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Tips For Cycling In Hot Weather – The Dangerous Truths Behind Those ‘Perfect’ Riding Days

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That’s what we all think when temperatures rise.

But hold onto your water bottles, fellow cyclists – that beautiful sunny weather might be more challenging than you’d expect. 

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Here’s some tips on beating the heat and why you should take it seriously

5 Tips To Stay Cool & Safe When Riding Your Bike On Hot Days

Heat exhaustion or heat stroke are difficult to defend against if factors conspire against you.

1. Stay On Top Of Hydration

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If you want to avoid heat exhaustion or heat stroke, you should be careful to stay hydrated off the bike as well as on.

Most adults require between 2 and 3 liters per day for good hydration. Don’t separate this need from bike rides.

The body becomes very efficient at sweating as you become fitter, which in turn cools you down by evaporation. But the fluids you lose during this process must be replaced to retain bodily function and maintain cycling performance.

Video: Hydration Tips For Cyclists and Other Athletes

Adequate fluid replacement during exercise helps to counteract increases in heart rate during hot weather, too.

Read more: Our guide to bike water bottles

2. Consume Sodium

You lose far more sodium than any other electrolyte through sweat, and low blood sodium levels (hyponatremia) can induce headaches, cramps, nausea and confusion.

Electrolytes help counter this issue.

💡 Tip: I like to mix electrolyte tablets in with my water bottle. I can easily carry these tablets (see image below) in my saddle bag, top tube bag or back pocket. Then I simply add a tablet each time I top up the water. 🚰

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SiS Electrolyte tablets

Not all electrolyte drinks contain enough sodium to reverse these symptoms. This is something you can look at if you have a high concentration of sodium in your sweat, indicated by salt crystals left on your skin or clothing after exercise.

As well as paying attention to salt content in drinks, you can eat salty snacks during or after a ride (e.g. pretzels, crackers, peanut butter.)

Video: Why Sodium Is Important For Athletes

This helps keep the brain sharp and the body reactive.

3. Wear A Heart Rate Monitor

Many people don’t like wearing a heart-rate monitor because they link it with taking cycling too seriously and not enjoying their ride.

Wahoo TICKRheart rate monitor unused
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I use the Wahoo TICKR Heart Rate Monitor

However, cyclists who routinely ride fairly intensively, as many amateurs do, can find their heart rate pushed to “threshold” levels in extreme heat as they try maintaining their usual speed and performance. By definition, that’s sustainable for one hour.

If you see that your heart rate is at an unsustainable level in hot weather, you can bring it back down by curbing intensity and regularly hydrating.

You can also use wrist monitors…

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4. Go Out Earlier

It’s an obvious one, this, but an early-morning bike ride is always cooler than riding in the mid-afternoon. Riding habits are hard to break, so you may have to adjust your sleep times, breakfast time and clothing to get out early on your bike.

If you need extra motivation for this, on top of avoiding heat exhaustion, a scientific study by the University of Bath suggests there are significant health benefits to riding before breakfast.

Periodic pre-breakfast bike rides can lower risk of cardiovascular disease and type-2 diabetes.

Fasted rides such as this are generally low intensity for 60-90 minutes.

Video: Early Morning Bike Ride

5. Acclimate And Get Fitter

Improving your aerobic fitness level helps your body to adapt quicker to high temperatures. Even with this fitness, you still need to acclimate to hot weather if you’re unused to it.

Cycling regularly for up to two weeks in high temperatures will help you to acclimate. Keep intensity low and duration relatively short during this time. Passive acclimation like sitting in a sauna or sunbathing doesn’t work as well.

You also need to maintain your hydration regime while acclimating. Deliberate dehydration is not useful in this process and is potentially harmful.

Video: Heat Acclimation Cycling Tips

Why Riding In The Heat Can Be Dangerous

When cycling in hot weather, your heart rate goes up as it increases blood flow to the skin. It does this to dissipate heat and moderate core temperature, but it’s easy to overwhelm this system as muscle and skin compete for blood flow.

🚨 Your core temperature only needs to go up by a few degrees centigrade to put your health and even your life in danger.

