Aerobic Development for Athletic Performance – Part 2


Part 2: Cardiovascular Training for Sport

In part 1 of this article on aerobics, we took a deep dive into the physiology of the cardiovascular system and how we go about testing it.  I highly recommend reading Part 1 as it provides the context as to why we would make certain decisions going forward.  In Part 2, I’ll provide a logical application model based upon the information we gathered in Part 1.  This will provide coaches and athletes a way to start applying these principles to maximize aerobic development.  Part 3 will tie all these concepts together and show how aerobic conditioning can integrate seamlessly into your current strength & conditioning program, along with example periodization parameters based upon sport.

As you’ll recall from Part 1, our preferred method of aerobic testing at Paragon Health & Fitness is a lactate test.  The lactate test gives us specific turnpoints- the intensity level at which a given athlete maximizes the contributions from the aerobic energy system, known as Aerobic Threshold (AeT) as well as the intensity level at which the athlete is relying almost entirely on contributions from the glycolytic system, known as Anaerobic Threshold (AnT).

Zone training:

Now that we’ve assessed a blood lactate levels, it’s time to plan our training based on the assessment data.  We do this via “zone training.”  There are several different models of zone training.

This point is important to avoid confusion:

At Paragon we like to keep things simple and just bucket our training sessions into low, medium, or high intensity.  In this 3 Zone model, Zone 1 is low intensity, zone 2 is medium intensity, zone 3 is high intensity. Simple.

HOWEVER, your watch or tracker may refer to a 5-zone model or 6 zone model, and so the “Zone 2” I reference here might be a completely different system than Zone 2 on your FitBit. In a 6 zone model, for example, zones 1 and 2 are low intensity (correlating to our Zone 1), zones 3 and 4 are medium intensity (correlating to our Zone 2), and zones 5 and 6 are high intensity (correlating to our Zone 3).

Please note I will refer to zones 1, 2 and 3 in this article based upon our 3-zone model. 

Let’s use an example to put this into practice.  A 20-year-old male performs a blood lactate test with the following results:

Aerobic threshold (2 mmol/L): 130 bpm heart rate

Anaerobic threshold (4 mmol/L): 150 bpm heart rate

His aerobic training prescription, depending on goals and exercise experience would look something like this:

Notice we are spending a TON of time in zone 1.  This is long, slow duration cardio and yes it can be boring if you’re stuck walking on a treadmill.  This is the opportunity to get outside and hike, walk, lightly jog, ride a bike, etc.  It is supposed to be relatively easy.  But to train this system and make your body more and more capable of utilizing this robust energy system, you must spend lots of time here.  It’s going to feel too easy at first, and that’s okay.  The goal here is not to work harder, the goal is to work longer.  In the words of Dr. Stephen Seiler, we need to stretch ourselves horizontally first, meaning we are racking up hours in Zone 1 to build up our aerobic base.  Only when we’ve built this aerobic base sufficiently does it make any sense to start training at any kind of intensity level by doing things like sprints and intervals.  And even the most aerobically fit athletes on earth generally spend a ridiculously small percentage of their training time, sometimes as little as 10% of their total time, doing high intensity work.  This is because the muscle fibers utilized in Zone 1 NEED a ton of volume to become stressed enough to adapt.  The muscle fibers in Zone 3 NEED a ton of intensity to adapt, but not much volume.

When we don’t know our zones, what tends to happen is people overestimate their aerobic threshold (zone 1), and as a result their “low intensity” days end up being way too hard.  They don’t prioritize fat utilization and they stress the system excessively, for the reasons we already talked about when we were discussing energy systems.  Because their easy days are more glycolytic in nature than oxidative, they don’t have enough gas in the tank to really go hard on their hard intensity days.  As a result, their easy days become too hard, their hard days become not hard enough, and they get stuck in that middle “no man’s land” zone 2.  We suggest spending no more than 5% of your training sessions in Zone 2, but unfortunately this is where most people live.

Why do we stay away from Zone 2, that slow glycolytic zone in the middle?

Let me start by saying that humans have a glycolytic energy system for a reason.  It might be easy to conclude, based upon the first half of this article, that I am implying that we don’t need the energy system, or that we should avoid lactate production and high intensity work at all costs.  This is not the case, particularly with athletes.  We know that athletes will be using the glycolytic system during practice and competition, and so the ability to quickly turn sugar into fuel is quite important for performance.  Perhaps more important is the ability to clear and reuse the products of glycolysis as the athlete starts to fatigue.

