What are the physiological concerns of exercising in a
cold environment? What preventative measures need to
be taken to avoid negative outcomes?
Exercising in the cold is not an attractive option for many athletes; however, defining what represents cold
is
difficult and is not standard for all events.
If the exercise is prolonged and undertaken at a moderate intensity, environmental temperatures around
52F can be an advantage. If the intensity is lower than this value and the individual does not generate
sufficient metabolic heat to offset the effects imposed by the cold environment, then temperatures of 52F
can be detrimental to performance. Similarly, when the performance involves dynamic explosive
contractions, then a cold ambient temperature can have a negative influence.
Additional factors such as the exercising medium, air or water, and the anthropometric characteristics of
the athlete will also make a difference to the strategies that can be adopted to offset any negative impact
of a cold environment on performance.
Sufficient
protection
prevents
cooling.
However,
protection
itself
may
cause
unwanted,
adverse
effects. The problem is
illustrated
Statistics
It is evident that there is a pronounced effect of cold on muscular
function and performance. Cooling of muscle tissue reduces blood
flow and slows down neural processes like transmission of nerve
signals and synaptic function.
In addition, viscosity of tissues increases, resulting in higher
internal friction during motion.
Isometric force output is reduced by 2% per °C of lowered muscle
temperature. Dynamic force output is reduced by 2 to 4% per °C
of lowered muscle temperature. In other words, cooling reduces
the force output of muscles and has an even greater effect on
dynamic contractions.
Cooling of the core may also have a direct effect on the
contractility of the heart muscle.
Work capacity, as measured by maximal aerobic capacity,
decreases by 5 to 6% per °C lowered core temperature. Thus,
endurance may deteriorate rapidly as the practical consequence of
the lowered maximal capacity and with an increased energy
requirement of muscular work.
Estimated gross effects on manual performance at
different levels of hand/finger temperature.
Phase
Core temperat Physiological reactions Psychological
ure (°C)
reactions
Normal
37
Normal body temperature Thermoneutral sensation
36
Vasoconstriction, cold
hands and feet
Discomfort
35
Intense shivering,
reduced work capacity
Impaired judgement,
Phase
Core te Physiological Psychological
mperatu reactions
reactions
disorientation,
apathy
re (°C)
34
Fatigue
Conscious
Normal
37
Normal body Thermoneutr
temperature al sensation
36
Vasoconstricti Discomfort
and responsive
on, cold
33
Fumbling and stumbling
Mild hypothermia
Moderate hypother 32
mia
Human responses to cooling:
Indicative reactions to different levels
of hypothermia
hands and
feet
Mild
35
hypothermi
Intense
shivering,
Impaired
judgement,
Muscle rigidity
a
reduced work disorientatio
Progressive
unconsciou
capacity
n, apathy
sness, hallucinations
34
Fatigue
Conscious
Faint breathing
ve
Consciousness
clouds
33
Fumbling and
and responsi
31
30
29
Severe hypothermia 28
27
25
Stuporous
Moderate h 32
No nerve reflexes, heart
rate slow and almost
unnoticeable
ypothermia
31
Death due to ventricular
fibrillation or asystole
Muscle
rigidity
Progressive
unconsciousn
ess, hallucina
tions
Faint
breathing
Consciousnes
s clouds
30
Stuporous
29
No nerve
reflexes, heart
rate slow and
almost
unnoticeable
Severe
28
hypothermi
a
Heart
dysrhythmias
(atrial and/or
ventricular)
27
Pupils non
reactive
to light, deep
tendon
and superfici
al
reflexes abse
nt
25
Death due to
ventricular
fibrillation or
asystole
Heart dysrhythmias
(atrial and/or ventricular)
Pupils non reactive
to light, deep tendon
and superficial
reflexes absent
stumbling
Progressive cooling of the body results in a
number of physio-logical and mental
effects. Table indicates some typical
responses associated with different levels of
core temperature.
Graphics
Differentiate between cold AIR and cold WATER exposure – the key difference is that the heat LOSSES in
water are so much greater than on land, that you’re far less likely to develop any kind of hypothermia (low body
temperature) on land. In fact, water conducts heat about 25 times better than air. So, when water moves
across your skin you will lose heat more quickly compared to air simply because of its physical properties.
