“Capacity Training” Is the Key to Long-Term Running Endurance

What makes a good endurance runner? There are many skills that help endurance runners perform at their best, like:

– Power (the ability to produce force quickly)
– Mental toughness (the ability to psychologically endure discomfort)
– Economy (the efficiency of your stride)
– VO2 Max (the maximum amount of oxygen you can process)
– Speed (a high maximum velocity)
– Endurance (the ability to withstand fatigue at high workloads)

But of all these skills, endurance is the most important. And fortunately, for us, it’s one of the most trainable skills.

But what exactly is endurance? At its most fundamental level, endurance is the ability to run in an aerobic state (when our bodies are using oxygen as their primary source of energy) while withstanding fatigue. It’s having a highly developed aerobic energy system.  Runners who can seemingly run forever have exceptional endurance.

Think of your training as a pyramid. Everything you do—from lifting weights, running hard workouts, using a foam roller, or completing a series of strides—forms your training pyramid. Easy running helps us gain endurance the most, and it forms the base of the pyramid.

This “training pyramid” has easy runs, long runs, and aerobic workouts as its foundation. They are the most fundamental building blocks of our capabilities as endurance runners. And that’s because these are capacity-building runs!

What Is “Capacity” Training?

“Capacity” training is the key to being the best endurance runner you can be. Examples of capacity training are the runs and workouts in your program that build long-term capacity for endurance, like:

– Easy runs (which should make up approximately 80-90 percent of your training volume)
– Long runs (my personal favorite endurance-builder)
– Aerobic workouts (lactate threshold, half-marathon, or marathon pace workouts)

These training sessions improve your long-term potential by creating structural adaptations within your body. Quite literally, you’re changing how your body is structured to benefit your highest endurance potential in three main ways:

– Mitochondria (the energy factories in your cells) become denser and more numerous
– Capillaries grow, allowing for better distribution of blood flow and oxygen
– Heart grows stronger and bigger, pumping a larger volume of blood to working muscles

These adaptations allow your body to complete a higher workload (i.e., train more) while becoming more efficient over time. Now let’s compare capacity training to its counterpart: utilization training.

Think of “capacity” like your bank account. It represents your spending ability. Utilization is like your credit card statement in that it represents how you’ve used your spending ability. Utilization training fine-tunes capacity. It improves your utilization of the fitness you already have.

Short, fast repetitions and hard VO2 max workouts represent utilization training. They’re necessary, but they don’t really build additional fitness or improve your capacity for endurance. These types of workouts also naturally have more risk for injury or over-training, so they must be completed strategically and less frequently than capacity-building sessions.

For that, we have to include the building blocks of capacity throughout the training cycle.

How to Prioritize Capacity

When asking yourself what types of running can build your long-term capacity for endurance, think “base training.” The focus of base training is the same as capacity-oriented running: general endurance and aerobic strength. We could easily rename “base training” and call it, more accurately, “capacity training.”

Here are the three capacity-building run types:

1) Easy running
2) Long runs
3) Aerobic workouts

Each one has its special place in your training so let’s make sure we understand each.

Easy Running. Easy running forms the cornerstone of every endurance runner’s program. In fact, 80-90 percent of your total mileage should be at an easy effort. But how do we know if we’re truly running easy?

There are three ways to figure out if you’re running at an easy effort:

1) First, rely on perceived effort. If your run is comfortable, controlled, and conversational, it’s likely an easy effort. Simple.

2) Second, use a pace calculator. Plug in a few of your race Personal Bests and you’ll be given a range of what is likely your easy pace. This is usually accurate and a good starting point.

3) Finally, heart rate is another good option for determining your easy pace. Once you know your maximum heart rate (ideally by wearing a chest heart rate strap during a short, intense race), you can run at approximately 60-70 percent of your maximum. This is commonly known as Zone 2 training.

When in doubt, just run a little slower. Your body will barely know the difference and you’ll still be gaining all the benefits of easy running.

Long Runs. While there are many types of long runs a runner can do, the simplest tactic is just a longer easy run. It’s the longest run of the week, typically 20-40 percent longer than any other run. And, much like other runs, long runs are run at an easy effort.

Most runners should aim to complete a long run every week, with a cutback distance every 4-8 weeks depending on fatigue and training goals. A cutback long run is simply a shorter long run where the distance is reduced by 2-5 miles to make it easier.

Aerobic Workouts. Aerobic workouts are the last strategy we have to continue building our capacity for endurance. These are faster training sessions run at any pace at or slower than lactate threshold (commonly known as “tempo runs.”) That includes a variety of efforts. Here they are in order of fastest to slowest:

– Lactate threshold (the fastest you can run while still working aerobically)
– Half Marathon Pace (sometimes called steady-state pace)
– Marathon Pace (the pace-per-mile from your fastest marathon)

If you’re running a workout at these slower efforts, you’re running an aerobic training session.

Bonus Strategy: Cross-Training. For those athletes who might be injury-prone, we don’t have to exclusively rely on running to build our endurance capacity. If higher mileage (i.e. more easy runs), longer long runs, and aerobic workouts present an injury risk, we can use cross-training to bridge the gap.

Aerobic cross-training like cycling, pool running, power hiking (especially uphill), or the elliptical can help athletes build more endurance without the added injury risk of running.

While cross-training is not running (and we should not expect to harvest carrots after planting potatoes), fitness does indeed carry over to your running. It can be helpful to estimate about 15 minutes of cross-training is aerobically equivalent to a mile of running.

So, if you’re a runner who is worried about running more (or doing too frequent workouts) because of over-training or injury fears, cross-training can help you add extra endurance without the risk.

Achieving your potential as a runner takes a long-term, patient approach that prioritizes the fundamentals. A consistent focus on training your capacity through lots of easy running, consistent long runs, and aerobic workouts will help get you there.

Jason Fitzgerald is the host of the Strength Running Podcast and the founder of Strength Running. A 2:39 marathoner, he’s coached thousands of runners to faster finishing times and fewer injuries with his results-oriented coaching philosophy. He writes the Performance Corner column for Trail Runner. Follow him on Instagram or YouTube.