Recall back to Part 1 of this article, where I referred to heat and hydrogen as threats to our internal homeostasis.  Heat and hydrogen are produced during glycolysis and so anytime we have lactate production, we have heat and hydrogen production.  However, that does not make lactate itself threatening.  In fact, lactate has been shown 1, 2 to be a powerful fuel source.  This research suggests that elite athletes have the unique ability to quickly clear the by products of glycolysis and utilize lactate for fuel at high effort levels.  Brooks & colleagues pitted elite athletes against people with metabolic syndrome, to compare the most metabolically fit individuals on earth to the most metabolically challenged.  In addition to having a significantly higher Aerobic Threshold (obviously), the elite athletes also displayed greater ability to utilize lactate for fuel once they reached higher intensity levels.  This is the result of an increase in mitochondrial density that occurs with training.  Not just any type of training, however.  The increase in mitochondrial density happens because of the accumulation of hours upon hours of work in the low-intensity aerobic zones.  If we want an athlete to have exceptional glycolytic performance, and the ability to sustain high levels of effort for long periods of time, they must first develop an aerobic system capable of handling the metabolic demands.

The other reason we don’t spend much, if any of our aerobic training time in Zone 2, is because these athletes are not just endurance athletes.  Regardless of sport, our expectation is that every athlete is going to spend a minimum of 3 hours each week in the weight room.  They’re going to be performing high intensity activities such as jumping and lifting several times each week even outside of their individual sport practice.  Our effort levels in the weight room are going to be relatively high, regardless of where they’re at in their mesocycle.  Even with loads as light as 55% of 1RM, we’re going to be looking for bar speed and other characteristics that keep the intensity level significantly above aerobic threshold range- this becomes the athlete’s primary glycolytic training tool.  If I’m going to work on developing the glycolytic system, I’d much rather do so with heavy lifting than with 60 second “sprints” on the air bike.  I am much more accepting of the potential negatives associated with glycolytic work (high stress, central fatigue, etc.) when I’m getting all the other benefits that come along with strength training.

On our low intensity days, we’re prioritizing all things aerobic capacity. And when it comes to our high intensity days, we want to drive those anaerobic adaptations to the max as well.  We cannot do this if we live in a constant state of moderate intensity.  Moderate intensity sessions come with far more negative stress responses than Zone 1, but do not provide any additional physiologic benefits.

Now you’ll notice in the training chart above, there’s also very little time spent in Zone 3, just 5% of total sessions.  To be honest, this number might even be a little high.  The example 20-year-old mentioned above has failed what we call the 10% test:  There is a greater than 10% gap between his aerobic threshold and his anaerobic threshold.  We use this test to determine when an athlete is ready to and would benefit from high intensity aerobic work like sprint training.  With a greater than 10% gap, we’d suggest spending all his aerobic training time dedicated to building aerobic base. He should get comfortable there and be patient.  Let it develop into a base that we can build from.

What if I don’t I have a heart rate monitor or access to blood lactate testing?

First and foremost, getting an aerobic assessment and getting yourself a reliable chest strap heart monitor are two relatively inexpensive ways to make a gigantic impact on the effectiveness of your aerobic training. The more aerobically fit you become, the more important it is to be specific with your training dosage.

That said, if you’re a complete beginner, or perhaps your gym doesn’t have a way to test your aerobic capacity, there are a few low-tech ways to ensure you’re staying in the aerobic zone when you train:

You can breathe through your nose the entire workout: When you have to breathe through your mouth, your body is searching for a way to get more oxygen because it’s butting up against the upper limits of your aerobic capabilities.

You can maintain your pace for a long time, preferably 60 minutes or longer, without having to slow down.

The session will send you “straight to the dinner table,” in the words of Dr. Seiler. Remember those suicide sprints your high school coach made you run that left you dripping in sweat and panting on the floor? You would rather throw up than eat anything after one of those sessions, right? That’s because a high intensity sprint workout is extremely taxing on the central nervous system, sending us into fight or flight mode during and after the session. That’s not what we’re looking for here. After a proper aerobic base workout, you should feel like you’ve “emptied the tank” of your energy supplies, but with very little stress to the central nervous system. Afterwards, you’re in rest and digest mode rather than fight or flight.

