Transcript ACSM 2005 Exercise in the Cold

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
Does cold change the FITT principle?
Safety and prevention of cold injuries
CV disease & asthma
How cold is cold?
Ambient temperature
Wind Chill Temperature Index
National Weather Service, 2001
Immersion
Cold-Wet
Protection Against the Cold
•Physiological Adjustments
Vasoconstriction (Heat Conservation)
Shivering (Heat Production)
•Behavioral Thermoregulation
Wear Clothing
Seek Shelter
Utilize Heat Sources
Exercise
S = M - (±W) ± R ± C ± K ± E
Gisolfi & Wenger
Cold
alpha-adrenergic mediated constriction
reduces cutaneous blood flow
lower skin temperature
lower skin to ambient temperature gradient
reduced heat loss
INSULATION
TRUNK AND
HEAD
ADJUSTABLE CIRCULATORY
INSULATION
MR
MEX
MTG
ADJUSTABLE SURFACE
FILM INSULATION
TSK
CT
C1
TA
TRUNK
CORE
SKIN
FIXED INSULATION
FAT AND BODY STRUCTURE
EXTREMITIES
MUSCLE
BLOOD
FLOW
ADJUSTABLE PERIPHERAL
CIRCULATORY INSULATION
TSK
ADJUSTABLE SURFACE
FILM INSULATION
TA
MEX
MTG
C2
TM
EXTREMITY
CORE
SKIN
FIXED INSULATION
FAT AND BODY STRUCTURE
TC - TSK
TSK - TA
Lowering Of Peripheral Skin Temperatures
Causes Cold-induced Vasodilation
Nailbed
Pad
Blood Flow
1500
20
1000
15
10
500
Blood Flow (mV)
Skin Temperature (oC)
40
5
0
0
-5
0
5
10
15
20
25
30
Time (min)
O’Brien, J. Appl. Physiol., 2005
Metabolic Heat Production (W·m-2)
Shivering
200
1500
#
150
Tcore = 35.8°C
Tskin = 21°C
100
50
0
30
60
90
120
Time (min)
Castellani et al., J. Appl.Physiol., 1998
Comparison Of Metabolic Costs
16
14
12
METS
10
8
6
4
2
0
REST
SHIVERING
12°C Tsk
35°C core
6 MPH
JOG
MAX
EXERCISE
Shivering Is Related To Exercise Intensity
OXYGEN UPTAKE
AMBIENT CONDITIONS
TEMPERATE
COLD
~ 60% VO2max
POWER OUTPUT
Stroke Volume Increases During
Cold Air Exposure (5°C)
STROKE VOLUME (L)
125
100
75
0
30
60
90
EXPOSURE TIME (min)
Muza et al. , 1988
Heart Rate (bpm)
130
▼
▲
22.5°C
▼
▲
100
5.5°C
70
▲
200
▼
600
1000
1400
Oxygen Uptake (ml/min)
Hanna et al., 1975
Cold Vasoconstriction Increases TPR And BP
Epstein et al., NEJM, 1969
Increased Afterload And Increased Work Of Heart
Epstein et al., NEJM, 1969
Cold Acclimitization
Young, Handbook of Physiology, 1996
Cold Acclimation Effects On Skin Temperature
Skin temperature (°C)
3
5
P
R
E
A
C
C
L
I
M
A
T
I
O
N
P
O
S
T
A
C
C
L
I
M
A
T
I
O
N
3
0
2
5
2
0
1
5
0
3
0
6
0
9
0
Exposure Time (min)
Young et. al, 1986
Physiological Responses:
Modifiers
Individual-Related Factors
•Low Body Fat
•Fatigue & Fitness
•Dehydration
•Age
•Alcohol
•Sleep Loss
•Nicotine
•Illness
•Poor Nutrition
•Poor Clothing/Equipment
•Prior Cold Injury
Less Subcutaneous Fat = Greater Fall
In Rectal Temperature
FALL IN RECTAL TEMPERATURE (°C)
2.5
2.0
1.5
1.0
0.5
0.0
20
10
6.7
5
4
MEAN SKINFOLD THICKNESS (mm-1)
Keatinge, 1960
Metabolic Rate During Cold Air Exposure
As A Function Of Physical Fitness
1°C
M [ W·m-2 ]
200
160
120
80
40
60
80
.
