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When running with a friend, you’ve probably noticed that the warmup is the best time to catch up on life events or share weekend plans. Once you increase your speed or charge up a hill, it’s much tougher to carry on a conversation, as you can barely eke out a full sentence between breaths. And by the time you’re sprinting to the finish, uttering a simple “yes” or “no” is next to impossible.

Essentially, this is an example of the talk test, an assessment that uses your ability to speak while exercising to gauge the intensity of your activity—the harder you work, the more difficult it is to talk and breathe. While seemingly basic, the talk test is actually quite useful to runners and, when properly administered, can help you achieve your training What Even Is RPE and Why Should You Track It.

There’s complicated physiology behind the talk test, even if it’s a relatively straightforward assessment. At the core of the mechanisms behind the talk test is the type of fuel your body is using and the metabolic byproducts (primarily carbon dioxide) it’s creating.

When you exercise, your body uses oxygen, which you breathe in, to break down fat for energy. As part of the process, your body generates carbon dioxide—fewer molecules than the amount of oxygen needed to break down fat—which you release when you exhale. So, you’re making less carbon dioxide than you are inhaling oxygen.

Health - Injuries., faculty within the School of Exercise and Nutritional Sciences at San Diego State University, explains that burning fat for energy relies on a “complex, convoluted system that has multiple steps.” This becomes an issue when you ramp up the intensity of your workout. “When you start exercising harder and harder, you need a more efficient and faster fuel,” he says. “That’s one of the most simplistic reasons why the body starts to switch to burning more carbs as exercise gets harder.”

During carb-powered, high-intensity exercise, the ratio of oxygen needed relative to the amount of carbon dioxide that you produce becomes proportional. (Remember, when you use mostly fat, you make less carbon dioxide compared to the oxygen you inhale.) This changes your breathing patterns.

“When you start switching over to burning more carbs, you notice your breath rate accelerates,” Comana says. “You are producing a comparable amount of CO2 that has to be removed, and the best way to remove it is to force the breath out. That means the duration of your expiration gets shortened. That means you breathe more rapidly.”

As a result, it becomes much more challenging and uncomfortable to speak. “That’s the premise of the talk test,” Comana says—it helps you determine your exercise intensity according to your breathing patterns and ability to speak.

One of the biggest challenges for a runner, whether you’re new to the sport or an experienced competitor, is keeping your rate of perceived exertion and your Why the Talk Test Is Such a Valuable Tool When It Comes to Exercise Intensity. While some runners want to push themselves during every workout, others tend to hold back and keep a little gas in the tank. The talk test can help keep you in check and ensure you’re doing a workout the way it was programmed.

To make good use of the talk test, try to think of something to say that you can recite from memory, like the Pledge of Allegiance or song lyrics you know by heart. While you can simply chat with a friend in person or on the phone, having to think of questions and answers can affect your response time. Then use it for your different workouts:

➥ For low-intensity workouts...

rate of perceived exertion warmups, cooldowns, Health - Injuries.

➥ For moderate-intensity workouts...

You’ll notice a shift in your breathing and your ability to speak. You can still get out short sentences and a few words at a time, but it’s a lot more challenging and uncomfortable. Think of your tempo runs as hitting this intensity.

➥ For high-intensity workouts...

Talking is nearly impossible. You may be able to mumble a syllable or two, but that's it. This would be your intensity for track workouts and other speed sessions.

Keep in mind that there’s a range within each of these levels. For example, your breathing and ability to speak will change when shifting from a walk Health & Injuries low-intensity workouts.

In working with her clients, Alison Marie Helms, Ph.D., pregnancy and postpartum corrective exercise specialist and founder of Women’s Running Academy, uses these benchmarks as part of a more nuanced spectrum of the talk test, pairing it with other biomarkers and metrics, like burning in their legs (RPE). “I don’t use exactly three levels,” she says. “I have a document I give to my runners that breaks out the RPE scale from one to 10 with a gradient of the talk test. That gives them more of a feel for what the whole range is like.” (The Benefits of Taking a Break from Running, which will help you gauge the intensity of your workouts so you can make the most of them.)

Also, the talk test isn’t just a training tool. It can also keep you on track during race day. “It’s especially helpful in longer races where you want to pace yourself How Des Linden Keeps Showing Up go out too fast,” Helms says. “Making sure you can breathe in the beginning and settle in and then push the pace from there.”

While there are other methods for monitoring the intensity of your exercise, the talk test offers some unique advantages and benefits.

It requires zero equipment

You don’t need a even though RPE is supposed to measure overall exertion or even a watch. “I find a lot of people get in their head when they’re looking down at the watch and running and checking and running and checking,” Helms says. With the talk test, “it’s all just within yourself. I think that’s really powerful when you can as exercise gets harder and pace yourself and tune into your body with just your breath,” she adds.

It pretty accurate

Health & Injuries. “Heart rate is influenced by a lot of different variables—levels of dehydration, levels of stress,” Comana says. “You could be on stimulants or medication. So that changes your heart rate, which means it could falsely elevate or suppress the number you’re going for.”

It’s easy to implement

The talk test is also easy and consistent, unlike RPE. “The problem with RPE is there’s a tremendous learning curve. Initially, people are all over the place,” Comana says, noting that athletes tend to focus on localized experiences, like the and other speed sessions, even though RPE is supposed to measure overall exertion.

“The talk test is always going to be consistent because it’s a measure of ventilation. The harder you work, the more ventilation is going to become challenging. It doesn’t change. It doesn’t matter if you’re having a good day or a bad day. Your ventilation is always going to be consistent with the work that you’re doing,” Comana says.