Category Archives: Freediving training

Become a better diver with strength training for freediving

How should we train? Is strength training for freediving a good idea? Are bigger muscles better or worse? Should we hit up the gym in the off season?

I have alluded to some of these questions in previous posts and newsletters. In my mind, there is no doubt that a well trained muscle performs better during freediving activities. Unless you are purely interested in statics, strength training will benefit you.

Muscles store both energy and oxygen, and a trained muscle can store more of both. But (there is always a but), it is difficult to load a muscle with oxygen, or rather, the oxygen carrying protein myoglobin. So instead I’ll show you how you can load it with energy, or rather, the phoshate molecule creatine phosphate.

Continue reading Become a better diver with strength training for freediving

Design a 15-minute daily ritual you can stick to this year

Rome wasn’t built in one day, you won’t be able to do the split tomorrow and you are not going to increase your breath hold by 3 minutes overnight.

You might have some freediving goals for yourself in 2018. Perhaps a CWT dive to 50 m, or a 7-minute breath hold. Chances are that you have already trained for over 20 hours to get there. But what if that training intensity doesn’t last throughout the year?

In this article you can read how to create a daily ritual to get you to your goals. You will achieve more by 15 minutes of training per day over the course of a year, than by training several hours per day for a few weeks. No matter what the goal. You also get a blueprint to design your own 15-minute daily ritual.

Continue reading Design a 15-minute daily ritual you can stick to this year

Breathe better and deeper: increase lung volume with these exercises

So you want to increase lung volume? There are several ways to do this, but you should probably start with becoming a better breather. That means, you should be able to fill up the entire volume of your lungs with a deep inhale before you actively start to do exercises that will increase lung volume.

Let me show you what I mean.

Active breathing vs. passive breathing

Most people go through life without taking active control of their breathing. The autonomous nervous system takes over the act of breathing if you don’t think about it, which means that you don’t have to think about it…

And that means that most of us never think about breathing.

The body responds to simple stimuli that will increase or decrease the breathing rate. For example, the breathing rate will increase if CO2 in the body increases or if the temperature decreases.

The body does not optimize each breath. If you are relatively untrained your inhales could be short and you may be using less than 75% of your vital capacity for each breath.

Optimizing the respiratory system is something we have to do by consciously using it. In other words, you need to become aware of your breathing, and consciously change the way you breathe.

Get your shoulders out of the way first

But first, let’s become somewhat aware of what our posture does to our breathing. The shoulders are only attached to the rest of the skeleton by the collar bone. Because of that, a substantial weight pushes down on the widest part of the rib cage: the weight of your shoulders and arms combined.

Don’t believe me? Then try this:

  1. Stand up or sit up straight with your arms hanging down the side of your body. Breathe in as deep as you can.
  2. Stand up or sit up straight with your hands on your hips and your elbows out. Breathe in as deep as you can.

If you noticed it was easier to breathe in that second time, you felt what I am talking about.If you did not you are either a blessed freak of nature or you are hardly using your upper intercostal muscles.

Funny side note. Opera singers have their arms wide and in front of them when they sing a strong note for a reason: it opens the chest.

In order to loosen up the shoulders:

  1. Stretch arms out overhead, and in a wide arc let the left arm come underneath the right. Clasp your hands together (as best you can). Hold for one minute and then switch sides. This is part of the yoga ‘eagle pose‘.
  2. Put your hands on your glutes, fingers pointing down look forward and up so that your spine is slightly arced back. Try to gently move the elbows closer to each other behind your back. You should feel a stretch in your front shoulders.

This simple preparation goes a long way. It won’t help you actively increase lung volume yet but it will allow you to get the most out of your breathing later. There are many more ways to open the chest with stretches but let’s move on to the actual breathing.

Three simple breathing exercises

increase lung volume
Trust me, my hamstrings are probably tighter than yours (it’s not me in that photo). I grow tired of the classic shot of a beautiful person doing supposedly peaceful meditation on an empty beach while the sun sets, in a position that 99% of humanity will never experience. The truth is that you can meditate anywhere, in any position. For breathing exercises, all you need to make sure of is that you have a straight back (this person seems to be a bit crooked, but it might just be the baggy t-shirt). You can sit cross legged, on a couch or chair, or stand up straight.

