To state the obvious, cycling hard makes you hot. But what is often overlooked, especially when the mercury rises, is how important it is to your performance to help your body dissipate that extra heat and stay cool.
This is because keeping a constant temperature of close to 37 degrees C is vital for all the complex chemical reactions that make up the metabolic process. According to Stuart Galloway, professor of sports science at Stirling University, even for intense exercise, only one or two degrees hotter than this is still the optimum. Anything higher will mean a rapid drop in performance, and if you really over-heat, potentially even heat exhaustion.
But it’s not just exercise that affects body temperature, as ambient temperature and weather conditions also vary widely during rides, either making your body’s job easier or harder. According to a study by Galloway and Dr Ron Maughan in 1997, 10.5 degrees C is the optimal ambient riding temperature, but even in the temperate UK, average July temperatures can swing between 11 and 20 degrees C. And with just a stiff breeze of 16 mph dropping skin temperature by a further 5 degrees, windchill can factor too.
Keep your cool
The body’s primary way of losing heat is by vasodilation, whereby blood vessels near to the skin dilate and let hot blood be pumped to the surface to be cooled. The cooling process is then accelerated by the evaporation of sweat from the skin’s surface. The best way you can help your body with these two processes is by wearing the right clothing. It should be:
Wicking: The layer next to your skin should be capable of transferring your sweat away from your skin to the surface of the material where it can evaporate. Not only will this help cooling but keep you from the discomfort of riding with a sweat-soaked shirt next to your skin. To the same end, the best jerseys will have the lightest material at the hottest parts of your torso – namely your underarms and down your spine – as well as a full zip for quick cooling on the hottest climbs.
Versatile: With temperatures and weather capable of varying so widely during just one UK day, clothing should be adaptable as you ride. The best way to achieve this is by layering. That way arm and knee warmers can be rolled up, down or off, and caps, lightweight packable gillets or showerproof jackets can be put on or taken off according to the conditions.
With thermoregulation so important to metabolism, your body will sweat even if it means dehydrating you, so drinking is vital to replace lost water. How much to drink depends on your sweat rate, which can vary from 0.5 to 2 litres an hour, depending on your sweat rate and conditions.
You can estimate your sweat rate by comparing your pre and post workout weight, and factoring in the volume of ﬂuid you drink during the session. You should aim to drink approximately 1.5 times this quantity during your rides, including electrolytes to replace salts and minerals lost while riding.
What are the extreme dangers of getting too hot, and how do you spot the signs?
- Intense cycling in the heat with inadequate hydration or electrolyte replacement can cause heavy sweating, weakness, dizzyness and nausea.
- Rest and electrolyte fluids needed.
- Abdomen cramping caused by salt deficiency due to high concentration of electrolytes lost.
- Rehydrate with an electrolyte drink.
- Fainting spell following a large increase in core temperature and drop in blood pressure.
- Shade in a cooler area, fluids and rest in a supine position should lead to a full recovery.
- The core body temperature reaches in excess of 40 degrees C causing vomiting, diarrhoea, convulsions, confusion, coma and even death.
- Immediate hospitalisation is needed...