VO2 max [ ml· min-1·kg-1 ]
Bittel et. al, 1988
Skin Temperature During Cold Air Exposure
As A Function Of Physical Fitness
28
Tsk [ °C ]
1°C
25
22
19
40
60
80
.
VO2 max [ ml· min-1·kg-1 ]
Bittel et. al, 1988
Dehydration has no effect on
whole-body thermoregulation
RECTAL TEMPERATURE ( OC)
3
7
.
5
E
U
H
Y
D
R
A
T
I
O
N
H
Y
P
E
R
O
S
M
O
T
I
C
H
Y
P
O
H
Y
D
R
A
T
I
O
N
I
S
O
S
M
O
T
I
C
H
Y
P
O
H
Y
D
R
A
T
I
O
N
3
7
.
0
3
6
.
5
3
6
.
0
0
3
0
6
0
9
0
1
2
0
T
I
M
E
(
M
I
N
)
O’Brien et al., J. Appl. Physiol. 1998
Hypohydration & CIVD
Temperature (oC)
40
euhydration
20
15
Pad
10
Nailbed
5
0
0
10
20
30
Time (min)
O’Brien & Montain, J. Appl. Physiol., 2003
Aging Blunts The CIVD Response To Cold
FINGER SKIN TEMPERATURE
°C
1
6
6
1
7
0
y
r
s
5
1
6
0
y
r
s
4
1
5
0
y
r
s
3
1
4
0
y
r
s
2
0
3
0
y
r
s
1
5
1
4
1
3
1
2
1
1
1
0
9
8
7
6
5
4
0
5
1
0
1
5
2
0
2
5
3
0
IMMERSION DURATION, min
Mathew et. al, 1986
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
Does Cold-Weather Affect How
We Prescribe Exercise?
Cardiovascular
Resistance Exercise
Flexibility
Safety of Participants
Cardiovascular Conditioning
No change
Frequency
Intensity
Time
Type
To achieve
same HR at low
work, need to work harder
No change
No change
Heart Rate Related To Exercise Intensity?
AMBIENT CONDITIONS
Heart Rate
TEMPERATE
COLD
??
POWER OUTPUT
Risk Reduction
&
Prevention of Cold Injuries
Risk Management
5. Supervise
Evaluate &
Correct
Controls
4. Implement
Controls
Adopt &
Implement
Controls into
Plans
1. Identify
Hazard
How cold is
it?
2. Assess Hazards
•Analyze Mission
Requirements
•Determine Uniform &
Equipment
•Identify High Risk
People
3. Develop
Controls
Implement
Cold
Mitigation
Hypothermia Avoidance
Risk Factors
Decreased Heat
Production
Training Factors
Inactivity
Fatigue
Energy depletion
Endocrine
Hypopituitarism
Hypoadrenalism
Hypothyroidism
Hypoglycemia
Diabetes
Increased Heat
Loss
Environmental
Factors
Immersion
Rain
Wet clothing from
sweat
Wind
Erythrodermas
Burns
Psoriasis
Icthyosis
Exfoliative
dermatitis
Sunburn
Iatrogenic
Emergency birth
Cold infusions
Heat illness
treatment
Impaired
Thermoregulation
Peripheral Failure
Trauma
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
abuse
Miscellaneous
Clinical States
Infection
Renal failure
Cancer
Exercise in
the Rain
Thompson & Hayward, 1996
Cold-Weather Clothing
Creating a microenvironment
Clothing Principles
• Insulation
• Use loose layering to trap air
• Keep clothing dry
• Ventilation
• Avoid overheating
• Evaporate moisture
• Environmental Protection
• Windproof, waterproof
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
Cold Weather Clothing System
Clothing Requirements
10
9
Clothing Insulation (clo)
8
7
6
1 Met
5
2 Mets
4
3 Mets
3
4 Mets
2
1
5 Mets
0
-40
-20
0
20
40
60
Temperature (°F)
ISO, 1993
Example: 3 METS, 0°F, what clo needed?
