My watch pace changed: should I speed up during the race?

Learn to weigh the pace shown by your GPS, your effort and the course context before changing the way you run.

You turn onto a street lined with buildings. You keep the same stride, but your watch shows your pace has slowed. Your first reaction is to speed up to get back to your planned number.

Before you do, ask yourself: did the reading change because you slowed down or because the watch had trouble measuring?

A single fluctuation on your watch needs context. The device helps you track your race, but your decision also depends on your effort, the stretch of course you're on and the strategy you prepared.

What the pace on your screen means

Pace usually appears in minutes per kilometer. A lower number means you're running faster.

Depending on the device and the screen you've chosen, you may be seeing an estimate of your current pace, the average for a lap or the average since the start. These fields answer different questions.

Overall average includes everything that's happened up to that point. Lap average covers only that segment. Current pace tries to represent the moment and depends on how the device calculates it.

So before the race, find out which field you're using. Reading your overall average as if it were your speed at that instant can lead to a poor decision.

Why GPS can produce a different reading

Your watch uses satellite signals to estimate your position and movement. COROS documentation states that tall buildings and dense vegetation can interfere with the signal and affect distance, pace and track. COROS Help Center

There's independent evidence, too. A study published in 2020 evaluated eight watches in urban, forest and track environments. Distance accuracy was lower in the urban and forest areas. PMC

The study looked at devices from that time and short routes. It doesn't allow you to apply the same margin of error to a current model or to conclude that every pace fluctuation is a GPS glitch.

The practical takeaway is simple: when the number changes unexpectedly, look at other information before you react.

Compare the data with your effort and the course

Picture two situations.

In the first, you pass between buildings and see a sudden change on the screen, while your running form feels steady.

In the second, you hit a hill and have to work harder to hold your previous pace.

These are illustrative examples. In the first, there may be a measurement problem. In the second, the terrain changed the demands of the run. In both, speeding up right away to fix the number could go against your plan.

Ask yourself: Am I on a hill? Is there a crowd of runners? Have my breathing and the effort to move my legs changed? Does the pace shown make sense for what's happening?

A 2022 review explains that perceived exertion involves how hard and demanding an activity feels, including the effort of moving and breathing. The authors note that using scales requires clear instructions and familiarization.

You can develop this awareness in training, with guidance. It doesn't turn every sensation into a sign that you're safe.

Effort, pain and feeling unwell need different kinds of attention

A race can be demanding. That doesn't mean it's okay to ignore symptoms to hit a goal.

The review distinguishes perceived exertion from other sensations, such as pain. Don't treat localized pain or feeling unusually unwell as just a high effort number.

On hot days, the guidance is to stop exercising and find a cool place if you feel faint or weak. If this happens during a race, ask the event staff for help and seek medical care if there are signs of heat-related illness.

Your watch reading doesn't give you clearance to keep going while you feel unwell.

Have a backup plan before the start

As a general guideline, test a simple setup in training. It might include elapsed time, distance and a pace field you know how to read.

Average lap pace can help you watch a stretch without reacting to every change in the current reading. However, if the lap and its distance depend on GPS, the average can be affected too. Switching fields doesn't eliminate the measurement problem.

When the organizers provide reliable markers, the time between points on the course can give you another piece of information. Manual laps are an option if you already know the feature and have practiced using it.
Also check your battery, satellite settings and signal acquisition according to your device's manual. Do this early enough to keep up with the start-line procedures.

You don't need to buy another watch to start making better sense of the one you have.

What if my device already built my strategy?

Automated features can suggest goals and distribute paces across segments. Check your device's documentation: it may, for example, describe calculations based on your estimated fitness and the route profile.

That tells you how the feature works. It doesn't guarantee the suggestion is right for your race day.

Talk with your coach about your goal and the conditions for adjusting it. For your debut, finishing with an experience that matches your training can be goal enough.

For advanced and professional runners, planning can be more detailed. The need to interpret measurements remains; this article doesn't replace an individual strategy.

Ask three questions when the screen surprises you

Before you speed up, check:
- 1. Data: am I looking at current, lap or overall pace?
- 2. Effort: has the demand changed in a way that makes sense?
- 3. Context: have I hit a hill, an area with poor signal or a crowded stretch?

These questions help organize what you observe. They're not a safety test or a validated protocol for determining your ideal pace.
On your next run, practice reading one watch field together with your effort and the course. Bring your questions to whoever oversees your training. On race day, that familiarity helps you make a more informed decision when the number changes.

General guidance; not an individual intensity prescription or fitness assessment.