Audible inhales

One of the best ways to actively increase your lung volume is by limiting the flow of air through your throat and training yourself to keep that flow constant. Try it:

  • Keep one hand on your belly, and one on your chest.
  • Inhale slowly and constrict your throat slightly so that your inhale is audible (another way to inhale audibly is to make a whistling sound with the lips).
  • Focus on the belly first. Your lower hand should be moving outward.
  • Keep the sound of your breath constant.
  • Once it becomes difficult to keep that lower hand moving out, your chest should start to inflate. Try to keep the lower hand outwards as much as you can and continue with inflating the chest. Exhale slowly and repeat.

Alternate nostril breathing

Alternate nostril breathing is a similar exercise but additionally clears your nasal cavities. The exercise is fairly straightforward.

  • Sit with a straight back and close your right nostril with your right thumb. Inhale fully and slowly through the left nostril.
  • At the top of your inhale, pause and release your right thumb. Close the left nostril with the ring finger of the same hand.
  • Exhale fully and slowly through the right nostril, and then inhale fully and slowly. Pause and close the right nostril.

End range of motion exercise

When I was recovering from a rotator cuff injury I was given an exercise to work on the power and strength at the end of my range of motion. It was an easy exercise and I realized it could be done with intercostal muscles as well. I believe that out of the three exercises here this one will give you the fastest results.

  • Sit with a straight back
  • Put your hand on your hips (so the shoulders don’t weigh down the ribcage)
  • Inhale slowly and fully
  • Once you are at the max inhale, use your diaphragm and intercostals to keep it at the max.
  • Do not lock the throat or mouth. The air should be able to move freely from your mouth into your lungs, and you need to use your respiratory muscles to keep it in the lungs
  • Exhale after 10 seconds
  • repeat 5 times

How long should you exercise? Just remember that five minutes per day beats one hour once per month.

Forget about packing for now

Packing, or over-inflation of the lungs, is a simple tool that can increase lung volume directly and dramatically. However, because it is a passive tool it works against the resistance of the rib cage. The over-pressure in the lungs has caused embolisms resulting in partial paralysis, and a range of other serious injuries in freedivers on land and in the pool. It should be avoided for anything but dives that are well below residual volume. From AIDA’s Facebook announcements:

“Recently several packing related incidents with lung damage and/or transient neurological symptoms have been reported. Keep in mind that lung packing and pack stretching are very advanced techniques that may lead to serious medical conditions and even death. Packing should be performed with care and is something that we do not recommend in the AIDA education program”

Packing alone is not worth your time. Breathing exercises are always good, both to increase lung volume and better breathing overall. Once you are going to push the numbers during very deep dives packing is something you may want to consider. If you are interested in more info, Walter Johnson has a great article on packing on his website Freediving Solutions.

When and how many exercises should I do?

Great question. When considering how much time to put in any exercise remember that consistency and moderation are the long term winners. Five minutes per day will increase lung volume, but one hour on one day per month is not going to do much for you. The best time to do these exercises is right in the morning, so you can reap the benefits all day.


Training for freediving with the Moxy muscle oxygen monitor

This post goes with a webinar that I gave on data collected with the Moxy Muscle oxygen monitor. In the webinar I test some specific exercises and try to speculate on myoglobin desaturation and training to increase myoglobin stores.

I want to use this post to give some extra thought to some keypoints, and to make the webinar a bit more understandable. But first, keep these things in mind:

  • The Moxy measures oxygen in the muscles. I put it on my left Vastus Lateralis (quadriceps).
  • The Moxy gives you one number for total SmO2 (muscle oxygen). This number is a weighted average of myoglobin and hemoglobin.
  • Everything I tested only relates to me and my (left) quad. The numbers will be different for you. The squats that work for me may not work for you. The apnea walks that don’t work for me may work for you.
  • On all the graphs in the presentation, the x axis = time in seconds. The left y axis is for heart rate, muscle oxygen and SaO2. The right y axis pertains to Thb and is a measure of blood flow to the muscles.

Ok now you can watch:

I used the Moxy to test a series of exercises. What do these exercises actually do?

Apnea walks

For example, the apnea walks that I described here actually did not train my muscles to perform under hypoxia at all. The body has a fantastic set of feedback mechanisms in place to make sure that oxygen is delivered where it is needed, and without the vasoconstriction and blood shift during a dive that oxygen will go right into your muscles. Apnea walks debunked. Sorry everyone.

It didn’t matter whether I did them on an exhale or inhale.  I think that apnea walks on an inhale probably don’t work for anyone. On an exhale, they may work for some people, but I doubt it.

What about holding your breath until contractions and then starting exercise? Same thing. The muscles actually never get hypoxic. In fact, even doing this with a more strenuous exercise like a wall sit the muscles never dipped below ~35 %.

