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ACSM Expert Consensus Statement: Injury Prevention and Exercise Performance during Cold-Weather Exercise

November 2021
Current Sports Medicine Reports 20(11):594-607

DOI:10.1249/jsr.0000000000000907

Authors:

John Castellani

United States Army Research Institute of Environmental Medicine

Clare Eglin

University of Portsmouth

Tiina Maria Ikäheimo

UiT The Arctic University of Norway

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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.

Treatment algorithm for patients with accidental hypothermia, from (96). Definitions of parenthetical numbers are: (1) decapitation,

…

Factors predisposing to frostbite and NFCI.

…

Traditional historical classification of frostbite adapted from Fudge (48).

…

Signs and symptoms of hypothermia at different levels (98).

…

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ACSM Expert Consensus Statement: Injury

Prevention and Exercise Performance during

Cold-Weather Exercise

John W. Castellani, PhD;

Clare M. Eglin, PhD;

Tiina M. Ikäheimo, PhD;

3,4

Hugh Montgomery, MBBS, BSc, MD;

Peter Paal, MD, PD, MBA;

and Michael J. Tipton, PhD

Abstract

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.

Introduction

American College of Sports Medicine (ACSM) Expert

Consensus Statements are created by a small group of recog-

nized leaders in a field. They highlight knowledge gaps, pres-

ent existing knowledge, and provide recommendations for

clinical practice. The new, shorter format is intended to make

the text more focused and accessible.

This statement addresses the deleterious aspects of expo-

sure to cold. The use of cold in injury prevention, treatment,

or recovery is beyond its scope and is dealt with elsewhere

(1). As well, the reader is referred to review articles on the de-

tailed physiological responses to acute and chronic cold expo-

sure and effects of cold acclimatization (2,3). This statement

updates and replaces the ACSM position statement published

in 2006, entitled “Prevention of Cold Injuries during Exer-

cise”(4). As an official pronouncement of the college, it re-

flects the college's position on the scientific and clinical aspects

of cold injury during exercise.

Many people work or exercise in or

near a cold environment, be that cold

air or cold water. Cooling can impair

performance and threaten life, and cold

is a leading cause of death among people

engaged in sports (5). The breadth and

seriousness of the challenge represented

by cold are reflected in the topics covered in this statement

and include frostbite, nonfreezing cold injury (NFCI), hypo-

thermia, avalanche burial, snow blindness, drowning, and

sudden cardiac death. In addition, cold can constitute part of

a combined environmental threat, for example in combination

with hypoxia in high mountains. It follows that an under-

standing of the impact of cold environments and approaches

to mitigate these threats is essential for those hoping to per-

form in cold conditions.

Cold Air (Frostbite)

Frostbite is a direct freezing injury occurring when the skin

surface freezes in saltwater at ~ −0.55°C (31°F) (6) and in air

below −3°C (26.6°F) (7–9). Exposed tissues with poor perfu-

sion are most commonly affected (hands, feet, head) (10–12).

Exposure times for injury vary from seconds to hours, depend-

ing on the type and intensity of cold exposure, degree of phys-

ical activity, protective clothing, and various individual factors

(Table 1) (47). At subfreezing tissue temperatures, extracellular

ice crystals form in susceptible tissue, leading to cellular mechani-

cal damage and increased osmotic pressure, causing inflammation,

microvascular thrombosis, ischemia, and hypoxia. Formation of

intracellular ice crystals may then occur. Thawing increases tissue

edema and provokes an inflammatory response and reperfusion

injury (11). Frostbite is classified as described in Table 2.

Skin numbness is a sign of a heightened cold injury risk. A

pale spot on the skin indicates superficial cold injury, which

is characterized by partial skin freezing and mild edema (50).

The injured area should be rewarmed by contact with warm

skin (their own, or someone else's) and further cooling avoided.

With more severe frostbite, the injured area is cold to the touch,

andpatientsoftencomplainthatitfeels“like a block of wood”

(11). If possible, the frozen part or area should not be rewarmed

unless refreezing can be avoided (51).

SPECIAL COMMUNICATION

United States Army Research Institute of Environmental Medicine, Thermal

and Mountain Medicine Division, Natick, MA;

University of Portsmouth,

School of Sport, Health and Exercise Science, Portsmouth, United Kingdom;

University of Oulu, Oulu, Finland;

Department of Community Medicine,

UiT-The Arctic University of Norway, Tromsø, Norway;

University College

London, Centre for Human Health and Performance, London, United

Kingdom; and

Hospitallers Brothers Hospital, Anaesthesiology and

Intensive Care Medicine, Salzburg, Austria

Address for correspondence: John W. Castellani, PhD, United States Army

Research Institute of Environmental Medicine, 10 General Greene Avenue,

Building 42, Natick, MA; E-mail: john.w.castellani.civ@mail.mil.

1537-890X/2011/594–607

Current Sports Medicine Reports

594 Vol u m e 20 Number 11 November 2021 Special Communication

Frostbite occurrence ranges from 7% to 11% among the

general population in Scandinavian countries (10,13,14,52).

It also occurs in military training (15,53,54). It is more com-

mon in rural, northern climates (13,16), in occupations in-

volving high physical strain and extended cold exposure

(14); and in leisure/sporting activities, such as mountaineering

(17,18,55,56), cold climate hiking (57), use of all-terrain vehi-

cles in the cold or of snowmobiles (16); and sports activities

generating high wind speed, such as alpine skiing or sledding

(58), or associated with prolonged stationary posture, such

as kite skiing and hang gliding (59,60). A recent study con-

cluded that the incidence of frostbite injuries in the Austrian

Alps is low (56), mainly due to better awareness and clothing.

Age (19), sex (10,13,14,16,50,56), and ethnic background

(20,21) affect frostbite risk (Table 1). Diseases affecting neural,

vascular, and metabolic functions and related tissue perfusion

and microvascular function, as well as metabolic heat produc-

tion also may increase frostbite risk. Autonomic and peripheral

neuropathies (e.g., diabetes) impair neural control and thermal

sensations (22), central neurological disease (e.g.,multiplescle-

rosis, spinal cord injury) can impair mobility, thermoregula-

tion, cardiac and vascular control; and vascular disease can im-

pair tissue perfusion and responsiveness. Endocrine conditions

(e.g., hypothyroidism, hypopituitarism, adrenal insufficiency)

can decrease metabolic heat production in the cold. Psychiatric

illnesses can predispose to frostbite through increased risk be-

havior (14,22). Various medications that affect the circulation,

metabolism, and fluid balance may predispose to frostbite (22).

Impaired peripheral cold-induced vasodilation (CIVD) and

rewarming responses may predict frostbite risk, but the findings

are inconclusive (23,24,61–63).

Prevention

The primary strategy to reduce frostbite risk is to assess risk,

and to respond to it with appropriate mitigation strategies. The

wind chill temperature (WCT) index, which integrates temper-

ature and wind speed (64) provides an estimation of face

cooling and cheek frostbite risk (Fig. 1). Exposed fingers will

freeze at a warmer WCT than the cheek (65). Wind markedly

increases convective heat loss, decreases clothing insulation ca-

pacity, and increases evaporative heat loss (66). Frostbite risk

can be based on the WCT index and the period in which ex-

posed skin will freeze in more susceptible persons in the popu-

lation. The risk of frostbite on bare skin is less than 5% when

Table 1.

Factors predisposing to frostbite and NFCI.

Climate Individual Characteristics and Physiology

Wind

Wetness, Immersion in Cold Water

Contact with Cold Materials

High Altitude

Hypoxia

Long Duration or High Amount of Cold Exposure

African-American or Afro-Caribbean Ethnic Background

Male

Children

Elderly

Previous Cold Injury

Poor CIVD Response

Homeless

Behavioral Individual/clinical

Smoking

Alcohol use

Drug use

Inappropriate or constrictive clothing

Prolonged stationary situation, immobility

Fatigue, dehydration, malnutrition

Use of emollients

Military rank/task

Poor calorie intake

Coronary artery disease/ischemic heart disease, cardiac insufficiency, stroke

Peripheral vascular disease

Peripheral neuropathy

Cold sensitivity

Raynaud’s phenomenon, white fingers

Hand-arm-vibration syndrome, vibration

Diabetes

Hypothyroidism, hypopituitarism

Depression, schizophrenia, dementia

Neurovascular diseases

Sweating or hyperhidrosis

Previous cold injury

Medication (vasoconstrictors)

References: (7,10–46).

Table 2.

Traditional historical classification of frostbite adapted from Fudge (48).

