Running power has been part of IntervalCoach for a while, and it still generates a steady trickle of questions: which number does the coach use, why are my targets 0 W, does my Garmin count, and why does the coach hold me back on a run when it would let me push on the bike. This post answers those in one place.
Why power instead of pace
Pace is the natural unit for running, and for flat road running it works fine. It stops working the moment the course does something. A 4:10/km target on a 5% climb is a completely different effort than 4:10/km on the flat, and a headwind quietly turns a threshold interval into a VO2max one.
Power measures the work you are doing rather than the ground you are covering. An interval held at 280 W on a climb is the same physiological effort as 280 W on the flat. If you train on rolling terrain, in wind, or on a treadmill without GPS, a power target is the one that stays honest.
Where the reference number comes from
Every power target in a running workout is a percentage of your running FTP. It lives in Intervals.icu under the Run sport settings, and it is a separate value from your cycling FTP. Intervals.icu keeps two versions of it, and IntervalCoach follows the same FTP preference you set for cycling in Settings → Training:
- eFTP (the default): Intervals.icu estimates your running FTP from the power curve of your recent runs, so the number moves with your fitness without you touching it.
- Manual: the running FTP you typed into the Run sport settings yourself, for when you would rather train against a tested number.
Whichever you prefer, IntervalCoach falls back to the other one if it is missing. If neither exists, there is nothing to scale against and the targets in your workouts come out as 0 W. That is the most common reason a runner sees blank power targets. A few runs with power data give Intervals.icu enough to estimate an eFTP, or you can enter a manual value and be running on watts right away.
The reference number belongs to the device you measured it with. Two common sources give slightly different readings for the same effort:
- Stryd (the foot pod) produces a consistent, mechanical power estimate that most athletes find reliable across terrain and conditions. It does not depend on GPS, which makes it the better choice on a treadmill.
- Garmin running power (Running Dynamics Pod, HRM-Pro, or native on Forerunner and Fenix watches) uses a different algorithm and tends to read somewhat higher than Stryd on the flat. It is a different model of the same effort, and either one works.
IntervalCoach does not care which source your activities come from. It only cares that your running FTP was measured with the same source you run with. Switching from Garmin to Stryd mid-season without re-testing shifts every zone, so re-establish the number after a device change.
Turning it on
Power targets are a preference, not the default. Under Settings → Training → Running Workout Targets you pick how running workouts are prescribed:
- Pace-based: targets in min/km. The default, best for road running on consistent terrain.
- Heart Rate-based: targets as HR zones. Needs LTHR or max HR set in Intervals.icu, otherwise the coach falls back to pace.
- Power-based: targets as a percentage of your running FTP. Needs a running power source.
- Auto: heart rate for trail runs, pace for road runs.
You can also ask Coach+ to switch your runs to power targets from chat, and it changes the setting for you.
What a power-based run looks like
Once the preference is on, every running workout is generated with watt targets throughout. A threshold session reads "4 × 6 minutes at 275-290 W" instead of "4 × 6 minutes at 4:05-4:15/km". Warm-up, cooldown and recovery jogs carry watt ranges too, scaled from the same running FTP, so an easy run is prescribed at the easy end of your power range rather than at a pace-derived percentage that happens to be too low.
The structure of the session does not change with the target type. The coach picks the workout type and duration first, from your plan, your readiness and your recent load, and only then expresses it in watts, pace or heart rate. Switching target types changes the units you see, not the training you get.
Tracking your running power over time
If you run on power, the dashboard shows your running power form in watts, in the same spot a pace-based runner sees Critical Speed. Analytics has a Running Power (eFTP) history chart in the Running section, covering the last six months, so you can see whether the number you train against still matches where your fitness is.
If you train on the eFTP, that chart is also the number your targets are scaled from, so a rising line means the next workouts get a little harder on their own. If you train on a manual FTP, the chart is your cue to re-test: a manual number that has drifted from the estimate means every session is prescribed a little too easy or a little too hard.
Running fatigue is judged on a different scale
This is the part that matters more than the units. Running produces a higher perceived effort than cycling at the same training load. A 100 TSS run takes more out of you than a 100 TSS ride, even though the number is identical.
IntervalCoach's signals engine uses sport-specific fatigue thresholds based on Foster's 1998 work on session RPE across modalities. A runner is flagged as deeply fatigued at a TSB of -20, where a cyclist is not flagged until -30. The moderate-fatigue line and the "fresh" line move the same way. So when the daily adaptation swaps a runner's intervals for an easy run at a TSB a cyclist would train through, that is the reason.
If you do more than one sport
Each sport keeps its own zones and its own fatigue thresholds. Training load still blends across sports for CTL and TSB, so a hard run contributes to your fatigue for tomorrow's ride. But workout selection and intensity targets stay sport-specific, and a seven-hour week split across three sports is judged differently from seven hours of only cycling.
The same Training settings page has a Cycling Workout Targets preference. Cyclists without a power meter can set it to heart rate and get their cycling workouts against BPM ranges, with the same structure and periodization as power-based sessions.
A quick checklist
If you run with a power source and want watt targets:
- Make sure Intervals.icu has a running FTP for you: either a few power-recorded runs so it can estimate one, or a manual value in the Run sport settings, measured with the device you run with.
- In IntervalCoach, go to Settings → Training → Running Workout Targets and choose Power-based.
- Open your next running workout and confirm the targets are in watts. If they read 0 W, step one is missing.
- Glance at the Running Power chart in Analytics every few weeks. On eFTP the targets follow it; on a manual FTP it tells you when to re-test.
If you run on pace or heart rate, nothing here changes for you. The coach prescribes the same sessions in the units you chose. But if you have been wondering whether a running power meter is worth it, the honest answer from the coaching side is that it makes structured runs a lot easier to execute on anything other than a flat road.