RUNNING HOT & COLD
Are you a sun seeker, or do you crave the chill night air? Why do people’s bodies respond so differently to changes in temperature?
Why do people’s bodies respond so differently to changes in temperature?
Have you ever noticed how some people run hot? They can’t help but sweat on all but the chilliest of days, they warm up the bed without even trying, and others huddle into them to steal their warmth. They prefer winter to summer, when they practically melt and live for ice blocks and air conditioning.
For others, their body seems to run cold. They obsessively chase the sun, love summer, and leave the electric blanket on all night during winter. (If the first group did that, they’d spontaneously combust!)
Still others have a body that seems to have a very small range of ideal operating temperatures. Too hot and they become clammy, headachy and listless. Too cold and they can barely breathe. Even on the chilliest winter evening at the gym, they might go from freezing cold to boiling hot after about 30 seconds of warm-up time. Their body seems to constantly swing between extremes and is notoriously hard to regulate.
THE STARTING POINT
What’s behind our differing abilities to cope with various types of weather? The base body temperature of humans is generally remarkably similar from person to person in all but the most extreme of conditions, says Associate Professor Christopher Gordon, senior lecturer in the University of Sydney’s Faculty of Medicine and Health. People usually sit at around 37°C on average, but in the space of 24 hours, this will fluctuate slightly in time with their circadian rhythm. “Over a 24-hour period, your core body temperature will change by up to a degree. You are normally warmest in the late afternoon and coldest in the very early hours of the morning.”
A woman’s core temperature can also be affected by their menstrual cycle, according to Professor Jim
“WE CAN LEARN TO LIVE WITH EXTREME COLD OR HEAT.” CHRISTOPHER GORDON
Cotter from the School of Physical Education, Sport and Exercise Sciences at the University of Otago. “You start a bit warmer in the luteal phase, in the second half of the menstrual cycle, and that puts your core temperature up by 0.2 to 0.4 of a degree.”
The slight fluctuations or variations in a person’s base body temperatures are generally not a problem. Most people will be in dire straits, however, once their core temperature reaches below 35°C (hypothermia) or above 40.5°C (hyperthermia). Hypothermia can be caused by spending time in air below 10°C or water less than 20°C. Symptoms include drowsiness, being clumsy and uncoordinated, skin that is cold and pale, and uncontrollable shivering. In severe cases, a patient’s heart rate and breathing will slow down and they can slip into a coma.
Signs of heatstroke or hyperthermia, on the other hand, include intense thirst, headaches, vomiting, rapid pulse and breathing, confusion, hot and dry skin, and a swollen tongue. You can get it inside or outside, and are more likely to be affected if you are over 75, pregnant, or suffering from certain chronic diseases. Left untreated, it can lead to organ damage and death.
Those in occupations in which they regularly encounter extreme heat tend to have bodies that start at a lower base temperature, giving them a head start in combating the furnace-like conditions they sometimes throw themselves into.
“A decent athlete will start about 0.2 to 0.4 degrees cooler, as will somebody who’s used to getting really hot just from being in a really hot space, like a foundry worker or a firefighter,” says Cotter. “It gives them a bigger range. They start a little bit cooler and they can tolerate generally higher core temperatures.”
A person’s body composition also effects how they cope, says Cotter. “People who are particularly big and muscular tend not to go so well in hot temperatures because they generate a lot of heat, and they’ve got a big body-volume-to-surface area so they don’t offload it very well. But they’re the very two things that make them do really well in the cold.”
With age, our hypothalamus stops working as effectively and isn’t as good at detecting changes in temperature. Women’s estrogen levels also lower during menopause and this corresponds with them feeling the cold more as they get older. Similarly, men lose testosterone as they age and become more sensitive to the cold as well.
One of the other variables is simply personal preference, says Gordon. This can be influenced by your chronotype – whether you’re a morning person or a night owl. “For instance, if I’m an evening person, it’s unlikely that I’m going to be exposed to the early morning cold. That may affect how I react versus someone who is a morning person who may be able to cope very well.”
THE BIG CHILL
So what goes on inside the body when it detects a sudden shift in outside temperature, such as diving into a pool in the middle of winter? Our bodies struggle to adapt in response to extreme cold in the same way as we can to the heat, but we can learn to live with it. “People from Scandinavian countries often tolerate cold weather better than people from equatorial regions and Australia,” says Gordon. “They grow up with it. They still experience the cold and the pain the same way you and I do, but they get used to it.”
