When it comes to adult-onset swimming, I know what you’re going through and how to improve.

I started swimming just before my 30th birthday and was awful1. Despite being awful (to start), I trained myself to:

• A 19:59 1500m time, LCM.

• A sub-50 minutes Ironman swim.

• A 10 km open water swim where I led out the Ultraman World Champs and broke the, then, Day One bike record.

Swim Resources

Let’s start by giving you the key stuff I’ve published so far.

What Moves The Needle

The key lessons I’ve learned from coaching hundreds of adult-onset swimmers:

• Swim more often.

• Remove gaps, ie non-swimming weeks.

• Get someone to video you in the water.

• Relax and switch to 3-stroke breathing.

• If you swim in a squad then move down a lane.

• Use less gear for your main sets.

• Always pace so you could speed up at the end.

• Add a weekly, continuous easy swim.

• Add 15 minutes to your longest swim.

None of these require you to work harder.

Starting To Benchmark

This is from our Swim Chapter section called, Benchmarking Your Swim.

The workout is simple. 5x 400 on short rest. Swim each one a little quicker than the previous.

If you can’t speed up for each of the five 400s then you should assume that you do not have a Green Zone when you are swimming. All your swimming, even if it feels easy, is internally stressful. You’re likely to notice this via fatigue and increased appetite when you swim.

If that sounds familiar then have a look at the Swim Game section of our chapter. It will help you relax and learn to better control your efforts, while improving your swim fitness.

There’s more on my video channel. Here’s a link to a “swim” search.

Lactate Testing For Swimming

The 5x400 test works great for getting a rough idea about paces and training zones. However, it doesn’t give any insight into what’s happening inside the athlete. As well, because it is a “test” most athletes are doing to start at a Zone 2 effort (or higher).

From a recent swim lactate test of mine. Like many of you, the linear lactate curve indicates I started at a Zone 2 effort. The slowest pace in the test was 1:30 per 100 meters and I have the ability to swim at 1:35 and 1:40 per 100 meters. When we test again, I’ll aim for 7 steps. It will go 1:40, 1:35, 1:30, to start.

I like to see multiple steps at a flat baseline and see what it takes to bottom out lactate. Even experienced swimmers may find they don’t have the ability to bottom out lactate (ie get it below 1.5 mmol). If that’s the case then there is material upside from improving metabolic fitness by slowing down for a good chunk of your endurance work. This is even more important for triathletes and swim-runners.

The main set we used in the test:

• 5x 300 on 1 minute rest (sample lactate).

  • Descend each 300 by feeling Zone 1 to Zone 5.

• Swim as long as required to get lactate <= 3 mmol.

  • This took me 25 minutes, quite a while.

  • Slow clearance from hard efforts has important implications for fueling, pacing and energy management in long races.

• 5x 100 Upper Zone 3 pace on 25-30 seconds rest.

  • This was swum 1:20 per 100m, leaving on 1:45.

  • My lactate rose back into Zone 4, above the Golden Zone limit of 3 mmol.

  • This indicates it’s OK for me to slow down most of my main sets.

Jared’s assessment of my results.

Next, we want to compare our test results to a couple things:

1. What speeds am I actually swimming in open water?

   1. Ideally, non-drafting benchmarks to get a clear comparison with the pool results.

   2. Where is the mismatch between training and racing paces?

2. What does my training mix look like in the pool?

   1. Just like open water, we need an honest assessment when leading a lane, or swimming 10 seconds back.

When you consider these questions, you will find gaps. I sure did. I’ll walk you through common scenarios. I’ve coached, and lived, all of these.

The Missing Middle - My Current Profile

Your honest assessment may uncover a binary approach to swim training.

I discovered was either Zone 1 (slower than 1:30) or Red Zone (Lactate above 5 mmol). This wasn’t a surprise, it was the reason I asked for the test.

Lactate Always Up - My Profile When I Started

The swimmer who wants to make their pool time “count.”

Their first sample will be close to 3 mmol and they will tell you they are swimming easy (geez!). Maybe you have bad strips… Did you calibrate the lactate meter…

I’ve been there. When I returned to swimming, and self tested, my lactate was always up. Eventually, I gave up and stopped testing.

A million meters after giving up, I was fit enough to produce a linear lactate curve. I have a lot of upside, and so do you - if we are willing to back off for a portion of our swim training.

Triathletes Who Fade on the Run

If you’re fading at the end of your races then you should not be reinforcing poor pacing with fast pool swimming.

You will create all kinds of stories to explain why you don’t need to back off in the water. You will love hard training.

Until you’re running well, it’s all BS.

FWIW, I didn’t used to fade on the run. I would blow up so badly by the end of the swim, I would be recovering on the bike then run great. Go figure…

Triathletes Who Swim Slower In Open Water

Remove the walls, remove the draft from swimming in a conga line, make the “workout” a continuous swim without rest… and our true steady-state fitness is revealed.

If you have a large gap between training paces and racing paces then your program is top heavy. Keep one peppy day and shift the rest towards endurance and strength.

Working harder won’t close the gap between the pool and your races.

There Is A Cost To Everything

The individual prescription will depend on the time of year and whether the athlete would benefit from allocating energy to other things.

What other things? Getting tired in the pool means less energy is available for:

• Healing injuries.

• Immune system function.

• Improving cycling and running.

• Getting stronger.

• Adapt to all other forms of stress.

If you’re having fun and improving then focus on that. Your approach is working.

When you plateau, come back to this article for ideas on how to breakthrough to the next level.

Back to eBook Table of Contents

Access the earlier parts of the series here:

• Part One - Marius Bakken’s Book

• Part Two - For Developing Athletes

• Part Three - For Advanced Athletes

Elite Week Structure

In a recent podcast (below), Jack Kelly had Solveig Løvseth run through her basic week. Solveig’s approach is a pattern used by elites around the world.

• Monday: Easy Day: Swim/Bike and Gym

• Tuesday: Hard Swim and Hard Bike or Run, third sport (bike or run) easy

• Wednesday - Long Endurance Swim/Bike/Run

• Thursday: Hard Swim and Hard Bike or Run, whatever you didn’t do hard on Tuesday, you do today, third sport easy

• Friday: As per Monday

• Saturday: Race Pace Bike

• Sunday: Race Pace Run

Closer to a key race, Saturday becomes a key swim and Sunday becomes a Race Simulation Brick. We don’t need to guess at the structure of the brick workouts because Solveig told us in an earlier podcast.

The session breaks down as:

• Bike 4.5 hours insert 2x 2 hours at IM effort.

• Rest One Hour.

• Run 30 km insert 2x 14 km at Core Pace.

The weekend before winning Ironman Texas the brick had a different structure (links below are to her Strava):

• Bike 3.0 hours insert 60/45/30 minutes at ~245w with full race setup.

• Rest One Hour.

• Run 27 km progressive to faster than Core Pace.

When a Norwegian says “hard” I interpret as “a challenging loading session using Zone 3 (ie Nordic Threshold).” It is the method I used to structure my key sessions when I was an elite.

Solveig’s week is going to feed into a year with a heck of a lot of volume. She doesn’t publish her total numbers but we have a study available of elite Norwegians. The study places the triathletes at 1,200 to 1,400 hours a year.

We can assume Kristian Blummenfelt (KB) is at the top of the range. He was the subject of a study that tracked him for three-years. Speaking about KB, Solveig noted he tended to push the volume, and intensity, compared to the rest of the Norwegians, who all train similarly to each other.

So that’s the elite plan. Now I will step it down to give you ideas at three different athlete levels:

1. Top Amateur - flexible schedule, but a constitution less strong than a 20-something world champion.

2. Competitive Amateur - focused, committed, with a family and career.

3. Developing Athlete - with a busy schedule and greater recovery needs.

After we run through the modified weeks, I’ll give you tips for implementation.

Top Amateur Structure

The core program will be 4/4/4, meaning four sessions of each of the three sports. To better guide our athlete, we will remove the word “hard” from the week structure.

• Monday: Easy Day: Swim, Optional Gym

• Tuesday: Key Swim and Key Bike, with Transition Run

• Wednesday: Flex Day

  • Don’t screw up tomorrow.

  • If you train then keep it easy.

  • PT Exercises, links to a video - great for the day before key run

• Thursday: Key Swim and Key Run

• Friday: Easy Day: Bike, Optional Gym

• Saturday: Key Day Alternates Between

  • Do-Everything Day, and

  • Bike-Focused Endurance Day

• Sunday: Flex Day

  • #1 Goal is to setup next week.

  • A good day for an easy run, longer is OK if it won’t compromise next week

We end up with loading days on Tuesday, Thursday and Saturday. Sunday/Monday should be used to set up the following week.

I made gym “optional” in a nod to Dr. John Hellemans. My choice would be to “opt in” to traditional strength work, John would likely have you do sport-specific resistance work. To break the tie, give a listen to Erin Carson, who sat down with Alan/Iñaki and trains the best athletes in Boulder.

The Science of Maximal Athletic Development

MSMRL 15: Strength Training for Endurance Athletes - You're Doing It Wrong (w/Erin Carson, CSCS)

There are few areas in endurance sport that generate as much confusion - and as much misinformation - as strength training…

Listen now

13 days ago · 40 likes · Alan Couzens and Iñaki de la Parra

Please refer to Parts One, Two and Three (linked at the top) for tips on intensity control and remember the power of the program comes from stacking weeks, not killer workouts.

