Running in the Heat of Hong Kong

2022年7月3日|Physiology, Trail running

Summer training is not easy. With temperatures rising, high levels of humidity, and burning sun, it can feel cataclysmic to attempt to get in a good run. So what to do?

To race is foolhardy and even a long run or fast workout is hard enough. Like a friend of mine always asks but never takes the advice, (we are all aware of the common askhole) ” how can ever you feel good when running in the heat and humidity?”

To run consistently through the humidity of summer takes a well-planned approach that combines timing of the run, proper gear, and a comprehension of what exactly is happening that makes running in the heat tough in the first place.

But understand this advice only mitigates — running in such a hot humid place as Hong Kong at this time of the year is tough! I remember a few years ago meeting one of the fastest trail runners in the world. Who after catching kms on a stopover announced ‘give me altitude over this day on a day out!

Even the pros hate summer running!

But let’s approach this dilemma with some cognition. Instead of complaining about how difficult it is to run in the heat, let’s do this with a limiting of injuring ourselves or of putting our health in danger. The benefits will always come in Autumn!

Why Is It So Hard to Run in the Heat?

For runners in hot climates, Christopher McDougall’s fantastic book Born to Run gives us some clues. For a host of physiological reasons, you’ll remember that humans are amazing endurance animals when it comes to running.

Our physiology includes:- a large achilles tendon that produces a significant energy return when running. Big strong gluts which are plain and simple running muscles. We also have a special ligament that attaches to the spine with our skull which stops our head from bobbling around. And the final point is what interests us here! A (mostly) hairless body and highly evolved sweat system. So keeping yourself tidy is essential so in summer I am keeping my hair short and with the issues of covid this has kept my locks in check.

Can you guess which adaptation here is impacted by running in the summer? It’s our incredible sweat system, of course.

Perspiration helps cool us off because as our sweat evaporates from our skin, it takes heat with it. However, as humidity rises, it reduces the evaporation rate of the body because there’s already so much water in the air. Soon, you will feel overheated and have to slow down.

If you live in an arid place like Colorado where the humidity is low, a hot summer day can still wreak havoc on your training for two important reasons. So be careful if you travel way from HK to such a climate and expect to benefit!

First, the dry air evaporates sweat from your body almost as quickly as you’re producing it, so you can become dehydrated much more quickly. If you start a run slightly dehydrated or run long without any fluids, your performance will significantly decrease (and you’ll feel like death).

Second, as you become more and more dehydrated throughout a run, your heart needs to work harder at the same pace. This is known as cardiac drift: your heart rate increases over the course of a run even when the intensity stays the same.

Let’s not also forget the heat and sun, both of which increase your core body temperature. Your Rate of Perceived Exertion (RPE) will rise — sometimes drastically — even if you’re running a pace that’s usually comfortable.

Less evaporation because of higher humidity levels, increased chance of dehydration, and a higher core body temperature means that you’ll have to run slower to maintain the same effort. An unfortunate reality of summer training.

The Dangers of Running in the Heat

This article isn’t meant to put you off but being forewarned is to be forearmed!

It is true that the dangers are real. If you run too hard at noon in July, you might experience some type of heat illness. Here’s how to avoid these pitfalls.

Heat Cramps: these are muscle spasms that are caused by large fluid and electrolyte losses from sweating. These can occur while running but also in the hours after your run. No need to worry, they’re not serious — but make sure you stay hydrated and get enough electrolytes with sports drinks or more importantly through adequate an adequate diet including fruit like bananas.

Severe dehydration: We’re all familiar with dehydration. Up to a 4% loss in fluid levels from exercise is still safe, but any more than that and you may experience dizziness, fatigue, and even mental disorientation.

Preventing this level of dehydration is vital. One way to do is by starting your run already hydrated (your urine should be a straw color) and replacing your lost fluids as soon as you finish running. You can figure out exactly how much fluid you’ve lost by weighing yourself before and after a hot run.

Heat Exhaustion: If you work out too hard in the heat, you may come down with heat exhaustion — a case of dehydration, headache, nausea, and a core body temperature of up to 104 degrees. It’s much more common in runners who aren’t adapted to the heat.

If you think you have heat exhaustion, stop running, get out of the sun, and cool down with a cold drink and preferably air-conditioning. And next time, run earlier in the day!

Heat Stroke: Danger! Heat stroke is very serious because your core body temperature is probably over 105 degrees. Symptoms include disorientation and clumsiness, confusion, poor balance, and a lack of sweating. Immediate medical attention is required where you’ll be cooled with a cold bath, air conditioning, and cold liquids. More than once I have met hikers and runners in Hong Kong suffering such symptoms. Hence I carry emergency water for more than myself.

What You Can Do to Beat the Heat

The heat of summer isn’t the time to run your hardest workout and biggest mileage weeks — unless you’re super careful. Keep these tips in mind to stay safe and healthy:

Run by effort, not pace. Running in the heat is the perfect opportunity to work on the skill of running safely. Instead of strictly following pace targets that you might normally follow, run by time and effort rather than distance and pace.

Run early. There’s no perfect time to run in the heat of summer. But the early morning hours offer the lowest temperatures and a break from the strongest hours of sunlight (even though the humidity will be at its highest). It also means that you are done for the day!

Get off the roads! Asphalt and concrete absorb heat and radiate it back onto your poor, wilting body. The summer months are a good time to try more trail running. in Hong Kong. You have to run a little slower on trails and they’re usually shaded, both of which will keep you slightly cooler. Win-win.

Adjust your expectations. If the HK Weather Observatory issues a heat advisory (when the Heat Index, a score that reflects a combination of both heat and humidity, is over 105 degrees) running fast or long will be difficult and dangerous.

Even if there’s no heat advisory, remember why it’s so hard to run like you normally do in summer weather. Maintain the same effort and don’t prioritise the pace.

Don’t wear dark colours or cotton. Gear matters in extreme conditions so dress appropriately! Synthetic fabric like polyester is used in most running gear these days — take advantage of it.

Start your run hydrated (and keep hydrating). Even though hydration has been overemphasized by many it is it’s important to hydrate well before and after your run. Unless you’re running for more than 60–75 minutes, you probably don’t need to take any water with you. But learn what works for you.

Plan your run around water. I always carry enough water for two people but also plan routes where I have access to water to cool off in and vending machines or small trail teahouses. Enjoy your running!