Running based on power (Watts) instead of pace allows you to manage effort perfectly on any terrain, preventing you from burning out on hills or against the wind.
- Pace per mile isn’t always a valid reference: on hills, you slow down even if you are working twice as hard.
- Power (Watts) measures instantaneous mechanical effort, not the consequence (speed).
- Running in “isopower” mode (constant Watts) is the secret to not bonking on hilly routes.
- Unlike heart rate, which has a lag, Power is immediate.
Have you ever run up a hill, looked at your watch, and seen a pace like 13:00/mile, while your lungs were trying to escape your ribcage and your legs burned like you were sprinting?
In that moment, your GPS was telling you the result (you are going slow), but it completely ignored the cost (you are pushing like crazy).
This is where Power, measured in Watts, comes into play.
If you come from a cycling background, you know what I’m talking about—it’s been the standard there for years. In running, it is a relatively new frontier, but one that is changing how we train and race.
Let’s be honest: running based on pace is great if you are on a track or a flat road on a windless day. But real life is full of hills, descents, and headwinds. Even heart rate isn’t always reliable because it can be influenced by external factors (stress, sleep, diet).
So—while pace, heart rate, and RPE (Rate of Perceived Exertion) are useful—power is a more universal, objective parameter.
What Is Running Power? Measuring Work, Not Speed
Without getting into a physics lecture, power is the measure of work you do per unit of time. In running, it is a complex mix of speed, slope, and body weight.
Today, almost all modern sport watches (Garmin, Polar, Apple Watch) estimate it directly from the wrist. However, this is a software estimate, not hardware, so it isn’t always perfectly precise. Alternatively, there are external sensors (like the famous Stryd) that attach to the shoe and are much more accurate.
The huge advantage of Watts over heart rate is immediacy.
The heart is a “slow” organ: if you sprint now, your beats will rise in 10–20 seconds. If you stop, they take a while to come down. Watts, on the other hand, spike the exact moment you push and drop as soon as you slow down. It is real-time data.
The Problem with Pace: Why GPS Lies on Hills and in Wind
There is another invisible enemy that GPS doesn’t see: the wind.
Running at a 8:00/mile pace with a 20 mph headwind requires a monstrous effort, comparable to running at 7:00 or 6:50 pace. But your watch will just say “8:00/mile,” making you feel slow and inadequate.
A power meter (especially shoe-based ones with wind sensors) detects that resistance. It will say: “Hey, you’re moving at 8:00 pace, but you’re putting out 300 Watts. That’s your fast race effort. Good job!”
The difference is that pace judges the result. Power rewards the effort.
From the perspective of Running Economy and energy management, knowing how much fuel you are burning is fundamental.
Running “Isopower”: The Strategy to Avoid Bonking on Hilly Routes
This is the most important part, the one that saves your race experience on rolling hills or trails. It is called the isopower strategy.
It means trying to keep your power line flat and constant, regardless of the terrain.
- On Flats: Run your pace, Watts are stable.
- On Uphills: Your instinct tells you to push so you don’t lose too much speed. Instead, look at the Watts. If they spike, slow down intentionally until they return to your flat-ground value. Yes, you will go slow. But you won’t go into the “red zone.”
- On Downhills: The opposite happens. To maintain the same Watts, you must let your legs go and run fast (without braking), otherwise power drops because gravity is helping you.
Running this way, you reach the top of the hill without gasping for air, and you still have legs to push afterward. It is the most efficient way to manage human resources.
How to Read the Number (And Find Your Magic Number)
“Okay, but what number should I see?”
Here is the catch: Watts are personal. They depend heavily on your weight. A 200 lb runner will generate many more Watts than a 110 lb runner at the same speed, simply because they have to move more mass.
Don’t look at your friends’ numbers on Strava. You need to find your Critical Power (or rFTP, Functional Threshold Power). Many sport watches calculate this automatically after a few weeks of use.
Once you have that number (let’s say, for example, 250 Watts), you know that is your “threshold.” If you stay under it, you can run for a long time. If you go over, the timer on your exhaustion has started ticking.
Using power doesn’t mean becoming a robot or turning running into a video game. It means having a more precise dashboard to drive the amazing machine that is your body.
It means facing wind and hills with metrics that allow you to dominate elevation and the elements.