Competitive Amateurs

Next we want a week that targets the essentials for a competitive amateur. The plan needs to be focused due to this athlete’s commitments.

• Monday: Work-Focused Day

  • Start the week with a win at the office

  • Easy Swim

• Tuesday: Key Bike, with Transition Run

  • For the key bike, you focus on endurance or the principles I explained in Chapter Ten of How To Train.

• Wednesday: Swim and Gym

  • Include PT Exercises, links to a video - great for the day before key run

• Thursday: Key Run, done first thing

  • If you want to experiment with Bakken Double Threshold then this is the day to do it.

  • If you are not doing double runs, or all three sports on Saturday, then swim for your second session.

• Friday: Easy Bike, done first thing

  • Clear the decks at work for the weekend.

  • Rather than jamming in a low-quality workout late in the day, do something with your family (before your key day, tomorrow).

• Saturday: Key Day Alternates Between

  • Do-Everything Day, and

  • Bike-Focused Endurance Day

• Sunday: Family Day

  • Whatever sport had the lowest frequency (Monday to Saturday), start your day with an easy session in that sport.

  • Bonus points for an easy run before dinner.

If you have the mindset of the typical competitive amateur then this week should feel too easy the first few times you do it. Good. That means it will be sustainable for the 40-odd weeks you’ll be repeating it across the year.

Developing Athletes

Now we want to strip things down a bit more. The overall goal is building general capacity towards the completion of a goal event, perhaps even a long one.

• Monday: Work-Focused Day

  • Start the week with a win at the office

  • Easy Swim

• Tuesday: Key Bike, with Transition Run

  • Most weeks this will have an endurance focus.

  • If you are doing endurance today then include higher cadence work to expand your range of comfortable cadences.

• Wednesday: Flex day

  • See how you are feeling.

    • First choice is whatever sport you didn’t do on Monday or Tuesday.

    • Alternatively, start the day with an easy workout of whatever catches your fancy.

    • If you’re not doing formal training then aim to get 10,000 steps by using walk breaks. This tip also applies to Sunday.

  • Bonus points for including PT Exercises, links to a video - great for the day before key run. They only take 15 minutes.

• Thursday: Key Bike Focus

  • Double threshold isn’t recommended for developing athletes.

  • If you didn’t run yesterday then this is a good day for an easy run before dinner.

• Friday: Easy Bike, done first thing

  • Clear the decks at work for the weekend.

  • Rather than jamming in a low-quality workout late in the day, do something with your family (before your key day, tomorrow).

• Saturday: Key Day Alternates Between

  • Do-Everything Day, and

  • Bike-Focused Endurance Day

• Sunday: Family Day

  • Off or Easy run to start the day.

You should end up with two workouts of each sport during the week. On the weekend, have one day that builds your overall endurance and make the other day life/family focused. This will set up the following week.

Tips For All Athletes

The first thing you should have noticed is the weeks are similar across athlete levels. As you build fitness, it’s better to include more work, rather than shifting intensity upwards.

If you are new to this week structure then repeat the week 10x without main sets. I know this sounds extreme but I did my week more than 50x before I tolerated much real training. Even then, I couldn’t tolerate much. The good news is it didn’t matter for me, and won’t matter for you. What does matter is finding a week you enjoy and can repeat. It is the compound load that will drive your gains. Make sure you’re having fun along the way.

Our basic week is set before life happens. When life happens, I want you to keep moving forward. Don’t try to make up workouts or missed sessions. Leave them in the past and get back on your program.

Doc Hellemans taught me an excellent rule for missed sessions.

• Never worry about one miss per week, it’s part of the normal variation in our bodies.

• Two misses might be the start of a pattern, pay attention and consider if targets have been set too high.

• Three misses is signal that the plan needs to be adjusted down.

Bakken’s book has an excellent section on training through illness and returning from injury. Chapter Nine starts on page 179 and reflects his experience as a medical doctor and the reality of being a highly focused (somewhat obsessed) athlete. The end of the chapter discusses recommendations for iron, vitamin D and B12.

Back to The Physics of Performance

Back to eBook Table of Contents

What does it take to be the best you can be?

At this point of our story, we are a little more than halfway through my first 1,000-day block. Excited by seeing gains and eager to prove my run fitness, I’d been distracted. Fortunately, I learned my lesson and returned to what is required to improve.

My goal for 2024 was to attend Epic Camp France with my friends. Epic Camp is a business I founded with Scott Molina. When we started the business, the idea was to do monster training camps in fun locations. Inside the camps, we’d have daily competitions, climb & sprint bonuses, and incentives to do a ton of volume.

The camps would last from 8 to 12 days and were held in New Zealand, Colorado, Australia, Italy, France and Canada. To give you an idea on volume, the most I ever did was 84 hours across the 12 days of Epic Camp Australia. In hindsight, that was 24 hours too much. Binge training is what I call it now.

Years ago, after a 15-day tour from the top to the bottom of New Zealand, Scott and I handed the business off to John Newsom. John and his team have kept the business going. John organized Epic Camp France for the summer of 2024. I signed myself up knowing that the camp would motivate me to ride lots.

Epic Camp France included several mountain stages that were expected to add up to 40,000 vertical feet of climbing. The camp ended with the Alpe d’Huez triathlon (Alpe Tri) that was rumored to contain 10,000 feet of climbing and a bike course that ended by riding up to the village of Alpe d’Huez.

John offered a Mount Ventoux prologue and about half the campers signed up. So, before the official camp started, a bunch of us would drive south and ride up the Giant of Provence, a 21-km/13-mile climb with an average gradient of 7.7%. A 7%-grade doesn’t sound bad on paper but seems to wreck many excellent cyclists.

Big picture, I needed to prepare my body to handle six massive days, which would happen across 11 total days. To make the challenge bigger, the 11^th day would be the Alpe Tri. When I was younger, this type of block was my favorite thing to do in the world.

How would I handle the preparation, execution and racing in my 50s?

We were about to find out.

Getting ready for a series of big days is different than seeking to peak on a single day. I knew that if I arrived in France with the necessary general fitness, then the camp would improve my specific fitness. General fitness is the ability to get through the camp, itself. Specific fitness is the ability to perform on the final race day. The tricky part would be managing total fatigue, so I didn’t fall apart during the camp, or the Alpe Tri race on the final day.

ÖtillÖ and Epic Camp France were events at the limit of my endurance. By choosing them, I was giving myself an incentive to focus on two more of the foundational concepts of fitness:

• Maintain base training if it continues to shift the curve.

• The bike is the safest place to ramp endurance volume.

I explained shifting the curve in Chapter Eight. The tests I showed you were done fresh. There is another important dimension to fitness: time. Endurance performance changes, sometimes dramatically, as we move through time. At Epic Camp France, I’d need to maintain my form across 11 days, culminating in race that was expected to last ~80% of an Ironman duration. I would need all-day, and multi-day, fitness.

My plan was simple, and one you should use on yourself:

1. Get Gym Strong

2. Get Sport-Specific Strong

3. Get Fit

Strength goals are compared at the individual level. Focus on you vs. you. Unless you have been focusing on strength training for the last three years, you can be far stronger than you are right now. Stronger is faster, period.

Fitness is defined based on the requirements of your goal event. For example, fit for a 10 km run is different than fit for a 100-mile Grand Fondo. Similarly, running a marathon (or half-marathon) has very different requirements when placed at the end of a triathlon.

Regardless of the specific capacity you ultimately require, I recommend you follow a seasonal approach:

• Gym strong by the end of Winter

• Sport-specific strong by the end of Spring

• General preparation in place by mid-Summer

• Then, a short-specific preparation block completes the process before your main event.

In 2023, I didn’t have the general capacity to tolerate any specific training for ÖtillÖ. Due to a lack of fitness, my training was general right up to race week. If you are stepping up to ultradistance racing, then this should be your default approach.

In 2024, I was able to tolerate a few specific sessions that I’ll share with you. However, training specific to Epic Camp is likely to be different than you expect.

Read more

Bakken is too humble. At a time of world domination by African runners, he committed to doing everything he could to get the best out of himself. His campaign was successful.

Much respect.

I’m seeking to do something similar. Instead of being up again other athletes, I’m up against time and my habit of ramping load until something breaks.

The Norwegian method’s promise is a predictable response to loading will result in more work done.

That’s a promise I can get behind. Endurance training protocols are a contest of work over time. Bakken’s approach is designed to result in more work over time.

• So how might we pull his loading advice into a competitive triathlete’s program?

• What about his advice on the Golden Zone?

• How might the Golden Zone apply to top amateur athletes?

These are our topics today.

What’s Likely To Happen?

Reading the book and writing out the core tenets (shared in Part One), I realized my approach is broadly similar to what’s laid out. There’s nothing radical contained in the book. I’ve done most of the workouts previously.

So, I asked myself:

1. What would happen if I embraced the method for the next 12 months?

2. What additional information do I need?

Since I was exposed to Swedish 5:2 Loading, I have hoped to bring my general capacity to the point where I could consistently handle 4-5 loading days in a week.

The last four years have shown me:

• This isn’t going to happen. It requires more mojo than I have.

• Even if it could happen, I improve quickly with at least 50% low stress days.

Maybe I’d get even better with more loading days but the risk profile dramatically increases, and my enjoyment decreases. It doesn’t seem worth it. So I was primed to receive Bakken’s advice about the ideal week having no more than three loading days.

Resource: My article on Swedish Athletic Excellence explains 5:2 loading.

