hydrater-en-hivers

The importance of hydration in winter

22 January, 2013 | Written by Recuperat-ion Recuperat-ion

The cold: a cooling factor for the body

Article by David Padaré
In winter, the rider’s body faces much higher
thermal amplitude than in summer. Thermal amplitude refers to the temperature
difference, sometimes significant, when moving from one environment to another,
from one moment of the day to another or from one place to another. Thus the
thermal amplitude in winter is influenced by a higher temperature difference
between:
• Day and night
• Areas exposed to the sun and those in the
shade (the solar energy warms the air and surfaces)
• Areas exposed to the wind and areas that are
more protected (concept of “cold feeling”)
• Areas with snow and areas without (the
reverberation effect of the snow …)
In fact, the rider’s body is more susceptible
to cooling in winter. The cooling rate will be influenced by:
• The falling of the air temperature
• The humidity rate or hygrometry (influence
of the thermal conductivity of water)
• The intensity and frequency of the wind.
The thermal conductivity of an element refers
to its ability to conduct or exchange its own temperature to its environment
(exchange of heat or cold …). The thermal conductivity of water is more than 20
times that of the air. So a humid cold is much more “chilling” than a
dry cold, due to the thermal exchange that is enhanced by humidity.
Similarly, the wind exposure is a factor that increases
the thermal exchange and therefore the cooling rate of the body. In fact, the
wind prevents the body from maintaining its small thermal layer of warm air
between the skin and the hairs. This natural barrier normally helps the body
isolate its internal temperature.
What are the body’s natural mechanisms to fight against the cold?
The body reacts to the cold by
vasoconstriction, meaning a contraction of the blood vessels responsible for
irrigating the tissues. This reaction reduces the thermal exchange. Indeed, by
reducing the skin irrigation, the body decreases its heat loss through the
skin. The skin is less conductor of heat, increasing its insulating capability.
The body also reacts to the cold by increasing
the thermogenesis, meaning an increase in internal heat production. It operates
through:
–         
Shivering (involuntary contraction of skeletal muscles)
–         
A greater oxidation of the body fat under hormonal control (action of
adrenaline and noradrenaline)
But these two physiological adaptations
(vasoconstriction and shivering), by increasing the metabolic cost of the
activity, also contribute to increase the venous lactate and lower the lactate
threshold (first ventilatory threshold). The increase of the CO2 solubility at
low temperatures reinforces in this context the evolution towards acidosis.
Image
courtesy of Evgeni Dinev at FreeDigitalPhotos.net

Muscular work also helps maintain internal heat

Two activities can indirectly increase the
internal heat and thus provide a valuable calorific contribution to the body in
its fight against the cold:
• The muscular work: the muscular work is
based on the muscle contraction, which generates heat in the tissues involved
• The digestive work: the digestive work
generates a release of heat at the digestive organs and muscles (deep muscles
called smooth). The heat is 2 to 4 times higher for protein-rich foods than
other food (lipids, carbohydrates).
Which nutritional strategy to adopt when exercising in the cold?
All mechanisms used to fight against the cold
(natural or induced) consume more energy, water and electrolytes (in addition
to the usual requirements related to muscular work). Therefore they tend to
increase the depletion of energy, water and electrolytes from the body. Moreover,
the risk of dehydration is reinforced by the inhibitory action of the cold on
the antidiuretic hormone, which increases the emission of water and sodium
Building a strategy when exercising in the
cold means therefore seeking to compensate, progressively and at an equivalent
level, energy, fluid and electrolyte losses in the body:
–         
Compensating energy losses: through the consumption of high energy
density food combining carbohydrate ingredients (honey, cereals, flours, dried
fruits …), fat (almonds, walnuts, hazelnuts, chocolate …) and protein
(protein egg, milk or hemp …). This aspect is important because the cold
contributes to lowering the first ventilatory threshold. Having a snack every
45 minutes of activity is sufficient (1 cereal bar or almond or 1 gingerbread
…)
–         
Compensating water losses: through regular consumption of sports drinks,
usually more concentrated and enriched with electrolytes (sodium and
potassium). Intakes will be more regular (1 sip of 20ml every 5/10min)
Conclusion on the importance of
hydration in winter
The sports activity in winter causes water losses of 3 categories:
• The usual losses related to the muscular work
• The specific losses related to the thermoregulation
• The specific losses related to the inhibition of the antidiuretic
hormone
It is therefore essential to adopt a real hydration strategy before,
during and after sports activities during the winter season, without waiting
for the usual signals of thirst, which are less efficient during this period of
the year.

Information about the author:
David Padare is a dietician nutritionist specialized in preferred
disciplines such as endurance sports and outdoor running, trail running,
cycling, triathlon, swimming….
He accompanies many athletes in their diverse and varied challenges:
ultra trail, trails stages, marathons, 100kms, 24h….
Member of the AFDN (French Association of Dietitian Nutritionist) and
the nivernais network RESEDIA for the management of DIABETES and OBESITY, he
also put his knowledge to the treatment of pathologies such as obesity,
diabetes, heart disease, food allergies…
Find David in magazines such as Running Coach and Cyclo Coach
Cyclosport, Running attitude trail magazine, running 100%feminin, 
nutricycle.comcourirdeplaisir.com, nutritiondusportif, traileur outdoor zsport.com…..
Nuteoconsult is the structure founded to bring together expertise from
various backgrounds (diet, coach, mind trainer…) for one purpose: to provide
simple and clear answers to each level of practice.
Recuperat-ion – Hydration and Nutrition Experts

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