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...



Addressing some of the comments:

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
You were probably doing intervals, or at least your effort was at a high effort for several minutes, followed by a recovery for several minutes, and another high effort rather than an extended "steady" output to exhaustion. 

In general, you're right, the maximum mean power for a duration should be a monotonically decreasing function of duration. However, for any single ride, especially when you're doing intervals, the MMP for that ride needn't be monotonic. 

Here's a simple (too simple) numerical example. Suppose you were doing repeated 5 minute intervals, with 5 minutes at 325 watts followed by a 5 minute recovery at half that, or 162 watts. If you were to calculate the MMP for a duration of 9:00, it would be 252 watts; the MMP for 13 minutes would be higher than that, at 262 watts. You didn't do an extended effort for either 9 or 13 minutes but that doesn't prevent the arithmetic of calculating an average power over 9 or 13 minutes. In your case, it appears that your workout was on an ergometer and involved at least one 1 minute interval at 450 watts. Depending on how long your work and recovery intervals were, and at what levels, you can see non-monotonic MMP curves.