May 7, 2025
Ever notice how some athletes can hold pace deep into a marathon or long ride while others fade dramatically? In the world of endurance sports, we often hear about VO₂max, lactate thresholds, and running or cycling economy as the three pillars of athletic performance. But there’s another essential ingredient—often overlooked—that can significantly impact your performance: […]
Ever notice how some athletes can hold pace deep into a marathon or long ride while others fade dramatically? In the world of endurance sports, we often hear about VO₂max, lactate thresholds, and running or cycling economy as the three pillars of athletic performance. But there’s another essential ingredient—often overlooked—that can significantly impact your performance: endurancedurability.
This post explains what endurance durability is, why it matters, how we can measure it (inside the lab and out on the road), what factors influence it, and what might improve it.
In endurance sport, durability is the ability to maintain your “fresh” performance capacity as fatigue accumulates.
Example. Two cyclists have identical lab‑tested fitness: First Ventilatory Threshold (VT1) power = 230 W when fresh. Both go for a 3 h ride ~20 W below their VT1 power – A reasonably comfortable Zone 2 effort.
Athlete A’s physiology “holds up” far better—that’s a visual representation of an athlete with ‘better’ durability.
In marathons, triathlons, or cycling races lasting several hours, you might start with impressive numbers—great economy, high lactate threshold, superior VO₂max—but as we’ve just learnt, these will deteriorate as you fatigue. Your success becomes less about the peak numbers you’ve achieved in the lab and more about how well you can maintain them as the race progresses.
Suppose two athletes both have a marathon pace of, say, 4:30 per kilometre based on fresh fitness, but one has poorer durability. In that case, they might start slowing dramatically after 25–30 km because their effective threshold has decreased – what was once a ‘Zone 3’ race pace has now become an unsustainable ‘Zone 4’ pace above their second threshold. The more durable runner can keep 4:30/km rolling much deeper into the race.
It’s important to note that the between-athlete variability is huge: studies show threshold power declines on average ~10% after multiple hours of exercise; however, at an individual level, the decline can be anywhere from < 1 % (world‑class cyclists) to > 30 %! So unpacking how you can move the needle towards the lower end of that decline is of interest to all of us concerned with performance.
There are two primary ways to measure durability:
Side note: The next major step for Sports Science 3.0 is to figure out how we can actually measure physiological durability in real-time so athletes can adjust their effort in response to changes in their performance capacity during a race or training session.
Athletica’s Workout Reserve holds promise to be used as a pseudo-measurement of performance durability by giving you real-time insights into how far your current effort is from your historical best effort.
Not all races and training sessions are created equally! There are several factors that will affect your durability and should be considered/controlled for when implementing assessment protocols:
Exercise Intensity and Duration
Nutrition
Environmental Conditions
One of the biggest unknowns is how to improve durability in endurance athletes. As of May 2025, it’s still unclear how to actually ‘train’ our durability, but a recently published paper by Jones and Kirby and another by Hunter, Maunder and others suggests these steps may be the best training methods to build durability in endurance athletes:
So, in essence, ensure to follow an appropriate training plan, or better yet, work with a coach that knows how to titrate your training load appropriately to achieve maximum gains while avoiding ‘over-training’ (such as Athletica’s AI Coach!). This is crucial so you can stay consistent with training, injury-free, hopefully more durable, and ultimately perform better!
You might ask: What is the difference between VO₂max and durability in endurance sports?
Durability refers to an athlete’s ability to maintain their “fresh” physiological performance—like VO₂max, pace, power, or threshold—despite accumulating fatigue over time. It’s a key determinant of race-day success, especially in long events like marathons or Ironman triathlons.
Durability can be measured in two main ways:
Key factors include:
While durability is still being fully decoded by sports science, current evidence suggests it can be enhanced by:
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