Doing a wall sit or even one-leg stand with breath did not help either. You can do a wall sit until failure, but there will be plenty of oxygen in your quads. It’s not a lack of oxygen that causes your muscles to fail, it’s the accumulation of waste.

RV squats

The only exercise that I found effective was a set of isometric squats with short recovery intervals, done after a forceful exhale. Using these squats and tinkering with the variables (length of recovery, initial static, and squat) I was able to consistently let SmO2 dip below 10%.

Now before you all start doing a 150 kg squat on breath hold, remember that if you do this with too much resistance you might simply be training for fast twitch muscle. If I focus on slow twitch muscle I try to stick to no higher than 30% of my personal max resistance.

How do you know this works? Are you increasing myoglobin in the muscles?

I don’t know if this works. But here is my rationale. In order to get the body to generate hemoglobin (red blood cells) you need to desaturate the blood of oxygen. This is why being at altitude increases your red blood cell count. The body will automatically create more red blood cells once it realizes it does not have enough of them to efficiently bring oxygen to where it is needed.

Along the same lines of logic, we need to desaturate myoglobin of oxygen in order to tell the body to create more of it. This happens naturally on some deeper or longer dives thanks to vasoconstriction and blood shift, but is hard to achieve when cross training.

I can’t promise you that by lowering SmO2 you will cause more myoglobin to be generated. I do think it is a sound hypothesis. Keep SaO2 high, and decrease SmO2. This is what naturally happens in our bodies during a dive, and one of the things to aim for during cross training.

The in-water method of training for myoglobin is called the Foundational Training and described in Eric Fattah’s book Holistic Freediving.

Free webinar: Training with a MOXY muscle oxygen sensor

The MOXY is a muscle oxygen sensor that can measure the saturation of hemoglobin and myoglobin of for example your quads.

Do you think your apnea walks are effective?

They might be. You can practice apnea walking with an oximeter, but it is hard to know exactly what is going on in the muscles. For some training you don’t need the oxygen in the muscles to drop, and for other training it needs to drop as much as possible.

Now, the guesswork is over.

Using a MOXY muscle oxygen sensor it is possible to measure the oxygen content in the muscles. You can strap the MOXY to your quad, biceps, or any other muscle to gauge the level of oxygen during exercise.

MOXY oxygen monitor.
The MOXY can be used to measure the oxygen levels in your muscles during exercise. Image taken from here

I have tested a set of exercises, including apnea walking, apnea squats, and bicycle interval training using the MOXY and will be sharing my results during a free webinar. The webinar will start at 12 noon CST, Tuesday December 12th, and run until about 12.45. There will be ample time for questions.

Register for the free webinar now!

Hope to see you there.

A practical guide to apnea walking as training for freediving

You have probably heard about apnea walking as a form of training. But how does it really work? What are you actually training? There are a few specific ways to practice apnea walking. Here I will describe the method I use.

As you know from our previous posts on muscle fiber type, and muscle metabolism, different metabolic pathways and muscle fibers are active during different parts of the dive. With apnea walking, you train the ascent phase of your dives. During the ascent phase, your legs are gradually becoming more hypoxic as a result of vasoconstriction and overall oxygen depletion.

If you feel like your legs are always tired when you are coming up, apnea walking is worth a try.

Should I practice apnea walking with full or empty lungs?

Apnea walking is a good way to train the muscles under hypoxic conditions. If you do a static with full lungs, your oxygen saturation only starts to decline after several minutes. It starts to decline within a minute if you do a static with empty lungs. The same thing happens if you are walking. Empty lung apnea walks result in lower oxygen saturation, and will be shorter as a result.

Because I find the dive reflex is hard to initiate on land, I do most of my dry apnea with empty lungs. I always train with an oximeter. If the goal is 85% SaO2 it does not matter whether I get there with full or empty lungs.

For me, training with empty lungs is faster and more comfortable. If you have no problem doing long full lung breath holds on land you can fully inflate your lungs before apnea walks.

apnea walking
A simple oximeter that I use for apnea walking. It is far from perfect, but definitely allows me to track my performance better.

I use an initial static of around 30 seconds to become slightly hypoxic before I start the walk. The reason for this is that my body might maintain blood flow to the muscles if I start walking prior to the onset of the dive reflex (or HR drop). This is an obvious issue if the goal is to train the muscles under hypoxic conditions.

