Impacts that are often little known. Precautions to take.
Doing sports in winter, when nature has adorned itself with a beautiful coat of frost or snow, can bring a lot of pleasure. But when it’s cold, certain precautions are necessary to avoid serious health concerns, especially cardio-vascular ones. Explanations.
The risks related to cold
In winter, the cold makes the effort much more difficult, and therefore the work of the heart more painful. According to the Federation of Cardiology (FFC), a simple walk in the cold would be equivalent to running a 100 meters!
“Too little is said about the impact of cold on cardiovascular risk, which is still not well known. The number of cardiovascular accidents increases in winter and these are responsible for about half of the excess mortality during this season,” explains Professor Claire Mounier-Vehier, a cardiologist at Lille University Hospital and President of the Federation of Cardiology.
Our body must indeed adapt to low temperatures, in particular, struggle to maintain its internal temperature. This is the point that requires the most attention from us before practicing a sport in cold weather. The bronchial tubes exposed to the freezing air.
The joints exposed to the cold and subjected to more stress. Muscles are more vulnerable to injury and extremities to frostbite. Cold weather sport is therefore more demanding on our bodies. You must take precautions accordingly to avoid any potentially serious health problems.
The heart: risks to take seriously
To function properly, our body must maintain an internal temperature around 37°C. It must then activate a number of mechanisms to ensure this function, especially if the temperature drops. This work results in an increase in heart rate (the heart must beat faster to meet the body’s needs), blood pressure, and blood viscosity.
All of which together constitute a risk of contracting certain serious diseases such as myocardial infarction, angina pectoris, or stroke. Risks increased with pollution. We explain in more detail the mechanisms involved later in this article.
If we practice a sport in cold weather, the heart is even more solicited because it has to supply the necessary oxygen to the muscles in action. This cardiac effort is all the more difficult because the cold causes vasoconstriction of the blood vessels in the muscles, thus making it more difficult to feed them. Thus, when the thermometer shows negative temperatures, the slightest effort becomes a real test of strength.
The cold, on the other hand, promotes dehydration and thus contributes to increasing blood viscosity, which makes the work of the heart even more difficult!
Age effects and sports
While the risk of cardiovascular accidents is lower in young and healthy people, it increases with age and must be seriously taken into account if there is a history of heart disease or aggravating factors (cholesterol, diabetes, smoking, stress, high blood pressure, heart failure, etc.). In general, the CTF recommends monitoring your heart after the age of 40 and always prepare your heart and body well for exercise.
However, these health risks should not discourage you to the point of not going out when the thermometer drops! Not everyone has a heart attack when they go out in the cold.
In fact, the cold acts as a trigger factor that reveals pathologies that are already in place earlier than expected, and that would have been revealed a few years later at milder temperatures. It is therefore more of a warning inviting everyone, regardless of age and physical condition, to take the necessary precautions to limit these risks.
Bronchial tubes: sensitivity to cold, dry air
Our bronchial tubes are sensitive to the cold air we breathe. This causes them to narrow and irritate, which can trigger an asthma attack. Various experiments conducted on the subject are however contradictory (Kotaniemi et al. 2003, Larsson et al. 1993, Leuppi et al. 1998, Sue-Chu et al. 1996).
If the air is dry, as is generally the case in winter in Western Europe, mucous membranes can dry out and make the bronchial tubes less resistant to infection. This makes it easier to get sick. You should also avoid doing sports in cold weather when you are sick, even if you just have a cold.
Muscles: risk of injury
When cold (without warming up), our muscles, tendons, and ligaments are stiff and therefore more easily subject to injury (e.g. tearing). The synovium, the fluid surrounding our joints, is less abundant and less fluid when cold than when hot. The joints are like “rusty”.
The cold accentuates this effect by contracting the blood vessels and decreasing the irrigation of the muscles. This is why a prior warm-up is essential before practicing sports, especially in cold weather.
