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Prescribing Exercise for Cold-Weather Environments. John W. Castellani, Ph.D. Thermal & Mountain Medicine Division US Army Research Institute of Environmental Medicine Natick, MA 01760 [email protected] Outline. How cold is it? Physiological responses to cold

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slide1

Prescribing Exercise for

Cold-Weather Environments

John W. Castellani, Ph.D.

Thermal & Mountain Medicine Division

US Army Research Institute of Environmental Medicine

Natick, MA 01760

[email protected]

slide2

Outline

How cold is it?

Physiological responses to cold

Does cold change the FITT principle?

Safety and prevention of cold injuries

CV disease & asthma

slide3

How cold is cold?

Ambient temperature

slide4

Wind Chill Temperature Index

National Weather Service, 2001

slide7

Protection Against the Cold

  • Physiological Adjustments
  • Vasoconstriction (Heat Conservation)
  • Shivering (Heat Production)
  • Behavioral Thermoregulation
  • Wear Clothing
  • Seek Shelter
  • Utilize Heat Sources
  • Exercise
slide9

Cold

alpha-adrenergic mediated constriction

reduces cutaneous blood flow

lower skin temperature

lower skin to ambient temperature gradient

reduced heat loss

slide11

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slide12

Lowering Of Peripheral Skin Temperatures

Causes Cold-induced Vasodilation

O’Brien, J. Appl. Physiol., 2005

slide13

Shivering

Metabolic Heat Production (W·m-2)

Tcore = 35.8°C

Tskin = 21°C

Castellani et al., J. Appl.Physiol., 1998

slide14

METS

REST

6 MPH

JOG

SHIVERING

12°C Tsk

35°C core

MAX

EXERCISE

Comparison Of Metabolic Costs

slide15

Shivering Is Related To Exercise Intensity

AMBIENT CONDITIONS

TEMPERATE

COLD

OXYGEN UPTAKE

~ 60% VO2max

POWER OUTPUT

slide16

Stroke Volume Increases During

Cold Air Exposure (5°C)

STROKE VOLUME (L)

EXPOSURE TIME (min)

Muza et al. , 1988

slide17

130

22.5°C

Heart Rate (bpm)

100

5.5°C

70

Oxygen Uptake (ml/min)

200

600

1000

1400

Hanna et al., 1975

slide20

Cold Acclimitization

Young, Handbook of Physiology, 1996

slide21

Cold Acclimation Effects On Skin Temperature

Skin temperature (°C)

Exposure Time (min)

Young et. al, 1986

slide23

Individual-Related Factors

  • Low Body Fat
  • Fatigue & Fitness
  • Dehydration
  • Age
  • Alcohol
  • Sleep Loss
  • Nicotine
  • Illness
  • Poor Nutrition
  • Poor Clothing/Equipment
  • Prior Cold Injury
slide24

Less Subcutaneous Fat = Greater Fall

In Rectal Temperature

FALL IN RECTAL TEMPERATURE (°C)

10

5

4

6.7

20

MEAN SKINFOLD THICKNESS (mm-1)

Keatinge, 1960

slide25

Metabolic Rate During Cold Air Exposure

As A Function Of Physical Fitness

1°C

M [ W·m-2 ]

.

VO2 max [ ml· min-1·kg-1 ]

Bittel et. al, 1988

slide26

Skin Temperature During Cold Air Exposure

As A Function Of Physical Fitness

1°C

Tsk [ °C]

.

VO2 max [ ml· min-1·kg-1 ]

Bittel et. al, 1988

slide27

Dehydration has no effect on

whole-body thermoregulation

O’Brien et al., J. Appl. Physiol. 1998

slide28

Hypohydration & CIVD

euhydration

O’Brien & Montain, J. Appl. Physiol., 2003

slide29

Aging Blunts The CIVD Response To Cold

FINGER SKIN TEMPERATURE

°C

IMMERSION DURATION, min

Mathew et. al, 1986

slide30

Exercise Prescription

  • Enhance physical fitness
  • Promote health by reducing risk for
  • future development of disease
  • Ensure safety during participation in exercise

ACSM, Guidelines for Exercise Testing & Prescription, 4th Edition

slide31

Does Cold-Weather Affect How

We Prescribe Exercise?

