By Lucas Guaraldo*
Um Grau e Meio talks to Laura Olivia Tavares Souto, a resident doctor in metabology and endocrinology.
In this interview, she discusses the physiological effects of practicing sports and outdoor activities in extreme heat, as well as the health risks and palliative care that can be adopted.
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What are the physical effects of practicing outdoor sports in extreme temperatures?
The most obvious is an increase in body temperature. In these conditions of extreme heat, the body will find it more difficult to dissipate the heat generated by exercise because of the temperature, which is even a bit of that bad feeling we get in these situations. Our body always wants to be in homeostasis [the body’s ability to maintain a stable temperature], so if you’re doing physical activity in a very hot environment, your body will work hard to maintain this homeostasis.
To try to cool itself down, our body increases blood flow to the skin, there will be more sweating and the demand for blood from the muscle will also be much greater, increasing the heart rate. All this reduces our physical performance a little and because of the sweat we lose sodium, potassium and magnesium.
I imagine there’s a limit to this. What happens when we reach our body’s limit for maintaining this homeostasis, but the physical activity and the heat continue?
If you exceed the limit, there will come a time when your body stops and you faint. If you expose your body to an extreme environment like this, which is extremely hot and doesn’t allow homeostasis, there will come a time when it reaches its limit. Exceeding this limit can mean fainting, cardiac arrest and even death.
We have an example of this, even if it’s not exactly a physical activity, but that’s what happened to the girl at the Taylor Swift concert in Rio de Janeiro. She wasn’t exercising, but she was at a concert that demanded as much energy as exercise. Her body was dehydrated, losing salts and she lost consciousness because of this imbalance. It was an extreme case.
Why is this kind of situation so dangerous physiologically?
It’s very much based on the issue of cardiovascular overload. We have natural physiological responses. So you and I, we’re talking here, my heart rate is at a baseline of around 60 to 100, that’s the normal value.
If we start exercising, our hearts will naturally beat more strongly. After a workout, your heart might be beating at 150, for example. Does that mean your heart is in trouble? No, it means it’s responding to a stimulus.
So if we expose ourselves in a place where high heat makes our body increase blood flow and oxygen demand, our heart will have to beat faster to keep up. If you exercise in extreme heat, there will be a time when your heart won’t be able to keep up with your body’s demand. It would have to beat at 300, but it only reaches 200.
Before this extreme, what are some of the symptoms that appear when we are exposed to these scenarios?
The characteristic symptom of this imbalance is tremor. A lot of shaking. You also have to watch out for disorientation, tiredness and mental confusion. Thinking more dramatically, these symptoms can evolve into a loss of consciousness.
What can be done to make practicing high-intensity sports in this context less harmful?
If you have to expose yourself to a situation like this, if you’re a professional athlete, for example, and you have to play on a very hot pitch, gradual acclimatization is key. You need to train your body for this and not expose yourself to everything at once. In the same way that if someone is going to run a marathon, I need to train my body little by little. That’s the first thing.
The second thing is hydration. We generally recommend 30 to 35 ml of fluid per kilo, so it’s different for each person. It’s important that you hydrate before, during and after and keep an eye on the most typical symptoms of when our body reaches the limit of this exposure. You have to respect the limits.
Another thing is clothing. So choose clothes that are lighter, that let you perspire, that aren’t so heavy. Choose the best time and place, such as early morning and late afternoon, when the temperature is milder.
In Brazil, we have hydration breaks during soccer matches when the temperature rises above 28 °C. Is that enough to guarantee hydration?
No. I don’t know what criteria are used to create these breaks, but it’s not enough because these athletes need to be trained for this. We need to do all this beforehand. Acclimatize your body to the high temperatures and hydrate at various times.
*IPAM journalist, lucas.itaborahy@ipam.org.br