Exercising in the Heat and Humidity – Facts – Tips

As temperatures and humidity rise what are our top tips to beat the heat – why do we over-heat? The hot summer season requires us to think more about our training regimes.

What do we notice when temperatures and humidity rise…

Early fatigue during only moderate exercise – a feeling of reduced capacity to exercise or increased levels of perceived exertion needed

An increase in core body temperature

Increased sweat rates

A higher risk of dehydration

Getting used to higher temperatures takes time..

• During the initial days of training in a hot environment athletes display a reduced ability to exercise at the same intensity or duration when compared to cooler temperatures. However after a few days the heat tolerance of athletes improves

• In the initial stages of exercising in a hot environment it is important to dialing down the duration and intensity of the sessions. The warm up intensity and duration should be decreased to keep core temperatures from rising too much during full training.

• It can take between 7-14 days to properly acclimatize to training in the heat and if temperatures and humidity are very high even after that don’t expect sessions to be as long or intense as they can be in cooler temperatures.

What is happening to your body in the heat?

• When your core body temperature rises, your heart rate will go up in an attempt to cool you down, there will be more blood flow to the surface areas and less to the muscles.

• The raised body temperature in combination with dehydration causes fatigue and this in turn can increase lactate production and the demand of your body for carbohydrates.

• Especially high intensity training in heat and humidity can also create an extra adrenaline response in the body which in turn will further increase the rate with which your body wants to burn carbohydrates as opposed to fat.

• Heat is an additional stress factor. Bear in mind that exercising in the heat puts additional stress on the body and intense workouts in the heat require longer recovery and rest (more sleep).

Why this is harder in high humidity

• Your own body will try to reduce its temperature by sweating in the hope that the action of evaporation will cool you down. However when humidity is high there is little evaporation and hence you will over-heat more quickly.


• Heat causes an increase in the sweat rates and with it electrolyte loss. It is important to ensure adequate rehydration with liquids and electrolytes to avoid excessive dehydration. Just drinking water is not enough.

• Hydration Pre Workout: It is useful to ingest extra fluids and electrolytes, between 400 and 600ml approx 20 minutes prior to exercise as this can increase sweat rates and bring about a smaller rise in core temperatures

• Hydration Strategy During: Take extra fluids with electrolytes with you. For longer runs or cycles in hot temperatures, it is important to have a carefully thought out strategy based on estimated fluid loss over the course of the session. Sweat loss in the heat can rise to 2 liters per hour.

• It is easier for your body to absorb an electrolyte drink that also contains some carbohydrate.

Increased need for carbohydrates in the heat

• Carbohydrate needs can be higher in the heat (see above), so make sure you have fuel with you even if you would normally go fasted.

• Remember it is always worth having that extra “emergency” isotonic gel in your back pocket for when it is required

Competing at an event in hot and humid conditions?

A good example of this would be for the athlete based in the UK who is competing in the IronMan world championships in Hawaii in October? That could be a severe shock to the system if you have undertaken all of your preparation in a cool damp English summer!! Average temperatures in Kona are around 26 degrees with 85% humidity. If your budget allows arrive 10-14 days before the start of the event to begin the heat acclimatisation process to ensure that you have the best day possible at the office.

Posted on 15th Aug 2020