Fitness Signature – Knowledgebase

A Fitness Signature is a unique set of three physiological values—Threshold Power (TP), High Intensity Energy (HIE), and Peak Power (PP)—that together describe an athlete’s ability to produce, sustain, and repeat high power efforts. Xert uses this signature to drive performance analysis, workout personalization, and training recommendations, updating it automatically from maximal effort data.

Summary Generated by AI

Definition

Your Fitness Signature is a set of three values that define your unique physiological capabilities - just like a “fitness fingerprint.” It consists of:

Threshold Power (TP)
High Intensity Energy (HIE)
Peak Power (PP)

Together, these values describe your ability to produce, sustain, and repeat high power efforts.

What It Represents

The Fitness Signature models your performance across different intensity domains:

TP reflects your long term steady-state power capacity & is analogous to FTP
HIE represents your ability to perform work above threshold & is analogous to W' or AWC
PP defines your short-duration explosive power & is analogous to Max Power (Pmax)

Unlike a single FTP number, your Fitness Signature captures both sustained and variable-intensity performance, making it a more complete representation of your capabilities.

Xert continuously analyzes your power data to identify maximal efforts and automatically extracts and updates these values when you have Breakthrough performances.

How Xert Uses It

Your Fitness Signature is foundational to the Xert system and drives:

MPA (Maximal Power Available) calculations during activities and workouts
Breakthrough detection, which updates your signature when new maximal efforts are achieved
XSS and Training Load calculations
Forecast AI projections and training recommendations

Your fitness signature can also be used to calculate your power-duration curve. Interestingly, your Power Curve in Xert isn’t based on historical maxes like you might see in other platforms. Instead, it represents the maximum average power you could theoretically achieve over a range of times - specifically above your threshold power - considering your unique fitness profile.

When you achieve a Fitness Breakthrough, Xert automatically recalculates the Fitness Signature values required to explain your performance.

Where You’ll See It

You can view your Fitness Signature:

At the bottom of each Activity Details page
In your Fitness Planner
In Forecast AI projections
On compatible real-time data fields (e.g., MPA & Power, Xert Dashboard, etc.)

Common Misunderstandings

Your Fitness Signature is not typically set manually. It is derived automatically from your maximal efforts.
If your data lacks true maximal efforts, your signature may be underestimated. This can often be corrected by performing a few maximal sprints along with a longer, sustained effort to failure, allowing Xert to accurately recalibrate your capabilities.
Xert workouts are not built around %FTP alone. Instead, workout targets are based on all three components of your Fitness Signature (TP, HIE, and PP), ensuring sessions are tailored to your unique strengths and limitations.
Training only FTP may not fully prepare you for racing. Many events require repeated hard efforts above threshold. Xert helps you develop both your sustained power (TP) and your ability to handle high-intensity strain through your HIE and PP systems.

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