BY Maintaining core temperature is a priority for the body and there are a number of strategies we can use to slow down the rise in temperature, which also help delay fatigue and optimise running performance.
Why is running in heat and humidity SO exhausting?
Humidity compounds the effects of a hot environment and heat generated in the body by running. Sweat evaporation is reduced or absent, so the process of sweating is not efficient at cooling. This cascades into increased heart rate, increased sweating- but still no cooling, and so it continues with the body becoming progressively more dehydrated. In Singapore we are all familiar with sweat running off our body and not being evaporated so really need to be proactive about keeping cool.
Dehydration reduces plasma (blood) volume which in turn decreases stoke volume i.e. the volume of blood pumped from the heart per beat. With decreased stroke volume, heart rate increases to compensate. So, it is easy to understand why dehydration exacerbates fatigue and reduces performance.
When running, we want a good blood supply to muscles to provide oxygen and glucose for energy and power. Whilst this is a priority to us when we want to run fast and /or far, cooling and maintaining core temperature are priorities for survival. As soon as we lose water and become hot, blood will partially be diverted away from muscles to the heart and to the skin, less blood flow to the muscle increases fatigue and ultimately performance and, dare I say it, enjoyment.
Let’s Get Practical
Maintain excellent daily hydration
On a day to day basis, drink little and often, water is great but all fluids count. Ideally, keep sweetened beverages as treats or integrate them into a fueling strategy.
Know your own sweat losses and plan a hydration strategy
Sweat losses during exercise vary hugely from person to person. Take time to measure your own losses as follows:
Keeping, the calculation easy, go for a run and do not drink until after you have completed your weigh in at the end of the run.
- Go to the bathroom.
- Weigh yourself naked or in minimal clothing before a run (do not wear those same clothes when running, keep them for the post run weigh-in).
- Go and run and note how long you run for. An hour is a good amount of time.
- Dry your skin of sweat.
- Weigh yourself naked or wearing the same clothes that you wore before you started running.
- Calculate body weight difference. 1kg lost equates to a 1 litre sweat loss.
Replace sodium losses from sweat
Salt (sodium) is lost in sweat and needs replacing, but salt also promotes fluid retention. Depending on the run, have an isotonic sport drink if you also need fuel or add electrolytes to water. Electrolyte powders and tabs usually contain magnesium, potassium and other electrolytes, the amount of these are less important than the sodium content. Look for a drink or supplement that provides approximately 1g sodium per litre.
Cool your Body
Cool the skin with water and ice. Ice in hats and t-shirts, a cup of water over your head, arms and legs - anything that is practical, and the colder the better.
Wear clothing that wicks the sweat away from skin.
Drink iced drinks. For a long run, freeze your chosen sports drink then blend into a slushy.
Top tip: Iced drinks seem to be particularly helpful at improving performance if they are drunk before exercise starts.
Alarm Signals
Headaches, nausea and vomiting, feeling faint or dizzy are all signs of heat stress. Take note and cool, hydrate and rest.
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