Frostbite Degree Physical Findings

1st Degree Numbness, central white or yellow, waxy discoloration, surrounded by erythema

and edema, desquamation, dysesthesia

2nd Degree Surface blisters containing clear or opalescent fluid surrounded by erythema and edema

3rd Degree May initially present as 2nd degree, but hemorrhagic blisters appear within 24 h,

tissue loss involving entire thickness of skin

4th Degree Injury is through the dermis, into subcutaneous tissue, muscle, and bone

For field use, a simpler two-tier classification may be more appropriate (superficial —no or minimal anticipated tissue loss, corresponding to 1st- and

2nd-degree injury: deep —anticipated tissue loss, corresponding to 3rd- and 4th-degree injury (49).

www.acsm-csmr.org Current Sports Medicine Reports 595

the ambient temperature is above −15°C (5°F), but increased

safety surveillance is warranted when the WCT index falls be-

low −27°C (−17°F), when frostbite can occur in 30 min or less

(4). Wet skin cools more rapidly and may increase risk (67). Ex-

posure to volatile liquids (which evaporate easily —such as

light liquid fuels) is of even greater risk. Exercise of sufficient in-

tensity increases skin perfusion and reduces skin cooling and

cold injury risk (25,67).

Touching or gripping cold material elicits contact cooling

and can cause a frostbite injury within a few seconds (26).

The degree of skin cooling depends on the surface tempera-

ture, type of material, contact duration, and several individual

factors. Human tissue in saltwater freezes at −0.55°C (31°F),

whereas seawater freezes at −1.9°C (28.6°F), so frostbite can

occur in very cold seas. Altitudes above 5000 m (18) increase

frostbite risk with the risk potentiated by wind and possibly by

factors, such as dehydration. Many factors may contribute to

this, with low environmental temperatures perhaps combining

with hypobaric hypoxia (27).

In all circumstances, frostbite risk is mitigated through the

maintenance of core body temperature, by reducing risk of con-

tact freezing (rapid heat loss through a conductor at a temper-

ature below zero), and through a general approach aimed at re-

ducing heat loss with clothing. Thus, skin exposure should be

avoided, windproof external layers used, excellent thermal in-

sulation (trapping warmed air, and limiting conduction from

Figure 1: WCT Index in°F (A) and °C (B). Frostbite time indicated onboth charts is the risk of cheek frostbite in the most susceptible 5% of the

population. From (64).

596 Vol u m e 20 Number 11 November 2021 Special Communication

the skin) used. Where appropriate, multiple layers can help

(e.g., thinner gloves worn under mitts offer dexterity for short

periods when the hands are removed from those thicker mitts).

In extreme conditions, portable heating devices (whether chem-

ical or powered pads) can offer value. In freezing conditions,

liquid should be rapidly removed from exposed skin. This is es-

pecially important where the liquid might evaporate fast or

conduct easily (e.g., some liquid fuels).

Treatment

If frostbite is suspected, any further cold exposure should be

avoided with the casualty placed in a warm, dry environment.

Wet clothing should be removed and the injured region protected

from direct mechanical injury (e.g., no weight bearing if lower

limb affected). If hypothermia is present, this should be treated

first, with systemic hydration restored and maintained. Routine

antibiotic administration should be avoided, as should spon-

taneous thawing or rewarming through friction or via heat

sources (e.g., flame, vehicle engine) (68). The region should

only be thawed if refreezing can be prevented (69). Thawing

may initially use the body heat of the casualty or rescuers (e.g.,

placing the affected region in the axilla). When available, a 37°C

to 39°C (98.6°F to 102.2°F) waterbath should be used until the

skin has softened and is reddening (11). Once dried, loose dress-

ings and bandages can be applied. Swelling can lead to bandages

tightening and restricting blood flow. Thawing can be painful; ad-

ministration of analgesics (non-steroidal anti-inflammatory drugs,

paracetamol, sometimes opioids) may be required. Blister integrity

should be preserved, and efforts made to prevent secondary infec-

tion. Expert medical evaluation is required (70).

Nonfreezing Cold Injury

Nonfreezing cold injury (previously referred to as trenchfoot)

often results from exposure to cold-wet conditions causing tissue

temperatures to fall below 15°C (59°F) for a prolonged period.

The periphery is more commonly affected (not only fingers/toes

but also nose/ears). Unlike frostbite, the tissues do not freeze; in-

stead, protracted intense vasoconstriction and associated ische-

mia and/or reperfusion cause neurovascular damage (71).

Chilblains, a mild form of NFCI, occur following 1 to 5 h of

cold-wet exposure (above freezing) and predominantly affect

finger and toe skin (72). They are small, swollen, itchy, ery-

thematous papules, which may be tender or painful (73). A

hyperemic response to rewarming is characterized by red,

hot, and swollen skin accompanied by an itching or burning

sensation that may persist for several hours. Long-lasting effects

are rare (73). More severe NFCI has not only long affected the

military (28) but also occurs among athletes, such as ice skaters

(74), cyclists (75), divers (76), and long-distance Polar rowers

(77) and is a potential risk for hikers and mountaineers who be-

come incapacitated (78).

The “dose”of cold (temperature and duration) required to

cause NFCI is not known and varies between and, possibly,

within individuals. Most reports of NFCI have involved sev-

eral days to weeks of cold exposure (28,75,77,79); however,

exposures <24 h can cause NFCI (76,80). Short cold expo-

sures may result in NFCI if there is inadequate rewarming

and, therefore, prolonged low tissue temperature. The affected

area is pale, cold, and numb during cold exposure. On

rewarming, it becomes cyanotic while remaining cold and

numb; it may swell in severe cases. In very mild cases, recovery

occurs within a few days with nolasting symptoms (81,82). In

others, a subsequent hyperemic phase lasts between 2 wk and

3 months and is characterized by hot, red, and dry skin with

some paresthesia and, in severe cases, blistering (50,81). The

extent of tissue damage can only be assessed after this hyper-

emic phase. Chronic symptoms may then occur, lasting from

a few months tomany years, and include (in varying combina-

tions and severity): cold sensitivity, sensory neuropathy, pain,

and hyperhidrosis.

Cold sensitivity is characterized by cool skin temperatures

even in a warm environment and slow rewarming (due to re-

duced skin blood flow) following local cooling (83,84). In

combination with hyperhidrosis, which will increase evapora-

tive cooling, cold sensitivity increases the risk of subsequent

cold injury (29,85). Responses to peripheral cooling are di-

verse (86); a large proportion of the general population are

cold sensitive, some perhaps having subclinical forms of NFCI

(84,87–89). Athletes, such as windsurfers (90) and cold-water

swimmers, may develop cold sensitivity through cold expo-

sure, although altered sensory thermal sensation or endothe-

lial dysfunction is not generally observed (89).

Individuals from African-Caribbean backgrounds are more

susceptible to NFCI (21,82) as are those with previous cold in-

jury (29). Women also may be at greater risk due to their

greater rate of hand and foot cooling in the cold (91). The ev-

idence for either dehydration (28,71,77,82,92,93) or smoking

(28,30,82,94) increasing the risk of NFCI is equivocal.

Prevention

NFCI prevention should focus on keeping the body warm

by remaining active; feeling generally cold and being static

are NFCI risk factors (82). It also is essential that risk be

assessed in the manner suggested for frostbite and, likewise,

that tissues are protected from heat loss through conduction,

convection, radiation, and evaporation (see above). Of partic-

ular note is that wet or damp conditions greatly increase risk,

because of the enhanced ability of water to conduct heat, and

to drive cooling through evaporation. Appropriate clothing

(waterproof, windproof, breathable, and able to maintain its

insulation even in wet windy conditions) is essential, as is pro-

tection of the hands and feet. Waterproof boots and gloves

with breathable membranes to prevent sweat accumulation

during periods of high activity and subsequent cooling

through evaporation and conduction during periods of rest

are required (31). In cold-wet conditions, socks and gloves

should be changed frequentlyto ensure the feet and hands stay

dry. Restrictive footwear reduces blood flow and increases

foot cooling rates and should be avoided (31).

Interindividual NFCI susceptibility varies greatly, even when

clothing, environment, and tasking are identical (28,77). There-

fore, risk mitigation needs to be on an individual basis, with

anyone reporting feeling cold, complaining of cold extremities

being closely monitored or withdrawn from the event. If NFCI

is suspected, individuals should be removed from the cold-wet

environment to prevent further cooling and enable core

rewarming if the individual is hypothermic. The affected

feet/hands should be rewarmed slowly (11,50).

Accidental Hypothermia

Accidental hypothermia is defined as a drop in deep body

(core) temperature (T

deep

) to <35°C (95°F) (95,96). Primary

www.acsm-csmr.org Current Sports Medicine Reports 597

hypothermia (commonest type of hypothermia in sports settings

among young and healthy athletes) results from environmental

cold exposure, and secondary hypothermia from factors, such

as exhaustion, trauma, insufficient home heating/insulation, dis-

ease and intoxication, advanced age, or multimorbidity (97). The

signs and symptoms of hypothermia are presented in Table 3.

