# How to interpret Strava power curves?

Check out the power curve at the bottom of the post, it's composed of two screen caps from the same ride, stacked on the same image:

Apparently on the ride in question the cyclist rode at:

• 291W for 12min 55s
• 270W for 9min 10s

But I would have though that if you rode for 291W for 12min 55s, you also rode at least 291W for 9min 10s ... right? ... 🤷‍♂️

What are these dips? How are we meant to interpret this data?

I would expect power curves to either be flat (usually a result of ERG mode on a trainer) or constantly falling as the time period increases.

I reached out to Strava and their facebook rep said it was 'complex' and to send in a query to the support email - they haven't replied.

I had a look here: What method or algorithm is used for computing Power Curve on Strava?

It's good info, but the example given there doesn't have a dip, and doesn't discuss it - but it does make make me think that the answer might just be what I'm trying to avoid suggesting...

At a casual glance I'll agree that power curves do show power plotted against time, but don't be mistaken in to thinking that they show instantaneous power over time.

Power curves show the maximum power a rider rode for a duration (averaged via various means, some algorithms more clunky than others), and as has been confirmed to my satisfaction they should be a 'monotonically decreasing function of duration' - but they're not on Strava, (which prompted my original query...)

Here is a visual example of how power curves are different from power with respect to time:

## Instantaneous power over time:

(This was a Zwift ramp test in ERG mode until failure when it slipped in to free ride)

## Power Curve plot from the same data:

Note that:

• They are under different sections in Strava
• They don't look alike
• The 418W at 1 min on the power curve correlates to the 1 minute duration that 418W was held (around the 21min 40s period seen in the instantaneous plot and not 1 minute in to the ride)
• The power curve has a logarithmic time scale
• The measurements shown are instantaneous. At about 9 minutes you were starting to tire, but when you saw that cute girl you had to show off, so you were doing 30 watts better for a few minutes. May 20, 2020 at 1:59
• @DanielRHicks, 🤦‍♂️ Not sure that you understand what power curves are. Instantaneous power is presented in 'Analysis' and look like this: i.stack.imgur.com/QjUp4.png. I'm talking about power curves. If you're a subscriber have a read at Strava's glossary.. May 20, 2020 at 2:26
• In my experience, the strava estimated power numbers are directly calculated off your speed and your bodyweight (under settings) and modified by the grade at that point. In other words, completely useless.
– Criggie
May 20, 2020 at 3:21
• @Criggie, I agree somewhat, as there is still use in relative measurements with your own data over time - but in this case the data wasn't estimated, it was from actual power meter data. May 20, 2020 at 3:22
• @DanielRHicks No, the greyed-in area is the highest values on record for each duration over many rides, and the dark-colored line is the highest value for each duration during this particular ride. These are called the MMP or "maximal mean power" for all rides and for just this ride. The name tells you exactly what the algorithm is. May 21, 2020 at 1:06