Durability: The Missing Piece in Endurance Performance

For years, endurance performance has been measured in a fresh state. Metrics like threshold power and VO₂max tell us how strong an athlete is at the start of a session—but they don’t tell us what happens an hour, two hours, or three hours later.

That’s where races are decided.

Durability is the ability to maintain performance as fatigue builds. It’s the difference between holding your power late into a ride and watching it steadily decline. And until now, it hasn’t been captured in a single, meaningful way.

Introducing the Durability Score

The Durability Score (0–100) is a composite metric designed to quantify how well you hold power as workload increases.

Instead of focusing only on peak or fresh performance, it captures how your physiology behaves under stress, when energy stores are depleted, efficiency drops, and fatigue accumulates.

In simple terms: it tells you not just how strong you are, but how well that strength lasts.

Durability is now shown on both the free physiological Testing page and, within the platform, on the Abilities dashboard, with benchmark labels (Developing → Exceptional) and population comparison data. The radar chart and ability tables show how your profile degrades at different kJ accumulation points during a race.

What Goes Into Durability?

Durability is the result of several interacting systems. The score combines four key components:

• Fatigue Resistance: How much work you can do before your power starts to fall

• Efficiency Under Fatigue: How well your body converts energy into power as you tire

• Fuel Utilisation: How effectively you rely on fat vs carbohydrates at higher intensities

• Baseline Efficiency: How much power you produce per unit of energy when fresh

Each of these plays a role in how quickly (or slowly) your performance declines over the course of a ride.

Why It Matters

Two athletes can have identical threshold power, but very different outcomes in a race.

One might hold their numbers deep into the final hour. The other might fade long before the decisive moments.

Durability explains that difference.

By quantifying how your performance degrades over time, you can:

• Identify where you begin to fade

• Understand how your physiology responds to long efforts

• Track improvements that traditional metrics miss

  
  

This shifts the focus from 'how strong am I?' to 'how long can I stay strong?'

From Lab Fitness to Real-World Performance

Traditional metrics are still valuable, but they’re incomplete.

They describe your capabilities in controlled, fresh conditions. Durability extends that picture into the real world, where fatigue, fueling, and efficiency all interact dynamically.

This is especially important for long events, where success depends less on peak output and more on how well you can sustain it.

Training for Durability

The key insight behind durability is that it’s trainable.

Improving durability isn’t just about increasing power, it’s about improving how your body handles fatigue. That can include:

• Building higher training volume over time

• Developing better fueling strategies

• Improving metabolic efficiency

• Accumulating quality work in a fatigued state

  
  

With a clear score and breakdown, you can now see whether your training is improving not just your top-end, but your ability to hold it when it matters most.

A More Complete Athlete Profile

Durability adds a new dimension to performance analysis.

It bridges the gap between physiology and execution, between what you can do fresh, and what you can actually deliver when it counts.

Because in endurance sport, performance isn’t defined at the start line: it’s defined by what’s left at the end.

If you're not yet using Topp Cycling for your training and nutrition plans, you can see your Durability score via our free physiological testing tool.