Endurance and Durability: The Key to Better Performance

Have you ever noticed how some athletes maintain their pace late into a marathon or long ride, while others experience a significant drop-off? In endurance sports, VO₂max, lactate thresholds, and running or cycling economy are often cited as the key components of athletic performance. However, there's another crucial, yet frequently overlooked, element that can greatly affect performance: endurance durability.

This post delves into what endurance durability is, why it is important, how it can be measured both in the lab and on the road, the factors that influence it, and ways to enhance it.

Understanding Durability in Endurance Sports

In endurance sports, durability refers to the capacity to sustain your initial performance level as fatigue builds up.

Example. Consider two cyclists with the same lab-tested fitness: their First Ventilatory Threshold (VT1) power is 230 W when they are fresh. Both embark on a 3-hour ride at approximately 20 W below their VT1 power—a fairly comfortable Zone 2 effort.

Athlete A’s physiology maintains performance much better, illustrating an athlete with superior durability.

Does endurance durability affect performance?

In marathons, triathlons, or cycling races that last several hours, you might begin with impressive metrics—excellent economy, high lactate threshold, outstanding VO₂max—but as we've learned, these will decline as you become fatigued. Your success depends less on the peak numbers achieved in the lab and more on how effectively you can maintain them as the race continues.

Why Durability Matters More Than You Think

Imagine two athletes both capable of running a marathon at a pace of 4:30 per kilometre based on their fresh fitness levels. If one athlete has less durability, they might begin to slow down significantly after 25–30 km because their effective threshold has dropped. What was once a ‘Zone 3’ race pace has now turned into an unsustainable ‘Zone 4’ pace above their second threshold. The more durable runner can maintain a 4:30/km pace much further into the race.

It's crucial to understand that there is significant variability between athletes: studies indicate that threshold power declines by an average of ~10% after several hours of exercise. However, at an individual level, this decline can range from less than 1% (as seen in world-class cyclists) to over 30%! Thus, exploring ways to minimise this decline is of great interest to anyone focused on performance.

How is durability measured?

Durability can be assessed in two main ways:

1. Physiological durability (Involves tracking changes in physiological metrics – Requires lab testing)

2. Assess key variables such as your first or second threshold, VO₂max, or economy before and immediately after a prolonged session. Smaller, later declines indicate greater durability.

3. Observe the decoupling of heart rate or ventilatory measures, like breathing frequency, relative to speed or power

4. Performance durability (Tracks changes in maximal mean power or speed)

5. Evaluate how your maximal mean power (MMP)—the peak power or speed you can sustain for a set duration—changes during efforts of 1-20 minutes after accumulated fatigue (e.g., a 5‑minute time trial following 2.5 hours of cycling).

6. Many professional cycling teams now monitor durability this way, as it can be done in the field using any power meter.

What Influences Durability?

Not all races and training sessions are the same! Various factors impact your durability and should be considered and managed when implementing assessment protocols:

Exercise Intensity and Duration

• Higher intensity or longer duration leads to a greater decline in durability.

• Research indicates that even small amounts of high-intensity exercise can cause significant performance drops compared to lower intensity exercise with the same total workload.

  
  

Nutrition

• Carbohydrate availability greatly affects durability. Athletes who maintain a consistent carbohydrate supply during prolonged exercise show smaller decreases in both first and second thresholds, as well as performance.

• Developing exercise and nutrition plans that enhance your ability to use fat as a fuel source can help conserve the limited carbohydrate stores in the body, thereby improving durability similarly to carbohydrate intake.

  
  

Environmental Conditions

• Although direct studies are yet to be published, it is assumed that heat and altitude will accelerate the decline in performance and physiological functions. 

• Training in and adapting to these environments is likely to reduce the decline in durability.

  
  

How to Train for Durability

Improving durability in endurance athletes remains one of the biggest mysteries. As of May 2025, the exact methods to 'train' durability are still uncertain. However, a recent study by Jones and Kirby and another by Hunter, Maunder, and colleagues propose these steps as effective training methods to enhance durability in endurance athletes:

• Maintaining long-term consistency and high cumulative training volumes over several years

• Regularly incorporating prolonged training sessions, particularly those with progressive intensity or high-intensity efforts

• Adding heavy strength and plyometric exercises to your training regimen, especially for runners.

  
  

In summary, it's important to follow a suitable training plan or, ideally, work with a coach who can appropriately adjust your training load to maximise gains while preventing 'over-training'. This approach is vital to remain consistent, avoid injuries, potentially increase durability, and ultimately enhance performance!

Key Takeaways

1. Durability is considered the “fourth pillar” of endurance performance, alongside VO₂ max, lactate thresholds, and movement economy.

2. While laboratory testing is still the gold standard for measuring durability, field methods (MMP after accumulated fatigue) have become common among professional athletes and cycling teams.

3. Factors such as nutrition, environment, and smart training all have an impact on it.

4. Deciphering how to train for durability could lead to significant improvements in endurance performance, transforming good lab results into race-day success!

   
   

Frequently Asked Questions (FAQs) About Durability

1. What does durability mean in endurance sports?

How does durability differ from VO₂max in endurance sports?

Durability is the capacity of an athlete to sustain their optimal physiological performance—such as VO₂max, pace, power, or threshold—while enduring fatigue over time. It is crucial for success in long-distance events like marathons or Ironman triathlons.

2. How can athletes measure their durability?

There are two primary methods to measure durability:

• Physiological durability (through lab testing): evaluating changes in VO₂max, thresholds, and efficiency after fatigue.

• Performance durability (in practical settings): Coaches now assess endurance training durability using power meters, specifically by monitoring maximal mean power or pace after extended exercise.

  
  

3. What causes a decline in durability during a race?

Main factors include:

• Exercise duration and intensity: Higher intensities lead to more significant declines.

• Nutrition: Insufficient carbohydrate availability reduces durability.

• Environmental stress: Conditions like heat and altitude can negatively affect durability.

  
  

4. Can durability be improved through training?

Although sports science is still exploring durability, current research indicates it can be improved by:

• Engaging in consistent, high-volume endurance training over several years

• Incorporating long sessions with varying or high intensity

• Including strength and plyometric training (particularly for runners)