If, however, we’re plunged into cold water suddenly, our bodies react in a similar way to our fight-or-flight
impulse, says Gordon. “The body goes through this big physiological surge – you increase your blood pressure, pulse rate and breathing.”
If the water is very cold – less than 5°C – the results can be serious or even fatal. “People dropped into a very cold ocean can experience something called ‘cold shock’ and that can cause heart arrhythmia, and it can actually precipitate death.”
Various illnesses such as asthma and diabetes, as well as the medications used to treat them, can alter the way our bodies handle hot and cold temperatures.
A Canadian study in 2016 found having either type 1 or type 2 diabetes can result in a decreased ability to regulate internal temperatures in response to extreme heat and extreme cold. This is particularly the case if blood-sugar levels are not well controlled.
Cardiovascular diseases have a particular impact on the body’s ability to cope with heat. “You can’t fight high blood pressure and be good in the heat as well, because they’re competing demands,” says Cotter. “If you don’t have a really healthy cardiovascular system, particularly the quality of your blood vessels, you don’t offload heat well. You can’t pump blood well and you can’t distribute it to the skin well.”
Asthmatics, on the other hand, can be in trouble when the air temperature drops. Cold air can cause irritation and inflammation in the airways and act as an asthma trigger, particularly in combination with winter viruses and flus.
So, what’s going on in your body when you experience a fever or chills?
Gordon says this process is usually kicked off by a bacterial infection. The hypothalamus in the brain produces a fever as a kind of defence mechanism. “It’s sending the blood centrally and raising the body temperature by getting you to shiver, which produces metabolic heat,” says Gordon. “It literally raises your body temperature, which the bacteria don’t like. They don’t grow as well in that.”
There’s some debate in the scientific community about whether we should intervene and bring down the fever, as we’re interfering with our body’s natural way of fighting the illness. On the other hand, you’re left feeling terrible while the fever rages in your system.
MAKING CHANGES
There are some measures you can take to train your body to cope with changes in temperature or extreme hot and cold. Getting out in the elements will definitely help, but exercising in it is even better.
According to Gordon, when it comes to the heat, it’s wise to gradually increase your tolerance by regularly exposing yourself to uncomfortable temperatures. “You need to do it progressively and you need to build it up, but the important thing, and we know this from the research, is that you need to do something almost every day.”
It’s not enough to go for a jog outside once a week or so. The best approach is to push yourself consistently, but do it in a sensible, sustainable way by ensuring you stay hydrated and venture out in the slightly cooler hours of the day.
“You’d want to do it either in the morning or the evening,” says Gordon. “Your body is going to adapt relatively quickly if you do something every day. You’ll get a good adaptation within about 10 days to two weeks.”
When it comes to the cold, you can insulate yourself against the effects of cold shock, says Cotter. This can be done by immersing yourself in cold water several times across the space of a week to teach your body to deal with it. “The studies typically do about six or eight exposures across a week, only a couple of minutes each,” says Cotter. “It might just be turning on a cold shower or jumping into cold water, but you’ll halve your cold shock.” The benefits are long lasting – even if you’re not exposed to cold water again for a year, you’ll still exhibit half your initial cold-shock response, which is impressive. On the flip side, the body’s response to prolonged exposure to cold water rather than short bursts isn’t so awe-inspiring.
“If you put somebody in cold water and leave them there for an hour every day for a couple of weeks, they actually get worse. They cool down faster. They fail to store heat and they fail to generate heat,” Cotter says. What this approach does achieve, says Cotter, is making the person feel more accustomed to the discomfort. “They feel better, and we call that habituation. You get used to the environment, but it’s actually less survivable.”
There aren’t any particular vitamins or other easy fixes you can use to assist in the process. Mostly, the best approach is to maintain a healthy lifestyle by eating well, getting plenty of exercise, and making sure you stay hydrated.
In general, getting out into the environment often and exercising in varying temperatures and conditions will help your body adapt and cope in future with seasonal extremes. In this way, we’re taking full advantage of the incredible systems in our bodies.
“Humans are amazing – our thermoregulatory system is completely unmatched,” says Cotter. “Get out and get in it. Be active, make your body the best it can be.”