This danger manifests itself in two stages: heat exhaustion and heat stroke.

They are two sides of the same perilous coin, though not everyone experiences or notices heat exhaustion before getting heat stroke.

Heat Exhaustion – 38-39°C

If you experience any of the following symptoms when riding in extreme heat, you should stop immediately, preferably in shade, and allow yourself to cool down:

  • Dizziness and feeling faint
  • Excessive sweating
  • Cool, pale and clammy skin
  • Nausea or vomiting
  • Muscle cramps
  • Poor coordination
  • Weak pulse
  • Headache
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These symptoms will usually pass within 20-30 minutes, but you may feel weak and disoriented afterwards and should be wary of cycling in heavy traffic.

Although elite athletes tend to be more resistant to hot weather, even they can suffer its effects. Scottish runner Callum Hawkins collapsed from heat exhaustion while competing in the 2018 Commonwealth Games.

Video: Signs Of Heat Exhaustion

Heat Stroke – 40°C and over

If you push on through heat exhaustion, or even if you don’t experience it, heat stroke may occur.

This can lead to a coma, brain damage or death, so it’s not trivial!

The symptoms of heat stroke are not the same as heat exhaustion:

  • No sweating (body stops sweating at this point)
  • Hot, dry skin
  • Bad headache
  • Rapid, strong pulse
  • Nausea or vomiting
  • Seizures
  • Loss of consciousness
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Even top cyclists can get heat stroke. Young Belgian rider Enzo Wouters collapsed with heat stroke in the U23 World Championships road race in 2016.

Typically, the cyclists you see on TV undergo a meticulous hydration regime at the hands of their team nutritionists. And drinks are in constant supply during a race from team cars and roadside soigneurs.

Nevertheless, they still get dehydrated.

Video: What Happens When You Get Heat Stroke?

Heat Stress & The Body’s Response

We’ve described what can happen to you if you start overheating, but what’s going on in the body leading up to that point?

Heart Beats Faster

Cycling on a hot day, your heart rate is likely to increase by 10 to 20 bpm above the norm—your norm—within a short space of time.

Since this increase in heart rate is closely related to sweat rate and dehydration, you can try countering it by riding less intensely and drinking enough to replace lost fluids. You shouldn’t gain weight during a ride.

Blood Flow

When you begin to exercise, your “cardiac output” increases. This is your heart rate x stroke volume (the amount of blood being ejected with each beat).

At about 40-60% of maximum intensity, the stroke volume in most people plateaus and cardiac output increases by heart rate only.

During hyperthermia, stroke volume reduces slightly despite significant increases in heart rate and skin blood flow. A reduction in stroke volume and cardiac output theoretically leads to fatigue through a drop in oxygen delivery.

“Another aspect of oxygen transport is the delivery of oxygen to the tissues each minute. This oxygen delivery depends on both cardiac output (CO) and the arterial oxygen content (CaO)” source

Oxygen delivery = cardiac output x arterial oxygen content.

Skin blood flow sharply curtails once core temperature reaches around 38°C. Thus, one of the body’s heat-stress defenses stalls, even if you’re still getting hotter.

The Heat Is….Off!

The info above should help you offset the dangers of cycling in hot weather.

Remember to hydrate on and off the bike, listen to your body and take it easy.

Did you enjoy this article? Please feel free to add your own comments below and tips or share it with friends.

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Mark BikePush
Article By:
Mark is the founder of BikePush, a bicycle commuting website. When he's not working on BikePush, you can find him out riding.

2 thoughts on “Tips For Cycling In Hot Weather – The Dangerous Truths Behind Those ‘Perfect’ Riding Days”

  1. I suspect I experienced symptoms of heat exhaustion during today’s trail ride. We biked in direct sunlight in 80+ degree weather and high humidity. When we took a break, I felt sick and dizzy and had to lie down with a wet shirt on my head. This article will definitely help me take better precautions in the future. Thank you!

    Reply
    • Oh no, Jessica!

      Yes, it’s so important to take precautions. Electrolytes before, during and after the ride help a lot. Even with them the other precautions should be taken. I hope you recovered ok!

      Reply

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