether thermal face protection limits finger cooling and thereby improves thermal comfort and manual dexterity during prolonged cold exposure. T f was measured in ten volunteers d...

Non-freezing cold injury (NFCI) is the Cinderella of thermal injuries and is a clinical syndrome that occurs when tissues are exposed to cold temperatures close to freezing point for sustained periods. NFCI is insidious in onset, often difficult to recognize and problematic to treat, and yet the condition accounts for significant morbidity in both...

Hypoxia often causes body water deficits (hypohydration, HYPO); however, the effects of HYPO on aerobic exercise performance and prevalence of acute mountain sickness (AMS) at high altitude (ALT) have not been reported. We hypothesized that 1) HYPO and ALT would each degrade aerobic performance relative to sea level (SL)-euhydrated (EUH) conditions...

Participants in prolonged, physically demanding cold-weather activities are at risk for a condition called "thermoregulatory fatigue". During cold exposure, the increased gradient favoring body heat loss to the environment is opposed by physiological responses and clothing and behavioral strategies that conserve body heat stores to defend body temp...

Vascular fluid dynamics [plasma volume (PV) and total circulating protein (TCP)] during acute (8‐h) high‐altitude (ALT) exposure are poorly described and the impact of hypohydration (HYPO) on these responses has not been reported. Seven men (25 ± 7 yr; 44.1 ± 4.9 ml/kg/min V0 2peak completed 4 experimental trials in a counterbalanced design. Subjec...

This study examined vertical jump performance using a force platform and weighted vest to determine why hypohydration (approximately 4% body mass) does not improve jump height. Measures of functional performance from a force platform were determined for 15 healthy and active males when euhydrated (EUH), hypohydrated (HYP) and hypohydrated while wea...

Acute cold stress is often accompanied by exposure to other adverse factors, such as sleep loss, under-nutrition, and psychological stress that singly and together may affect cognitive function. The effect of moderate cold stress on cognitive function was investigated in 15 male volunteers exposed to cold air (10 degrees C) for 4 h after they had c...

Epidemiological evidence suggests that AMS has a higher incidence (I AMS ) in people who are dehydrated, yet the effect of dehydration on I AMS and severity (S AMS ) has not been prospectively tested. This study assessed AMS following rapid ascent to 3048m (ALT) in euhydrated (EU) and dehydrated (DE) subjects (SS). Seven males (mean±SD, 25±7yr, 82±...

To present recommendations for the prevention, recognition, and treatment of environmental cold injuries. Individuals engaged in sport-related or work-related physical activity in cold, wet, or windy conditions are at risk for environmental cold injuries. An understanding of the physiology and pathophysiology, risk management, recognition, and imme...

The effects of elevating plasma osmolality (P osm) on thirst ratings was studied in eight dehydrated males during exposure to 4°C. On two occasions, subjects were dehydrated (DH; 3–4% body mass) via 90 min exercise-heat exposure and overnight fluid restriction (day 1). On a third occasion, subjects were exposed to heat but were given fluid (EU). On...