“Quick and Dirty” Threshold Power Estimate Without Testing

There are a number of reasons to do at least somewhat regular threshold testing throughout the year but in order to get reliable data over time, you need to create the same conditions each time you test and you may need to factor in recovery time after testing.  Accurate testing requires a cutback and specific preparation that can eat into a training cycle.

When you want to get a sense of your threshold without testing, there’s an easy way to get into the ballpark.  After a strong ride (can be of any distance but I’ve found that 60 to 90 minute rides tend to show the best data) you can review your Power Distribution Chart to get an idea of your threshold.  

In Training Peaks, expand your workout file to the “Analyze” screen.  Scroll down to the “Power Distribution Chart” and click the “Exclude Zero” checkbox.  I find it helpful to adjust the bins to 5 watts (from the default 15).  (To adjust bin size, click the “hamburger” in the top right corner of the chart, select the “5w” button, and click “Apply”, then close the menu.)

The resulting chart will look like the examples below.  You are looking for the “right shoulder” on the chart.  This is the bar after which the bars start dropping off significantly.  Some rides will produce a more noticeable shoulder–particularly rides during which you pushed a climb or included an extended section of hard, but not all-out riding.

Take a look at the following examples–the red arrow shows the estimated threshold.

Where the distribution is smoother/less skewed, it can be trickier to identify the shoulder (as below).  There is often a tick up before the fall off.

The following chart is from a Zwift group ride that included one significant climb.  Although there are two humps on this chart (as a result of part of the time sitting in a pack and part of the time pushing the climb), you can clearly see the threshold shoulder.

Even rides that produce positive/right-skewed distributions can show your threshold (as below), but negative/left-skewed distributions (like the first and third examples above) are easier to work with.

A few caveats to consider when selecting a ride to analyze:  This method works on indoor or outdoor rides, but note that if you’re riding indoors, a distribution from a ride in erg mode is not a reliable sample.  You also should not expect to get reliable data from structured workouts, unless they include threshold intervals (where you may or may not get the data you need, depending on the specific workout).  You will not get reliable data from easy/recovery rides or even Z2 aerobic rides.  You need to review a ride that includes some hard efforts.

Remember that this kind of analysis is not necessarily a substitute for a true threshold test, but it can definitely give you a sense of your threshold number.