Cardiovascular

Resistance Exercise

Flexibility

Safety of Participants

slide32

Cardiovascular Conditioning

No change

Frequency

Intensity

Time

Type

To achieve

same HR at low

work, need to work harder

No change

No change

slide33

Heart Rate Related To Exercise Intensity?

AMBIENT CONDITIONS

TEMPERATE

COLD

Heart Rate

??

POWER OUTPUT

slide34

Risk Reduction

&

Prevention of Cold Injuries

slide35

Risk Management

1. Identify Hazard

How cold is it?

  • 2. Assess Hazards
  • Analyze Mission Requirements
  • Determine Uniform & Equipment
  • Identify High Risk People

5. Supervise

Evaluate & Correct Controls

4. Implement Controls

Adopt & Implement Controls into Plans

3. Develop Controls

Implement Cold Mitigation

slide38

Exercise in

the Rain

Thompson & Hayward, 1996

cold weather clothing
Cold-Weather Clothing

Creating a microenvironment

clothing principles
Clothing Principles
  • Insulation
    • Use loose layering to trap air
    • Keep clothing dry
  • Ventilation
    • Avoid overheating
    • Evaporate moisture
  • Environmental Protection
    • Windproof, waterproof
layering fabrics
Layering & Fabrics

Inner layer – thin layer against the skin to wick moisture

Mid-layer – primary insulation

Outer shell – windproof, waterproof, breathable

Limited vapor transfer rate; Use pit zips, side zips to ventilate

Cotton – absorbs moisture; heavy / bulky when wet; slow to dry

Wool – absorbs moisture; heavy / bulky when wet; coarse fibers

resist compression thus retain insulation when wet

Polypropylene – fibers do not absorb any moisture - wicks by capillary action; lightweight; quick drying; melts in high heat

Polyester – treated to be hydrophobic; wicks moisture; lightweight; quick drying; melts in high heat

Nylon – absorbs moisture; wind resistant; quick drying

Leather – absorbs water, dries slowly. Treat for water repellency

slide45

Keys to Working in Cold Weather

No sweat

Remove & add layers

Be aware of weather changing

Know your athletes/clients limits

Encourage people to speak up

slide47

Wind Chill Temperature Index

National Weather Service, 2001

slide48

Does finger respond to exercise in cold (-10°C)?

Dexterity Threshold

Mäkinen et al. Comp. Physiol. Biochem., 2001

slide49

Does nose respond to exercise in cold (-10°C)?

Gavhed et al. Int. J. Biometerol., 2003

slide50

Caloric Requirements

10-40% higher (?)

  • Why?
  • Expend more energy - combination of clothing &
  • equipment & terrain
  • Shivering if get cold enough
slide52

Dehydration

  • How in Cold?:
  • Sweating
  • Lower thirst
  • Cold-induced diuresis
  • Respiratory losses
  • Conscious under-drinking
  • Poor water availability
  • Dehydration Causes:
  • Decreases Physical Work Ability
  • Degrades Cognitive function
  • Reduces Appetite
  • Reduces Alertness
  • Constipation
  • Kidney Ailments
  • Urinary Infections
clothing and the cold
Clothing provides a protective barrier (keeps cold out)

Clothing also keeps heat in – but usually inhibits sweat evaporation

Sweat losses of >1 L/hr are still common in very cold weather when heavily clothed (and therefore, dehydration is still a potential concern)

Clothing and the Cold
slide54

Monitoring Hydration

  • Watch out for:
  • Infrequent urination
  • Small volume of urine
  • Dark urine

Canteens and water containers can freeze

Camelbacks are susceptible, esp. tubing

Do not eat snow & ice (also watch out for potability)

  • Try to get warm beverages & hot meals

during extended stays

slide55

Exercising in the Cold

with Cardiovascular Disease

slide57

How could the cold physiologically increase risk?