Extremities: high heat loss and risk of frostbite
The extremities must be well covered in cold weather for several reasons:
They are responsible for 70% of heat loss, 30% of which is from the head alone! If they are not covered, the best clothing will remain ineffective against the cold. The health risks mentioned above (heart, bronchial tubes) increase if the extremities are neglected!
Under the effect of the cold, the small capillaries located under the skin close to limit heat loss from the body. This protection creates a defect in blood irrigation and a lack of tissue oxygenation that can cause frostbite. They are not serious but painful. Hands, feet, nose and ears are affected and must be carefully protected.
Precautions and tips for practicing sports in cold weather
Practicing a sport when it is cold requires special precautions, even if one is a young and trained sportsman. Whatever your situation, seek the advice of a doctor, especially if you are over 40 years old or if you are starting or returning to sports. Be aware that a stress test is recommended after the age of 40 and should be repeated every 5 years.
Cover yourself accordingly
Covering up well is essential in cold weather, including extremities which are major sources of heat loss (see above). It is not a question of multiplying thick layers or covering oneself excessively, but of covering, in one to several layers, technical clothing, i.e. warm, breathable, and light.
Protect joints that are sensitive to cold. Running tights or long cycling shorts will keep your legs warm, but also keep your joints warm in the cold. To prevent frostbite, cover the extremities. Avoid anything that cuts off blood circulation such as elastics, clothing or shoes that are too tight. To reduce water and caloric losses related to the inhalation of cold and dry air and to relieve your body, breathe through your nose or through a scarf.
Warm yourself up in a warm place and avoid violent efforts.
Warm up, if possible indoors, before you start, so that your muscles, tendons, ligaments, joints (by synovial secretion and reduction of its viscosity), heart and lungs are ready for the effort and to avoid additional work for the body.
The colder it gets, the more you have to limit the intensity of the effort. Cold intensifies the difficulty. A leisurely walk or jog can require as much effort from the body as a sprint in mild temperatures.
Avoid sports if it is very cold. It is difficult to give a reference temperature because it depends on many parameters (physical condition, age, wind, humidity level, etc.). In Western Europe, where the winter is generally dry, -5°C to -10°C seems to be a reasonable limit, but it can go down to -20°C in other more humid countries. These figures are arbitrary and given as an indication.
Cold weather leads to significant water losses with consequences that are often underestimated. Hydrate before, during, and after the outing. For outings lasting more than an hour, plan an isotonic drink (see how to prepare it yourself).
Beware of thermal shocks
An icy wind on the face can cause enough heat shock to trigger health problems. Speed sports (cycling, skiing, etc.) are more exposed due to wind chill caused by the speed of travel and possibly the wind. Avoid sudden temperature changes if possible, cover your head (hood, headband, hat) or even your face with a scarf, wear a windproof jacket and gloves. More information.
Avoid pollution peaks
Pollution increases the risk of contracting respiratory and cardiovascular diseases. According to the FFC, it is responsible for 400,000 deaths per year in Europe, 80% of which are cardiovascular diseases and heart attacks. So many reasons to avoid pollution peaks and to avoid sports in the city if you can.
Avoid going out in case of illness
Don’t go out if you’re sick, even if it’s just a cold, or if you’re sleepy. A weakened immune system or illness are additional risk factors, especially for bronchial tubes (asthma).
The Federation of Cardiology recommends paying particular attention to the slightest symptom: the feeling of tightness in the chest, palpitation, shortness of breath, chest pain on effort, or dizziness. These are all warning signals inviting to stop immediately and to consult without delay.
The effects of cold on the body
Cold responsible for serious cardiovascular accidents
The cold is a great strain on the body and claims many victims every year. Its effects are often underestimated. As we pointed out above, half of the excess mortality observed in winter is linked to cardiovascular accidents caused by the cold.
