Prevention of Cold Injuries during Exercise

John W. Castellani, Ph.D., FACSM; Andrew J. Young, Ph.D., FACSM; Michel B. Ducharme, Ph.D.; Gordon G. Giesbrecht, Ph.D.; Ellen Glickman, Ph.D., FACSM; Robert E. Sallis, M.D., FACSM

Disclosures

March 01, 2010

Abstract and Introduction

Abstract

It is the position of the American College of Sports Medicine that exercise can be performed safely in most cold-weather environments without incurring cold-weather injuries. The key to prevention is use of a comprehensive risk management strategy that: a) identifies/assesses the cold hazard; b) identifies/assesses contributing factors for cold-weather injuries; c) develops controls to mitigate cold stress/strain; d) implements controls into formal plans; and e) utilizes administrative oversight to ensure controls are enforced or modified. The American College of Sports Medicine recommends that: 1) coaches/athletes/medical personnel know the signs/symptoms and risk factors for hypothermia, frostbite, and nonfreezing cold injuries, identify individuals susceptible to cold injuries, and have the latest up-to-date information about current and future weather conditions before conducting training sessions or competitions; 2) cold-weather clothing be chosen based on each individual's requirements and that standardized clothing ensembles not be mandated for entire groups; 3) the wind-chill temperature index be used to estimate the relative risk of frostbite and that heightened surveillance of exercisers be used at wind-chill temperatures below −27°C (−18°F); and 4) individuals with asthma and cardiovascular disease can exercise in cold environments, but should be monitored closely.

Introduction

People exercise and work in many cold-weather environments (low temperature, high winds, low solar radiation, rain/water exposure). For the most part, cold-weather is not a barrier to performing physical activity. Successful and safe exploration to the North and South Poles, and swimming for hours across the English Channel are clearly indicative that human beings can perform in extreme cold. Many factors, including the environment, clothing, anthropometric factors, health status, age, and exercise intensity, interact to determine if exercising in the cold elicits additional physiological strain and injury risk beyond that associated with the same exercise done under temperate conditions. In many cases, exercise in the cold does not increase strain or injury risk, and David Bass, the noted environmental physiologist, once stated that "man in the cold is not necessarily a cold man."^[6] However, there are scenarios (immersion, rain, low ambient temperature with wind) where whole-body or local thermal balance cannot be maintained during exercise-cold stress, contributing to cold-weather injuries and diminished exercise capability and performance. Furthermore, exercise-cold stress can increase the risk of morbidity and mortality in certain susceptible populations.^[45,84,98]

This position statement provides guidance to enable people exercising in the cold to avoid cold-weather injuries. Objectives of the Position Stand are to: 1) define the most common cold-weather injuries expected during exercise-cold stress, 2) present factors that increase the risk of sustaining a cold-weather injury, and 3) provide appropriate guidance to prevent or lower susceptibility to cold-weather injuries. Cold-weather outcomes or cold-related injuries include hypothermia, frostbite, cold urticaria, and nonfreezing cold injuries, and also outcomes secondary to being in the cold including cold-induced asthma and acute cardiovascular events such as myocardial infarction. Cold stress refers to environmental and/or personal conditions that tend to remove body heat and decrease body temperature. Cold strain refers to physiological and/or psychological consequences of cold stress. This position statement is applicable to all athletic activities in the cold including those that are short-term (jogging, running, skiing, biathlon, speed skating, outdoor hockey), medium term (adventure racing, triathlon, marathons, long-distance swimming), and long-term (mountaineering and expeditions).

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Table 1. Strength of recommendation taxonomy.
Strength of Recommendation	Definition
A	Recommendation based on consistent and good quality patient oriented evidence (morbidity, mortality, symptom improvement, cost reduction, and quality of life).
B	Recommendation based on inconsistent or limited-quality patient-oriented evidence.
C	Recommendation based on consensus, usual practice, opinion, disease-oriented evidence (measures of intermediate, physiologic, or surrogate end-points that may or may not reflect improvements in patient outcomes), or case series for studies of diagnosis, treatment, prevention, or screening.

Table 2. Core temperature and associated physiological changes that occur as core temperature falls. Individuals respond differently at each level of core temperature.
Stage	Core Temperature		Physiological Changes
Stage	°F	°C	Physiological Changes
Normothermia	98.6	37.0
Mild	95.0	35.0	Maximal shivering, increased blood pressure
	93.2	34.0	Amnesia; dysarthria; poor judgment; behavior change
	91.4	33.0	Ataxia; apathy
Moderate Hypothermia	89.6	32.0	Stupor
	87.8	31.0	Shivering ceases; pupils dilate
	85.2	30.0	Cardiac arrhythmias; decreased cardiac output
	85.2	29.0	Unconsciousness
Severe Hypothermia	82.4	28.0	Ventricular fibrillation likely; hypoventilation
	80.6	27.0	Loss of reflexes and voluntary motion
	78.8	26.0	Acid-base disturbances; no response to pain
	77.0	25.0	Reduced cerebral blood flow
	75.2	24.0	Hypotension; bradycardia; pulmonary edema
	73.4	23.0	No corneal reflexes; areflexia
	66.2	19.0	Electroencephalographic silence
	64.4	18.0	Asystole
	59.2	15.2	Lowest infant survival from accidental hypothermia
	56.7	13.7	Lowest adult survival from accidental hypothermia