In primary accidental hypothermia, body heat loss exceeds heat

production. The rate of cooling depends on factors, including

clothing worn, environmental conditions (e.g., water exposure,

temperature, wind), and exercise intensity. Cooling during seden-

tary cold water (10°C to 16°C) immersion in normothermic indi-

viduals ranges from ~1.0 to 1.8°C·h

−1

(1.8 to 3.2°F·h

−1

)(99–101).

It has been measured as high as 9°C·h

−1

(16.2°F·h

−1

) when buried

in avalanche snow (102,103). In air, physical activity attenuates

deep

cooling due to significantly increased heat production com-

pared with resting (4). Other factors also impact T

deep

cooling;

for example, shivering heat production is substantially impaired

by a central mechanism if hypoglycemia occurs (104). In cold

air, hypothermia is most likely to occur if an individual be-

comes injured or exhausted and is no longer able to exercise.

Prevention

When combined with exercise-induced heat production,

appropriate clothing provides the greatest protection against

hypothermia by reducing convective and evaporative heat loss

through windproofing and waterproofing, and insulation pro-

vided by air trapping (105). Clothing requirements vary with

changes in ambient air temperature, rainfall, and exercise inten-

sity (105,106). In the case of water immersion, the depth of im-

mersion (surface area of body exposed, compressive impact on

clothing insulation), water temperature, and movement also

will determine clothing requirements. Thermal models estimat-

ing whole-body cooling and needed clothing insulation, such as

the Insulation Required (107) and Cold-Weather Ensemble De-

cision Aid (108,109) predict the amount of clothing needed for

individuals to maintain T

deep

based on ambient temperatures

andexerciseintensities.Athigherexerciseworkloads,less

clothing is needed to protect against a fall in T

deep

Typical cold-weather clothing consists of three layers: an in-

ner layer, which is in direct contact with the skin and does not

readily absorb moisture, but wicks moisture to the outer layers

where it can evaporate; a middle layer, which provides the pri-

mary insulation; and an outer layer, which is designed to al-

low moisture transfer to the air while repelling wind and rain.

Sweating can easily exceed the vapor transfer rate of the outer

shell layer, causing moisture to accumulate on the inside, even

if the outer layer has substantial venting (e.g., zippers in

armpits) to allow moisture to escape. The outer layer should

typically not be worn during exercise (unless it is raining or

very windy) but should be donned during subsequent rest pe-

riods. In group settings, individuals should adjust clothing to

their own physiological responses (e.g., sweating) and not

wear a standard amount of clothing. A common problem is

that people begin exercising while still wearing clothing layers

appropriate for resting conditions, and thus are “overdressed”

after initiating exercise. If the combination of environmental

conditions, work intensity, and available clothing suggest that

body heat content cannot be maintained (e.g., low exercise in-

tensity in rainy conditions), then supervision or use of the

buddy system should be encouraged. Remaining dry, especially

for those exercising in remote regions, is extremely important

and carrying extra clothing that is waterproof, and dry cloth-

ing to change into, is important.

Treatment

Vital signs diminish as cooling progresses (Table 4, [95]).

Accurate T

deep

measurement using rectal or esophageal probes

is difficult in a field situation. In such a situation, accidental

hypothermia should be diagnosed by measuring tympanic tem-

perature with an insulated thermistor-based probe, allowing

readings of <32°C (89.6°F) (113). This can later be confirmed

with a rectal temperature using a low reading thermometer,

where and when practical.

Without accurate temperature measurements, the diagnosis

and classification of hypothermia must rely on medical history

and clinical findings (e.g., trunk feels cold, quality of vital

signs; Table 4). A revised hypothermia staging/classification

has been proposed (96), which correlates the level of con-

sciousness with the risk of hypothermia-induced cardiac arrest

(Table 5). Young and healthy casualties may have vital signs

still present at T

deep

< 24°C (75.2°F) (115). Signs of breathing

or cardiac activity (and/or respiratory and pulse rate) should

be sought for at least 1 min because respiratory rates may be

as low as 3 to 4 min, pulse rates as low as 10 to 15 bpm,

and pulse volume low and breaths shallow (95,96,115).

Treatment algorithms have been published for patients with

accidental hypothermia (Fig. 2) (95,96,116). Out-of-hospital

treatment consists of limiting further cooling. Patients should

be removed from wind and water. In a warm shelter, remove

wet and cold clothing. Out-of-hospital rewarming is almost

impossible with limited technical equipment; transport to a

hospital should take precedence (see below). In many patients,

deep

will continue to fall after rescue (i.e.,“afterdrop”). The

risk of hypothermia-induced cardiac arrest commences once

Tab l e 3 .

Signs and symptoms of hypothermia at different levels (98).

Mild (32–35°C; 89.6–95°F) Moderate (28–31°C; 82.4–88°F) Severe (<28°C; <82.4°F)

Cold extremities Apathy, poor judgment Inappropriate behavior

Shivering Reduced shivering Total loss of shivering

Tachycardia Weakness and drowsiness Cardiac arrhythmias

Tachypnea Slurred speech and amnesia Pulmonary edema

Urinary urgency Dehydration Hypotension and bradycardia

Mild incoordination Decreased coordination or clumsiness Reduced level of consciousness

Fatigue Muscle rigidity

598 Vol u m e 20 Number 11 November 2021 Special Communication

deep

is <30°C (86°F) in young and healthy casualties; in the

elderly and multimorbid the risk increases at T

deep

< 32°C

(89.6°F) (96).

For mildly hypothermic patients in a field environment,

warm clothing and drinks with sugar should be given with su-

pervision and active rewarming encouraged. In mild hypo-

thermia cases that recover fully and risk factors are mitigated,

there is no need to evacuate. For moderate and severe hypo-

thermia and the critically ill, patients need to be handled very

gently (as mechanical impact can trigger cardiac arrest), kept

insulated, passively rewarmed slowly (0.75 to 1.0°C·h

−1

)

and evacuated.

Table 4.

The two main clinical classification systems for accidental hypothermia: The original Swiss system (110) and the wilderness medical society

classification (111).

Swiss System (110) WMS (111)

Category Clinical Findings

Estimated Core

Temperature (°C, °F) Category Clinical Findings

Estimated Core

Temperature (°C; °F)

Stage 1 Clear consciousness

with shivering

35°C to 32°C Mild Normal mental status,

shivering, but not

functioning normally/

able to care for self

35°C to 32°C

95°F to 89.6°F 95°F to 89.6°F

Stage 2 Impaired consciousness

without shivering

<32°C to 28°C Moderate Abnormal mental

status with shivering,

or abnormal mental

status without

shivering, but

conscious

32°C to 28°C

<89.6°F to 82.4°F <89.6°F to 82.4°F

Stage 3 Unconsciousness <28°C to 24°C Severe/profound Unconscious <28°C

<82.4°F to 75.2°F <82.4°F

Stage 4 Apparent death 24°C to 11.8°C

75.2°F to 53.2°F

Stage 5 Death due to irreversible

hypothermia

<11.8°C

<53.2°F

Core temperature data from stages 4 and 5 from Mroczek et al. (112).

WMS, Wilderness Medical Society.

Table 5.

Revised Swiss system for staging of accidental hypothermia (114).

AVPU denotes Alert, Verbal, Painful and Unconscious, respectively.

In the Revised Swiss System, “Alert”corresponds to a GCS score of 15; “Verbal”corresponds to a GCS score of 9 to 14, including confused patients;

“Painful”and “Unconscious”correspond to a GCS score <9. While shivering is not used as a stage-defining sign in the Revised Swiss System, its presence

usually means that the temperature is >30°C (86°F), a temperature at which hypothermic CA is unlikely to occur.

No respiration, no palpable carotid or femoral pulse, no measurable blood pressure. Check for signs of life (pulse and, especially, respiration) for up to

1min.