After my 30 seconds empty lung static I walk for approximately a minute while maintaining the breath hold. At the end of my static I try to be at SaO2 80 – 85%. I take about 10 recovery breaths, and note the final SaO2. My total recovery interval is 1:30 between walks. I get a maximum of 5 contractions per breath hold this way and I can easily keep it up for more than 10 repetitions.

Interested in cross training for freediving and spearfishing?

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Empty lung apnea walking

Apnea walking in point form:

Get your oximeter and a timer ready. If you do not have an oximeter you can still do the exercise but it will be harder to tweak it to your needs.

  • Warm up with a couple breath holds or simply breathe slowly for a few minutes
  • Do an initial static
  • Walk
  • Take up to 10 recovery breaths (quick breaths) and relax. Your total recovery interval is 1:30
  • While in recovery the numbers on your oximeter may keep dropping. Note the lowest value. If this value is lower than your target, reduce your next static and/or walk
  • Repeat for 12 cycles

I use the ‘runtastic’ timer app for iOS in order to time my training (I am not affiliated with this app in any way).

I use the runtastic timer app for my apnea walks
I use the runtastic timer app for my apnea walks

Tweaking the exercise

Your initial static should be short enough to allow for a decent walk. If you have a strong dive reflex on land you may not even need the static. I suggest starting the static at 30 – 50 % of your onset of contraction time. For example a diver that gets contractions at 1 minute on an empty lung static should start with a static of 20 – 30 seconds. If you have an oximeter with heart rate monitor, stop the static and start the walk when you see your heart rate drop (if you see a heart rate drop at all – I often don’t).

Your oximeter will not show the current oxygen saturation. Rather, it records a moving average. Because of that you will have to keep checking your oximeter during your recovery. The lowest value should show up within 15 seconds after you start breathing. Compare this value to your target value.

Your apnea walks should be of a comfort level that you can keep up for more than 10 repetitions. The reason is that you are simply not going to induce adaptations by only one minute of hypoxic walking per training session.

Before you start training, know the risks. Any exercise involving apnea can lead to loss of consciousness, injury, or even death. Choose a safe site to train. Do not attempt this training with a heart condition. Always train with a buddy/spotter.

How do you train your apnea walks? Leave a comment!



Training and Performance by Sara Campbell review

This post was submitted by Luca Malaguti.

In Training and Performance Sara guides you through a series of hands-on and practical exercises that apply to all facets of freedive training. I really like that Sara starts off the program by explaining a few things we tend to forget in athletic training, and especially in freediving.

Cultivating continuous improvement

Sara teaches us about the balance between sustainability and challenge. We should strive for continuous gradual improvement. In order to achieve that we need to set attainable goals that gradually lead to improvement. Setting the bar too high may lead be demoralizing, undermine our confidence, and take the enjoyment out of the dives.  Sara emphasizes that it is important to advance patiently and step outside of our comfort zone during training, but not venture too far beyond it, in order to allow for continuous progress.

'Yoga For Freediving' is a series of online yoga courses by Sara Campbell
‘Yoga For Freediving’ is a series of online yoga courses by Sara Campbell

Just as many positions (asana) in hatha yoga seem intimidating at first, breathing exercises (pranayama) can be equally daunting. Recall your first wobbly downward dog? However, Sara presents the exercises in a way that they gradually become more complicated and demanding. This I particularly appreciate. For this reason her video lessons are very effective. You have a mentor in front of you guiding your practice step by step. A lot of the exercises Sara goes over I have read them in books many times over, but having Sara in front of me belly pumping for 3 minutes pushes me to keep up with her and advance my practice so that I feel those new sensations. On my own I would probably stop after 60 seconds.

Training and Performance videos

Sara’s course contains 6 specific videos:

  • Training zone (~10 min lecture)
  • Comfort zone (~10 min lecture)
  • Pranayama – basic breath series (~45 min breathing exercise)

I found it effective to start with a few breath cycles before starting alternate nostril breathing. This way the nasal cavities are somewhat clear before the alternate nostril breathing exercise. Alternate nostril breathing is an important exercise to begin your practice with because it gets you “in the mood” to continue. Whether it is the effect of nitric oxides or just an overall cleansing sensation, this exercise first thing in the morning can really put a smile on your face.

  • Kriya – basic spinal energizer (~50 min exercise)

The spinal energizer is a truly fantastic exercise. However, if you find it painful to sit in the lotus or the partial lotus position (for example because of a knee injury, my problem), you can try sitting down with your bum touching your heels. This is known as vajra-asana or position of the diamond. This position may help to relieve some of the tension on the knees generated by the twisting.

