Winter impacts the exerciser’s body in many ways – physiologists discuss the benefits and disadvantages
When it is dark and below freezing outside, fitness enthusiasts feel it in their bodies.
The physiological effects of the cold still hold many mysteries for researchers. Recent years have brought a new perspective on how cold regulates our metabolism and heat production. Assessing the effects becomes more complicated as soon as you start exercising in the cold.
"The problem is when we start to exercise, many adaptive responses start to change, and it all becomes unclear. We still have a lot of work to do to clearly assess how exercise in the cold influence our metabolism, health, and for some of us, our physical performance, says exercise physiologist Dominique Gagnon at the Ä¢¹½Ö±²¥.
But much is already known. Three exercise physiology experts from the Ä¢¹½Ö±²¥ explain the mechanisms by which winter affects exercise and what athletes or fitness enthusiasts need to know about the effects of cold weather.
Cold weather helps us exercise longer
Dominique Gagnon is an exercise physiologist who studies the effects of heat stress on metabolism. He is a lecturer at the Ä¢¹½Ö±²¥, Faculty of Sport and Health Sciences. Gagnon is the co-founder of EP2 Finland, an environmental exercise physiology programme aiming at improving performance, health and safety, for those conducting sports and work in extreme environments.
He explains why you can train longer in the cold.
How does training in the cold affect an athlete’s physiology?
There are numerous physiological systems in the human body that are affected by temperature. Two very important ones are the cardiovascular and the muscular systems. Under cold stress, blood from the extremities is being redirected towards the head, heart, and internal organs to protect us from losing heat. But by doing so, it also increases blood returning to the heart, which in turn slows down our heart rate during submaximal exercise. This can be beneficial during exercise as it lowers cardiovascular strain.
The more vigorous the intensity of the exercise and the longer you do it for, the more your muscles use carbohydrates and glycogen as a source of energy. As those get depleted, it leads to fatigue and exercise stoppage.
In the cold, our muscles prefer using lipids as an energy source.
The body’s fat reserves are nearly limitless, which helps us save carbohydrates and glycogen so we can exercise longer.
Moreover, using more lipids during exercise may also offer additional health benefits since many people exhibit excess fat deposits in their muscles, which is linked to metabolic dysfunctions. The ability to use more lipids during exercise is a key feature in athletic performance and it seems that exercising in the cold supports this very well.
How can a winter athlete maximise their performance, i.e. what to consider when eating or training?
A central mechanism of performance limit during exercise is central core temperature. As our core temperature rises, it becomes more and more challenging to exercise.
In the winter, we have an ability to delay this rise in core temperature, which allows us to exercise at a higher intensity and for a longer period of time.
This is dependent on what we wear and the outside air temperature. For example, on a 0°C day, a light jog can be done safely with only shorts and a t-shirt since we know that the heat produced by exercise should be much greater than the heat loss to the environment. As the environment gets colder, or with high winds, adding some additional clothing layers is needed.
One way to know that you are dressed too warmly is when sweating starts. If sweating is initiated, open your jacket, remove a clothing layer, and try to cool as soon as possible. By doing so you will maximize your performance and use the cold environment to your advantage.
How does training in the cold affect an athlete’s recovery?
A fundamental feature of post-exercise recovery is increased blood flow to remove metabolic by-products and waste in the muscles. Training in the cold may sometimes limit blood flow to certain muscles and some heating may be needed.
A nice sauna or warm shower after exercising in the cold may help that. Moreover, since training in the cold may lead to exercise bouts that are longer and more intense, more muscle fatigue and damage may occur. We recommend considering additional recovery when those bouts occur.
Does regular winter exercise increase or decrease the risk of flu?
Individuals that exercise regularly are at lower risk for infections and diseases because regular exercise has numerous immune boosting properties. Interestingly, during exercise in a cold environment, the humidity level tends to be low, which makes the air dry, and may ultimately irritate airways. Heavily breathing cold and dry air during exercise may lead to throat discomfort and minor tissue damage that becomes more prone to infections.
Even if some airway irritation may sometimes be bothersome, we still recommend exercising regularly in the winter as the immune benefits of exercise far exceed the potential risks of getting the flu.
What are the main risks to an athlete’s health or performance from cold weather?
Despite being very safe when dressed adequately, the main risks of exercising in the cold remain freezing extremities such as fingers, toes, ears, and other areas due to lower blood flow. Freezing injuries may seem benign but once superficial freezing of tissues has occurred, those areas are more likely to freeze again in the future. Make sure you have warm mittens, extra warm socks if needed, and a good hat so that your extremities stay warm at all times.
The need for carbohydrates increases during winter sports
Enni-Maria Hietavala is an exercise physiologist and sports nutrition expert who studies eating behaviour. She works as a senior lecturer in the Faculty of Sport and Health Sciences.
She explains how people exercising during the winter should eat and drink – and how exercising in cold weather affects the body’s beneficial brown fat.
What should an athlete or active exerciser eat during the winter?
The basic principles of a balanced diet do not obviously change according to the seasons, but when training or exercising in cold weather a few things are worth noting.
In general, the need for energy increases when you’re exposed to cold temperatures as the body must produce more heat.
