2023-07-09 08:23:20
by Anna Fregonara
The heart is under stress and the fatigue is felt more. If the effort is prolonged, hydration must start from the day before. Practical advice to reduce the risk of heatstroke
I know how much more tiring it is to train on hot and humid days. To recover faster, we could draw inspiration from the American soldiers who, at the time of Desert Storm, put their hands in a sort of cold oven for a few minutes to bring the temperature down rapidly also for the rest of the body. A trick that acts on areas with high thermal dispersion, ie the hands and feet and that does not give the defense systems against the cold time to activate, explains Matteo Cerri, neurophysiologist and professor at the University of Bologna. On the practical side, therefore, putting your hands in cold water when we are hot after a run, for example, makes us feel better in a short time. A remedy that helps our cooling system which is based on the evaporation of sweat. The amount of water vapor that can evaporate from our bodies depends on how much of it is already present in the environment, Cerri explains. If the air is saturated with it, sweat cannot evaporate and body heat cannot be dispersed effectively.
Calorie exchanges
To this thermal imbalance is added, in making us feel more tired, the cardiovascular system, rather than under stress. The heart, in fact, must continue to support the function of the muscles which receive, however, less blood because it is diverted towards the skin. This deviation has the purpose of increasing the body surface useful for caloric exchanges and thus dissipating excess heat more easily, explains Roberto Pedretti, director of the Cardiovascular Department at the Irccs MultiMedica of Sesto San Giovanni (Milan) and member of the Board of Directors of the European Association of Preventive Cardiology. Obviously the efficiency of the muscle function, and therefore the performance, can be affected by the smaller amount of blood available and therefore the heart will try to increase its work in a compensatory way, accelerating its contraction frequency, a mechanism that can only be effective up to at a certain point. This functional imbalance is accentuated by dehydration due to excessive sweating.
Practical advice
In order for training to be effective, the first rule is acclimatising. This means reducing workloads than usual, gradually increasing exercise to get used to the heat and humidity, which can take 2-3 weeks, recommends Gianfranco Beltrami, specialist in sports medicine and cardiology, vice president of the Medical Federation Italian sportswoman. The program, with the most suitable increments which can be from 1 minute to 10 minutes more per day, must be personalized on the basis of the subject’s age, sex, any pathologies and level of training. This strategy reduces the risk of heatstroke and dehydration. An acclimatised body can expel up to 4-6 liters of sweat every hour when the ambient temperature rises significantly. However, it is better to train outdoors in the cooler hours of the morning or in air-conditioned gyms. Finally, technical clothing helps heat dispersion unlike cotton.
When to drink
If the training lasts about an hour, it is possible not to drink during the effort, especially if you start well hydrated and, at the end, sip fresh water every quarter of an hour until you replenish the losses which can be quantified by weighing yourself before and after the activity. In the case of long-lasting training, it is very important to pre-hydrate the day before and then continue to drink modest quantities (150-250 ml) of liquids during the effort, approximately every 20 minutes. The intake of mineral waters with a high saline content containing calcium, potassium, magnesium and sodium is also useful and, in some cases, it is advisable to take mineral salts together with the water. The same rule for everyone: drink before the feeling of thirst appears. Cold foods and drinks can provide brief relief, but if they are very cold they can send a contradictory signal to the brain which may think it should increase heat production instead of decreasing it, Cerri finally points out.
Exertional heatstroke
In hot and humid conditions (relative humidity >75%), athletes can be susceptible to exertional heatstroke. Nausea, headache, dizziness or cramps may indicate heat stress not compensated by the body’s cooling capacity, Pedretti points out. it is advisable to stop, shelter from the sun, drink water or sports drinks, take off as much clothing as possible, lie down if you feel symptoms that may herald fainting (tiredness, dizziness, blurred vision), put a cold cloth on your neck, armpits and groin. In more serious situations, exertional heatstroke is characterized by collapse: core temperature above 40-40.5C. The absence of neurological signs distinguishes exertional heat stroke from so-called heat stroke. Rapid cooling, within 30 minutes, is the most effective strategy to minimize risks: cold water immersion, ice/wet towel rotation indicated. Once a reasonable temperature has been reached (for example, about 39 C), go to the emergency room.
July 9, 2023 (change July 9, 2023 | 08:22)
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