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Over many years the human body has had to evolve to adapt to changing climate and environment. We have all shivered when exposed to sudden cold as the body attempts to generate heat through muscle contractions. But what other processes occur in our bodies to adapt to cold and altitude?
Mechanisms for adaptation to cold involve managing blood flow, and metabolism changes such as burning brown fat, as well as shivering. Mechanisms for adaptation to altitude in the short term include faster and deeper breathing and a faster heartbeat. Long-term adaptation involves the production of extra hemoglobin for circulation.
Feel The Cold At The Beginning Of Winter
Most people notice that with the onset of winter, the first cold days feel particularly sharp. However, by spring, even if there is a particularly cold day, we don’t seem to feel it in the same way. Over the months our bodies have gradually adapted to the change in temperature so we can cope much better.
The body has evolved to adapt to heat and altitude more effectively than the cold. No one understands why this is the case, but as a rule, humans do naturally gravitate to warmer, lowland regions rather than cold, elevated ones. Perhaps because we all originated from the plains of Africa.
The availability of shelter and food could be obvious reasons for this choice. So it may just be we have more experience as a race of adapting to warmer temperatures rather than cold.
Adaptation To Cold Is Slower
Key Takeaway: The process of adaptation to cold weather is slower in the human body than the same adaptation to heat. It involves a number of physiological and metabolic processes altering, which enable the body to operate more efficiently.
The changes include:
1. Blood Vessels
When the temperature drops below 50° F (10° C) this stimulates blood vessels to alternate between dilating and constricting. When dilated more blood flows to the surface capillaries, which is why you get rosy cheeks outside in winter.
The body is managing the compromise between keeping an adequate temperature for the internal organs, and the heat loss from the extremities. As your body becomes adapted to the cold it becomes more effective at managing this cycle.
When you are first exposed to the chill of winter, your body’s natural protective mechanism of shivering will be one of the first symptoms. It is an involuntary process, fuelled by glucose, and is created as the body contracts and relaxes muscles throughout the body in quick succession.
This action mimics the muscles as if they are working and thereby creates heat to keep the body warm. As the body adapts to cold weather the shivering response lessens because the movement of blood from internal organs to the extremities also becomes more efficient, so shivering is no longer required.
As the body adapts to cold weather the metabolism, which drives all the body’s processes, increases the resting rate of fat metabolism. In particular, brown fat can be utilized by the body, where it is metabolized to create body heat as it helps the body adapt to cold weather.
Skiers, climbers, and even natives of high-altitude regions all must cope with the effects of high altitude. For skiers and climbers, the effects are often much more short-lived, but they can still cause debilitating and dangerous consequences.
Tip: The problem of ascending to a higher altitude is down to the lack of oxygen, which decreases with the ascent. As the air pressure falls the higher you go so the density of molecules in the air is also lower.
At ground level, the air is made up of 78% nitrogen, 21% oxygen, and 1% other mixed gases. This ratio doesn’t vary with altitude, however, because the density of the air is so much lower higher up the 21% oxygen at altitude contains a lot fewer molecules.
At Higher Altitudes, The Air Pressure Is Lower With Less Oxygen
Consequently, humans must maximize the intake of this thinner air by breathing in more deeply (taking in more air) and breathing faster (exchanging the air more). This lack of oxygen is detected by organs called carotid bodies in the carotid arteries, which run down the side of your neck.
These manage the level of carbon dioxide, oxygen, and the acidity of the blood, so when low oxygen is detected, messages are sent to increase the breathing and heart rate as well. This feedback system is very clever, but it is only a short-term solution.
Advice: For long-term adaptation to altitude, the body recognizes the lower availability of oxygen in the blood and starts to produce higher concentrations of hemoglobin. This enables the same volume of blood to carry more oxygen around the circulation.
Extra Hemoglobin Picks Up More Oxygen
However, the extra hemoglobin changes the physical properties of the blood, making it thicker and stickier, which can easily put extra strain on the heart to pump it through the blood vessels. In extreme cases, this can lead to chronic mountain sickness.
It takes some time for the body to manufacture the extra hemoglobin so achieving full adaptation to an altitude of 10,000 feet will take 37 days. The process is fully reversible so that someone descending to sea level permanently will see their hemoglobin fall back to its prior concentration.
How Do The Cold And Altitude Affect Skiers Staying At Higher Resorts?
For skiers in higher resorts, the threat posed by the cold is limited. Accommodation is modern and heated and out on the runs, the modern fabrics of ski clothes mean it is not difficult to stay comfortably warm even in the harshest temperatures. However, altitude poses more problems for some people.
The resorts of Breckenridge, Colorado (9600 ft 2900 m) and Val Thorens, France (7545 ft 2300m) are high enough for some visitors to feel the effects of altitude sickness which is a mild form feels like a hangover with dizziness, headache, muscle aches, and nausea. To combat this some US resorts now provide oxygen concentrator machines for rental during your trip.