The transition of colors between stages represents the overlap of patients within groups. The estimated risk of cardiac arrest is based on accidental hy-

pothermia being the only cause of the clinical findings. If other conditions impair consciousness, such as asphyxia, intoxication, high altitude cerebral edema

or trauma, the revised Swiss System may falsely predict a higher risk of cardiac arrest due to hypothermia. Caution should be taken if a patient remains

“alert”or“verbal”showing signs of hemodynamic or respiratory instability like bradycardia, bradypnea,hypotension because this maysuggest transition to

a stage with higher risk of cardiac arrest.

www.acsm-csmr.org Current Sports Medicine Reports 599

Figure 2: Treatment algorithm for patients with accidental hypothermia, from (96). Definitions of parenthetical numbers are: (1) decapitation,

truncal transection, whole body decomposed, or whole body frozen solid (chest wall not compressible); (2) SBP < 90 mm Hg is a reasonable

prehospital estimate of cardiocirculatory instability but for in-hospital decisions, the minimum sufficient circulation for a deeply hypothermicpa-

tient (e.g., <28°C) has not been defined; (3) Swiss staging of accidental hypothermia; (4) direct transport to an ECMO center is recommended

in an arrested hypothermic patient. In remote areas, transport decisions should balance the risk of increased transport time with the potential ben-

efit of treatment in an ECLS center (e.g., 6 h). (5) Warm environment, chemical, electrical, or forced air heating packs or blankets, and warm IV

fluids (38°C to 42°C). In case of cardiac instability refractory to medical management, consider rewarming with ECLS.(6) If the decision is made

to stop at an intermediate hospital to measure serum potassium, a hospital en route to an ECLS center should be chosen. HOPE and ICE scores

should not be used in children; instead consider expert consultation. DNR, do not resuscitate HT, hypothermia, MD, medical doctor, ROSC, return

of spontaneous circulation, SBP, systolic blood pressure.

600 Vol u m e 20 Number 11 November 2021 Special Communication

Out-of-hospital, casualties with stage 1 hypothermia (Table 5)

should be transported to a hospital able to deal with concomitant

illnesses or injuries (95,96). With colder patients, the risk of im-

minent cardiac arrest has to be evaluated (i.e.,systolicbloodpres-

sure <90 mm Hg, ventricular arrhythmia, T

deep

<30°C(86°F);

Fig. 2). If only one risk factor is present, the patient should be

transported to a hospital with the possibility to rewarm them

with extracorporeal life support (ECLS). Without any risk fac-

tor of imminent cardiac arrest, the patient can be carefully and

gently transported to the closest appropriate hospital and

rewarmed actively (e.g., forced warm air). If a patient has suf-

fered a hypothermia-induced cardiac arrest (stage 4), cardiopul-

monary resuscitation (CPR) should be initiated immediately.

Modifications to CPR have been proposed for hypothermia-

induced cardiac arrest patients, for example, at a T

deep

<30°C

(86°F), no epinephrine and a maximum of three shocks should

be attempted (95,96). Transport of a hypothermic patient in

cardiac arrest should be directly to a hospital with ECLS

rewarming capability.

In the hospital, prognostication of outcome after ECLS

rewarming should be performed with specific scores (Hypo-

thermia outcome prediction after extra-corporeal life support

(HOPE) or International accidental hypothermia extracorpo-

real life support (ICE)) (117–119), which are more reliable

than the traditional potassium triage (120,121).

Avalanche Burial

During avalanche burial, smaller people lose heat more rap-

idly than larger individuals because of a higher surface-area

ratio and smaller muscle mass (122). Regarding cooling rate,

the amount of subcutaneous adipose tissue and insulation

provided by clothing also are important. For example, while

wearing a thin monolayer garment, commonly used by back-

country skiing athletes during ascent, body core cooling can

approach 9°C·h

−1

during an avalanche burial. With thick

multilayer clothing ensembles, including helmet and gloves,

used in downhill skiing, cooling is slower (123).

Of all avalanche-buried persons, 10% to 20% die in the

first 30 min from trauma to the head, cervical and thoracic

spine, or from multiple trauma (124). More than 60% die

from asphyxia (i.e., lack of oxygen), most commonly within

the first 35 min of burial because either the airways are

obstructed or snow in front of the mouth and nose inhibits

air inhalation. The longer someone is buried following an

avalanche, the less chance of survival (124,125). Data in

European skiers from 1981 to 1991 (126,127) suggest three

phases of avalanche burial (survival, asphyxiation, waiting)

before rescue. For survival, 93% of avalanche victims are still

alive in the first 15 to 20 min and with asphyxiation, 65% die

during the next 15 min due to freezing snow caused by breath-

ing leading to a limited oxygen availability. Survival to 45 min

and beyond suggests an open-air pocket exists (i.e.,patentair-

ways with space in front of mouth and nose with access to

open air). These casualties will survive until an avalanche-

specific combination of hypothermia, hypoxia, and hypercap-

nia sets in (128). Less than 20% survive for more than 2 h

(129). Climate and topography affect the survival from ava-

lanche burial (126). In humid climates (e.g.,maritimecoast),

snow is denser, and asphyxia has an earlier onset than in the

Swiss Alps with a continental climate. Skiing in slightly for-

ested or rocky terrain results in more fatalities due to trauma.

Reduced burial depth is positively correlated with survival.

Only 4.4% of partially buried casualties (i.e.,headandchest

outside of the snow) compared with 51.3% of fully buried

casualties (i.e., head and chest below the snow) die (130).

An avalanche airbag reduces the risk of full burial and also

may reduce burial depth. The reduction in mortality is less

when the airbag does not inflate: in one study, noninflation oc-

curred in 20% of use, 60% of which was attributed to a de-

ployment failure by the user (131). With risk of avalanches,

winter sport athletes who are outside protected slopes should

be equipped with, and trained in the use of, an avalanche

airbag, an avalanche transceiver, a probe, and a metal-headed

shovel. Companions should quickly track the location with

an avalanche transceiver, probe the exact location and depth,

and excavate the buried casualty. Using digital instead of ana-

log avalanche transceivers, attending avalanche rescue courses

on correct tracking and probing, as well as regular training in

deploying an avalanche airbag and working in coordinated

groups will allow faster extrication. In mountain regions close

to urban centers, helicopter rescue has revolutionized avalanche

rescue because of fast transport times. Still, professional rescue

should not be expected on scene within the first 20 min. Thus,

rescue by peers on-site is of utmost importance to increase

survival chances.

Once extricated, patients are treated according to specific

avalanche resuscitation guidelines (96,118,119). In normo-

thermic patients, asphyxia triggered cardiac arrest can only

be survived for a few minutes and has a poor outcome. In hy-

pothermia triggered cardiac arrest (usually <30°C; 86°F), out-

come is substantially better (96,132,133).

Snow Blindness

The structures of the eye are vulnerable to damage from ex-

posure to ultraviolet (UV) light, with risk increasing at high al-

titudes (rising 4% per 300 m ascent). Being protected by the

brow, nose, and upper lid, the eye is mainly exposed to UV-

light that is reflected (emphasizing a need for lateral eye pro-

tection). The reflective incidence of water and snow are two-

fold and eightfold greater than grass. In a snowy environment

at 2000 m, UV exposure is doubled (134,135).

“Snow blindness”results from acute UV ocular injury. The

degree of conjunctival and corneal injury (“ultraviolet keratitis”)

depends on energy intensity and exposure duration. Limbic in-

jury causes pain when trying to focus the lens. Symptoms begin

4to10hafterexposureandrangefroma“gritty”sensation to

severe pain, blurred vision, uncontrolled blinking, eye-watering,

photophobia, and blepharospasm. Symptoms last <48 h, or

several days if severe. Injury can be compounded by corneal

swelling, which results from altitude-and wind-related hyp-

oxia and corneal evaporative drying, with hypoxia worsened

by contact lens use (135,136). A fluorescein eye stain test can

locate corneal injuries.

Prevention

Sunglasses or goggles with side protection, which absorb

>95% of all UV light, should be worn. Soft contact lenses,

which block UV-light and cover the pupil and limbus, offer

good protection. Brimmed hats offer additional shade.

www.acsm-csmr.org Current Sports Medicine Reports 601

Tr e a t m e n t

Close eyes and rest until pain eases. In a first step, cool gently

through the closed eyelid (135). In a next step use oral analgesics

(e.g., paracetamol 1 g, four time a day). If available, administer a

topical lubricant (e.g., antioxidant artificial tears), and apply

nonsteroidal anti-inflammatory eyedrops (e.g., diclofenac

0.1%). Topical anesthetics slow corneal recovery and should

not be used outside emergency situations (e.g., descent from

high altitude). Consider topical antibiotics in severe cases to

prevent infection. Cycloplegic eye-drops (cyclopentolate 1%)

may relieve pain but impair vision (135,136).

Cold Water

The great cooling power of water means that some of the re-

sponses described for cold air (e.g., hypothermia) also occur in

cold water, but sooner. Humans cool four to five times faster

in cold water than in air at the same temperature (137).

