Exercising in the Heat and Humidity

With the scorching heat of the summer season outside, pre-season training or just simply wanting to keep up with your outdoor running routine can be a bit of a challenge. It is often tough enough finding the motivation to get out and even mow the lawn, but don’t let the heat add on the extra challenge to your exercise routine by taking the following points into considerations.

The added thermal load from the bright, hot sun increases stress on the heart. During physical exertion, the heart’s workload is already elevated to provide blood and oxygen to the exercising muscles. The added heat results in the need for cooling, thus the heart has to work even harder to pump blood through capillary in the skin at a faster rate, with the aim to remove heat via evaporation of our sweat. Why is it important to know this mechanism is because it explains why Switzerland’s Gabriela Andersen-Schiess was in such an exhausting condition at the last 400m of the 42.195 km Los Angeles 1984 Summer Women’s Olympic marathon. She described the experience as ‘[her] muscles just didn’t respond’, ‘it was painful’ and ‘not feeling good for a week’. Despite suffering from dehydration, Gabriela completed the race at 37th place and had became an iconic figure, an unforgettable moment in Olympic history of an individual demonstrating sheer commitment and raw determination.

It is through the videos captured as shown in this Olympic rewind that demonstrate clearly to us the effect of Exertional Heat Illness (EHI), otherwise known as heatstroke, heat syncope and cramps. Besides the symptoms described by Gabriel in her reflection, other symptoms could be dizziness, nausea and vomiting. More serious symptoms such as disorientation and blacking out sometimes warrant urgent medical attention in severe cases such as that of the Olympic athlete.

So the next time during your cricket game, under the burning sun and you start to experience some of these symptoms after earning lots of runs for the team, what should you do?

Some suggestions are:

  • Ask for a rest period, sit or lie down in a cool, shaded and well ventilated place
  • Remove excess clothing
  • Replenish with plenty of fluid, either cool water or sport drink
  • Sponge the body with cool water and fan to promote evaporation (not cold water or ice as this will stimulate the blood vessels in the skin to constrict and retain body heat).

The simplest and easiest strategy to avoid heat stress is to use your common sense … avoid excessive sport, exercise or physical work tasks in the hottest part of the day (which is between about 10am and 4pm in summer day).

However, if it is out of your control, like let’s say a scheduled cricket match, marathon race, underground mining or outdoor, open field occupations where exposure to the heat and humidity is inevitable, then there are ways to improve your performance and reduce the likelihood of suffering heat-related injuries.

  • Be aware and stay alert for symptoms of heat stress and dehydration
  • Take regular breaks to allow the body to cool down
  • Ensure adequate hydration before, during and after physical exertion. A crude measure of your fluid requirement is to weigh yourself before and after the physical task and replace one litre of fluid for every kilogram loss. A general rule of thumb is to take at least ½ L of fluids in the two hours before, 200mL every 20 minutes during  and at least ½ L of fluids in the two hours after. Avoid drinking alcohol the day before as it dehydrates the body.
  • Wear loose-fitting, light-coloured and comfortable clothing that allow sweat to evaporate quickly and wear a hat (of similar material) and sunscreen when under the sun.

The two most important considerations, in my opinion, to take into account are:

  • Acclimatization, aka. “getting used to it”  – gradually increasing the exposure to the challenging environment to allow the body time to adapt and recover and improve its endurance. This could be done by either slowly increasing the intensity and duration of the training routine/ physical work tasks in the hot and humid environment. And/or maintain training/ work intensity during the cooler months.
  • Cardio-vascular fitness level: A good fitness level means greater capacity for the heart to stay under safe limits in challenging environments. This could be achieved by exercising in cooler situation. Incorporating gym-based or hydro-based sessions into an athlete training program is a good way to put it.

In summary, it is crucial to take at least this one point from this reading: be able to identify the symptoms of heat stress. Symptoms such as muscle cramps, decreased in performance, dizziness and headache signifies the need to stop for a break, re-hydration and allow the body to cool down. Furthermore, knowing when to stop and how hard to push is most important in the process of acclimates and training to improve the endurance under hot and humid conditions.


Author:  Huy Vu, B.Physiotherapy

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