How do I find my threshold power?

How do I find my threshold power?

Threshold Power is an important representation of your running fitness.

You can use it for training targets, to track fitness improvements as you train for an event and many other things.

But how do you find your threshold power?

You can find your Threshold Power using specific models and test protocols.

Models

The three most commonly used models are a Critical Power test (CP), modelled Functional Threshold Power (FTP) and Automatically calculated Critical Power (Auto-CP).

The models differ but are similar in their approach and purpose – they:
🔹 use the results from two or more maximum effort runs at differing durations
🔹 identify a power level that’s close to (or within) your threshold
🔹 do not rely on lab tests – instead, they are field-based

Maximum Effort runs

The models rely on maximum effort runs. These are runs at the highest average effort you can achieve over a specific duration.

For example, your 3-minute maximum effort is the highest average power you can achieve over 3 minutes (elapsed).

You should include regular maximum effort runs (at various durations) in your training plan, so that your threshold power continues to reflect your running fitness – a threshold power that may have been ‘accurate’ 60 days ago is not necessarily ‘accurate’ today.

What if you can’t manage maximum effort runs?

There may be times when maximum effort runs won’t be possible, for example if you’re new to running or you’re recovering from injury.

As an alternative to maximum effort runs, you can estimate your threshold power using easy runs.

This method isn’t as accurate for finding your threshold – you should only do this until you can complete maximum effort runs.

Can I use a treadmill-based lactate test to find my threshold power?

You may think that a treadmill-based lactate test would be a better way to find your threshold power.

But …

❌ It’s not possible to convert blood lactate readings to power numbers – unless you wear a power meter that can produce power numbers on a treadmill (e.g. a Stryd footpod) and correlate the blood lactate readings with numbers taken from the power meter

❌ Power numbers from treadmill running will not be valid for outdoor running without additional calculations to estimate air power, heat and humidity differences from running indoors vs. outdoors.

❌ Threshold power from lactate testing will be dependent on the multiple definitions, protocols, and models used to identify lactate threshold, and not necessarily well-aligned with a valid threshold power estimate.

In brief, you’ll be trying to ‘fit a square peg into a round hole’, and the resulting threshold power will likely be less accurate than using easy runs, and definitely less accurate than using maximum effort runs.

For more information on the CP, modelled FTP and Auto-CP models and protocols, please see A Compendium of CP and FTP Resources, part of the Palladino Article Library.