According to a study published in 2010 by the British Medical Journal, every 1°C drop in average temperature would increase the risk of myocardial infarction by 2% in the 4 weeks that follow. This study shows us that the risk is not only related to the cold but to the variation in temperature and that the effects are not necessarily immediate but can occur several days later.
Why is cold so dangerous for the body?
When it is cold, the slightest effort is perceived by our body as a sustained effort. Indeed, to maintain its internal temperature around 37°C, the body activates thermogenesis, the mechanism by which it produces heat. However, this process requires a lot of extra effort, especially at the heart. Several mechanisms come into action in thermogenesis:
- A contraction of the capillaries: the blood capillaries in the areas exposed to the cold decrease in diameter in order to insulate the central part of the body and protect the deep vital organs (brain, heart, kidneys) from the cold. This vasoconstriction is triggered by the release of adrenaline into the bloodstream. It is accompanied by a reflex, goosebumps, which aims to reinforce this thermal insulation.
- An increase in cellular metabolism: this process produces heat at the cellular level.
- A voluntary muscular activity or thermal shivers: the muscular activity increases the metabolism and produces heat. It can be voluntary (moving to keep warm) or automatically triggered by the body (muscle spasms that cause shivers).
As explained in an investigation report written by the Institut de Veille Sanitaire (3), these different mechanisms cause the heart to beat faster, in particular, to provide for the increased oxygen needs of the body, including the heart itself because of the extra work it has to do.
Blood pressure increases due to the contraction of the vessels and, with the redistribution of blood to the organs, there is a 10% increase in the plasma concentration of red blood cells, leukocytes, platelets, cholesterol, and fibrinogen, and a 20% increase in blood viscosity. Dehydration caused by the cold (dryness of the air and a tendency to become less hydrated due to reduced sensations of thirst when it is cold) reduces blood fluidity and contributes to increasing these phenomena.
Heart Diseases and sports
All of this can lead to serious heart disease (angina, heart attack, stroke, etc.) through a variety of scenarios. For example, the heart may no longer be able to meet the body’s need for oxygen (heart failure). The cold can also trigger a coronary spasm, which is a tightening of the muscles within the arteries of the heart causing them to narrow.
The resulting lack of oxygen can then lead to angina pectoris (a kind of asphyxiation of the heart). The spasm can also cause fatty deposits on the walls of the arteries to detach and cause arterial thrombosis, a clot that forms in an artery and clogs it. Depending on the artery involved (coronary or cerebral, for example), the clot can lead to a myocardial infarction (heart attack) or stroke.
As we wrote above, these problems are not directly related to the cold but to pathologies already in place and revealed in an accelerated manner by an external factor, the cold here. These risks must nevertheless be considered as a warning and an obvious reason to take all the necessary precautions for an outing, sporting or not, in the cold!
Increased risks with age, history, and risk factors
According to the CTF, people most at risk are those with a history of heart, heart, brain, or vascular disease and disorders. The risk also increases with age: beyond the age of 70, the body no longer adapts as well to temperature variations and the basic metabolism is weakened. The FFC also recommends a follow-up after the age of 40, especially when starting or resuming sports. Consult a doctor for medical advice.
Cold affects the body, especially the heart and arteries. Practicing a sport in cold weather puts more strain on these organs while exposing the athlete to other health consequences (injuries, frostbite, etc.). It is therefore important to take the necessary precautions before considering an outing.
However, these risks should not prevent you from practicing a sport in winter. If the necessary precautions are taken, training outdoors or a relaxing outing will be safe and satisfying, as well as being beneficial to your health.
Regular physical activity maintains the heart, dilates the arteries, reduces the risk of diabetes, increases good cholesterol, reduces stress, and blood pressure: all of which reduce the risk of cardiovascular disease. Going out in the cold well covered allows you to take a breath of fresh air, restores colors, invigorates the body, and mental health. So many reasons that should on the contrary encourage us all to take advantage of this beautiful season that is winter.