Read more

Based on Bakken’s book, Part One ended with this advice:

• Every single week contains, three easy days where you cap (not target) your heart rate at 70% of max.

• Easy days are structured to reduce tone.

• Every week contain two back-to-back easy days.

• The goal of the week is long-term development using a week that can be repeated 40x a year.

• The core of your faster work is blocks of interval training capped at the lower of:

  • 85% of maximum heart rate, and

  • 3 mmol of lactate.

• One day a week (your X day), you schedule something challenging for your individual needs.

  • This need not be high-intensity. For many readers, it’s going to be going long, rather than fast.

  • The most important part of the X day is a return to the optimal start zone 48 hours later.

The four bold points at the top are NOT what you are likely to do. You are most likely to find the toughest workout in the book and place it into your existing week.

If you do this then you will be proving Bakken’s point…

Successful implementation of the method requires a focus on managing tone and learning how to execute the core of the method.

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The rest of this article will explain:

• Tone and Tension.

• Weekly Planning For Working Athletes.

• The Challenge With Lowering Tone.

• Train Like A Pro, rather than an amateur.

Read more

Today, in Part One, I will introduce the aspects of Bakken’s method that trip people up.

The next installment will cover how Developing Athletes can apply Bakken’s method.

In the third part, I will share what I learned from the book personally. Long time readers will recognize my approach mirrors what’s explained in the book.

Finally, we will start a new series on energy turnover. Examining the role of energy turnover will enable us to extend Bakken’s ideas beyond running and understand why zombie training works (until it doesn’t).

Repeat The Week

Bakken favors flat weeks. Meaning athletes, of all levels, find a sustainable week and repeat it 40x a year.

Three years ago, John Hellemans and I wrote you a series that mirrors this advice.

Go further back and you’ll come across a similar line of thinking with the great Arthur Lydiard.

And what might a Bakken week look like? His ideal week mirrors what we suggested in the dynamic loading section of Chapter Ten.

We have:

• Three loading days.

• Three easy days.

• One rest day.

In the ideal week, four out of seven days are low stress, and every week ends with back-to-back easy days returning the athlete to full recovery.

This is a different from overload weeks that gradually break the athlete down until they need a week, or more, to return to an optimal start zone.

Running Is Muscularly Limited

Bakken repeats this many times in the book, and makes a strong case for muscular tone being the most important thing to manage.

But what is tone? To get the full picture you must read the book. Here’s a figure from the book to help today’s discussion.

Muscle tone is baseline tension at rest.

To Bakken’s concept of tone, I would add nervous system tone. I define nervous tone as baseline excitement (sympathetic activation) at rest. This concept will help us expand his method into other sports, than aren’t muscularly constrained.

If you look across the week (above), then you’ll see three peaks in muscular tone.

• Baseline tension peaks the morning after a loading day.

• The highest tension peak occurs after the third loading day. Bakken calls this the X day. It is a day that varies across the year and is specific to the individual needs of the athlete.

• Following the tone peak for the week, the back-to-back easy days are sufficient to return the athlete to an optimal start zone.

The basic week must be repeatable, 40x per annum.

Smart Loading

If you follow the chronically injured/exhausted on socials you will notice they have a deep desire to overload, smash themselves and test their limits. When they find their limits, they struggle to learn and improve their method.

If you follow the clueless on socials then you will see them write about the need to max out their hard training. They give public advice to go “as hard as you can go” on high-intensity intervals.

Both of these approaches are contrary to Bakken’s method, which is about sustainable load.

Sustainable load has two aspects:

1. What is an easy day?

2. What is a loading day?

Easy Days Capped at 70% of HRmax

The concept of muscular tone makes it easier to manage easy days.

Did my muscular tone reduce today?

• Yes? It was an easy day.

• No? It was not an easy day.

I added the concept of nervous tone to extend Bakken’s definition of tone, specifically as it relates to an easy day.

I hypothesize low nervous tone implies a state where we are ready to absorb training. This isn’t revolutionary, Marco Altini has a book on heart rate variability coming out that (I expect) will make this case in detail. My performance progression across the last four years makes the case as well. A central premise of my method is half my days are easy. Bakken has given us a method to track “easy.” To have a truly easy day, we need both muscular and nervous tone to reduce.

Dr. Bakken’s prescription is simple and clear. On an easy day all training must be performed under 70% of HRmax, no exceptions.

“No exceptions” gave me a smile because I train easier than anyone I know and I make exceptions when I’m feeling good. The good doctor caught me out… more on that in Part Three.

Norwegian Threshold Doesn’t Mean What You Think

It means Tempo / Moderately-Hard / Zone 3.

Norwegian Threshold is American Tempo

Bakken defines the center of the method as a core block of interval training performed between 77 and 89% of HRmax depending on athlete level. This is covered (very clearly) in the first 50 pages of the book.

The center is a core block of Zone 3 / Moderately-Hard, every week, carefully managed using a mix of short, medium and long intervals. The interval duration runs from 45 seconds to 10 minutes.

This presentation is completely different than how influencers present the Norwegian Method. The drawbacks of the influencer method is clearly explained in my Hybrid Athlete article.

• If you have access to lactate testing, Bakken limits tempo to 3 mmol.

• A 3 mmol lactate cap is lower than you expect (or can execute) when you hear someone say “threshold.”

When I test athletes in the field during endurance training, they are often 3 mmol, or higher. If your lactate is chronically elevated then you are training more intensely than you realize. I made you video explaining more.

Threshold Doesn’t Feel Like You’d Expect

Big Picture

When you apply the book, include the following:

• Every single week contains, three easy days where we cap (not target) our heart rate at 70% of max.

• Easy days are structured to reduce muscular and nervous tone.

• Every week contain two back-to-back easy days, the second of which is our lightest of the week and brings the total number of easy days to four per week.

• The program works via long-term development and uses a week that can be repeated 40x a year.

• The core of the faster work is blocks of interval training capped at the lower of:

  • 85% of maximum heart rate, and

  • 3 mmol of lactate.

• One day a week (the X day), schedule something challenging for our individual needs.

  • This need not be high-intensity. For many readers, it’s going to be going long, rather than fast.

  • The most important part of the X day is a return to the optimal start zone 48 hours later.

Don’t create strain on any of the loading days.

Use consistency as your main protocol.

In Part Two => applying Bakken’s method for a working triathlete at the developmental level. Early in my return to training, I found using Bakken’s Golden Zone left me feeling exhausted. To help you, I have an alternative approach to consider.

In Part Three => applying the method for competitive athletes.

I look at the flagged values, in Gordo’s case, low white cells, low neutrophils, low bioavailable testosterone and elevated creatine levels.

My questions to Gordo are:

• “You feel well?” His answer is yes

• “Training going as expected?” His answer is yes

That is where I start, rather than with the numbers. My mantra has always been to train, test and treat the athlete, not the numbers.

Now I will have a look at the numbers. Most lab ranges are built around the general population, not people who willingly spend hours stressing their bodies week after week.

Endurance athletes live slightly outside the boundaries of the general public.

• Lower white blood cells? Common.

• Lower haemoglobin and haematocrit? Often just dilution from increased plasma volume.

• Lower testosterone? Frequently, a reflection of training load, not a deficiency.

• Elevated creatinine. More muscle mass, higher training loads, higher protein intake, and even creatine supplementation. All of these can push creatinine up.

These changes are signs of adaptation, not pathology.

What matters more is the story around the numbers.

• Are you excessively tired/lethargic?

• Is your motivation slipping?

• Are you not recovering, not sleeping, not eating?

• Do you want to sleep all the time?

• Any other symptoms?

That’s when a “low” or “abnormal” value can start to mean something. But in a healthy athlete who is training, eating and recovering well, who is performing, and enjoying the process, an isolated abnormal result is just that: a data point. Not a diagnosis.

Testosterone

I will expand a bit on the low testosterone, as it’s an easy one to overreact to. Total testosterone is the first-line test and reflects the total amount of testosterone in the blood, including both protein-bound and free fractions. Free testosterone is the small, unbound portion and the biologically active form that can readily enter cells and exert its effects. Bioavailable testosterone includes free testosterone together with the fraction loosely bound to albumin, which is also readily available to tissues. As such, free and bioavailable testosterone are generally more clinically relevant, as they better reflect the hormonally active component. Gordo rightly requested his bioavailable testosterone levels to be included.

Note that our testosterone levels fluctuate during the day. Usually, it peaks in the morning, so it makes sense to check it then. Yes, endurance training can suppress it. Yes, it can show up as “low” on a report. But unless there are clear symptoms, intervening, especially with replacement therapy, often creates more problems than it solves. See also the list of potential side effects in Gordo’s article. And then there is the small issue that it is actually illegal to supplement with testosterone in competitive sports.

The same applies to artificially boosting red blood cells. There are ways to do it, of course. But they sit firmly in the realm of risk, ethics, and illegality in sport.

Creatinine

An elevated creatinine is another result which causes a lot of unnecessary worry. Creatinine is one of those markers that looks deceptively simple. In the general population, it’s often used as a proxy for kidney function. But in athletes, particularly those who have spent years training hard, it behaves differently. I have already mentioned the factors that contribute to a higher-than-normal creatinine reading. These include high training loads, high protein intake, creatine supplementation, and greater muscle mass. In athletes, mildly elevated creatinine levels are often entirely expected.

The key is context again. If the reading is stable over time, there are no other markers of kidney dysfunction, and it aligns with the athlete’s build and training, it is unlikely that there is an underlying medical issue.