  • Respecting your body (~10 min lecture)
  • Visualization – perfect dive (20 min exercise)

Training and Performance also comes with more than 20 extra videos and other materials to help you with your practice. The lectures and visualisation are available in MP3 format so you can bring them with you and listen to them before you dive, or on the road.

Training and performance
Training and Performance is the 4th part of Sara Campbell’s ‘Yoga For Freediving’ series.

In Training and Performance Sara goes over excellent exercises that connect movements with breath. I look forward to using them to advance my practice in freediving, while enjoying having my teacher in front of me guiding and motivating me through my practice. The way that Sara interacts with her viewers brings them by her side, and allows them to imagine a morning of diaphragm exercises on the beaches in Dahab.

Go to Yoga For Freediving by Sara Campbell (external link)

Other reviews of Yoga for Freediving by Sara Campbell





Muscle metabolism during breath hold dives

Muscle metabolism in a nutshell (recap of part 1)

This is part two of the ‘muscle metabolism’ article series. In part one (link) we have analysed human muscle metabolism, how muscles are supplied with oxygen, and how they store fuel. We learned that muscles store fuel in the form of ATP (adenosine triphosphate) and CP (creatine phosphate). These fuels are metabolized without using O2 or producing CO2. Muscles are supplied oxygen from the lungs through the bloodstream and through myoglobin. Slow twitch muscle fibers (those that you engage while walking around) contain more myoglobin. However, human muscle contains limited amounts of myoglobin compared to freediving mammals. Fast twitch muscle fibers (those you use during strenuous exercise) contain more high energy phosphates (ATP and CP).

We also analysed the metabolic pathways in muscle. Aerobic glycolysis is slow but is the most efficient metabolic pathway. It generates 34 ATP molecules out of one glucose molecule. Anaerobic glycolysis produces lactate and generates only 2 ATP molecules out of one glucose molecule. Because the reaction occurs faster more energy can be liberated quickly. This process can be dominant for a maximum of 75 – 120 seconds. Anaerobic alactic metabolism uses only high energy phosphates (ATP and CP) present in muscle and can be dominant for about 5 – 15 seconds.

Did you miss part 1 of the muscle metabolism series? Find it here.

Muscle metabolism: concurrent metabolic pathways

A persistent myth in exercise physiology is that all these metabolic pathways are active sequentially. On the contrary, they are actually concurrent. In the figure below you can see the relative contribution of the different metabolic pathways to power output during maximum intensity exercise.

muscle metabolism
Muscle metabolism during maximum power output over time. The ATP-CP (adenosine triphosphate – creatine phosphate) system is depleted first, then AN-G (anaerobic glycolysis) provides the majority of power, followed by A-G and AL (aerobic glycolysis and aerobic lipolysis). The maximum power output decreases over time.

You can see the overlap in time between the different metabolic pathways, but also that the anaerobic systems contribute more at the onset of exercise than at the end. Of course a dive is not a continuous maximum power output. This might be what happens during sub-maximal power output:

muscle metabolism
This may be what happens during sub-maximal power output. Depending on the required power output anaerobic glycolysis will occur or not.

Regardless of the intensity of the exercise, the ATP-CP system is the quickest to respond to a muscles’ energy demand. The ATP-CP system essentially fuels the muscles while the blood flow to the muscle increases as a response to the increased oxygen demand. The increased blood flow allows aerobic metabolic pathways to provide energy. If the energy demand is low the lactic anaerobic system will not be a major contributor.

What happens if we run out of oxygen?

But what happens if oxygen is removed from the equation? How does the body respond?

During a dive you try to conserve as much energy and oxygen as possible. Freedivers work hard only for the first 10 or 20 seconds in order to overcome positive buoyancy, and perhaps a bit longer on very deep dives.

In the figure below is a hypothetical ideal dive and the energy systems that are major contributors to it. The dive consists of three phases, the dive phase, the sink phase and the ascension. During the dive phase you are actively swimming down. Ideally the ATP-CP system is the only contributor to the entire swim to neutral buoyancy. During the sink phase you stop moving and the aerobic system is able to supply enough oxygen to your body for basal metabolic functions. During the ascent most of your energy will be derived from anaerobic and aerobic glycolysis.

muscle metabolsim
In an ideal situation, the ATP-CP system is the only system active during the descent. A combination of aerobic and anaerobic glycolysis provides the energy to surface. As hypoxia becomes more severe, anaerobic glycolysis becomes more important.

