Training In The Heat

Training In The Heat: Why Your Normal Pace Suddenly Feels Harder

You head out for a run at a pace that normally feels comfortable. Ten minutes in, your heart rate is higher than expected, and the effort feels harder. You’re sweating heavily, and the pace on your watch isn’t particularly impressive.

Or maybe you’re on the bike. A climb you’ve ridden dozens of times suddenly feels much harder than it did a few weeks ago. You’re producing less power for what feels like more effort.

It’s easy to look at the numbers and wonder:

Am I losing fitness?

Probably not.

When the temperature climbs, the physiological cost of training changes. Understanding that can help you make better decisions about pace, intensity, hydration and, perhaps most importantly, your expectations.

Your Body Has Two Jobs Now

Exercise generates heat. On a cooler day, your body has a relatively straightforward job of getting rid of that heat. As the temperature rises, particularly when humidity is also high, that job becomes more difficult.

Your body responds by sending more blood toward the skin to help dissipate heat. You also sweat, and the evaporation of that sweat helps cool you. At the same time, your working muscles still need blood and oxygen.

In other words, your cardiovascular system is being asked to support the workout and help regulate your temperature. Your heart rate may climb higher than usual for the same pace or power output, and an effort that normally feels manageable can start feeling considerably harder.

That’s not necessarily a sign that your fitness has declined, it’s a sign that the environment has changed the cost of producing that performance.

Stop Comparing A Hot August Run To A Cool May Run

This is where watches, bike computers and training apps can sometimes work against us.

We have access to an enormous amount of data, which can be very useful. But the numbers need context.

A 5:30/km pace isn’t physiologically identical under every set of conditions; neither is 200 watts on the bike.

Temperature, humidity, direct sun, wind, hydration status, sleep and accumulated fatigue can all influence what it takes to produce a particular number.

So if your normal easy pace suddenly requires a much higher heart rate and feels more like a moderate effort, forcing yourself to maintain that pace simply because it’s what you normally run may change the purpose of the workout. Your easy run isn’t really easy anymore.

The same applies to cycling. Chasing your usual power numbers during a long, exposed ride on a very hot afternoon may turn a manageable endurance session into something much more demanding.

Sometimes the smarter target is effort rather than pace or power.

Heat Acclimatization Is Real

There’s also some good news. The body adapts.

With repeated exposure to exercise in the heat, we become better at handling it. Heat acclimatization can improve our ability to dissipate heat and tolerate exercise in warmer conditions, but adaptation takes time.

This is particularly important during the first significant stretch of hot weather. You may be fit, but that doesn’t automatically mean you’re adapted to the heat.

Someone can have excellent cardiovascular fitness and still struggle during their first few hot rides or runs of the season.

Health Canada specifically recommends starting gradually when exercising in hot conditions and not expecting your usual performance during extreme heat. Give your body some time to catch up.

Hydration Matters, But It Isn’t The Whole Story

It’s impossible to talk about training in the heat without talking about hydration.

Sweating means losing fluid, and longer or harder sessions in hot conditions can substantially increase those losses.

Starting a workout well hydrated matters. Drinking during longer sessions matters. For athletes doing prolonged training with significant sweat losses, replacing electrolytes can also become part of the equation.

Hydration shouldn’t become a strategy for ignoring the conditions. You can’t simply drink enough water to make a very hot day behave like a cool one. Sometimes the better decision is still to change the route, start earlier, shorten the session, reduce the intensity or move indoors.

Hydration supports good training in the heat. It doesn’t eliminate the effects of heat.

Change The Workout Before The Workout Changes You

Imagine you have a two-hour run or a four-hour ride planned and the forecast is calling for significant heat. You don’t necessarily need to abandon the session, but you might need to change how you approach it.

Starting early can make a significant difference. Choosing a shaded running route or a cycling route with reliable places to refill bottles can help. Reducing intensity may preserve the intended purpose of the workout. Sometimes moving a hard interval session indoors while keeping an easier outdoor session makes more sense.

The important thing is to make these decisions deliberately rather than waiting until you’re already overheating halfway through the workout. This becomes particularly important for long rides, runs and hikes where turning around or finding somewhere cool may not be easy.

The farther you travel from home, the more important planning becomes.

Know When It’s More Than Just A Hard Workout

There is a difference between feeling the normal strain of exercising on a hot day and developing signs of heat illness.

Headache, dizziness, nausea, extreme thirst, muscle cramps and feeling unusually unwell are signs that should get your attention. Move somewhere cool, stop or reduce activity, cool yourself and rehydrate.

Confusion, fainting, loss of coordination or a very high body temperature are much more serious. Heat stroke is a medical emergency and requires immediate medical attention.

Being fit doesn’t make you immune.

In fact, athletes can sometimes get themselves into trouble precisely because they’re accustomed to pushing through discomfort.

Knowing when not to push is part of being an experienced athlete too.

Your Pace Isn’t Your Fitness

We talk a lot about consistency at Groundwork Athletics, but consistency doesn’t mean producing the same numbers every time you train. Good training responds to the environment you’re training in.

On a hot day, that might mean running slower at the same effort. It might mean producing a little less power on the bike. It might mean taking an extra break on a long hike, carrying more fluid, changing the route or moving the workout to a cooler part of the day.

None of those things mean you’re getting less fit. They mean you’re accounting for the additional stress the environment is placing on your body.

The goal isn’t to prove that you can force your normal pace regardless of the conditions. The goal is to apply the right amount of stress, recover from it, and come back ready to train again.

That’s how fitness is built, not through one heroic workout in the heat, but through months and years of good decisions.

Sometimes, slowing down is part of moving forward.