Power Metrics (FTP, CP, and W')

Stride tracks three power metrics that describe your cycling at different effort levels, plus threshold paces for running and swimming and threshold heart rate. You can show any of them as tiles on your dashboard and follow them over time with a Metric History widget.

Functional Threshold Power (FTP)#

FTP is the highest average power you can sustain for about an hour. It is measured in watts, and Stride uses it for your power zones, your workout targets and your power-to-weight ratio (W/kg).

Stride estimates your FTP from your rides. After each ride with power, it fits your best efforts between about 2 and 30 minutes and saves a new FTP if the ride shows you are stronger than your current value. Indoor, virtual and e-bike rides all count. Rides marked with Mark suspicious power are ignored. If an activity's name contains "ramp test", Stride estimates your FTP as 75% of your best one-minute power from that ride, and saves it if it beats your current FTP.

Estimates only ever raise your FTP. It comes down slowly if you stop producing efforts that support it (see When FTP goes down, below).

To set your FTP yourself, open Metrics in the sidebar, select Add metric and choose FTP. In the app, tap Add (or +) and choose Record Metric.

When FTP goes down#

If more than eight weeks pass without a ride that raises your FTP, Stride lowers it by 1%, unless you are still training regularly. Each reduction restarts the clock, so your FTP falls by at most about 1% every nine weeks. Your Critical Power is lowered at the same time.

If you set FTP manually#

A manual FTP counts like any other value, and Stride only saves an estimate that beats your latest FTP. So if you enter an FTP higher than your rides support, automatic estimates stop until your riding catches up.

To go back to estimates, delete the manual value, then rebuild your FTP from your rides:

1. Delete the value. On the web, open Metrics in the sidebar and delete it there. In the iPhone app, tap FTP at the top of the home screen to open its history, then swipe the value left and tap Delete. The Android app cannot delete a past FTP yet.
2. Deleting it does not re-estimate on its own. On the web, go to Settings > Account, find Threshold Estimation and select Estimate now. The apps do not have this button.

Both steps on the web need a computer or a large tablet: on a phone, stride.is sends you to the app instead.

If your history was built on a wrong FTP, add the correct value on the Metrics page dated from when it applied.

Automatic estimation is controlled by the Threshold Estimation setting. It switches on once your first activity history has been imported.

Critical Power (CP)#

Critical Power is the highest power you can sustain aerobically, the boundary between the heavy and severe exercise domains. Stride models it from the same efforts it uses for FTP. In Stride, your CP sits about 4% above your FTP and moves with it.

On the dashboard, the Power / Weight tile switches between FTP and CP, with your W/kg alongside.

W′ (W Prime)#

W′ (pronounced "W prime") is your anaerobic work capacity: the total amount of work you can do above your Critical Power before exhaustion. It is measured in kilojoules (kJ).

Think of W′ as a battery that drains when you ride above CP and recharges when you ride below it. A larger W′ means you can handle more high-intensity work before you need to ease off, which matters for racing, sprinting and intervals. W′ balance on an activity uses your CP and W′ as they were on that date.

Pace Metrics#

For running and swimming, Stride tracks your threshold pace: the pace you can sustain for about an hour.

• Running Pace: your threshold running pace, per kilometre or per mile.
• Swimming Pace: your threshold swimming pace (Critical Swim Speed), estimated from your swims.

Both are estimated from your activities of 15 minutes to two hours and set your running and swimming zones. Like FTP, estimates only make them faster; they ease off slightly after 16 weeks without a faster effort.

Threshold Heart Rate#

Your threshold heart rate is your heart rate at threshold, and sets your heart rate zones. Stride estimates it as 95% of your best 20-minute heart rate, and keeps separate cycling, running and swimming values alongside an overall one. These values do not decay. If you set a heart rate value yourself, Stride stops estimating that one.

Tracking changes over time#

Add a Metric History widget to your dashboard and choose FTP or threshold heart rate. Each point shows where the value came from (an activity or a manual entry), and you can open the activity behind it. Every value is also listed on the Metrics page, where you can add or delete one.

HRV and Recovery#

Heart Rate Variability (HRV) measures the variation in time between heartbeats. Higher values generally mean better recovery. Add a Metric tile set to HRV to see your latest value in milliseconds and how it has changed, or one set to Recovery for your device's 0-100 recovery score. Recovery History charts that score day by day, and on days your devices do not send one (only WHOOP, Oura and COROS do), it charts Stride's Health Score instead. Your calendar shows each day's HRV too.

Stride also works out its own Sleep Score, Resilience and Health Score. Sleep Score, Resilience and Health Score explains what each one means.

You need a device that records HRV. See Connecting Your Devices.