In Gordo’s case, it is also telling that, as training volume reduced over the years, the value drifted back toward the “normal” range. Not because something was wrong before, but because Gordo’s physiology changed.

Ferritin

This is where the conversation becomes a little more nuanced.

Gordo noted that a ferritin of 71 ng/mL is “low-normal” for him, and that he feels better above 100 with supplementation. That may well be true, but we have to be careful about how he arrived at that conclusion.

Ferritin is a marker of iron stores, and in endurance athletes, it’s one we watch closely. Low levels can impair performance and, if severe, lead to iron deficiency anaemia. But 71 ng/mL is, by most standards, a perfectly adequate level, well within the normal range. This also applies to athletes

So, the question becomes: what makes 71 too low? Is there clear evidence of symptoms, fatigue, reduced performance, and poor recovery that consistently improve when ferritin is higher? Or could those symptoms be explained by training load, energy availability, sleep, or life stress?

In other words, we need to be sure we’re not attributing normal training fatigue to a number on a page.

That doesn’t mean Gordo is wrong. Some athletes do feel and perform better at higher ferritin levels. But the principle is important: Correlation is not always causation.

Before supplementing, it’s worth asking:

• Is the athlete in a heavy training block?

• Is his/her energy intake sufficient?

• Is recovery adequate?

• Are there any medical symptoms that require further investigation first? For example, could there be an underlying cause such as a stomach ulcer, various forms of cancer, hemorrhoids, or a more obvious cause like menstruation or blood loss?

Only once this is addressed does targeted supplementation make sense. Gordo’s approach, short-term, monitored supplementation with medical oversight, is sensible and safe.

Note that the ferritin value should never be considered in isolation. Iron-binding capacity, iron saturation, and free iron, all under the umbrella of “iron studies,” need to be included to get a fuller picture. In addition, hemoglobin and hematocrit levels also need to be taken into consideration.

Ferritin levels can be affected by illness, including inflammation, infections and dehydration. This also applies to other blood tests, especially in relation to the white blood cell count. Therefore, blood screening should always be done in a standardised way, preferably when the body is healthy and in a resting state, fully hydrated, e.g., early morning. Hard training the day before can also affect results due to low-grade muscle inflammation.

Vitamin D and B Vitamins

Vitamin D deficiency is widespread, particularly in athletes training indoors or at higher latitudes. B vitamins can also dip, depending on diet and training stress.

The approach is straightforward. Identify deficiency by doing a blood test, supplement under medical supervision and re-test after three months

What matters is avoiding the trap of permanent supplementation without reassessment.

Stepping Back

As we wrap up, what stands out isn’t any individual marker, but the overall approach.

Gordo’s system is thoughtful, structured, and, importantly, repeatable. That’s what makes it valuable. He uses the data but does not become a slave to it.

Takeaways:

• Your “normal” may not match the lab’s normal.

• Look at trends over time, not single results.

• Symptoms matter more than numbers.

• Many “abnormalities” are training adaptations.

• Fix lifestyle and recovery before considering intervention.

• Athlete physiology often sits outside standard lab ranges.

• Creatinine is frequently elevated in trained individuals, and often benign.

• A “low-normal” ferritin needs context before treating.

• Supplement with a plan, and reassess, don’t guess or blindly follow trends.

• Longitudinal tracking beats one-off testing.

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Resources:

• My article on Top Ten Supplements for Endurance Athletes includes sections on Iron and Vitamin D supplementation.

• My chapter on The Tired Athlete contains medical screening tests for common medical conditions which have symptoms which can mimic overtraining.

As an endurance athlete, I’ve been tracking my blood for 25 years. We’re going to start with my layman’s explanation and, in Part 2, we will bring in Doc Hellemans to share his decades of experience advising athletes (at all levels) inside his sport medicine practice.

Bookmark this one as you’ll want to refer back over time.

Back in December, the good people at Masterlete were kind enough to offer me a full profile. It was the most extensive set of blood work I’ve ever done. You can run through the full list of tests we did here.

Establish A Healthy Baseline

I like testing in early winter because I’ve had my off-season and have completed 4-8 weeks of normal training. Testing at this point of the year enables me to understand my baseline health.

Getting to the lab before my annual checkup enables me to meet with my primary care physician (PCP) to discuss:

• Tests results that were flagged.

• Supplements I’m taking: brand, dosages and expected duration of supplementation.

• Additional tests that might be warranted, and their timing.

My December 2025 results flagged a few items:

• Bioavailable Testosterone - low.

• White Blood Cell Count - low.

• Absolute Neutrophils - low.

White Blood Cells

As an endurance athlete, my WBCs and Neutrophils have been flagged low in every blood test I’ve ever taken. I’ve never been inside the normal range. While that’s normal for me, my research showed only ~15% of endurance athletes are flagged low.

Bioavailable Testosterone

When my bioavailable testosterone got flagged low, it made me smile. Before talking with my PCP, I was wondering if the normal range had been set to generate business for lifestyle doctors.

• When meeting with my PCP, I said to him, “If I’m flagged low then the ‘bioavailable’ marker must flag every male over 45 in your practice.”

• He noted my total testosterone (662 ng/dL) was more than double the value where he would consider supplementation and, even then, it would only be if the patient was symptomatic of having low testosterone.

Separate from a test result, I think you’ll do much better by addressing lifestyle factors that impair testosterone production/utilization. It seems illogical to supplement a hormone to continue to live a sub-optimal lifestyle. This is separate from the laundry list of well-established side effects.

Other Blood Markers

Over the years, I’ve tracked other markers closely.

Creatinine

As an elite, my creatinine was always elevated. Compared to the general population (on whom normal ranges are based), I was more muscular, training far more volume and eating far more protein in absolute grams. All of these factors still apply. However, I’m less of an extreme outlier with exercise volume and protein intake.

Back in the day, I consulted with a nephrologist (see our Kidneys section) and we decided it was benign and related to my elite training, lifestyle and nutrition. I reverted to normal as I aged out of elite sport. These days, I take 5g of exogenous creatine most days.

Ferritin

While the lab didn’t flag me, my Ferritin at 71 ng/mL is low-normal for me. With supplementation, I know I can get that figure over 100 ng/mL. I cleared a six-week supplementation plan with my PCP, we rested in March and I was back over 100 ng/mL.

• My view with iron (and other) supplementation is I want to get to a normal range by the start of serious training (May, most years) then stop taking supplements.

• It’s important that you disclose supplementation plans to your PCP as it’s possible to make ourselves sick from excess iron (and others, such as Vitamin D) supplementation.

D and B Vitamins

In the past, I’ve been deficient in both of these. I keep an eye on them and supplement (as needed) across the winter, then take a follow up test in the spring.

Your Plan

Let’s recap how you should approach:

• Test annually to get a healthy baseline.

• Discuss the results with your doc.

• Supplement as required.

• Retest prior to the start of serious training.

• Enjoy your competitive season.

• Take an off-season, where you focus on health.

• Re-start the annual review after you’ve returned to structured training.

I’ve taken the time to carefully explain:

• Workout protocol.

• Zone 5 targeting.

• Workout positioning.

• Options for additional sessions.

• Nutrition.

I’m thinking about all these things whenever I’m raising my heart rate.

Background Information

Links from last week’s article on Zone 6 training, as well as previously published content:

• Background - to get a feel for the general capacity necessary before adding a VO2 Block.

• Defining Terms - to help you understand zones and domains.

• Zone 5 Power was defined using a Pmax test with 3 minute / 40 watt steps.

• An example of a Submax Bike Test can be found in our Training Zones Chapter.

• Unsure if you need a VO2 Block? I wrote you an article, which includes a video.

• Here is the study that’s the source of the protocol I’m about to explain.

Making Sure We Benefit & Adapt

You’ve got decisions to make. Let’s start with how fresh you want to be for this challenging day.

Last time, I laid out a week schedule:

1. Endurance Day

2. Very Hard Day / HIIT Day => Zone 5

3. Easy Day

4. Fast Day / SIT Day => Zone 6

5. Easy Day

6. Easy Day

7. Endurance Day

In the week above, you have four days you can flex before the Very Hard Day:

5. Easy Day

6. Easy Day

7. Endurance Day

1. Endurance Day

Four days provide ample time to ensure you are ready to benefit from the session. Benefit is an important word and should dictate the placement of your all your training, especially the peppy stuff (above LT1).

Respect The Trend

I use heart rate metrics, soreness, subjective perception and training heart rate to track how I am coping. I’ll walk you through an example from my VO2 Block.

With additional context, it’s easy to see the periods where I appear to be ready to adsorb training. The HRV4 Training app also has a detected trend algorithm. Don’t fight the trend - we want to be stable or coping well.

It takes uncommon maturity to wait until we are ready to absorb. Maintaining freedom to delay planned sessions is why, even when I have a coach, I maintain control over my schedule.

Maturity, combined with a commitment to consistent Green Zone loading, explains why I adapt quickly for my age (57).

• Most athletes treat the written schedule as the Word of God and never deviate.

• Most athletes who train in groups, lack an ability to control intensity.

Both of these choices lead to underperformance.

Want to dig deeper? Head to the section I wrote on Dynamic Loading.

Structuring the HIIT Day

The core of the day is 4x4 minutes at Zone 5 power. Zone 5 has a range and it is easy to overshoot. You will need a protocol to determine your targets.

Previously, we have explained simple methods to estimate Zone 5 power/pace.

• 5x400 Test for Swimming.