There are four stages of immersion in cold water, each asso-

ciated with specific hazards and each related to the cooling of

different body tissues. Rapid skin cooling on initial immersion

stimulates the cutaneous cold receptors; their dynamic re-

sponse elicits the “cold shock,”a response not evoked by the

slower rates of skin cooling in air. Cold shock is regarded as

the most dangerous response caused by cold water immersion

and affects men and women to a similar extent (138,139). The

greatest responses are observed at water temperatures between

10°C and 15°C (50°F to 59°F) for lightly clothed (swim-suited)

individuals and include a “gasp”response, hyperventilation,

hypertension, and increased cardiac workload (140). These

can be precursors to drowning and cardiovascular issues. The

initial gasp response is 2 to 3 L (141,142), larger than the lethal

volume of seawater for drowning (1.5 L, [143]). The cold shock

response peaks in the first 30 s of immersion and usually abates

over the next 90 s as the peripheral cold receptors adapt to the

new skin temperature. There is a significant possibility of aspi-

rating water during initial immersion when conscious control

of breathing has been lost. In situations where the face also is

immersed on initial immersion, coactivation of sympathetic

and parasympathetic inputs to the heart can produce “auto-

nomic conflict,”resulting in potentially fatal arrhythmias in a

variety of sporting situations (e.g., open water swimming, tri-

athlon [144]).

After skin, the next body tissues to be affected by cooling are

the superficial nerves and muscle. The arms are particularly sus-

ceptible to cooling due to their anthropometry (thin cylinders),

anatomy (superficial nerves and muscles), and physiology (reli-

ance on blood flow for warming) (122). Within about 20 min

of immersion in water of 12°C (54°F) peripheral neuromuscular

cooling can significantly impair manual dexterity, grip strength

and coordination, impacting swimming ability (122,145).

Approximately 60% of cold-water immersion deaths occur

within the first minutes of immersion, long before hypother-

mia occurs (144). Under normal circumstances, adult humans

will not become hypothermic in under 30 min in even the

coldest water.

Prevention/Protection/Treatment

The cold shock response demonstrates temporal summa-

tion, with a greater response being observed with faster rates

of entry into cold water (146). Those entering cold water are

advised to rest with their airway clear of the water until they

have regained control of their breathing (“float first”). Pro-

longed head-in breath holding should be avoided oninitial im-

mersion. For open cold water swimming events, swimmers

should adapt to the water just before commencing the swim

(or have in-water starts); this reduces the chance of aspirating

water and makes the coordination of the swim stroke and

breathing easier.

Protection can be physiological or technological. Physiolog-

ical protection against cold shock can be achieved by cold ha-

bituation, with as few as six 2-min head-out cold water im-

mersions over 3 d reducing the cold shock response by 50%

by the last immersion (147). A reduction of 25% is still appar-

ent 14 months later (148). Although habituation will reduce

the ventilatory response on immersion, this may not translate

to an improved swimming capacity (149).

Importantly, repeated immersion in cold water does not

protect against neuromuscular incapacitation from peripheral

cooling; protection for this response can only be achieved by

limiting exposure or technological protection with protective

clothing. In terms of swim failure, it appears that the upper

arms (triceps region) are the most important region to protect

(145,150). However, insulation of the upper arms during a

simulated survival swim in 10°C water maintained warmer

arm skin temperature and swimming technique but did not

improve swimming duration or distance (151). Most sports

persons use wet suits rather than dry suits. The primary deter-

minants of the protection provided by a wet suit are its fit and

thickness. The fit should be as tight as possible commensurate

with sporting performance, and the thickness varies between

the torso and the arms, depending on the sport and require-

ments for regional flexibility. The minimum recommended

water temperature for triathlon racing is 12°C (54°F) in

wetsuits and 16°C (61°F) without wetsuits (152,153). It is rec-

ommended that water temperatures below 18°C (64°F) are

too cold for elite marathon swim racing without wet suit pro-

tection (154). Fédération Internationale de Natation rules

were changed in 2017 to make wetsuits compulsory below

18°C (64°F) and optional below 20°C (68°F) (155).

Protection also can be afforded by appropriate event orga-

nization. Swimming events, including mass starts, can be orga-

nized and supervised to minimize the chances of cardiac and

respiratory-related problems (156). Those providing safety

cover should be aware of the increased likelihood of cold-

related problems in the first (due to cold shock response)

and last (due to fatigue) minutes of an event and should be

trained to recognize impending swim failure (145).

Basic life support compressions and ventilations (2 rescue

breaths then CPR at 30:2 ratio) should be used and for drown-

ing victims, high concentrations of inspired oxygen given as

soon as possible. All those suspected of aspirating water should

be evacuated to hospital. For hypothermic casualties, follow the

advice given in the section on “Accidental Hypothermia.”

Cold and Performance

Cold air and water exposure can potentially have deleteri-

ous effects on aerobic and strength performance (157–163).

Interested readers are referred to previous reviews of the im-

pact of cold exposure on exercise performance and the physi-

ological mechanisms responsible for cold-related changes in

performance (122,164,165).

602 Vol u m e 20 Number 11 November 2021 Special Communication

Decreased muscle temperatures (T

muscle

)lowerV

2max

,ex-

ercise time, and power/sprint ability. For every 1°C fall in

muscle temperature, there is a 4% to 6% decline in these

markers of performance (166–168). For example, an 8°C de-

crease in T

muscle

decreases power output by 31% and maximal

voluntary contraction by 19% (169). Low T

muscle

(28°C to

29°C) also cause higher muscle lactate levels in both type 1

and type 2 muscle fibers (170,171), and overall, blood lactate

levels increase during exercise to a greater extent in cold com-

pared with temperate environments (157,172–177) suggest-

ing a greater reliance on anaerobic metabolism. Maximal

heart rate is lower by 10 to 30 bpm when T

deep

is lowered

by 0.5°C to 2.0°C (178) and cold water decreases leg muscle

blood flow during exercise (173,179).

In cold air, where there is little change in T

deep

or T

muscle

there is a lack of consensus on whether aerobic performance

declines: studies have demonstrated impairment (158–161),

improvement (180,181), or no change (182,183). Two studies

have examined, systematically, whether air temperature af-

fects performance. Cycling time to exhaustion at 70%

2max

was longest at an ambient temperature (T

amb

)of

11°C while wearing shorts/t-shirt (158) with decrements seen

at 4°C and 31°C. While wearing cross-country ski uniforms,

Sandsund et al. (160) observed maximal running performance

at T

amb

between −4°C (24.8°F) and 1°C (33.8°F), with perfor-

mance reduced at −14°C (6.8°F) and warmer T

amb

. The lower

amb

in the running study can perhaps be attributed to the ski

uniform conferring greater thermal protection and the higher

exercise intensity. However, it should be noted that if more

clothing is needed to protect against environmental cold expo-

sure, this could reduce performance due to increased energy de-

mands caused by heavy clothing, resistance to movement, and

other equipment (4,184). Upper-body performance in cross-

country skiers also is reduced at colder T

amb

(185,186). Cold

temperatures also can impact biomechanics and gait, increasing

the energy demands of exercise (187). Furthermore, athletes

need to be cognizant of terrain factors (i.e., ice, snow cover) that

can cause slipping and coordination issues. Proper nutrition

and hydration are important for maintaining performance in

cold-weather environments. Practical recommendations in-

clude maintaining adequate carbohydrate stores and monitor-

ing fluid intake/output by tracking body mass changes and

urine output/color (188).

Combined Stressors

In the natural world, it is rare for stressors, such as heat and

humidity, cold and altitude, and cold and hyperbaric stress,

not to be combined or experienced sequentially. However,

largely because of the way subject areas are organized, the im-

pact of combined stressors on human responses has received

much less attention than the impact of isolated stressors. Be-

tween 1948 and 2012, there were only 14 studies examining

these areas with human participants (189). Since 2012, the num-

ber of studies has increased dramatically and the importance

of this area of research for human performance, health, and

disease is beginning to be realized (190). The areas of com-

bined stressors not only include the beneficial or detrimental ef-

fects of combined stressors, such as cold and hypoxia, but also

include cross-adaptation and cross-tolerance between such

stressors (Fig. 3), at both the systemic and cellular levels

Focusing on the combination of cold and altitude (hypoxia)

(191), cold-induced thermogenesis is reduced in hypoxia (192),

and T

deep

falls faster (193). During cooling and warming, the

vasoconstrictor response can occur earlier and be released later

if hypoxia is combined with cold, thereby increasing the “dose”

of cold experienced and the likelihood of cold injuries

(193,194), although this remains a matter for debate (195).

Adaptation to the initial responses to cold water immersion

reduces the subsequent responses to a hypoxic exposure (196)

including plasma epinephrine and norepinephrine, sympa-

thetic nervous system response, heart rate, ventilation, oxygen

consumption, and carbon dioxide production, as well as

symptoms of hypoxia and their severity (196).