Perhaps the first, and maybe the most surprising
fact about cold water physiology, is that your
body has too much heat to become
hypothermic within about 30 minutes, no
matter how cold the water is! In other words, it is
not possible to get so cold that you’re in danger
unless you are in the water for more than about
30 minutes.
From this graph, you can see that even at water
temperatures of 0 degrees Celsius, 30 minutes
falls within the marginal zone, not the lethal zone.
Many would probably survive for close to an hour
– this is demonstrated by shipwreck victims, who
Linear regression of lower critical air and water
temperatures versus mean skinfold thickness.
Skinfold thickness reflects approximate range for a
double thickness of skin.
Swimming in the cold – a problem of breathing
and muscle weakness
It shows the BREATHING RATE in breaths per minute
against time in a person who stands in a cold shower
at 52F.
So the rate of breathing goes up from about 16
breaths per minute to 75 breaths per minute, within the
first 20 seconds. It then stays up at 40 breaths per
minute for the next few minutes. It is not difficult to see
how that would affect your ability to swim, because
your stroke rate would have to change substantially to
allow you just to breathe!
Humans are adaptable organisms, and just like we
make adaptations to things like marathon training, we
also make adaptations to stressors such as coldwater immersion. The data show that exposures to
cold water as short as three minutes in a 10 C
shower will attenuate the cold-shock response by
as much as 20-30%. In the graph, you can see the
same data, but this time, we’ve added in a
comparison with the breathing rate AFTER six 3minute-long exposures to the cold water.
So you can see that only six exposures is enough to
reduce the cold shock response by 20%. If you have
even longer exposures, you can bring it down by
50%. That is obviously a significant reduction, and the
implication is that swimming will be far easier if you
are simply adapted to the cold.
Performance in
air
The wind chill nomogram: interrelationships between ambient temperature and wind velocity, and perceptual
sensations and rate of heat loss (kcal × m 72 × h 71 ) from the skin. Under conditions of bright sunshine, cooling
is reduced by about 200 kcal × m 72 × h 71 . Expressions of relative comfort are based upon a lightly clad,
inactive individual. To convert kcal × m 72 × h 71 to W × m 72 , multiply by 1.163.
Connection to Exercise
Physiology
Voluntary physical activity can increase metabolic heat production more than shivering. Whereas maximal
shivering can elevate Vo2 (whole-body oxygen uptake) to about 2 liter/min, exercise can increase Vo2 to 5
liter/min or even higher. However, the effect of exercise on thermal balance depends on a complex
interaction among factors related to exercise intensity, environmental conditions, and mode of activity.
While exercise increases metabolic heat production, it also facilitates heat loss from the body by increasing
blood flow to the skin and active muscles. This flow enhances convective heat transfer from the central
core to peripheral shell. Thus, while metabolic heat production increases progressively as exercise intensity
increases, so too does heat loss due to increasing blood flow to muscle and skin. Also, limb movement
increases convective heat loss from the body surface by disrupting the stationary boundary layer of air or
water that develops at the skin surface in a still environment.
During submaximal exercise in the cold, Vo2 can
be higher than, or the same as in temperate
conditions, depending on the exercise intensity.
Figure schematically depicts the effect of cold
exposure on Vo2 during exercise over a range of
submaximal intensities. At low intensities, Vo2 is
higher in cold than in temperate conditions,
since metabolic heat production during lowintensity exercise is insufficient to maintain
core and skin temperatures high enough to
prevent the afferent stimulus for shivering.
This obviously has profound implications on ability to swim. And for all those who watched in despair as the character played by
Leonardo DiCaprio could not swim to safety in the movie Titanic, you now have a physiological explanation – he simply could not swim,
because his skin and muscles were too cold to contract normally! (Far be it for us to suggest that Hollywood portrayed that accurately!).
The principle remains, however – a good swimmer in warm water will be an average swimmer in the cold. And a weak swimmer in the
warm…well, that’s a recipe for trouble.
Epiphany
celebration
9 Myths About Exercising in the
Cold
Myth 1: Running in the cold can weaken your immune
system.