A less ideal dive

In a less than ideal situation the lactic anaerobic system may also supply some of the energy required for the descent.  In this case you deplete the ATP-CP system completely prior to reaching neutral buoyancy and anaerobic and perhaps also aerobic glycolysis supply significant amounts of energy. The obvious result is that there will be less energy available for the remainder of the dive. A larger reliance on the anaerobic glycolytic system will also lead to earlier muscle fatigue.  This may occur if you have a very thick suit, not enough weight, or you are not appropriately trained.

If the oxygen supply to the muscles becomes limited, either because of vasoconstriction, hypoxia or both, anaerobic glycolysis supplies the majority of the energy required. The dive reflex has a large impact on the oxygen supply to the muscles. Vasoconstriction limits the supply of oxygen and causes anaerobic glycolysis to start earlier. Anaerobic glycolysis leads to muscle fatigue, which you notice as burning legs on the way back to the surface.

Muscle metabolism in diving animals

The processes that operate in human muscles are similar in freediving animals. However, the muscle composition of species differ. Diving animals also have specific adaptations that help them dive longer and deeper.

Diving animals do long breath hold dives because adaptations. These adaptations include a high hemoglobin concentration, a high blood volume relative to body weight, and abundant myoglobin in the muscles. In addition they have metabolic adaptations that help them dive. Despite these adaptations, the basic metabolic pathways are the same as in humans.

Some animals, such as the Weddel seal, dive on an exhale so that they do not struggle to reach neutral buoyancy. The Weddel seal maintains low levels of aerobic metabolism throughout most dives. These seal have less of a dependency on blood borne oxygen because of the massive amounts of myoglobin in their muscles.

The seal wins in terms of dive duration and depth
The seal wins in terms of dive duration and depth

Other diving animals push to the anaerobic limit on nearly every dive, such as sea lions and penguins. The muscles of Weddel seals are predominantly composed of slow twitch muscle fiber and loaded with myoglobin. The muscles of sea lions and penguins contain more fast twitch muscle fibers.  The difference in muscle composition exists mainly because of foraging and hunting styles.

vivian island freediving
A steller sea lion, loaded with fast twitch muscle fiber.

What should you do? Hit up the gym and train for fast twitch muscles? Or try to be like a Weddel seal?

In essence the diver that emulates a Weddel seal will end up doing the longest and deepest dives. The dive profile of spearfishers is much like that of seals. They make a descent, stay at their target depth for a third of the dive, and then ascend. It is no coincidence that many spearfishers have hit amazing numbers at freediving competitions. And this despite the fact that they never did much training specifically for competitive freediving beforehand

So you tell me in the comments, are you going to hit up the gym, or start spearfishing?

Three studies that you may find interesting:

  • Kooyman, G. L., & Ponganis, P. J. (1998). The physiological basis of diving to depth: birds and mammals. Annual Review of Physiology, 60(1), 19–32.
  • Gastin, P. B. (2001). Energy system interaction and relative contribution during maximal exercise. Sports Medicine (Auckland, N.Z.), 31(10), 725–741.
  • Reed, J. Z., Butler, P. J., & Fedak, M. A. (1994). The Metabolic Characteristics of the Locomotory Muscles of Grey Seals (Halichoerus-Grypus), Harbor Seals (Phoca-Vitulina) and Antarctic Fur Seals (Arctocephalus-Gazella). Journal of Experimental Biology, 194, 33–46.

Muscle metabolism part 1: Muscle fiber types and freediving.




Muscle fiber types and freediving

This article is the first in a 3-part series on muscle composition, performance, and failure during breath holding. This article is long and fairly technical. In a rush? Just read everything in bold.

Muscle fiber types and freediving

Muscle fibers use fuel in order to deliver power. This fuel is metabolized via different reactions, called metabolic pathways. There are different types of fuel, different types of muscle fiber, and different metabolic pathways to consider. The purpose of this article is to provide you with an understanding of how muscles perform and metabolize under hypoxic conditions. In light of that will come some speculation on training for freediving. What types of muscle fiber are beneficial for freedivers? What type of fuel do we need in muscles and how do we increase the abundance of that fuel?

Anaerobic and aerobic metabolic pathways

Muscles can perform under either aerobic or anaerobic conditions. Under aerobic conditions, the supply of oxygen to the muscle is sufficient to keep up steady state performance. This includes for example walking and low speed running. Under aerobic conditions, glucose is converted to pyruvate. Pyruvate in turn enters the metabolic pathways called the krebs cycle and oxidative phosphorylation to yield ATP, which is used directly as a fuel in muscle fiber. It is an efficient process that yields 34 ATP molecules per glucose molecule.