The muscle tremors caused by frostbite, for example, use up the body’s carbohydrate reserves. Physical exercise, in which carbohydrates are an important source of energy, should not be done with low energy reserves even in cold weather. Be sure you have sufficient energy and carbohydrate intake when thinking about your total daily consumption.
To replenish the carbohydrate reserves of the muscles and liver, that is, the glycogen reserves, it is worth including in your diet a variety of porridges, pasta, potato, rice, quinoa, bread, vegetables, and fruit.
What about drinking?
Cold air is often dry, which increases the evaporation of fluid from the body, so adequate hydration should be ensured. It might be good to drink sports drinks containing carbohydrates while exercising when the session lasts at least over an hour. The total need for fluid and carbohydrates will ultimately depend on the duration and intensity of the exercise.
Keep in mind that our sense of thirst may also weaken in the cold.
Research results suggest that the body can withstand a slightly greater loss of fluid in cold conditions than in hot ones. The amount of fluid consumed in cold weather can be slightly less than in hot weather, but the actual drink can be stronger, that is, contain more sugar.
The cold increases useful brown fat: is it worth exercising while not wearing the right amount of clothing?
Exposure to cold activates brown fat, while also warming the body. Therefore, the activation of brown fat increases the body’s energy consumption and improve the metabolism of sugar.
The amount of brown fat can increase due to, for example, regular swims in icy water, but otherwise you should wear weather-appropriate clothing when exercising so that you avoid frostbite while achieving the other benefits of exercise.
Brown fat gets activated in the cold, even while wearing clothing.
Brown adipose tissue also gets activated due to eating. At the same time, the metabolic heat production rises, which can further curb our appetite. This way regular eating habits can also help people to manage the portions they eat and weight gain, but the role of the brown adipose tissue in humans related to these should be researched in more depth.
Light affects circadian rhythms as well as performance
Maria Schildt studies the effects of exercise and physical activity on well-being. She works as a university teacher at the Open University of the Ä¢¹½Ö±²¥.
Schildt says that light guides humans’ biological clock which in turn regulates circadian rhythms of the body’s physiological processes and thus affects physical performance.
Performance varies according to the time of day – a person is at their strongest in the afternoon.
What are circadian rhythms based on?
During evolution, all living things have evolved a biological clock that regulates their internal circadian rhythms. Their purpose is to assist people in adapting to the environment’s rhythmic changes.
The sleep/wake cycle is one of the clearest examples of the circadian rhythms.
Research has shown that even if a human being is isolated from their surroundings, their circadian rhythms still continue. In this case, the internal circadian rhythm would be about 25 hours.
The most important place for regulating circadian rhythms, the so-called central clock is located in the anterior part of the hypothalamus in the suprachiasmatic nucleus .
The junction of the optic nerve is near the central clock, and light is in fact one of the most important factors regulating the human circadian rhythm. In addition to the central clock, human also possess clock genes, which participate in regulating the circadian rhythm at the cellular level. The clocks are found e.g. in the kidneys and pancreas as well as adipose and muscle tissue.
Circadian rhythms are therefore endogenous, but they are also affected by environmental factors.
How does light guide the biological clock?
Light is one of the most important factors but not the only one which regulates the human biological clock, that is, our circadian rhythms. Sufficient exposure to light in the mornings helps us to synchronise the biological clock.
Light can also be used to regulate the circadian rhythms.
Light in the morning shifts the rhythms to an earlier phase, and light in the evening shifts them to a later phase.
It impacts the functioning of hormones, especially the circadian rhythms of melatonin and, through that, sleep. Melatonin plays an important role in regulating the rhythms of being awake and asleep by acting as a transmitter between the external photoreceptor stimuli and the hypothalamus.
Other environmental factors in addition to light also help regulating our circadian rhythms to fit the 24-hour world. Social relationships, meals, and exercise also help maintain these rhythms.
How do circadian rhythms affect physical performance?
Circadian rhythms can be displayed in the form of a wave. For example, body temperature is at its lowest early in the morning and highest in the evening. In addition, heart rate, blood pressure, metabolism, endocrine activity and physical performance also vary depending on the time of day.
On average, people are at their strongest in the evening and at their weakest in the morning.
Physical performance levels therefore vary during the day. For example, the maximum strength levels can increase by 5 to 21 percent during the day. Circadian rhythms do not, however, impact endurance performance as much.
The precise reasons for diurnal variations related to physical performance are unknown but they are likely affected by circadian rhythms in hormonal activity ( e.g., diurnal changes in the secretion of growth hormone, testosterone, cortisol), neural activity, body temperature, and alertness.
How does light impact physical activity, particularly exercising during the winter?
Good sleep quality and optimal sleep patterns are essential for recovery and performance. Disruption in circadian rhythms may make falling asleep difficult as well as impact the quality of sleep. In addition, the limited amount of light can cause a feeling of tiredness and low mood. One may not necessarily feel like exercising.
Exercise preferences are also influenced by the chronotype, that is, whether one is a morning or an evening person or something in between.
Morning people are more active in the morning and go to bed early, whereas other people are the most energetic in the evening. There is also a middle typ which is the most common.
Chronotype also affects people’s preferences regarding the time of physical exercise. Some people like to exercise in the morning, others in the evening. It’s important to find for yourself the best time to exercise during dark winter days. It is ultimately not important when exercise takes place, but that one exercises and that it fits one’s daily schedule.
