The Durable Athlete—Part II

What defines durability?

In Part I of the Durable Athlete Series, we looked at a recent study from Zanini et. al 2025 that highlighted the physiological variables that change, sometimes dramatically, the deeper we go into an endurance event.

You can read more about the study’s findings in the link to Part I below

We can talk all day about the variables that are changing, but what is more important for you to understand is how you can improve your ability to stay strong deep into a long endurance event such as a marathon, Ironman, or the like.

To start, we must harken back the the main figure from Part I that splits Durability into three main tenets of Stamina, Strength, and Speed.

All three areas work together to develop your system to handle all of the demands that your events may throw at you. This includes both sustaining your desired pace for a long duration and minimizing the penalty that terrain, weather, and perhaps competitors’ decisions may have on your day.

Stamina

Before worrying about how fast you go, you need to be sure you have enough in you to cover the distance. This is the definition that most people associate with fitness.

“I can keep up this pace all day”.

Building this capacity starts with a solid foundation, more commonly known as your base. This low-intensity training develops the physiological engine that allows you to go long and recover quickly. The deeper your base, the more capacity you have to handle harder sessions with less recovery cost, and the more effective those high-intensity efforts become for improving aerobic efficiency.

Once you've established a solid base, the next step is to assess how your performance holds up deep into long sessions. What happens to your pace or power in the third hour of a ride or the second hour of a long run?

• Do your legs feel heavy?

• Is your breathing noticeably deeper?

• Is your heart rate drifting upward despite a steady effort?

• Can you lift the pace when it matters?

A simple test of your durability is the negative split long session. Intentionally hold back in the first half of your ride or run, then gradually increase pace in the final miles. If you struggle to do this, it could mean:

• You burned matches too early (a pacing issue)

• Your fitness breaks down under fatigue (a durability issue)

Either way, this type of training gives you valuable feedback. Pacing can often be fixed quickly with awareness and discipline. True durability requires progressive training that challenges your system to maintain output under mounting fatigue.

A final area of focus in the Stamina category is understanding the demands of the race you have chosen. You may have a hilly course or a hot climate to deal with. You may be keen on winning a race where you have to respond to others trying to take you down.

If you do no training on hills or in the heat, you will struggle.

If you do no training to handle surges from competitors, you will struggle.

Practicing specific scenarios are important and you can go even a step further and address the physical attributes for adapting to dynamic conditions. The Strength and Speed components of durability help you do that.

Strength

Strength is an often misunderstood property amongst endurance athletes. Our goal is not to pack on muscle or achieve a physique that could win a bodybuilding competition. Our goal with respect to endurance is to build a chassis that supports the ability to go long, go fast, or both. The cardiovascular system works together with the muscular system. They are not independent.

Strength for endurance helps build structural integrity of your bones, muscles, and tendons, thereby improving your overall movement economy. In other words, you can go faster or longer before your mechanical system starts to break down.

With regular strength work, your effort deep into your marathon, for example, won’t be lost into the ether but rather, you’ll be able to maintain your velocity and composure.

Strength is a durability multiplier, adding a layer to your Stamina.

At the crux of showcasing strength is the ability to apply force. Alongside a consistent gym routine, you can enhance this force transmission with the use of plyometrics (skips, hops, jumps). A small time commitment weekly can yield significant returns for

• Reducing ground contact time in running

• Improving swim or bike propulsion

• Better prepare tissues for high mechanical loads (ie running >2 hours!)

These plyometrics can be integrated into warmups or into your strength training. You can find some ideas in the article below for how to implement strength and power work to your program.

At times, it is also important to get strong in a way that is specific to your sport. This is where hill reps in running, over gear work in cycling, or power/pull work in the pool can come in handy. It is not so much a situation where you are replacing your strength training, but rather applying and sustaining force in a way that complements it.

Applying and sustaining force is only possible if you have the efficiency to boot. We talked at length about efficiency in the Stamina section, but Speed is also an essential component to your durability as it improves the efficiency with which your body moves.

Speed

Raising your ceiling can help improve your endurance at a variety of efforts. We often think about Speed as training to be fast…and that is true. However, thinking about a speed reserve might sell you on making sure to move quickly at some point in your training program if your goals are to go long.

Let’s use a marathon runner for an example:

If Runner A has the speed necessary to run a 5:20 mile, then his marathon pace of, let’s say, 7:30 per mile becomes far further from his terminal limit than if his best mile was 6:00.

This is speed in reserve. With a higher ceiling, your working definition of marathon pace sits lower on the effort scale and may enable you to be better in those closing miles of the race. You can improve this speed reserve with short, fast intervals that improve neuromuscular sharpness and leg turnover:

• 6–8 x 20-second strides post-run

• 6 x 200m on the track with full recovery

• Hill sprints: 8–10 seconds, all-out, walking recovery

These are merely a few of many examples.

There are also mechanical improvements you can make by moving fast. Better motor patterns in your swim stroke, cycling pedal stroke, or running stride can result in less wasted energy. Your nervous system dictates your level of coordination and short, controlled, and fast efforts can train your system to operate more in tune.

A final area of Speed is its contribution to aerobic efficiency. You are probably well aware now that each component we have discussed so far has a tie to this efficiency concept. It is vital to your performance. This can be done by performing sustained intervals above your threshold and can improve

• VO₂max (your engine’s capacity)

• Lactate clearance

• Oxygen delivery to muscles

Key sessions may include a derivative of the following:

3-5x 3-5 minute intervals at ~95% maximal heart rate on a bike or with running.

In swimming one might use some shorter durations such as 50s or 100s to achieve a similar volume.

This type of work can be quite fatiguing and must be accounted for in the overall recovery plan for an athlete. They are also less focused on the neuromuscular aspect and more focused on improving some of the aforementioned variables.

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Final word

The Durable Athlete combines Stamina, Strength, and Speed to finish the job when others are crumbling.

Does that sound like something you are after?

Get out there. Get to work.

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