  • Use the pace for the last 400.

• Six-Minute Test For Running.

  • Use the average speed from the test.

• Full Profile For Cycling - test explanation & worked case study.

  • Use the power from the last five-minute step.

The above tests will get you an effective starting point for “Zone 5 Effort.” Zone 5 Effort is not a true max effort, especially for the first 90 seconds of each rep and the first interval.

For my current protocol, the HIIT intervals are targeted at 90-100% of Pmax, with Pmax being determined via this test.

Here’s the workout structure:

• Start with a Submax Test that builds to Zone 3 / Tempo power.

  • Use 10-minute steps.

  • I start at 125 or 150 watts and build to 240 or 250 watts, depending on the time of year.

• Rest 5-10 minutes

  • I take a gel and a big drink.

• (4x) 4 minutes On / 8 minutes Off

  • On power is 90-100% of Pmax.

  • Off power is LT1 watts.

  • Each On/Off cycle is 12 minutes long (4/8)

  • Know your targets and don’t go bananas.

• End with 20 minutes at LT1 Power

  • Include the 8 minutes after the final interval in this period

  • Sample lactate at 10 and 20 minutes.

  • What we want to see is how fast lactate clears and if it returns to normal for the power we are riding.

When sampling lactate, I give myself one minute to get the reading. This means an eight-minute Off interval at LT1 Power contains 1 minute of 0 watts and 7 minutes of LT1 watts.

With the 10-minute steps in the Submax test, I sample lactate at 8 minutes (as quickly as possible, say 30 seconds) and continue riding at target power so I have time for a second lactate sample, if required. On the final step, I ride the full 10 minutes before sampling.

I use erg mode for the warm-up and free ride for the main set.

I use indoor testing data for my indoor ride targets. It is the same bike, altitude and setup for everything you read in this series. This is important as there can be material differences between indoor/outdoor as well as between power meters, even the same make/model.

Data Examples

What Else To Include?

The HIIT training is the main event for the day. Your next decision is what else to include.

+++

New to HIIT or a Developing Athlete?

Keep it easy the rest of the day and the next day.

+++

Experienced athlete with deep general capacity?

I have two options for you:

1. Start the day with a half-dose track session and shorten the bike warm-up.

2. Follow the HIIT with an easy Transition Run and a masters swim session.

Half-Dose Track Session

This is a half dose of a favorite set from Coach Julie Dibens.

• Warm-up with 4-8 km. Negative split the distance for effort, first half is easy pace and second half is steady pace.

• Main Set is 2x100, 2x200, 2x300, 2x100. All reps are done at 5K pace with 100 very easy jog (or walk) after each interval.

• Cool-down with 800-1,600 easy jog.

When I take the track session option I get home quickly and shorten the bike warm-up.

The shortened bike warm-up is 10 minutes at LT1 watts followed by 15 minutes at Tempo watts. Then I take 5 to 10 minutes easy and start the main set (as outlined above).

T-Run and Masters Swim

This is just as it sounds. An easy transition run (after the bike workout) followed by a masters swim.

Seeing as I am married to my swim coach, I’m able to keep the swim reasonable. It’s typically 4,000 to 5,000 meters ending with a ~40-minute main set that’s endurance focused.

Because your heart rate has been up on the bike, watch that you don’t turn the T-run and swim into a hammerfest. It’s easy to cook yourself and you’ve got the rest of the week to be thinking about.

A Word On Nutrition

If we want to benefit from hard training then we need to eat like athletes. Touching VO2 max means I’ll be at my maximum rate of energy burn. The workout also includes ~90 minutes of LT1 wattage. In total, my session contains 1,250-1,400 kJ of mechanical work.

If I’m running off the bike, and swimming ~5,000 meters, then I need to fully fuel. This is exactly the situation where we want to consume ample fast-uptake carbs.

• Before the bike: my normal first breakfast.

• During the bike: ~700 kcal of carbs.

• During the run: just water.

• Between run and swim: recovery meal or more carbs - depends how I feel.

• During the swim: ~700 kcal of carbs.

• Recovery meal after the swim.

• Across the whole day: my normal core nutrition - I miss second breakfast because I’m training across that window & eating a lot of carbs.

It is a lot of intake because I want to benefit from the session and avoid the risk of depletion. I know that if I arrive at my masters swim depleted then I am likely to create strain and disrupt my week.

The art of training involves intensity control and appropriate fueling.

Save your best for race day.

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I run with Jonser most weeks - we talk about life, training and racing. Last week, we were chatting about Ironman and I realized there were a bunch of topics that I hadn’t been effective at highlighting for him. So, for his benefit, and yours, I’m going to pull them together and be crystal clear about what, how and why.

Know Your Real LT1

Jonser fed his recent lactate testing through Chat-GPT and it came back with a training zone guideline similar to the one I explained in my article on Training The Hybrid Athlete.

If you are gym-bro then aiming your endurance training at 2 mmol won’t do you any harm. However, you’re likely to find you don’t shift fat because you are doing all your training with your fax oxidation impaired. Your training is generating fatigue but not much metabolic improvement. Metabolics are foundational for Ironman performance.

To find your LT1, I need you to bottom out your lactate. Athletes who think they are bottoming out at 2 mmol either have awful metabolic fitness, or start their tests/workouts too intensely.

You want to measure your baseline lactate so you can compare your LT1 to the average pace/power you deliver on race day. This is an essential part of post-race analysis and future planning.

Spoiler: you are likely doing a lot of training faster than race pace, without knowing it. Amateur Ironman racing is a 10-17 hour day. It’s not possible to do a Tempo workout for that duration (though many give it a shot for the swim and first 60 miles of the bike).

Resources:

• How To Endurance - the section on Metabolics is required reading for the ultra distance athlete.

• Training Zone Essentials - specifically our sections on Zone 1 and Zone 2.

• Video: Why you are training more intensely than you realize.

Over-Joule Rides

The most important section in my Guide To Going Long is the article on Cycling Specific Endurance Workouts. You can hit the article for a detailed case study.

You want to schedule:

• Several rides where the total output is greater than your expected race day bike leg.

• Each ride should include long segments at, or slightly over, goal Ironman effort.

• Take on carbohydrate/fluid at, or slightly over, race rates.

After these rides, get off the bike and run an easy 10 km. If you aren’t seeing a normal heart rate vs pace profile then you will need to lower your pace targets.

Do not expect “the taper” “going to sea level” “resting up” to miraculously enable better performance than what was proven in training.

When you think you’ve got this bike session dialed then:

• Eat your race breakfast.

• Swim 5,000 meters before the ride.

• Repeat the ride.

• Follow with the 10 km reality-check run.

…and remember you have 20-miles to go on race day.

Resources:

• Key swims can be found in Part 2 of my Guide To Going Long

• Part 2 of my Guide to Going Long explains how to analyze your longest rides and assess what’s reasonable for race day.

Test Your Run Nutrition

We all have a plan to eat on the run. Trouble is, because it’s a hassle, we never train it.

Here’s the workout.

• 2 hour bike / 2 hour run.

• Inside both sessions perform 3x30 minutes at Ironman power/pace.

• Eat/drink at goal BIKE intake rates for both.

Think you’ve nailed the session? Perform the workout after swimming 5,000 meters and eating your race day breakfast. Even when we add the swim, this is less than half of our Ironman energy turnover.

Resources:

• Fuel, energy and performance - scale this case study to your size and burn rate.

• Using Sports Nutrition - examples for how to train your gut.

• Top Amateur Nutrition - we need to balance the days we eat a lot of sugar with real food days. Otherwise our gut health will go to hell.

Swimming & Non-Specific Fatigue

The key workouts I outlined above require a lot of energy. They are the most important sessions to prepare your body for race day.

You should eliminate all sources of non-specific fatigue.

Examples:

• High-intensity, variable paced group rides.

• High-intensity, short interval swims.

• Track sessions done far in excess of realistic Ironman pace.

• Travel.

• Alcohol and caffeine - aim for the minimum required.

Be careful with masters swimming. In a group environment, it is easy to generate a lot of fatigue that is better placed into a long ride. If you want to challenge yourself then hold back until the second half of your long swims. Follow your long swims with endurance riding so you can see how swimming impacts your general capacity on the bike.

Most of your peers will start their Ironman Day with a hard-effort 2.4 mile swim TT. This is madness. Cruise the swim and push the third-hour of the marathon. The swim workouts I linked will help you prove this to yourself.

Big Picture

If you haven’t raced Ironman before, or in a while, then you don’t know what’s going to happen after seven hours.

In the unlikely event you go too easy, a marathon offers ample opportunity to lift the pace and spend whatever energy you have left.

Keep eating until you see the blue carpet.

Gordo’s Guide To Going Long

Full eBook Table of Contents

• The HIIT day aims at Zone 5 - High Intensity Interval Training

• The SIT day aims at Zone 6 - Sprint Interval Training

What makes the protocol different is a focus on ultra-low cadence for the intervals. The low cadence generates high-torque values.

Background

Before starting my VO2 Block, I completed a 19-week Endurance & Strength Block. I mixed in the occasional low-priority race and focused on improving my swimming.

Unsure if you need a VO2 Block? I wrote you an article, which includes a video.

Athletes who are the best at what follows, typically need it the least.

Defining Terms

For endurance athletes, there are two zones above Zone 5 (defined below by John Hellemans).

Zone 6 is Fast.

Zone 7 is Very Fast.