In contrast to the clear interaction between cold and hyp-

oxia, it has been reported that cold acclimation does not alter

the physiological or perceptual responses during subsequent

exercise in the heat (197). The area of combined stressors is

clearly fertile ground for further investigation with regard to

the avoidance of injuries in the cold.

Figure 3: Theoretical overview of cross-adaptation(CA). CA1, adaptation to one stimulus providescross-tolerance to another. CA2, adaptation

to one stressor enhances adaptation to another stressor. CA3, combined adaptive effects of two stimuli providing beneficial responses to a third

variable. The cross-adaptive effect may “general”via some common pathway involving for example the autonomic nervous system or pathways

involved in cellular tolerance, or “specific”involving a more specific response to a stimulus such as shivering or vasoconstriction.

Cross-adaptation: “Adaptations made in response to one environmental

stressor are beneficial in another”Cross-acclimatization: “Adaptation de-

rived from a natural/terrestrial environment”Cross-acclimation: “Adapta-

tion derived from a simulated environment”Cross-tolerance: single or re-

peated exposures to a stressor eliciting a positive adaptive response in cel-

lular and molecular pathways during a subsequent exposure to a different

stressor (Gibson, 2017).

www.acsm-csmr.org Current Sports Medicine Reports 603

Conclusions

Coaches, athletes, medical personnel, and officials need to

understand the physiology, pathophysiology, prevention,

protection, and treatment of cold-related impacts on perfor-

mance. From this understanding come optimal interventions

for the maintenance of performance and avoidance of frost-

bite, nonfreezing cold injuries, hypothermia, drowning, and

other medical events.

Click here (SDC link needed to PowerPoint file, http://links.

lww.com/CSMR/A122) to download a slide deck that summa-

rizes this ACSM Expert Consensus Statement on Injury Preven-

tion and Exercise Performance during Cold-Weather Exercise.

The authors declare no conflict of interest and do not have

any financial disclosures.

J.W.C. and M.J.T. are co-chairs.

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Frostbite and Mortality in Mountaineering Women: A Scoping Review—UIAA Medical Commission Recommendations

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Oct 2023
HIGH ALT MED BIOL

Kriemler, Susi, Kastė Mateikaitė-Pipirienė, Alison Rosier, Linda E. Keyes, Peter Paal, Marija Andjelkovic, Beth A. Beidleman, Mia Derstine, Jacqueline Pichler Hefti, David Hillebrandt, Lenka Horakova, and Dominique Jean; for the UIAA MedCom Writing Group on Women's Health in the Mountains. Frostbite and mortality in mountaineering women: a scoping review-UIAA Medical Commission recommendations. High Alt Med Biol 00:000-000, 2023. Background: The harsh environment of high altitudes (HA) poses many serious health risks for mountaineers, including cold injuries and death. The aim of this work was to review whether female mountaineers are at special risk for frostbite or death at HA compared with their male counterparts. Methods: The UIAA Medical Commission convened an international author team to review women's health issues at HA and to publish updated recommendations. Pertinent literature from PubMed and Cochrane was identified with additional publications found by hand search. The primary search focus was for articles assessing cold injuries and death in women mountaineers at HA. Results: We reviewed the literature and identified 20 relevant studies: 2 studies on frostbite at HA, plus 7 studies and 1 report for death at HA. An additional 10 studies about frostbite at low altitude were included. We found that female mountaineers at HA were at lower risk of death than their male counterparts, but sex differences in frostbite were inconclusive. Conclusions: The frequency of cold injuries and mortality in female mountaineers is not yet well studied, and the studies that have been published tend to lack precise exposure data. More studies and registries with sex-differentiated data are needed.

Cold weather operations: Preventive strategies in a military context

Article

Full-text available

Oct 2024

Knowledge, attitudes, practice, and public health education demand regarding PARI prevention: a cross-sectional study among Chinese undergraduates

Article

Full-text available

Jun 2024

Objectives The purpose of this study was to assess the level of knowledge, attitudes, and practices (KAP) of university students in China regarding the need for PARI and public health education. Methods A cross-sectional online and offline survey was conducted in China website through Wenjuanxing and in different cities such as Changsha Hunan Province, Shanghai, Chongqing and in different public scenarios, such as hospitals, universities, and commercial venues between September 1 and September 7, 2023, using a 28-question questionnaire designed and reviewed by multidisciplinary experts. Results A total of 4,096 respondents were recruited for this study, with 3,957 valid questionnaires. The mean knowledge score was 1.84 ± 0.52, the mean attitude score was 2.12 ± 0.51, and the mean practice score was 3.18 ± 0.55. Regression analyses found that: region, grade, school, and weekly anaerobic exercise time were influences on the knowledge score; region, grade, school, and weekly anaerobic exercise time were influences on the attitude score; region, grade, school attended, weekly anaerobic exercise time and weekly anaerobic exercise time as influences on the practice score. Subgroup analyses revealed that undergraduates from southern regions and 985 schools had higher knowledge attitude scores and lower practice scores. As the grade level increased, the knowledge and attitude scores showed a V-shaped trend and the behavior scores showed an inverted V-shaped trend. Correlation analysis found a positive correlation between knowledge and attitude scores, and a negative correlation between both and behavior, respectively. The public health education needs survey found that undergraduate students generally preferred guided instruction methods and content centered on the RICE principles, they preferred learning through books and pamphlets, and they were happy to see relevant content promoted in the campus environment. Conclusion This study shows that Chinese undergraduate students have less knowledge, neutral attitudes, and good behaviors regarding PARI prevention. Special attention should be paid to meeting the needs of undergraduate students for public health education to equip them with relevant knowledge so that they can better behave in PARI prevention.

Cold Ambient Temperature Does Not Alter Subcutaneous Abdominal Adipose Tissue Lipolysis and Blood Flow in Endurance-Trained Cyclists

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Full-text available

Feb 2024

This study sought to investigate the effect of cold ambient temperature on subcutaneous abdominal adipose tissue (SCAAT) lipolysis and blood flow during steady-state endurance exercise in endurance-trained cyclists. Ten males (age: 23 ± 3 years; peak oxygen consumption: 60.60 ± 4.84 ml·kg ⁻¹ ·min ⁻¹ ; body fat: 18.4% ± 3.5%) participated in baseline lactate threshold (LT) and peak oxygen consumption testing, two familiarization trials, and two experimental trials. Experimental trials consisted of cycling in COLD (3 °C; 42% relative humidity) and neutral (NEU; 19 °C; 39% relative humidity) temperatures. Exercise consisted of 25 min cycling at 70% LT and 25 min at 90% LT. In situ SCAAT lipolysis and blood flow were measured via microdialysis. Heart rate, core temperature, carbohydrate and fat oxidation, blood glucose, and blood lactate were also measured. Heart rate, core temperature, oxygen consumption, and blood lactate increased with exercise but were not different between COLD and NEU. SCAAT blood flow did not change from rest to exercise or between COLD and NEU. Interstitial glycerol increased during exercise ( p < .001) with no difference between COLD and NEU. Fat oxidation increased ( p < .001) at the onset of exercise and remained elevated thereafter with no difference between COLD and NEU. Carbohydrate oxidation increased with increasing exercise intensity and was greater at 70% LT in COLD compared to NEU ( p = .030). No differences were observed between conditions for any other variable. Cycling exercise increased SCAAT lipolysis but not blood flow. Ambient temperature did not alter SCAAT metabolism, SCAAT blood flow, or fat oxidation in well-trained cyclists, though cold exposure increased whole-body carbohydrate oxidation at lower exercise intensities.

Effects of high-intensity interval training in a cold environment on arterial stiffness and cerebral hemodynamics in sedentary Chinese college female students post-COVID-19

Article

Full-text available

Nov 2024

Many patients with COVID-19 experience increased arterial stiffness and abnormal cerebral hemodynamics. Although previous studies have explored the effects of cold environments on cardiovascular health and cerebral hemodynamics, there is still no research on the changes in cardiovascular and cerebral hemodynamics in sedentary female students recovering from COVID-19 while performing high-intensity interval training (HIIT) in cold environments. This study investigates the effects of 1 week of HIIT in a cold environment on cerebral hemodynamics and arterial stiffness (AS) in sedentary female college students, providing new insights into the pathophysiological mechanisms in this specific context. Thirty-six participants were randomly divided into a control group (n = 12), a room temperature (RE) group (n = 12), and a cold environment (CE) group (n = 12). HIIT was performed for four 4-min running training sessions, with a 4-min interval between each training session, The training duration was 1 week, with a frequency of 2 sessions per day, while the control group did not undergo any training. After training, the AS in the CE group significantly decreased (p < 0.05), with an average reduction of 11% in brachial-ankle pulse wave velocity, showing a significantly greater improvement compared to the RE group and the control group (p < 0.05), while no significant changes were observed in the RE group (p > 0.05). In the Y-Balance Tests (YBTs), the concentrations of cerebral oxygenated hemoglobin and total hemoglobin significantly increased (p < 0.05) during unilateral leg support tests in both the CE and RE groups, and the increase of CE group is greater than that of RE group. In contrast, in the control group, the concentrations of cerebral oxygenated hemoglobin and total hemoglobin significantly decreased during left leg support (p < 0.05). Our study found that performing HIIT in a cold environment not only effectively reduces AS in sedentary female college students after COVID-19, improves cardiovascular function, but also significantly enhances cerebral hemodynamics, helping them alleviate the negative impacts of post-COVID-19 sequelae and sedentary behavior on health. Future research should further explore the mechanisms by which sedentary behavior, post-COVID-19 recovery status, and adaptation to cold environments collectively influence cardiovascular function and cerebral hemodynamics, providing a more comprehensive understanding of these factors.