Table 3. Predisposing factors for hypothermia based on cause. Table drawn from data presented in.^[31,143]
Decreased Heat Production	Increased Heat Loss	Impaired Thermoregulation	Miscellaneous Clinical States
Training factors Inactivity Fatigue Energy depletion Lack of sleep Endocrine Hypopituitarism Hypoadrenalism Hypothyroidism Hypoglycemia Diabetes Age (young & old)	Training factors Immersion Rain Wet clothing from sweat Wind Fatigue Low body fat Age (young & old) Erythrodermas Burns Psoriasis Icthyosis Exfoliative dermatitis Sunburn Iatrogenic Emergency birth Cold infusions Heat illness treatment Open wound	Peripheral failure Trauma Infection Neuropathies Acute spinal cord transection Central failure Central nervous system (CNS) lesions and trauma Stroke Subarachnoid hemorrhage Hypothalamic dysfunction Parkinson's disease Multiple sclerosis Pharmacologic Toxicologic Drug and alcohol buse	Infection Renal failure

Table 4. Approximate clothing insulation of various representative clothing ensembles that may be worn in cold weather.^[89] Values are tabulated from measurements on copper manikins.^[89] Insulation values provided in units of clo and SI units.
Clothing Ensemble	Clothing Insulation (I_cl)
Clothing Ensemble	Clo	m² · °C · W⁻¹
Shirt, light-weight trousers, socks, shoes, underwear briefs	0.6	0.095
Shirt, trousers, jacket, socks, shoes, underwear briefs	1	0.155
Windproof, waterproof jogging suit (shell jacket and pants), T-shirt, briefs, running shorts, athletic socks, athletic shoes	1.03	0.160
Fleece long-sleeve shirt, fleece pants, briefs athletic socks, athletic shoes	1.19	0.184
Lightweight jacket, thermal long underwear top and bottoms, briefs, shell pants, athletic socks, athletic shoes	1.24	0.192
Lightweight jacket, long sleeve fleece shirt, fleece pants, underwear briefs, shell pants, athletic socks, athletic shoes	1.67	0.259
Ski jacket with detachable fiberfill liner, thermal long underwear bottoms, knit turtleneck, sweater, fiberfill ski pants, knit hat, goggles, mitten shell with fleece glove inserts, thin knee-length ski socks, insulated waterproof boots	2.3	0.357
Extreme cold weather down-filled parka with hood, shell pants, fiberfill pants liner, thermal long underwear top and bottoms, sweat shirt, mitten shell with inner fleece gloves, thick socks, insulated waterproof boots	3.28	0.508
Extreme cold weather expedition suit with hood (down—filled, one—piece suit), thermal long underwear top and bottoms, sweat shirt, mittens with fleece liners, thick socks, insulated waterproof boots	3.67	0.569

Table 5. Predisposing factors for frostbite and peripheral cold injury. Table drawn from data presented in references.^{[24,32,33,44,94,106]}
Environmental	Mechanical	Physiological	Psychological
Temperature Wetness Exposure duration Wind chill Altitude POLs (petroleum, oil, lubricants) Contact with metals	Constrictive clothing Inadequate clothing & shelter Tight boots Cramped positioning	Hypothermia Race Sex Wet skin Prior peripheral cold injury Trauma Erythrodermas Hyperhidrosis Hypoxia Smoking Energy depletion Poor physical conditioning Hypotension Atherosclerosis Raynaud's syndrome Vasospastic disorders Diabetes Shock Vasoconstrictor drugs	Severe mental stress

Table 6. American College of Sports Medicine prevention of cold injuries during exercise Position Stand evidence statements.
Section Heading	Evidence Statement	Evidence Category
Hypothermia
	Exercising in water and rain significantly increases the risk for developing hypothermia.	A
	Individuals with high combined values of subcutaneous fat thickness, % fat, and muscle mass can maintain core temperature better than individuals with less fat and muscle.	B
	Core temperature responses to cold exposure between average men and women are primarily attributable to differences in body composition and anthropometry.	C
	Older individuals (G 60 yr) are at an increased risk of hypothermia due to blunted physiological and behavioral responses to cold. Children are at a greater risk of hypothermia than adults due to differences in body composition and anthropometry.	B
	Hypoglycemia impairs shivering and increases the risk for hypothermia.	B
	Physical fitness and training, per se, do not improve thermoregulatory responses to cold. Physical fitness does allow someone to exercise for a longer period at a higher metabolic rate, and may contribute to maintenance of normal core temperatures.	C
Prevention strategies for hypothermia
	Clothing insulation requirements during exercise are a function of metabolic rate and ambient temperature. Layering provides the most flexibility to adjust insulation to prevent sweating, over-heating, under-dressing, and remaining dry in wet conditions.	C
	Cold environments can increase energy expenditures and may cause fluid losses; dehydration does not impair vasoconstriction or shivering, thus dehydration does not increase susceptibility to cold injuries.	C
Prevention strategies for frostbite
	The risk of frostbite is less than 5% when the ambient temperature is above −15-C (5-F), but increased safety surveillance of exercisers is warranted when the WCT falls below −27-C (−18-F) since, in those conditions, frostbite can occur in 30 minutes or less in exposed skin.	C
Cold-related injuries
	Winter athletes, especially those exercising at high intensities and ventilation rates and in indoor ice rinks, have a higher incidence of EIB than the general population. Breathing dry air and skin/facial cooling act in synergy to trigger exercise-induced bronchospasm during winter activities. Indoor pollutants are also a trigger for EIB.	C
	Patients with CAD must use caution when exercising/working in the cold and should be knowledgeable of angina symptoms. Swimming in cold water may not be a good choice because it can potentially mask symptoms of angina.	C