4 Principles of Endurance Training

Endurance is one of the cornerstones of athletic performance.

Whether you’re a runner, cyclist, swimmer, or you participate in a sport that demands repeated sustained effort — like CrossFit — your endurance matters.

But building endurance is not just about putting in more miles. It’s also not about doing one high-intensity workout after another and hoping your engine improves.

Yes, hard work matters. Volume matters. Intensity matters.

But if you want to build real endurance — the kind that actually transfers to performance — you need a smarter approach.

You need structure.

You need progression.

And you need to understand the basic principles that make endurance training work.

Here are four key principles that can help you build a bigger engine and maximize your fitness level.

Principle #1: Build a Solid Base

Building an endurance base refers to the first phase of an endurance training program where the main goal is to develop a strong aerobic foundation.

This phase is important for athletes in any endurance sport — including CrossFit.

In fact, we are seeing more and more high-level CrossFit Games athletes take several weeks at the beginning of the season to focus on just this: building their base.

And it makes sense.

Your aerobic base is what allows you to recover between hard efforts, sustain output longer, and handle more training volume over time. Without a solid base, high-intensity training becomes harder to recover from and harder to improve.

This is where a lot of athletes go wrong.

They skip the base-building phase because it feels too easy. They want every workout to feel hard. They want to sweat, suffer, and feel like they did something.

But endurance is not built only by suffering.

A lot of it is built by spending time at controlled intensities and allowing the body to become more efficient.

In the Training Day Endurance Bundle, the first eight weeks begin with base training through Engine Builder Base.

Engine Builder Base follows four main principles:

Lots of Low- to Moderate-Intensity Training

The majority of the workouts are performed at a low to moderate intensity.

This usually means keeping your heart rate in the aerobic zone, which is typically around 60–75% of your maximum heart rate.

The goal is to improve your body’s ability to use oxygen efficiently.

This type of training helps build your aerobic engine, improves recovery, and allows you to accumulate more total work without constantly beating up your body.

Gradually Increased Volume

Training volume — or the total amount of time spent training — gradually increases.

This helps build muscular endurance, improve cardiovascular efficiency, and prepare the body for harder work later in the program.

The key word here is gradually.

Too much volume too soon can lead to excessive soreness, poor recovery, overuse issues, or burnout. A proper base phase gives your body time to adapt.

Consistent and Gradual Progression

Consistency is everything when it comes to endurance.

One great workout will not build your engine. But weeks and months of consistent training will.

The progression should be gradual and manageable. This allows you to build fitness while reducing the risk of injury and overtraining.

A good endurance program should never feel random. Each week should build on the previous one.

Variety in Training

Endurance training does not have to mean doing the exact same thing every day.

Including different types of workouts — such as long steady efforts, tempo work, intervals, and cross-training — helps build endurance while keeping training more balanced and interesting.

For the functional fitness athlete, this also matters because your sport is not one-dimensional.

You need to be able to run, row, bike, ski, and sustain mixed-modal work.

A proper base phase should help you become more durable across all of those domains.

Principle #2: Build on Your Base

Once you have built a foundation, the next step is to build on top of it.

After the base phase, athletes can move into more specific and intense phases of training. This is where the work starts to get harder, but it is now supported by the foundation built in the first phase.

That’s important.

High-intensity endurance work is valuable, but it works best when you have the aerobic base to support it.

After Engine Builder Base, the Training Day Endurance Bundle moves straight into the original Engine Builder program.

This program follows many of the same principles as the base phase, but both intensity and volume are increased.

Now the goal is not just to build general aerobic capacity. The goal is to improve your ability to sustain faster paces, recover from harder intervals, and push your ceiling higher.

This phase includes a greater focus on:

Increased Intensity

As the program progresses, you’ll see more tempo work, interval training, and harder sustained efforts.

These workouts help improve your lactate threshold, VO2 max, and ability to maintain higher outputs for longer periods.

This is where endurance starts to become more performance-specific.

Threshold Training

Threshold training focuses on efforts that are performed just below, at, or sometimes slightly above your lactate threshold.

Your lactate threshold is the point where fatigue starts accumulating faster and the effort becomes harder to sustain.

Improving this threshold is huge for endurance performance because it allows you to hold a higher pace without blowing up.

For CrossFit athletes, this matters because many workouts live near this uncomfortable middle ground — not quite a sprint, but definitely not easy.

You need to be able to live there without falling apart.

VO2 Max Workouts

VO2 max workouts are designed to push your maximum oxygen uptake.

These are usually harder intervals performed at a high intensity, with enough recovery to allow you to repeat quality efforts.

For example, this could include shorter, intense intervals on the rower, bike, ski, or run.

These workouts help raise your ceiling.

But again, they should not make up the entire program. They are one tool. They work best when built on top of a strong aerobic base.

That’s the real point of this second principle:

First, build the base.