10
9
Clothing Insulation (clo)
8
7
6
1 Met
5
2 Mets
4
3 Mets
3
4 Mets
2
1
5 Mets
0
-40
-20
0
20
Temperature (°F)
40
60
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
Frostbite Avoidance
Wind Chill Temperature Index
National Weather Service, 2001
Does finger respond to exercise in cold (-10°C)?
Finger Temperature (°C)
28
No Wind
Wind @ 1 m·s-1
Wind @ 5 m·s-1
26
24
22
20
18
Dexterity Threshold
16
14
12
10
200
220
240
260
280
300
320
340
360
Metabolic Rate (Watts)
Mäkinen et al. Comp. Physiol. Biochem., 2001
Does nose respond to exercise in cold (-10°C)?
Skin Temperature (°C)
18
16
14
Nose-no wind
Nose - 1 m·s-1
Nose - 5 m·s-1
12
10
8
6
4
2
0
220
350
Metabolic Rate (Watts)
Gavhed et al. Int. J. Biometerol., 2003
Caloric Requirements
10-40% higher (?)
Why?
•Expend more energy - combination of clothing &
equipment & terrain
•Shivering if get cold enough
Castellani et al., USARIEM Technical Note 02-2
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)
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
Exercising in the Cold
with Cardiovascular Disease
Mean % Increase in Mortality
for each 1°C fall from 18°C air
2.5
2.0
1.5
1.0
0.5
0.0
South
Finland
London
Athens
Palermo
EuroWinter Group, Lancet, 1997
How could the cold physiologically increase risk?
Coronary
Blood Flow
Work of the Heart
Requirements for CBF
Noble, Physiology 2004
Change in Coronary Blood Blow?
Change in Coronary Circulation After Cold Pressor Test
40
% Change
30
20
10
0
-10
-20
-30
Coronary
Rate
X-Sectional
Pressure Product
Area
Coronary
Blood Flow
Reis et al., CHEST, 1998
Cold increases Rate Pressure Product
-7.5°C air
157
144
Brown & Oldridge, MSSE, 1985
Cold decreases time to reach anginal threshold
-7.5°C air
7.8
100% of patients
with CAD had
an earlier onset
of angina
6.1
Brown & Oldridge, MSSE, 1985
Local Cooling
Facial Cooling
19 patients with CAD
Angina in 5 patients
Myocardial hypoxia in 7 patients
Neill et al. Am. J. Med., 1974
Local Cooling
Ice Cube Holding
Exercise tolerance until angina onset
45
# of trips on steps
40
35
30
25
20
47°F air
73°F air
73°F air +
ice cube
Friedman et al., Am. Heart J., 1944
Swimming and Angina
Supine Cycling
Swimming (18°C)
Patient Angina
ST
Dep.
HR
Angina ST
Dep.
HR
1
2
Yes
115
0
Yes
96
2
6
Yes
80
0
Yes
88
3
6
Yes
82
0
Yes
60
4
6
Yes
75
0
Yes
83
5
5
Yes
115
4
Yes
105
6
0
No
-
0
No
-
7
0
No
-
0
No
-
8
5
Yes
93
0
Yes
86
Magder et al., Circulation, 1981
Shoveling
Isometric Component
Valsalva Maneuver
Upper Body Exercise
Cardiac Demands in Healthy People
10
8
150
6
100
METS
Systolic Blood Pressure
200
4
50
2
0
0
Treadmill
Arm
Crank
Snow
Snowblower
Shoveling
Franklin et al., JAMA, 1995
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
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
Rate Pressure Product (HR X SBP)
CV Disease - Summary
Cold
Anginal Threshold
Warm
Exercise Intensity
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
Narrowing of intrathoracic airways
Cold air enhances EIB vs. warm air
- 3-10% Asymptomatic athletes
- 70-80% Asthmatics
Giesbrecht, 1995; Zeitoun et al., 2004
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
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
•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
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
“Man in a cold environment
is not necessarily a cold man”
David Bass, 1958
USARIEM Physiologist