If the supply of oxygen is reduced, or the intensity increased, aerobic processes may not be able to deliver enough energy for the work required. This occurs for instance if you are sprinting. The body will require much more oxygen than it can deliver to the muscle. Thankfully, anaerobic processes take over and supply more energy to the muscle, although they can only do so for a short period of time. During anaerobic exercise, the body develops an oxygen debt that needs to be paid later (as evident from increased ventilation after a sprint). Anaerobic high intensity exercise cannot be maintained for more than about 2 minutes. Anaerobic exercise can be alactic and lactic. Alactic anaerobic exercise consumes stored ATP, which is quickly replenished by creatine phosphate. As the name implies, no lactate is produced during alactic anaerobic processes, but they cannot fuel muscles for more than 10 seconds under high intensity exercise. Lactic anaerobic metabolic pathways take over after creatine phosphate and stored ATP is consumed and have the potential to keep you going for another minute or two. Glucose is converted into ATP quickly with lactate as a byproduct. For each glucose molecule only 2 ATP molecules are produced. Because the reaction proceeds much faster than aerobic processing of glucose, more energy can be made available for the muscles for a short duration. Any exercise that takes longer than 2 minutes has a major aerobic component.

Types of muscle fiber

Humans have three types of muscle fiber. They are called slow twitch, fast twitch A and fast twitch B fibers. In some texts these muscle fiber types are referred to as type 1 (slow twitch), type 2A and type 2B. Slow twitch muscle fibers have slow contraction time and a high resistance to fatigue. They rely primarly on oxidative pathways for energy supply (krebs cycle and oxidative phosphorylation). If you are running at a slow pace or walking you are mainly using slow twitch muscle fiber.

Fast twitch B muscle fibers are the opposite of slow twitch muscle fibers. These muscle fibers have a high dependency on fuels and ATP production methods that do not require oxygen. They contain abundant creatine phosphate and enzymes that allow ATP production in the absence of oxygen. These fibers produce high amounts of force, but are sensitive to fatigue. These muscle fibers are recruited for sprinting, powerlifting and other short lived high force activites. Fast twitch A muscle fibers are an intermediate variety between slow twitch and fast twitch B muscle fibers.

Fast twitch muscle fibers are ‘fast’ because of two processes: 1) the rate of calcium release into the muscle cell and 2) the the rate of ATP breakdown. Calcium release is necessary in order to allow contraction of muscle fibers and ATP is necessary in order to ‘reset’ the muscle fiber so it can continue to contract. Hence, the rate of calcium release and the rate of ATP breakdown broadly govern the speed with which individual muscle fibers can contract. As stated in the previous section, anaerobic glycolysis is much faster than aerobic glycolysis, so ATP can be made available faster during the anaerobic conversion of glucose.

Is my muscle aerobic or anaerobic?

By now you may believe that muscles are either aerobic or anaerobic. Of course there is another complication to add to the story here. A muscle fiber will become anaerobic if the supply of oxygen is too low for aerobic ATP production. The supply of oxygen itself is controlled by many variables such as capillary density, hemoglobin concentration in the blood and oxygen saturation. Vasoconstriction, which causes resistance to blood flow, is particularly important in freediving because it restricts the flow of oxygenated blood to the limbs after the onset of the dive reflex. Because of vasoconstriction during a dive, your limbs will be partly cut off from the supply of oxygen and muscles in your legs and arms are more likely to function anaerobic.

Is my muscle fiber aerobic or anaerobic?

Our quadriceps are the most important muscles for propulsion underwater. Just like any other muscle, the quadriceps contains all types of muscle fiber, type 1, 2A and 2B. The proportion of these muscle fiber types will depend partly on genetics and partly on training. While diving, one fiber type may function aerobically and the other anaerobically. For individual muscle fibers this depends on whether they are activated (are anaerobic muscle fibers recruited or not?) and the supply of oxygen.

 Sources of oxygen during breath-hold

At the start of a breath hold, an average human has about 44% of the oxygen stored in their blood, 42% in the lungs, and 14% in the muscles. Oxygen is transported from the lungs, through hemoglobin in the blood, into the muscle where it is consumed. Where does the oxygen in the muscles come from? The muscles of diving animals (birds, mammals and humans) contain a specific oxygen carrying protein called myoglobin. Myoglobin is predominantly found in slow twitch muscle fiber.