• Using John’s chart (above) we can estimate Zone 6 / Fast as a pace/power that can be maintained with difficulty for ~2 minutes.

• Zone 7 / Very Fast is defined as maximal pace/power that can only be maintained for seconds, explosive and short lived.

The 7 Zones can be grouped into 4 Domains:

• Moderate Domain: the Green Zone, Zones 1 & 2, targeted around the first lactate threshold (LT1) defined as the fastest pace/power achieved at baseline lactate.

• Heavy Domain: Zone 3, targeted at 1-2 mmol above baseline lactate.

• Severe Domain: the Red Zone, Zones 4 & 5, no true steady state is possible with VO2 drifting upwards towards VO2 max.

• Extreme Domain: Zone 6 & 7, characterized by task failure happening before the athlete reaches VO2 max.

Zones and domains sit along a dynamic continuum and do not have sharp edges.

For a deep dive please refer to our Training Zones Chapter.

Fast Day

Last year, when I used the VO2 Max Protocol, a single session was enough stimulus. With the benefit of increased general capacity, I’ve been able to turn my sprint-interval workout into a sprint-interval day.

Endurance protocols have a bias towards restricting rest intervals. Short rest is more uncomfortable and, I suppose, this leads many of us to believe it is more effective. I disagree. Short rest changes the nature of the session and prolongs recovery time.

I view Zone 6 training similar to strength training; its role is to support improved race performance. My race duration is 1 to 9 hours; optimizing 2-minute power/pace is a waste of energy. However, using 2-minute power/pace to improve all zones is a useful way to spend energy, especially when it doesn’t disrupt my week.

On my fast day, I perform three sports (swim, bike and run). At times, I move very quickly. It’s fun and addresses a relative weakness.

Next, I walk you through each session: swim, bike then run.

High-Power Swim

This session is either a race-simulation session or Zone 6 intervals. Last week was Zone 6 intervals and shared below.

My notes following the swim. I used a sleeveless wetsuit until the end of the main set.

High-Torque Bike

The bike uses the SIT protocol of 4x (30 seconds on / 90 seconds off). The main set is repeated twice with 25 minutes at LT1 (Upper Zone 1) between sets. Intervals are done with very low cadence, rest of the workout is choice cadence.

Once again, I like a long warm-up. I do a submax test with ten minutes steps that takes me to LT1 power. Then I do ten minutes of Tempo / Zone 3. Last week’s notes are below.

The workout is:

• Submax steps to LT1 (150/175/200w, for me) using 10 minute steps.

• 10 minutes of Tempo / Zone 3.

• Rest 5-10 minutes (I like a gel and a carb drink at this point)

• Set 1 of 4x (30/90)

• 25 minutes at LT1 Power (lactate might stay up, don’t panic)

• Set 2 of 4x (30/90)

• 20 minutes at LT1 Power sample lactate at 10 and 20 minutes.

Whenever I have time, I check my lactate clearance rate after peppy main sets. I sit on LT1 power and sample lactate at 10 minute intervals. You will find the better your general capacity, the faster lactate is brought down.

High-Velocity Run

The run session uses the same main set as the bike (4x30/90) repeated twice.

My on-pace is 20 kph (3 minutes per km) and my off-pace is 10 kph (6 minutes per km). My 5K pace is ~3:42 per km.

By using a treadmill acceleration is more gradual than outside. This is a low-stress, high-velocity session.

Fast Day Summary

We end up with ~4 hours of training that contains ~16 minutes of Zone 6 work. I always take an easy day (or two) following my fast day.

This year here’s how the week looks.

1. Endurance Day

2. HIIT Day

3. Easy Day

4. Fast Day / SIT Day

5. Easy Day

6. Easy Day

7. Endurance Day

If you need more recovery from the HIIT day (which tends to hit me harder) then put the back-to-back easy days before the SIT day.

The SIT day is non-specific, I don’t worry if I carry a little fatigue into it. What I want to ensure is I’m in a position to absorb, and benefit from, the Zone 6 work. Chapter Ten, Bringing It All Together offers you a deep dive on dynamic loading.

The use of intensity should lift your mood and performance. If that’s not happening then you’re carrying more fatigue than you realize, and/or lack the general capacity to tolerate this sort of training. This is not a big deal. Shed the fatigue and (a) perform a shortened VO2 Block, or (b) move to the next phase of your season.

A little goes a long way with this sort of training. Across a year, I only do a handful of these sessions. It truly is the cherry on top (of a lot of Zone 1 volume).

Save your best for race day.

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I want to build on last week’s article on Using Sports Nutrition and share tactics I’ve been experimenting with in my racing.

Last year, I heard Kristian Blummenfelt mention bicarb and long distance racing. Those of you in the ultrarunning community will have heard David Roche discuss his usage.

20+ years ago, we didn’t use sodium bicarbonate (bicarb), instead we used sodium citrate. The idea was to boost blood plasma volume. Back then, we’d drink a high-sodium beverage the night before our races. Basically, we were drinking very salty Gatorade.1

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Roll forward to 2026, and we have the option of the Maurten Bicarb System.

With bicarb, I was wondering if it might be possible to receive both buffering and blood plasma volume benefits. Doc Hellemans explained buffering agents in his Top Ten Supplements for Endurance Athletes article.

First I tried bicarb in training, then with 5K running races, then a half marathon race, and most recently, an intermediate-distance triathlon.

• I take the bicarb 30-40 minutes before the race, or hard session.

• After being OK with the bicarb, I took with a Maurten 100 caffeinated gel (100Caf gel).

• Finally, I had the bicarb, a 100Caf gel, and a Maurten 320 drink pack. It is a total intake of 1 liter of fluid and 580 kcal.

• I’m guessing I can boost the fluid intake another 500ml. For those of us racing hot, or long, events the benefit is clear. We will have more on board, earlier. We will also be processing food and fluids during the swim.

Big Picture: I have been gradually boosting my intake volume, and energy content, to see how I tolerate. Training my tolerance is expected to give me a performance benefit.

The bicarb contains a lot of sodium which boosts my thirst significantly, making me want to drink more fluids during my event. During the half marathons, I wasn’t able to drink much fluids but, during a triathlon, the bike leg enables me to easily drink water (and eat additional carbs).

When racing, I find it gets increasing difficult to consume fluids or calories as the race progresses. That said, when I’m motivated, I can eat with my heart rate in excess of 90% of max. If I can eat then I know I can drink. I simply need to figure out a system. I’m guessing the solution will be to carry a wide-mouth soft flask (or slow down and get more aid from the stations).

For calories, I like the Maurten hydrogels, they seem to do better in my gut than the alternatives when I’m not drinking much fluids.

Hope this helps you perform better.

See you at the races.

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A friend came down with an injury similar to something I dealt with 15 months ago. This article is intended to help her, and you.

At the start of 2025, I found myself with the symptoms of a bone stress injury in my femoral shaft. At the start of the injury process, my symptoms would appear in the evening and be gone by the morning. Eventually, I started waking up with the symptoms and that’s what prompted action.

In partnership with my physical therapist, we decided to treat the worst case scenario and shut down my running. Once my symptoms cleared, I went for an MRI before returning to running. The MRI showed no signs of bone injury. Absent bone injury, it seems my pain was caused by chronic tendonitis and bursitis.1

Above, if you look at the six weeks prior to the arrival of my injury then you will see I was running at a chronic weekly volume of ~60 km. Visually, you will also notice the weeks look dense, meaning high chronic volume relative to what I tolerated in the months prior. The injury demonstrated my ability to train to the point of self-harm.

This wasn’t a case of bad luck. It was a case of too much volume, for too long. Since finding that limit (6 weeks of 60 km or running, in my case), I haven’t come close to it. Despite having a low biomechanical limit (in running terms), I have been able to develop my fitness, race well and enjoy myself.

• I receive feedback on my limits without resistance. I accept the limits and adjust the forward plan.

• Because I use cross training, I’m able to get plenty done. I focus on consistent work over time.

So far, so good.

• The lesson at this stage, is we need a reliable training log so we have data on the load that causes breakdown.

• Then we need the maturity to train below the breaking point for the next year.

That second point is the big one. Highly-motivated athletes often have a pattern of ramping stress to the breaking point. It is a lack of maturity. This lack of maturity is often masked by:

• Poor record keeping — the training log is sparse so it’s difficult to see the truth.

• Abdication of Ownership — “I just do what the coach tells me.”

Here’s another one that I heard myself say before I was injured.

If something is going to break then I want it to happen in the winter so I have time to rehab it before my A-race.

…and…

Something broke, and I rehabbed it, and I had a great result at Challenge Roth. To my credit, I made it more than a year before something else gave out…

One of the nice things about swimming and cycling is the lower biomechanical load allows us to do a lot of volume. This past winter, I did a lot of both indoor cycling and swimming. It worked great for my fitness but my neck has been on edge for two months.

At first, I added:

• Stretching.

• Strengthening.

• Massage.

• Physical Therapy.

Adding works, it is always my first port of call. By adding, I managed to train through mild plantar fasciitis in December by catching it early, backing off volume and adding rehab exercises. I was able to maintain run frequency and set personal best in the half marathon and 5K.

But adding isn’t always the answer. Especially, for those of us with a track record of self-harm.

If you look at my post-injury run volume then you’ll see load fluctuating so I never get to the point of being chronically inflamed. It looks like I’ll need to do something similar with to keep my neck happy.