Energy Expenditure during Physical Work in Cold Environments: Physiology and Performance Considerations for Military Service Members

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Full-text available

Aug 2024

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) the extreme energy costs of performing militarily relevant physical work in cold environments, 2) key factors specific to cold environments that explain these additional energy costs, 3) additional environmental factors that modulate the metabolic burden, 4) medical readiness consequences associated with these circumstances, and 5) potential countermeasures to be developed to aid future military personnel. Key characteristics of the cold operational environment that cause excessive energy expenditure in military personnel include thermoregulatory mechanisms, winter apparel, inspiration of cold air, inclement weather, and activities specific to cold weather. The combination of cold temperatures with other environmental stressors, including altitude, wind, and wet environments exacerbates the overall metabolic strain on military service members. The high energy cost of working in these environments increases the risk of undesirable consequences, including negative energy balance, dehydration, and subsequent decrements in physical and cognitive performance. Such consequences may be mitigated by the application of enhanced clothing and equipment design, wearable technologies for biomechanical assistance and localized heating, thermogenic pharmaceuticals, and cold habituation and training guidance. Altogether, the reduction in energy expenditure of modern military personnel during physical work in cold environments would promote desirable operational outcomes and optimize the health and performance of service members.

Mass Participation and Tournament Event Management for the Team Physician: A Consensus Statement (2022 Update)

Article

Apr 2024
Curr Sports Med Rep

Mass participation events include endurance events ( e.g. , marathon, triathlon) and/or competitive tournaments ( e.g. , baseball, tennis, football (soccer) tournaments). Event management requires medical administrative and participant care planning. Medical management provides safety advice and care at the event that accounts for large numbers of participants, anticipated injury and illness, variable environment, repeated games or matches, and mixed age groups of varying athletic ability. This document does not pertain to the care of the spectator.

Mass Participation and Tournament Event Management for the Team Physician: A Consensus Statement (2022 Update)

Article

Nov 2023
MED SCI SPORT EXER

Mass participation events include endurance events (e.g., marathon, triathlon) and/or competitive tournaments (e.g., baseball, tennis, football (soccer) tournaments). Event management requires medical administrative and participant care planning. Medical management provides safety advice and care at the event that accounts for large numbers of participants, anticipated injury and illness, variable environment, repeated games or matches, and mixed age groups of varying athletic ability. This document does not pertain to the care of the spectator.

Endurance Capacity Impairment in Cold Air Ranging from Skin Cooling to Mild Hypothermia

Article

Nov 2023
J APPL PHYSIOL

Introduction: We tested the effects of cold air (0°C) exposure on endurance capacity to different levels of cold strain ranging from skin cooling to core cooling of ∆-1.0°C. Methods: Ten males completed cycling time-to-exhaustion (TTE) at 70% of their peak power output following: i) 30-min of exposure to 22°C thermoneutral air (TN), ii) 30-min exposure to 0°C air leading to a cold shell (CS), iii) 0°C air exposure causing mild hypothermia of -0.5°C from baseline rectal temperature (HYPO-0.5°C), and iv) 0°C air exposure causing mild hypothermia of -1.0°C from baseline rectal temperature (HYPO-1.0°C). The latter three conditions tested TTE in 0°C air. Results: Core temperature and seven-site mean skin temperature at the start of the TTE were: TN (37.0 ± 0.2°C, 31.2 ± 0.8°C), CS (37.1 ± 0.3°C, 25.5 ± 1.4°C), HYPO-0.5°C (36.6 ± 0.4°C, 22.3 ± 2.2°C), HYPO-1.0°C (36.4 ± 0.5°C, 21.4 ± 2.7°C). There was a significant condition effect ( p≤0.001) for TTE, where TTE declined from TN (23.75 ± 13.75 min) to CS (16.22 ± 10.30 min, ∆-30.9 ± 21.5%, p=0.055), HYPO-0.5°C (8.50 ± 5.23 min, ∆-61.4 ± 19.7, p≤0.001), and HYPO-1.0°C (6.50 ± 5.60 min, ∆-71.6 ± 16.4%, p≤0.001). Furthermore, participants had a greater endurance capacity in CS compared to HYPO-0.5°C ( p=0.046), and HYPO-1.0°C ( p=0.007), with no differences between HYPO-0.5°C and HYPO-1.0°C ( p=1.00). Conclusion: Endurance capacity impairment at 70% peak power output occurs early in cold exposure with skin cooling and inadequate clothing, with significantly larger impairments with mild hypothermia up to ∆-1.0°C.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 3: Heat and cold tolerance during exercise

Article

Full-text available

Oct 2023
EUR J APPL PHYSIOL

In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.

A digital tool for prevention and management of cold weather injuries—Cold Weather Ensemble Decision Aid (CoWEDA)

Article

Full-text available

Apr 2021

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 endurance times, which are the time intervals from initial exposure until the safety limits are reached. These safety limits correspond to conservative temperature thresholds that provide a warning of the approaching onset of frostbite and/or hypothermia. A validated six-cylinder thermoregulatory model is used to predict human thermal responses to cold while wearing different ensembles. The performance metrics, model, and a database of clothing properties were integrated into a user-friendly software application. CoWEDA is the first tool that allows users to build their own ensembles from the clothing menu (i.e., jackets, footwear, and accessories) for each body region (i.e., head, torso, lower body, hands, feet) and view their selections in the context of physiological strain and the operational consequences. Comparison of predicted values to skin and core temperatures, measured during 17 cold exposures ranging from 0 to −40°C, indicated that the accuracy of CoWEDA prediction is acceptable, and most predictions are within measured mean ± SD. CoWEDA predicts the risk of frostbite and hypothermia and ensures that a selected clothing ensemble is appropriate for expected weather conditions and activities. CoWEDA represents a significant enhancement of required clothing insulation (IREQ, ISO 11079) and wind chill index-based guidance for cold weather safety and survival.

Frostbite: Pathophysiology, Epidemiology, Diagnosis, Treatment, and Prevention

Article

Full-text available

Jan 2020

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 rewarmed unless the patient can remain in a warm environment; repeated freeze/thaw cycles cause further injury. Treatment involves rapid rewarming in a warm, circulating water bath 37°C to 39°C (99°F-102°F) or, if this is not possible, then contact with another human body. Thrombolytics show promise in the early treatment of frostbite. In the field, the depth and severity of the injury can be determined with laser Doppler ultrasound devices or thermography. In hospital settings, bone scintigraphy with single-photon emission computed tomography (SPECT) 2 to 4 days postinjury provides detailed information on the depth of the injury. Prevention is focused primarily on covering exposed skin with proper clothing and minimizing exposure to wind and moisture. The Generation III Extended Cold Weather Clothing System is an interchangeable 12-piece clothing ensemble designed for low temperatures and is compatible with other military systems. The Extreme Cold Vapor Barrier Boot has outer and inner layers composed of seamless rubber with wool insulation between, rated for low temperatures. The Generation 3 Modular Glove System consists of 11 different gloves and mitts with design features that assist in enhancing grip, aid in the use of mobile devices, and allow shooting firearms. Besides clothing, physical activity also increases body heat, reducing the risk of frostbite.

Successful resuscitation from accidental hypothermia of 11.8 C: where is the lower bound for human beings?

