Cycling in the Heat

When reflecting on my first ever bike race, I can honestly look back at what a novice I was. It was just outside of Riyadh, Saudi Arabia and I turned up with my usual North East of England lycra, my trusty bike and a couple of bottles of water. That was about it. I did consider that it felt quite ‘warm’ before we even set off, but how bad could that be, I love the heat! Turns out it could be very bad indeed.  I finished the race with cramp in both legs, my lycra was unrecognisable from the salty sweat stains and I was glad to have even crossed the finish line. The race left me not only in a shocking physical and mental state, but a ponderous one of how I can adjust my behaviour in order for this not to happen again.

Unfortunately I will have to admit that this happened again, multiple times. Poor planning of water stops, unforeseen heat waves and gritty hard races have led to me over-heating and underperforming several times. Now I find myself in Dubai and the hot days are no longer a one-off but a permanent fixture of living in the desert. This has led me to write this article on cycling in the heat, to advise you on how to combat overheating whilst maintaining your rigorous training.

So how does heat affect the body during cycling? What can be done to combat this? To avoid getting frustrated during your training and risk losing your mojo during the Great Dubai Bake Off, read on!

How do increased temperatures affect the body during cycling?

Simply put, your body is constantly working to maintain homeostasis. This is the optimal condition, within the body, for all physiological processes to occur such as aerobic metabolism. When you exercise, your body increases the energy production to meet the demand. A waste product of this is heat. The body then needs to work hard to get rid of this excess heat, in order to prevent the core temperature from rising to a hyperthermic state. Hyperthemia comes with side effects such as muscular cramps, heat exhaustion and could even lead to heat stroke. To prevent this, the body pushes the blood to the edge, right up to the surface of the skin, to dissipate this heat. You also sweat, 2.5 million eccrine glands all over the body pour liquid through the pores which evaporate taking some of that heat away. These responses maintain optimal physiological conditions. The image below beautifully illustrates the body's mechanisms of reducing heat during cycling.

 Image 1. The mechanisms of heat reduction during cycling.

Now for example, if I was cycling at zone 2 and the temperature outside is 17°C, my body is going to find it pretty easy to get rid of this built up heat. The difference between my core body temperature to the outside temperature is greater, therefore the heat gradient is steeper allowing the diffusion of heat to a lower temperature. This  results in heat easily escaping my body. Pump a little blood closer to the extremities and hey ho, homeostasis is maintained.

Welcome to summer in Dubai, the temperature is 40°C outside and your body has an internal temperature of 37.5°C, the heat gradient is not on your side. So what does the body do? It sweats even more, it increases the breaths per minute and redirects even more blood away from the working muscles straight to the surface of the skin. This means less oxygen is given to those hard working muscles, which then don’t get the supply of vital resources, fuel and oxygen, nor are the waste products removed which increases cellular acidity.

The dangerous thing about being on a bike during this is that the wind takes so much of that sweat off so quickly whilst you’re moving, you don’t even realise how much you are actually sweating. So don’t be alarmed when working at your zone 2 in the summer is significantly different to in the winter. Your performance ceiling is lowered because your body is working so hard to keep cool. Your ability to create energy and power is severely dampened, by as much as 15%!

What can I do to prevent overheating?

Hydration,  First and foremost your hydration needs to be managed. Make sure you’re taking on plenty of fluids before and during a ride. You lose a lot more than just water, so electrolytes will be better for rehydration and replacing lost ions. By staying hydrated your body is able to continue to cool during exercise without affecting performance as much. Rob Jones did an awesome video on measuring your sweat rate so click here to see that video.

Pre-cooling and cool things, Cooling down before a ride is a great way to prevent overheating, particularly during a time trial or short crit race. A cold and wet towel or cooling jacket before heading out on the bike has been proven to be beneficial. On the bike, frozen water bottles and cold energy gels are not only super refreshing, but also help cool your core temperature. It is also worth noting that water is not just for ingesting, chucking it over your body will take a lot of heat away.

Attire, It goes without saying but don’t wear thick clothing or hats, just because it might look cool. High wicking fabrics don’t trap the heat to your body, but allow you to get rid of heat quickly.

Planning, It’s simple, don’t go out in the middle of the day. Opt for early mornings or late evenings. Even better, get a turbo trainer for high quality training during the week, making the most of aircon and electric fans. You can perform intervals without being hampered by heat.

What does this mean for my training?

If you’re cycling outdoors during the summer and are using heart rate or power, it’s going to be very difficult to use it as a reliable source to train to. Zone 2 is near impossible to maintain or can be frustratingly slow due to the responses to heat and the reduction in power output. My best advice is to measure your outdoor rides on Rate Perceived Exertion (RPE). If you’re honest with yourself, it’s a pretty reliable means of measuring your training. Leave your harder session for indoor training where you can control the external environment. You can still train well, just don’t be a slave to numbers which are skewed by the heat, try the tips I’ve suggested so you enjoy the ride more and aren’t cooked for days after. Most of all just enjoy riding. That's the reason we do all of this, because we love it.

By: Rob Foster, Endurance Coach