Running in hot weather — practical tips for training and competition from sports medicine specialist Dr. Paul Schmidt-Hellinger

Jogging in the heat

or running on hot summer days in general puts training in a completely new light. Not only is an altered physiological reaction of the organism to be expected. Running in hot weather can quickly even pose a serious health threat if you don't handle it accordingly. In this article, we'll tell you how to correctly assess the topic and handle it for yourself.

Why is running particularly critical when it is hot?

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Running is a sport in which we have to activate many large muscle groups and exert high physical performance (compared to cycling, for example). The efficiency of our organism, i.e. the efficiency with which we energy generated in our muscle cells Even in kinetic form of energy, “putting it on the street” is just 20-25%. The rest is more or less lost in heat. A 70kg runner running over 10 km with approx. 400 watts of kinetic running energy would therefore have to produce a whopping 1600 watts of energy, 1200W of it as heat.

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The body has various ways of dissipating this heat, with sweating being the most important here. Sweating allows the athlete to remove heat, but it can also lead to dehydration. When the environment is hot and humid, it becomes more difficult to get the heat from Conduction and convection and we must rely more on sweating.

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How do I correctly estimate the heat when running?

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Hot doesn't always mean hot! Heat is best achieved with the so-called Cumulative climate measure Evaluate (so-called Wet Bulb Globe Temperature = WBGT) from dry temperature, humidity, radiation (sun and asphalt) and wind. A WBGT of around 30°C can be calculated, for example, from 38°C air temperature, 55% humidity with a little wind and lots of radiation from the street. Here For example, no harder physical exertion longer than 30 minutes is generally recommended and it is recommended to drink 1 l of water.

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How does heat affect running performance and training?

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Although relatively inefficient at a certain point, the body invests significantly more energy in the distribution of heat (convection). At the same time, the body loses fluid and therefore valuable minerals as a result of increased perspiration. The blood becomes a bit thicker, which is one of the reasons for the so-called “cardiac drift” and a first sign of mild dehydration. The cardiovascular system must do more work to supply the muscles with the same amount of oxygen. The effectively usable oxygen uptake decreases. Losses of 5-8% of effective VO2 max are not uncommon. This has a particular influence on long endurance events, while interestingly enough, shorter runs may even benefit from warmer climatic conditions As a recent study summarized.

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What can I do as a preparation during training to better tolerate running in hot weather?

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Preparing your body for running in hot weather is a very important aspect. In addition to the fact that you the adequate supply and intake of food and liquid while running Should absolutely train, so there are also a few tricks for “toughening up”. In general, it is necessary to expose the body to “stress” caused by heat more often in order to adapt to it. In this context, a recent study was able to show, for example, that there was an increase in performance for later runs in hot weather if, during training, people regularly took a hot bath AFTER running training. Even or especially when there are warm temperatures during training, the body can develop the regulation of core body temperature under load.

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What can I do while running in the heat to perform better?

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With maximum perspiration rate, you can cool down a bit in dry heat, but the best cooling is still cool water, which directly cools down skin and blood through heat conduction (convection) and also creates evaporative cooling (conduction). You can cool the core of your body a bit by drinking cold water. Here you can also cooling vests help (before the start of the race), which were developed specifically for this purpose. Maximum precooling with 5 minutes of full bath in the fountain at the start gave our sports medicine specialist the most in addition to a degressive race design at the race in Dresden.

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Here is an overview of the most important tips for running in hot weather:

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Drink at least 1 l of liquid per hour, make sure that the mineral content (especially sodium) is adequate!
Precooling immediately before the start with a cooling vest or ice bath (can also be a fountain at the racetrack)
little active heating (some dynamic stretching for my problem areas, a few jumps for tendon stiffness) and only in a shady, windy spot
Degressive race design
All drinks are ice-cold beforehand
Always wet the body and clothing with cold water when heated to save perspiration
Last meal with extra cooking salt (salt capsule or 50ml pickle water for me yesterday)
DO NOT get sunburn or heat fatigue the day before
Cold water bath within 10 minutes of crossing the finish line or heat collapse/heat exhaustion protects almost 100% against death due to heat stroke (yes, the whole thing can be quite dangerous!!!)

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