Durability Metric Setting

The Durability Metric in Xert determines how long-term fatigue is measured for your Durability Score, offering options based on Total Work, Work Above LTP, or Carbs Used. "Carbs Used" is the most accurate, but consistency in your chosen metric is key, and it only affects durability modeling, not other fitness metrics.

Summary Generated by AI

What It Does

The Durability Metric determines how Xert measures long-term fatigue when calculating your Durability Score.

It defines what variable is used to model how your Fitness Signature declines during long activities.

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Available Options

Option	Description	Units
Total Work	Durability decline is calculated based on total work (kJ) completed during the activity. This is a simple, general-purpose metric, but it does not account for intensity differences. For example, 1000 kJ performed at very low intensity (well below LTP) has far less impact on durability than 1000 kJ performed near or above Threshold Power.	% Decline per 1000 kJ
Work Above LTP	Durability decline is based only on work performed above Lower Threshold Power (LTP). This improves upon Total Work by emphasizing harder efforts, but it assumes work below LTP has no durability impact and treats all work above LTP as equally demanding.	% Decline per 200 kJ
Carbs Used	Durability decline is modeled based on estimated carbohydrate usage. This accounts for all intensities and naturally scales with higher effort levels, making it the most physiologically representative option. When using this metric, you can also input Carbs Replenished for each activity to account for fueling during the ride:	% Decline per 50 grams

Which Should You Choose?

For most athletes, Carbs Used provides the most accurate and meaningful assessment.

However:

• If you don’t track fueling → Total Work is simplest
• If you want a harder-effort-only model → Work Above LTP may suit your needs

The key is consistency - switching metrics may change how durability is interpreted across activities.

Where to Change It

You can select your Durability Metric in:

Profile Settings → General Tab → Durability Metric

Changes apply to future durability assessments.

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Important Notes:

• Durability assessment requires long rides (2–3+ hours) with a maximal effort late in the session. For more information about durability, read here.  (include link to article on durability)
• The Durability Metric only affects Durability modeling — not XSS, Training Load, or your Fitness Signature.
• Fueling inputs (when using Carbs Used) can significantly affect results. If using that option, be sure to keep track of your carbs consumed while riding!