Article

Full-text available

Nov 2020
EUR J CARDIO-THORAC

We present the case of a 27-month-old boy who underwent accidental hypothermia to 11.8°C and was resuscitated with prolonged rewarming with extracorporeal membrane oxygenation without significant neurological impairments. This is probably the lowest temperature ever documented, at which a human being has been successfully resuscitated from accidental hypothermia after the long period of circulatory arrest. © The Author(s) 2020. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Frostbite injuries and our experience treatment in the Samarkand area Uzbekistan

Article

Full-text available

Aug 2020

Babur Shakirov

Cold injury remains one of the most complex and actual problems of emergency medicine. Frosting injuries are also observed in the regions with warm climate particularly in Uzbekistan able - bodies men suffer most often, 85-90% of them are admitted in the condition of alcohol intoxication. A retrospective review was performed of patients admitted to the Burn Department of the Centre of Emergency Medical Care with frostbite injury 92 individuals of 19 to 63 years of age. The data on each patient were collected including age, sex, period of injury, injuries of extremities, bacteriological investigations, along with general warming of victims, all patients were given intravenous injection of infusion spasm and to improve microcircula determination of the injury area and different general and local treatment. Treatment of these patients is very prolonged, expensive, frequently requiring crippling operations, resulting in disability.

European Resuscitation Council Guidelines 2021: Cardiac arrest in special circumstances

Article

Mar 2021
RESUSCITATION

These European Resuscitation Council (ERC) Cardiac Arrest in Special Circumstances guidelines are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the modifications required to basic and advanced life support for the prevention and treatment of cardiac arrest in special circumstances; specifically special causes (hypoxia, trauma, anaphylaxis, sepsis, hypo/hyperkalaemia and other electrolyte disorders, hypothermia, avalanche, hyperthermia and malignant hyperthermia, pulmonary embolism, coronary thrombosis, cardiac tamponade, tension pneumothorax, toxic agents), special settings (operating room, cardiac surgery, catheter laboratory, dialysis unit, dental clinics, transportation (in-flight, cruise ships), sport, drowning, mass casualty incidents), and special patient groups (asthma and COPD, neurological disease, obesity, pregnancy).

Extreme Cooling Rates in Avalanche Victims: Case Report and Narrative Review

Article

Mar 2021
HIGH ALT MED BIOL

Mittermair, Christof, Eva Foidl, Bernd Wallner, Hermann Brugger, and Peter Paal. Extreme cooling rates in avalanche victims: case report and narrative review. High Alt Med Biol 00:000-000, 2021. Background: We report a 25-year-old female backcountry skier who was buried by an avalanche during ascent. A cooling rate of 8.5°C/h from burial to hospital is the fastest reported in a person with persistent circulation. Methods: A case report according to the CARE guidelines is presented. A literature search with the keywords "avalanche" AND "hypothermia" was performed and yielded 96 results, and the last update was on October 25, 2020. A narrative review complements this work. Results: A literature search revealed four avalanche patients with extreme cooling rates (>5°/h). References of included articles were searched for further relevant studies. Nineteen additional pertinent articles were included. Overall, 32 studies were included in this work. Discussion: An avalanche patient cools in different phases, and every phase may have different cooling rates: (1) during burial, (2) with postburial exposure on-site, and (3) during transport. It is important to measure the core temperature correctly, ideally with an esophageal probe. Contributing factors to fast cooling are sweating, impaired consciousness, no shivering, wearing thin monolayer clothing and head and hands uncovered, an air pocket, and development of hypercapnia, being slender. Conclusions: Rescuers should be prepared to encounter severely hypothermic subjects (<30°C) even after burials of <60 minutes. Subjects rescued from an avalanche may cool extremely fast the more contributing factors for rapid cooling exist. After avalanche burial (≥60 minutes) and unwitnessed cardiac arrest, chances of neurologically intact survival are small and depend on rapid cooling and onset of severe hypothermia (<30°C) before hypoxia-induced cardiac arrest.

In pursuit of the Unicorn

Article

Nov 2020

This short review was prompted by The Physiological Society's recent online symposium on variability. It does not deal with a specific methodology, but rather with the myth that certain environmentally-induced clinical conditions can be identified, quantified, simplified and monitored with a single methodology. Although this might be possible with some clinical conditions, others resist the prevailing reductionist approach of minimizing rather than exploring variation in pathogenesis and pathology, and will not be understood fully until the variation in cause and effect are embraced. This is likely to require comprehensive methodologies and collaboration.

Outcomes of patients suffering unwitnessed hypothermic cardiac arrest rewarmed with extracorporeal life support: A systematic review

Article

Sep 2020
ARTIF ORGANS

Introduction: Prolonged cardiac arrest (CA) may lead to neurologic deficit in survivors. Good outcome is especially rare when CA was unwitnessed. However, accidental hypothermia is a very specific cause of CA. Our goal was to describe the outcomes of patients who suffered from unwitnessed hypothermic cardiac arrest (UHCA) supported with Extracorporeal Life Support (ECLS). Methods: We included consecutive patients' cohorts identified by systematic literature review concerning patients suffering from UHCA and rewarmed with ECLS. Patients were divided into four subgroups regarding the mechanism of cooling, namely: air exposure; immersion; submersion; and avalanche. A statistical analysis was performed in order to identify the clinical parameters associated with good outcome (survival and absence of neurologic impairment). Results: A total of 221 patients were included into the study. The overall survival rate was 27% . Most of the survivors (83%), had no neurologic deficit. Asystole was the presenting CA rhythm in 48% survivors, of which 79% survived with good neurologic outcome. Variables associated with survival included the following: female gender (p<0.001); low core temperature (p=0.005); non-asphyxia-related mechanism of cooling (p<0.001); pulseless electrical activity as an initial rhythm (p<0.001); high blood pH (p<0.001); low lactate levels (p=0.003); low serum potassium concentration (p<0.001); and short resuscitation duration (p=0.004). Conclusions: Severely hypothermic patients with unwitnessed CA may survive with good neurologic outcome, including those presenting as asystole. The initial blood pH, potassium and lactate concentration may help predict outcome in hypothermic CA.

Integrative crosstalk between hypoxia and the cold: Old data and new opportunities

Article

Jun 2020

New findings: What is the topic of this review? The aim is to examine the influence of hypoxia on thermoregulatory and cardiovascular control in the cold. What advances does it highlight? Exposure to hypoxia seems to alter both thermoregulatory and cardiovascular control, but these conclusions are based on limited data and this review highlights the need for future research in this area. Abstract: Cold stress and hypoxia have been the subject of research for decades; however, humans often encounter these stressors together, such as in the alpine environment. Therefore, this review summarizes previous data with respect to the influence of hypoxia on thermoregulatory and cardiovascular control in the cold and presents new ideas for the future. Altogether, little to no evidence is available on the integrative and adaptive mechanisms about how the human body regulates heat conservation, oxygen delivery, and maintenance of blood pressure. This article is protected by copyright. All rights reserved.

Previous recreational cold exposure does not alter endothelial function or sensory thermal thresholds in the hands or feet

Article

May 2020

New findings: What is the central question of this study? Does recreational cold exposure result in cold sensitivity and is this associated with endothelial dysfunction and impaired sensory thermal thresholds? What is the main finding and its importance? Previous cold exposure was correlated with foot cold sensitivity which may indicate the development of a subclinical non-freezing cold injury. Endothelial function and thermal detection were not impaired in cold sensitive individuals therefore further research is required to understand the pathophysiology of subclinical and clinical forms of non-freezing cold injury. Abstract: This study investigated whether cold sensitive (CS) individuals, who rewarm more slowly following a mild cold challenge, have impaired endothelial function and sensory thermal thresholds (STT) and whether this was related to reported cold exposure. Twenty seven participants with varying previous cold exposure undertook three tests: STT: warm and cold STT of the fingers and dorsal foot. Endothelial function: measurement of cutaneous vascular conductance (CVC) during iontophoresis of acetylcholine on the forearm, finger and foot. CS test: involving immersion of a foot for 2 minutes in 15°C water followed by 10 minutes of rewarming in 30°C air. Toe skin temperature (Tsk) measured during the CS test was used to form a CS group (< 32°C prior to and 5 minutes after immersion) and an otherwise closely matched CONTROL group (Tsk > 32°C; n = 9 [4 women] for both groups). A moderate relationship was found between cold exposure ranking and Tsk rewarming (r = 0.408, P = 0.035, n = 27) but not STT or endothelial function. Tsk and blood flow were lower in CS compared to CONTROL before and after foot immersion (Tsk, mean [sd]: 30.3 [0.9]°C v 34.8 [0.8]°C; 27.9 [0.8]°C v 34.3 [0.8]°C; P < 0.001. CVC: 1.08 [0.79] flux.mmHg-1 v 3.82 [1.21] flux.mmHg-1 ; 0.79 [0.52] flux.mmHg-1 v 3.45 [1.07] flux.mmHg-1 , n = 9, P < 0.001 respectively). However, no physiologically significant differences were observed between groups for endothelial function or STT. A moderate correlation between previous cold exposure and toe Tsk rewarming following foot immersion was observed however, CS was not associated with impaired endothelial function or reduced thermal detection. This article is protected by copyright. All rights reserved.