Coronary

Blood Flow

Work of the Heart

Requirements for CBF

Noble, Physiology 2004

slide58

Change in Coronary Blood Blow?

Change in Coronary Circulation After Cold Pressor Test

Reis et al., CHEST, 1998

slide59

Cold increases Rate Pressure Product

-7.5°C air

157

144

Brown & Oldridge, MSSE, 1985

slide60

-7.5°C air

7.8

6.1

Cold decreases time to reach anginal threshold

100% of patients

with CAD had

an earlier onset

of angina

Brown & Oldridge, MSSE, 1985

slide61

Local Cooling

Facial Cooling

19 patients with CAD

Angina in 5 patients

Myocardial hypoxia in 7 patients

Neill et al. Am. J. Med., 1974

slide62

Local Cooling

Ice Cube Holding

Exercise tolerance until angina onset

Friedman et al., Am. Heart J., 1944

slide63

Swimming and Angina

Supine Cycling

Swimming (18°C)

Magder et al., Circulation, 1981

slide64

Shoveling

Isometric Component

Valsalva Maneuver

Upper Body Exercise

slide65

Cardiac Demands in Healthy People

Franklin et al., JAMA, 1995

slide66

Shoveling & Thermal Stress

in Low-Risk

Cardiac Patients

Cold = -8°C (18°F)

Neutral = 24°C (76°F)

Warm = 29°C (85°F)

No ST depression

No Angina

61% VO2peak

Sheldahl et al., MSSE, 1993

slide67

CV Disease - Summary

  • Increased mortality from CAD in winter,

especially in hypertensives

  • Whole body cold exposure lowers anginal threshold
  • Local cold exposure (face & hands)

lowers anginal threshold

  • Use of HR as a marker of exercise intensity

may be limited

  • Caution is warranted when swimming in cold pools

or the ocean

  • Shoveling is safe if exercise intensity is kept low
slide68

CV Disease - Summary

Cold

Rate Pressure Product (HR X SBP)

Anginal Threshold

Warm

Exercise Intensity

slide69

Exercise Prescription

  • Lower Exercise Intensity
  • Lower Target Heart Rate
  • Consider Testing with Arm Ergometry (occupational tasks)
  • Do Not Handle Cold Tools, Watch Out For Snowballs
  • Educate About Clothing For Cold Weather Exercise
  • Layering
  • No Sweating
  • Minimize Facial Cooling
  • Consult Your Client’s Physician
exercise induced bronchoconstriction
Exercise-Induced Bronchoconstriction

Narrowing of intrathoracic airways

Cold air enhances EIB vs. warm air

  • - 3-10% Asymptomatic athletes
  • 70-80% Asthmatics

Giesbrecht, 1995; Zeitoun et al., 2004

slide71

Possible mechanisms for

increased airways resistance

  • Airway smooth muscle contraction
  • Increased mucus production
  • Decreased mucociliary clearance
  • Vascular congestion
  • Epithelial damage and vascular leakage

Giesbrecht, Aviat. Space Environ. Med., 1995

slide72

Cold & Asthmatics

Skin & Head Cooling

Facial Cooling

lower with facial cooling

10.2% decrease

McFadden et al., 1997; Zeitoun et al., 2004

prevention of eib
Prevention of EIB
  • Training/acclimatization
  • (decrease in EIB in late winter)
  • Wear heat/moisture exchanger
  • 15-20 min. warm up
  • avoid polluted areas
  • follow physicians advice on medications
slide74

Information Sources

TB MED 508

Prevention And Management Of Cold Weather Injuries

Department of the Army, 2005

www.usariem.army.mil

Prevention of Cold Injuries During Exercise

ACSM Position Statement (in preparation)

Castellani, Young, Ducharme, Giesbrecht. Glickman, Sallis

slide75

“Man in a cold environment

is not necessarily a cold man”

David Bass, 1958

USARIEM Physiologist

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