Across the winter, I included more and more sessions. While most of these sessions are low heart rate, my neck discomfort is indicating I’m not recovering enough. The signal is the discomfort and it’s clear that more isn’t working to settle my neck.

What I recommend is simple mantras.

Here are ideas that work:

• Every week, two back-to-back easy days.

• Half of all training days are easy.

• Every 3rd (or 4th) week cut volume and frequency in half.

• Every 14 days, 5 days (in a row) off running - switch to cross training.

• Set a volume ceiling below the six-week mileage that caused the injury.

• Log the first sign of injury in the training log. You will learn what issues are normal muscular discomfort and which ones are a sign of potential problems.

Chronic injury (and/or frequent illness) is a clear signal that our approach needs to change. We will get better adaptation (and performance) from giving ourselves less stress. While the injury itself isn’t good news, learning we can get better from less stress is very good news. These ideas seem radical when we are in the grip of the compulsion to train.

What we struggle to see (inside the compulsion) is our adaption is reduced long before injuries appear. The goal is improved performance, enjoyment and a wonderful life. To get to that destination will require change.

Every setback is an opportunity to learn.

Back to The Physics of Performance

Back to eBook Table of Contents

ÖtillÖ had be a stretch. Both the summer preparation and the race itself. Following the race, I took a deep offseason (5 weeks) but, even with a five-week offseason, I still had fatigue to clear.

Like many highly-motivated athletes, perhaps even like you, I thought my frequent illnesses were bad luck. However, the signs were there. Each time I did a challenging workout, or low-priority race, I’d get run down afterwards. For you, the tip is to assume inconsistency implies lingering fatigue. This can be tough to face, especially if you’re having fun racing with your friends.

…and I was having a lot of fun.

Day 566 - ÖtillÖ Austin Pace Bend

November saw Team Feel The Byrn back in action racing in Texas. Axel and I had a blast racing outside Austin.

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Got a comment on last Monday’s article about Fuel, Energy & Performance that I often hear…

The high end nutrition products cost a fortune, I can’t afford to use them all the time. What would you suggest?

First up, you don’t need a lot of sports nutrition.

A few reasons for that:

• You don’t have the energy demands of the faster athletes (you follow on socials).

• You have many low-output days in your week.

• You can use real food options before/during/after your Green Zone sessions.

On energy demands, three resources for you:

1. My Top Amateur Nutrition Article => READ THIS ONE

2. Kilian Jornet’s Energy Expenditure Article

3. My Thoughts on Kilian’s Article

Understanding Needs

My series on Efficiency & Economy explains how to dial in your energy needs.

From that series:

• I’m currently ~78 kg / 172 lbs.

• At 240w, I burn ~1,000 kcal per hour with my heart rate in the low 130s.

• Beyond that point, my fatox rapidly declines.

Yesterday, I ran through Bek’s recent testing with him. Look for a future article from Bek that will give you additional context. He’s ~800 kcal per hour in his Zone 3.

Knowing the effort where energy cost materially kicks up is an essential part of appropriately fueling ourselves. We don’t need to visit Finland to figure this out. As we enter Zone 3, and lactate pops, the cost of exercise increases quickly.

• Green Zone: low cost training, we can easily process all types of foods. In this zone, we only need sports nutrition when performing race simulation workouts and/or for convenience on long sessions.

• Zone 3: costly overall because our fatox is reduced and we can sustain for moderately long periods of time.

• Zone 4: costly overall because our fatox is very low and energy burn is high.

• Zone 5: less energetically costly due to reduced duration. We fuel for improved economy/efficiency and faster recovery.

Creating Capacity

This stuff isn’t rocket science.

• From my testing, I’m burning 800-1,300 kcal per hour above LT1.

• I am a ~170 lb, 9-hour Ironman guy burning ~1,000 kcal per hour in Zone 3.

When Kilian talks about creating capacity, the above is what he means. I have demonstrated the ability to burn large amounts of energy for long periods of time. So I need to fuel it.

When I started, I didn’t have the capacity to burn large amounts of energy for long periods of time. I could either: (a) go moderately long; or (b) go moderately fast. At the time, it only took a little bit of Zone 3 for my heart rate to decouple from power/pace. To build capacity, I did a lot of Zone 1 training, which didn’t (and still doesn’t) require sports nutrition.

At the start, if I used too much sports nutrition then I gained fat. I wrote about my experience in two places:

1. A Simple Fix To Eliminate Weight Gain While Exercising.

2. How To Train, Chapter Four: Fueling The Burn.

If you are eating more sugar than you need => you will gain fat. I gain fat around my midsection. It’s easy to spot - I don’t need a spreadsheet, or even a scale.

As a rule of thumb, you’re not going to need much sports nutrition until you are training >15 hours per week. Even then, you’ll be able to fuel most days with real food.

Make an effort to balance high-sugar days with multiple days where you eat higher fiber, healthier food choices.

When To Use Sports Nutrition

There are three thing that drive my use of sports nutrition:

1. Meet high energy needs => intake.

2. Boost session performance => uptake.

3. Speed post-session recovery => faster adaptation.

For additional energy, I’d rather eat an extra meal (or two) than consume a lot of sugar. It’s better for my health and leaves me feeling more satiated.

But beware => if I allow myself to get depleted during a session, or across a day, I tend to overeat.

This is an important point => using appropriate amounts of sports nutrition, prevents depletion and excessive rebound eating.

Depletion doesn’t work because rebound eating results in excessive intake.

How I Use Sports Nutrition

Let’s review a few practical examples.

Fast Swim: 1:30-1:45 duration, 5-6,000 meters, with a 40-minute main set holding ~1:20 per 100m wearing a sleeveless wetsuit. Heart rate will be above my ~1,000 kcal burn rate (confirmed via bike/run tests). Across that session I will consume ~750 kcal of sports nutrition, via fast uptake sugars.

Key Bike: 2-3 hours duration, 1,500-2,000 kJ of mechanical work. I prefer to eat breakfast before the ride and take a real-food break in the middle of the ride. With virtual rides, I can choose courses with a descent in the middle of the ride. My real-food break contains a couple bananas, non-fat greek yogurt with granola and low-fat chocolate milk. I’ll run off the bike, sauna, then eat lunch. Lots of real food, some dark chocolate treats but zero sports nutrition. This day will often include strength work and a short swim.

Fast Run: If I’m running easy then I train on water, or nothing. However, if my heart rate is up then I want to train uptake and tolerance. During fast sessions, I aim to eat ~640 kcal in the first hour. I do this by taking a Maurten 160 gel every 4 km. During the speedy part of these sessions, I am burning ~1,250 kcal per hour with my fatox close to zero.

Long Ride: My article, Cycling Specific Endurance Workouts, has a breakdown of my intake for a race simulation ride. That case study worked out to ~400 kcal per hour. Now that I am racing faster, I’m going to increase my target to ~560 kcal per hour for future race-sim sessions. In the past, I’ve been able to eat up to ~600 kcal per hour.

Know Your Burn

Use my article: Fuel Energy & Performance to adjust your intake targets to your personal situation.

• All you need is a reasonably accurate starting point.

• From your starting point, track post-workout hunger, session performance and long-term weight trends

• Fine tune your total intake based on real-world experience.

Most my training is easy, and fueled with real food. You don’t need to consume a ton of sports nutrition and sugar.

Use the tips in our Body Performance Chapter to design your core nutrition strategy. With your core nutrition sorted, use the tips in this article to manage supplemental energy via sports nutrition.

Keep it simple, write down what you’re doing and iterate towards better.

Resources:

• Our Nutrition Chapter

• eBook Table of Contents

I had a question on instagram about wearing a wetsuit while swimming. I told the reader, I’d have to see their whole program to comment on their individual position. However, there are some general comments I can make as a guy who went from a barely-swimmer (at 30 years old) to sub-50 minute Ironman swimmer (as an elite).

Touch The Water

One of the nice things about learning a new skill, or getting back into shape, is there is tremendous upside from doing anything.

• Level One: do something.

• Level Two: do something consistently.

• Level Three: do more of the thing.

You get the drift. It’s not rocket science.

However, once we are reasonably skilled, it gets increasingly harder to make big gains. So the first thing to decide on both as a swimmer, and in your larger life, is…

…what’s good enough?

Good Enough

I have a clear idea of good enough.

I want to be comfortable sitting on 1:20 per 100 meters pace in a wetsuit.

That singular goal drives my swim program as well as the total energy I am willing to allocate to swim training. Energy spent swimming is not available for other aspects of my plan.

Define good enough and benchmark your current reality to that target.

Energy Management

It takes more energy to achieve a level than maintain it.

If you want to breakthrough with your swimming then you’ll need to devote more total energy to swimming.

• Total Energy. You must swim more and more often.

• Not intensification of your existing program. Swim squads are mostly plateaued, somewhat exhausted, people.

What’s this going to look like in practice?

• A relentless focus on improving swim economy with a goal of greatly reducing the energy cost of all submax paces.

• Consistent low-end aerobic volume to improve the metabolic efficiency of your swimming muscles.

• If you are weak overall then fix that limiter.

• Increase the total number of swims per month.

• Apply intensity in the most specific way possible.

Most everyone I swim with is a spray-and-pray trainer. They smash themselves at squad and hope the Red Zone sets miraculously make them better. It’s always been this way and will always be this way. You do not have to play their game.

Winter 2025 Case Study

The pie chart (left), combined with the bike/run zones chart (right), tells the story.