HIIT misses and wrap up

The reason High Intensity Intervals can be so alluring is because they create the illusion of getting a very high bang for your buck.  Instead of needing to spend hours doing steady state cardio, the HIIT crowd would argue that you can achieve the same results in half the time if you just work harder.  Just like most things in life, there are no short cuts here.  Yes, you can work hard, be dripping in sweat and be sore for days on end.  However, this feeling of being completely killed by a workout does NOT mean that we have given an appropriate stimulus to provoke the adaptation we desire.

Despite the clear HIIT “misses,” Gurus like Boyle have continued to put aerobic base training into the “bad exercise” group alongside crunches and burpees.  Not long ago Boyle had a “Bad Exercises” post about distance running on his Instagram where he says “The only thing it’s good for is getting injured” In typical Guru fashion, he then claims his point is based on “the statistics” but never actually references the statistics to support his notion that “somewhere between 50 and 75% of people who take up jogging end up injured.”

Instead, his clients/athletes sprint.  They do tempo work.  His mantra, one I used to wholeheartedly believe, is “train slow, get slow.”  Boyle references VO2max testing as pointless, which I agree that testing an athlete’s VO2max is highly over-rated and often unnecessary.  But he goes so far as to argue that sports which are not aerobic in nature (hint: all of them are aerobic, but let’s move past that for now) should never emphasize aerobic training and in fact a high VO2max might indicate that the athlete is ill-suited to play a “power based” sport, because VO2max has “never been correlated to performance.”  This highlights another horrible symptom of Guruism—thinking that anything related to health, wellness, or performance is black and white.  You either sprint, or you do long distance, there’s no middle ground and you can’t possibly do both.  And if your VO2max is high, it’s because you’re meant to be a distance runner.  Luckily for all of us, things are NEVER this black and white.  We’ll talk more about VO2max in the testing section of this article, but let’s finish Boyle off first.  In Boyle’s article about aerobic vs. anaerobic training he says:

“Conventional aerobic training (long slow distance) should never be done for ice hockey players unless it is infrequently used for recovery purposes. Instead, the aerobic system should be developed as a byproduct of anaerobic training. Interval training, (anaerobic intervals) will generally keep the recovery heart rate in the aerobic range (over 120 BPM) if the rest periods are controlled properly. Interval training will develop aerobic capacity but as a byproduct of the anaerobic work. This is obviously a more sport specific method of training the aerobic capabilities of an anaerobic athlete.”

This is where he has gone wrong for many, many years and we’ve developed a whole bunch of athletes with underdeveloped aerobic systems.  At the same time, we have a culture in the fitness industry full of people skipping the long, slow endurance training in favor of what they think is High Intensity Interval Training- and what they’re actually getting is moderate intensity blah training, which is neither long enough for aerobic improvement nor hard enough for anaerobic improvement.

It’s time we set aside the “wisdom” of our heroes and look objectively at our own physiology.  What are your goals?  Are your training methods putting you into a position where your body is forced to adapt in a direction that aligns with those goals?  If you’re not following any kind of program, I’m not sure you can possibly answer these questions, and if you haven’t assessed your current physiologic metrics, I question how accurate or individualized a program can be.  The answers are there for you, and if you’re going to spend hours each week devoted to exercise, you should be looking to maximize your efforts and push yourself towards your desired adaptations.


1) San-Millán I1,2, Brooks GA3. Assessment of Metabolic Flexibility by Means of Measuring Blood Lactate, Fat, and Carbohydrate Oxidation Responses to Exercise in Professional Endurance Athletes and Less-Fit Individuals.

2) The Science and Translation of Lactate Shuttle Theory George A. Brooks1, * 1Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA *Correspondence:

3) Foster C, Farland CV, Guidotti F, et al. The Effects of High Intensity Interval Training vs Steady State Training on Aerobic and Anaerobic Capacity. J Sports Sci Med. 2015;14(4):747–755. Published 2015 Nov 24.)

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About the author 

Adam Reeder

Adam Reeder is the owner of Paragon Health & Fitness, a private training center located near Cleveland, Ohio. Adam has over 12 years of experience in the strength and conditioning industry and has helped athletes of all ages, ability levels and sports. More information, including personal training services can be found at or by contacting Adam directly at

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