“This is true,” says Weiss. “Running and exercising in cold
weather is a double stressor for the body causing a greater
increase in nor-epinephrine and cortisol. This translates into
immune-depression and decreased ability to fight infection.” This
doesn't mean you can't run at all, though. To help keep your
immune system strong, he suggests decreasing the intensity
and duration of your outdoor workouts in cold weather.
Myth 2: Cold weather helps you lose weight.
Weiss says that while shivering can help to burn extra calories,
unless you spend all day sitting outside quivering (not
recommended), it’s not true that winter weather helps to aid
weight loss when compared to any other time of the year.
Myth 3: Cold weather makes you depressed.
“Not exactly true,” says Weiss. “Winter depression, aka
‘seasonal affective disorder’ (SAD), is not related to the
cold, but to light.” Because in some places it gets darker
earlier, many people aren’t exposed to enough
sunlight during the winter which can lead to feelings of
depression and sadness.
Myth 4: You need more sleep in the winter.
“This is not true,” says Weiss. “The pineal gland is
responsible for the sleep cycle and based on light not
temperature —in actuality the cold can keep you up longer.
As daylight fades, the pineal gland produces more
melatonin, which causes us to feel sleepy. In the morning,
the gland is instructed to stop producing the hormone,
which aids in waking up. We feel sleepier in the winter
because there’s less daylight, hence more melatonin.”
Myth 5: You shouldn’t exercise in the cold.
“This really depends on how cold, but for the most part this
myth is false,” says Weiss. “Almost everyone can exercise
safely during cold weather unless suffering from asthma, cv disease or Raynaud’s phenomenon. If the temperature
dips below zero degrees Fahrenheit (minus 17.8 Celsius)
or the wind chill is extreme, consider taking a break or
choosing an indoor exercise instead. If not, dress in layers
and decrease the duration of the workout.”
Myth 6: Cold weather makes you eat more.
Weiss says this “myth” is actually true. “Caloric intake tends
to increase as the weather turns colder,” he said.
“Increased melatonin levels may be a cause of increased
appetite. Furthermore, you tend to stay indoors more and
that can also lead to greater food intake.” He explained that
some researchers believe genetics and anthropology to be
additional factors that can cause an increase in food intake
during the winter. “We are genetically programmed to
conserve calories in the winter which in turn will give us
energy for the seasons when we need it more,” he said.
Myth 7: Injury recovery takes longer in the winter.
Weiss dubs this a total myth. “Unless you are living in the
wild, the wintertime should have no effect on your healing,”
he said. “I have helped professionals and Olympians heal
in the summer and winter equally. What’s more important is
seeing the macro view of your life and planning
accordingly.”
Myth 8: Drinking alcohol keeps you warm in cold
weather.
“True,” says Weiss. “Alcohol increases body temperature
acutely and a quick shot will definitely warm the body.”
However, he says that alcohol during exercise is bad idea
because, among other reasons, while your extremities will
become warmer temporarily, you will lose heat in your core
where it’s most important.
Myth 9: It’s OK to drink less water in the winter.
“If your winter experiences a cold climate, it’s always good
to go out of the way to hydrate for three reasons,” says
Weiss. “One, in the dry, cold climate we need extra water to
keep our mucous membranes moist as this helps ward off
infection. Second, in the winter you may not feel, hot,
parched and want to drink water because you feel cold. But
rest assured, just because you are not in a hot, sweaty
climate doesn’t mean you need less water (some actually
say you need more). Finally, greater core and peripheral
water level aids in the moisture of the skin and total blood
volume. This also helps prevent chapping, cracking,
opportunistic infection, and c-v function.”
References
1. Exercise in the Cold: Part II // A physiological trip
through cold water exposure
https://sportsscientists.com/2008/01/exercise-in-thecold-part-ii/
2. Physiology of Cold Exposure Andrew J.
Young1 Michael N. Sawka and Kent B. Pandolf
3. PHYSIOLOGICAL RESPONSES TO THE THERMAL
ENVIRONMENT W. Larry Kenney
4. https://www.theactivetimes.com/winter-workouts-9myths-about-exercising-cold
5. Exercise in cold - Mira Nimmo