Critical Power Plots

I discovered recently the concept of Critical Power Plot, after a user left a comment on the site. Critical Power is the maximum power you can maintain for a given period of time. The concept seems mostly used by cyclists. But it felt to me it could be extended to other data: What is the best pace I maintained for any given period of time? What is the maximum heart rate I maintained for a given period of time?

So I decided to give it a go and implement it in ConnectStats. All I had to do was maintain a rolling average every X seconds and keep track of its maximum. It’s quite an expensive computation: for N points, I need to do NxN computations, and the devices processing power is a bit low, so I chose 5 seconds for X, which seems to work well in practice even on my old iPhone 4.

Of course, the original data in the file produce by the watch isn’t nicely produced every 5 seconds and for the algorithm to work efficiently, I have to resample the original data at the average on that exact interval, which can result in a bit of loss from the original file. But in practice it didn’t appear too bad on most of the ride I looked at.

I end up with a new time serie evenly spaced every 5 seconds: the maximum average heart rate over 5 seconds, over 10 seconds, over 15 seconds, etc, etc.

Just had to come up with a name, cyclist refer to it for the power field as Critical Power, but “Critical Power” or “Critical Pace” felt a bit confusing to me, so I named it “Best Rolling Heart Rate” or “Best Rolling Pace”

Here is the example from my best 10k race for the heart rate.

This is quite nice and works also for power or pace.

Best Rolling Laps

Of course the plots are nice, but the next thing I wanted to know was for that best HR what were my others statistics for each of that given period of time where I reached that maximum?

So I enhanced the auto lap feature to show the best rolling lap corresponding to a few arbitrary periods of the plot. Below you can see the details for the Best Rolling Power or Critical Power of a friend, along with the distance, speed, HR for each of the correspond section of the ride.

The last missing piece was to plot on the map and highlight on the plot of another statistic where that best average was reached as below