Then, build on the base.

Principle #3: Properly Incorporate Recovery Periods in Your Training

Recovery is not a break from training.

Recovery is part of training.

Every program in the Training Day Endurance Bundle follows a systematic approach. Each week or block builds on the next. Most of the programs follow a three- to four-week build period where volume and intensity gradually increase, followed by a one-week deload where both volume and intensity are reduced.

This is not accidental.

You cannot just keep adding more work forever. Eventually, fatigue catches up.

Deload weeks are built into the program to allow the body to absorb the training, recover, and come back ready for the next block.

The full bundle is structured like this:

Weeks 1–4: Engine Builder Base
Weeks 5–16: Engine Builder Volume 1
Week 17: Rest/Deload
Weeks 18–25: Dominate the Row
Weeks 26–37: Engine Builder Volume 2
Week 38: Rest/Deload
Weeks 39–50: CrossFit to Half-Marathon

Deload weeks offer several benefits, including injury prevention, reduced risk of overtraining, mental refreshment, better performance, and important physiological recovery.

Let’s look at two of the biggest benefits.

Performance Improvement

One of the major benefits of a deload is something called supercompensation.

During hard training blocks, your body accumulates fatigue. Fitness is improving, but because fatigue is also high, you may not always feel your best.

When you reduce volume and intensity during a deload, your body has a chance to recover and adapt. When training resumes, performance can improve because the body is fresher and better prepared.

Deload weeks also help ensure that athletes are ready for the next hard block of training.

If you are constantly tired, you cannot perform well in your key workouts. And if you cannot perform well in your key workouts, the quality of your training goes down.

Recovery helps restore that quality.

Physiological Benefits

Deloads also allow your body to replenish and regulate important systems.

Reduced training volume allows glycogen stores to refill, which is essential for maintaining energy during harder workouts.

Deloading also helps manage hormones like cortisol, which can become elevated when training stress is too high for too long.

This matters because endurance training is not just about the work you do. It is about your ability to adapt to that work.

If you train hard but never recover, you are not building fitness as effectively as you could be.

You are just accumulating fatigue.

So, the third principle is simple:

Train hard, but recover on purpose.

Principle #4: Specificity of Training

Specificity in endurance training means your training should match the demands of the sport or goal you are preparing for.

The exercises, workouts, energy systems, and conditions should have some relationship to the thing you want to improve.

For a marathon runner, that means running.

For a cyclist, that means cycling.

For a swimmer, that means swimming.

For a CrossFit athlete, it gets a little more complicated.

CrossFit athletes need endurance across multiple domains. You may have to run in one workout, row in another, bike in another, and then combine all of them with gymnastics, barbells, and bodyweight movements.

That is why most of the programs in the Training Day Endurance Bundle are designed for the functional fitness athlete.

We use the air bike, rower, SkiErg, and running to train endurance because those are the tools most commonly used in CrossFit and functional fitness.

However, not every phase needs to train every domain equally.

The second half of the Training Day Endurance Bundle includes two programs that focus more specifically on one domain:

Dominate the Row
CrossFit to Half-Marathon

Overall, more than half of the 50 weeks of training included in this bundle incorporate multiple tools: bike, row, ski, and run.

But just under 20 weeks are dedicated to what I believe are two critical parts of endurance training for the functional fitness athlete: rowing and running.

The rower is included because it is a technical tool that requires consistent practice to master. Many athletes think rowing is just about pulling hard, but better rowing requires rhythm, timing, power application, breathing, and efficiency.

The better your technique, the less energy you waste.

And in CrossFit, that matters.

Running is included because it has a massive carryover. It is simple, accessible, and brutally honest. It also has a lot of overlap with general endurance because it challenges posture, breathing, tissue durability, pacing, and aerobic capacity.

A lot of CrossFit athletes avoid running because it exposes them.

That is exactly why they need to train it.

The goal is not to become only a runner or only a rower.

The goal is to build endurance that transfers back to functional fitness.

Specificity matters because your body adapts to what you repeatedly ask it to do.

So if you want to get better at CrossFit endurance, your training should include the tools, time domains, and movement demands that show up in CrossFit.

Final Thoughts

Endurance training does not need to be complicated, but it does need to be intentional.

If you want to build a better engine, you need more than random workouts and all-out efforts.

You need to build a base.

You need to build on that base with higher-intensity work.

You need to recover properly.

And you need to train in a way that matches the demands of your sport.

That is the purpose of the Training Day Endurance Bundle.

It gives you a full, structured progression that starts with aerobic base training, builds into harder endurance work, incorporates recovery periods, and finishes with more specific endurance training for the functional fitness athlete.

The end goal is simple:

Build a bigger engine.

Move better for longer.

Recover faster between efforts.

And become a more complete athlete.

Good luck, and happy training.

— Coach Damect

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