Energy is shifted to swimming (blue slice). Cycling and running intensity is downshifted with 96% of my time spent in Zone 1. Unexpectedly, I set over-50 bests in both the 5K and Half Marathon during this time period. I wrote about that experience.

The energy shift allowed me to spend about an hour per week holding my Core Pace, or faster, wearing a sleeveless wetsuit.

• This pace work represented 5% of my total weekly volume (all sports) and was split between two masters sessions.

• The rest of my swimming was easy.

In parallel to the swim training, I did a moderate amount of strength training. Some of this strength training targeted my upper body in a general fashion. Getting your upper body stronger boosts swimming, especially when you are swimming nearly every day.

The physiology of swimming is like the physiology of running.

• Frequency first.

• Then consistent easy volume, working to improve one technical area at a time.

• Get one, or two, longer workouts per week.

• Finally, add specific work aimed at Core Pace.

With cycling, more works great.

With running and swimming, you’ll do best using more often.

Chapter: Swimming Essentials

Video: Five Essentials For Amateur Swimming

eBook Table of Contents

To apply this chapter, scale my methodology up/down to your size, power and race duration.

• Write it out, just like I am going to explain.

• Your written document gives you a starting point.

• Then get out there and test it in conditions as similar as possible to race day.

People and Data Sources

Solveig Løvseth, 2025 Ironman World Champion

• Fueling Strategy Document - Precision Fuel & Hydration

• Race Simulation Workout - Scientific Triathlon Podcast

Taylor Knibb, Multiple World Champion, 2x Olympic Medalist

• Fueling Strategy Document & Race Review - The Feed

Kristian Blummenfelt, Olympic, WTCS, Ironman & Ironman 70.3 World Champion

• 2024 Article: Training Volume and Energy Expenditure of a World-Class Triathlete

Other important people, I’ll be referencing:

• Monica Caplan - my wife’s maiden name. Monica led Ironman Hawaii to the bike turnaround in Hawi, before being passed by a woman who subsequently tested positive for EPO.

• Scott Molina - my head coach across my elite career. 1988 Ironman Hawaii Champion.

• Mark Allen - my coach at the end of my elite career. 6x Ironman World Champion.

• Dave Scott - my coach at the peak of my elite career. 6x Ironman World Champion.

• Olav Aleksander Bu - Norwegian coach and generous podcast guest. I’ve listened to everything I can find in English. For those of you with access to his interviews in Norwegian, please reach out if you have deeper insights that he’s explained in his mother tongue.

Let’s get stuck in.

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Last time, we introduced:

• Henry Huffer, an inefficient amateur male at 80 kg (176 pounds).

• Ariana Arrow, an efficient elite female at 60 kg (132 pounds).

Let’s add a third athlete:

• Metabolic Marco, an efficient male at 75 kg (165 lbs),

From last time:

• Henry is not efficient. We’re going to assign him a mechanical efficiency of 19%. At his weight of 80 kg, this implies a relative VO2 requirement of 45 ml/kg to produce 240w.

• Ariana is a well-trained elite female with excellent efficiency. We’re assigning her a mechanical efficiency of 23%. At her weight, this implies a relative VO2 requirement of 50 ml/kg to produce 240w.

Marco has similar efficiency to Ariana (23%), which means to produce 240w he’s going to need 3.0 L/min of VO2. At this weight, that’s equivalent to a relative VO2 requirement of 40 ml/kg. Not only is Marco doing less work per kilo, he has more headroom above 240w than Henry and Ariana.

Three different types of athlete, three common profiles that you will see in male and female athletes.

• Henry => moderate engine size (liters of VO2), low efficiency, not well trained.1

• Ariana => moderate engine (liters of VO2), high efficiency, well trained.

• Marco => large engine, high efficiency, well trained.

All three of these athletes are going to think they need to get better, and that’s true. However, the pathway to better performance is different for each of them.

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I got to spend last weekend in Jackson as part of a six-day unload. Justin was there and he wrote a few thoughts up on his Substack…

Justin Daerr (all of it)

Notes from 35,000 feet: A Conversation with G

I have known Gordo Byrn for over 20 years. Back in early 2019, there was a surprise birthday party for him and everyone at the table was asked about how they first came to know, and meet, Gordo…

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3 months ago · 10 likes · 6 comments · Justin Daerr

My favorite part of the conversation was Justin’s observation…

I am not saying that sticking with something will guarantee success in any pursuit, but I do think that abandoning pursuits too early is what creates the greatest separation between those that make it and those that do not.

Justin made the point that there can be excellent reasons to abandon pursuits. In fact, a key part of creating a life with meaning is the ability to simplify both daily actions as well as what we’re working towards. This is going to require a fair amount of abandoning.

Today I want to expand on Justin’s concept as it applies to sport. You’ll need to decide for yourself if being intelligently stubborn (with sport) is right for you.

If not quitting is an important factor in our ultimate development then what’s strategy is most likely to keep us in the game?

This is a vastly different question from the way training strategy is typically presented - ie as an optimization problem.

How might we keep ourselves in the game? I promise you will discount what I’m about to explain. How do I know?

• Because I have to constantly remind myself that these methods work.

• Because they seem counterintuitive to the way our brains are wired.

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Stress & Adaptation

Half our days should be low stress. This applies up and down the performance ladder.

If I could make a prediction for the future of exercise physiology then it would be this… we will better understand the role of the nervous system in all aspects of performance.

Talk to world-class strength and speed athletes and you’ll hear a deep respect for the role of the sympathetic system. Endurance athletes tend to discount this lesson in their own programs, piling on chronic stress.

I think it goes further than the output side of the performance equation. My experiences with half my days being easy1 point towards adaptation and total work capacity being intimately linked to how my nervous system is doing.

At this stage, beyond morning resting heart rate (RHR), training heart rate (THR) and morning heart rate variability (HRV)… we don’t have a lot of tools to measure how we’re doing. Knowing my bias towards chronic fatigue, my heuristic is to ensure half my days are low stress. I think you should do the same.

Note low stress doesn’t mean no stress. You’ll want to stay active everyday.

Easy Volume

Just like we underestimate the adverse impact of chronic fatigue, we discount the value of easy volume. Outstanding metabolic fitness, and movement economy, is something I seldom come across in amateur populations.

Over 90% of what I do is in the Green Zone (Zones 1 & 2).

When you add my swimming volume, I’m performing ~12 hours a week of Zone 1 training. Easy means heart rate, subjective perception, breathing and lactate are comfortable. This is a powerful stimulus for strengthening training response as well as an important component of performance at all intensities.

Athletes need constant reassurance to slow down enough, and for long enough, to get the training benefits that accrue from easy volume. It’s a central theme of my book, How To Train.

Frequency

Because fitness is a continuous function, even a single, short session makes a difference. The lower your chronic volume, then the more this principle will apply.

Frequency swims with long, relaxed intervals. At present, my favorite is 2x1,000. The first kilometer is swum with a pull buoy and the second kilometer is swim with fins. I choose one aspect of my stroke and focus on improving it. The long intervals train my mind to relax and make my middle distance intervals easier mentally.

Frequency runs where the goal is simply to run as easy as possible. I’ve always used these with athletes of all abilities. Whether it’s a professional athlete running 4 minutes per km or an amateur running 6 minutes per km.

Exercises from my physical therapist (PT Exercises)2. One of my PTs shared something that stuck with me, “Even if you only do them once a week, these exercises will work.” Talking with Justin this past weekend, he also shared the observation that, “if an athlete is too tired to do the little things then they are clearly too tired.”

My PT Exercises have a dual function:

• Prevent small issues from derailing my training.

• Acting as an early warning system for when chronic fatigue is starting to impair training response.

A Virtuous Circle

Ample low-stress days, easy volume & frequency work together to reinforce our training adaptations. The best part about this approach is it takes the pressure off the vast majority of our sessions. Our goal is to enjoy ourselves and stay in the game. This frees our mind to focus on the handful of sessions we will find challenging. If your approach requires you to constantly amp yourself up then it’s not going to prove optimal, or sustainable.

We are 500 days into our journey and have had time to see the benefits of consistent training. We are going to explore two more foundational concepts:

• Fitness is expressed as a flattening, and rightward shift, of the lactate curve.

• There is an optimal sequence to training periodization. We start with a focus on health, shift towards metabolic fitness, add general capacity, and then finish with specific preparation.

The figure above is from a series of bike tests. We’re going to focus on the difference between the red curve (Upper, August 2022) and orange curve (Lower, August 2023).

The upper red curve shows lactate rising as soon as the test begins. This is called a linear curve because lactate rises as soon as power increases. When lactate rises on the second step, you should start subsequent tests at a lower power value. In this case, 100 watts would have been a better starting point.

The lower orange curve shows an extended period (150 to 210 watts) with lactate at steady baseline values. This type of curve is called a normal curve. While the curve is called normal, the profile is not normal in the general population. The linear curve is what you’re likely to see when you test initially.

Be cautious about drawing definitive conclusions between two tests. That’s why I included details on five tests (total) in the figure. With a series of tests, you will be able to clearly identify trends if they are present.

In the case of my data:

• We see the curves moving down and to the right.

• We see heart rate, for a given power, reducing.

• We see lactate, for a given power, reducing.

Importantly, you won’t always see an improvement in heart rate or lactate profiles, particularly if you test after an illness. If you look at the heart rate data (in parenthesis) for the green and solid black lines, you will see my point. The exact numbers in a test don’t matter. What matters is the trend over time, especially when you are comparing similar periods in your annual cycle (say August 2022 vs August 2023).

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