Freedivers aiming to reach maximum performance need to increase the oxygen carrying capacity of all three reservoirs: the lungs, the blood and the muscles. Stretching and packing are the ways to carry more oxygen in the lungs. Hemoglobin is the oxygen carrying protein in the blood, and the concentration of hemoglobin can be increased (for example) by doing altitude training. The oxygen store in muscles is myoglobin, an oxygen carrying protein. The concentration of myoglobin can potentially be increased by specific exercise.

How to increase the oxygen stores of muscles

Oxygen stores of muscles can only be increased by periodically desaturating the myoglobin content of muscles. This will induce myoglobin production. Diving mammals with abundant myoglobin are commonly born with low concentrations of myoglobin. Repetitive diving causes the genesis of myoglobin over time. Can humans do the same?

For humans, myoglobin desaturation is difficult to achieve without rigorous training. In order to desaturate myoglobin, muscles need to be contracted while hypoxic (either at the end of a breath hold or during severe vasoconstriction). Eric Fattah and Sebastian Murrat have attempted to developed different training regimes in order to desaturate myoglobin and improve apnea ability. Sebastian Murrat’s training involves apnea walking and FRC dynamics, and Eric Fattah’s technique is called ‘Foundational Freediving’. The Foundational Freediving method is accessible in Eric’s e-book ‘holistic freediving’. Unfortunately, scientific evidence of an increase in myoglobin after using these training techniques has never been published, partly due to the cost of muscle biopsies.

Increasing the anaerobic energy stores of muscles

Fast twitch muscle fibers store ATP and creatine phosphate. These phosphates can readily be used for muscle contraction and do not produce CO2, nor do they consume oxygen. Hence, you can adapt the muscles for breath hold conditions by increasing the abundance of phosphates, rather than by increasing the myoglobin content of muscles. This can be achieved for example by repetitive sprints or high resistance training.

In conclusion

The muscle fiber types that can potentially be recruited for freediving are both slow twitch and fast twitch. Slow twitch muscle fiber requires a supply of oxygen, which can come from the lungs, blood, or muscle fiber itself. The myoglobin concentration of slow twitch muscle fiber can potentially be increased through specific exercise. Fast twitch muscle fiber does not require oxygen and has a high potential for the storage of phosphates. Specific exercise can increase the phosphate content of muscles.

In part 2 we will take a look at different diving animals, muscle composition, and breath hold ability, and in part 3 we will get to the actual training methods. You can find it here.

Selected links:

Selected journal articles:

  • Ferretti, G. (2001). Extreme human breath-hold diving. European Journal of Applied Physiology, 84(4), 254–271.
  • Kanatous, S. B., Davis, R. W., Watson, R., Polasek, L., Williams, T. M., & Mathieu-Costello, O. (2002). Aerobic capacities in the skeletal muscles of Weddell seals: key to longer dive durations? The Journal of Experimental Biology, 205, 3601–3608.

Holistic Freediving by Eric Fattah

About Eric

If you have not heard of Eric Fattah but are interested in the history of competitive freediving, now is the time. In 1998 Eric invented fluid goggles, not realizing that Roland Specker had invented similar goggles in France but never marketed them. In 2001 Eric set the first world record with a monofin in constant weight (- 82 m). He dove to -80.5 m in Vancouver without a wetsuit in waters that are approximately 5 °C (41 Fahrenheit) below the thermocline. Eric dove FRC (Functional Residual Volume: diving on an exhale) for four full years, in an attempt to counter decompression sickness and registers his deepest FRC dive at Vertical Blue to 71.9 m. His experience with decompression sickness led him to implement the first experimental decompression sickness algorithm for freediving in his Liquivision dive computers.

Eric is a world class diver who has invented many techniques, and coached well known freedivers such as Branko Petrovic and William Trubridge. He wrote ‘Holistic Freediving’ in 2012, a book designed for freedivers who want to do targeted exercise to increase their CO2 tolerance, low O2 tolerance, diving reflex, and have specialized (cross-)training programs. The book is phenomenal and contains so many novel approaches to freediving that it is well worth the price tag (US$ 95).

Holistic Freediving by Eric Fattah
Eric Fattah

Holistic Freediving

One part of Eric’s phasic training that you will learn about in Holistic Freediving is ‘foundational training’. This training allows you to become better able to withstand hypercapnia and hypoxia. Even better, it will do so without pushing you to the limit and requiring many days of recovery. Forget max attempts until you have laid the foundation. You will be better able to cope with the deep dives, without having lost many training days because you needed to recover. The cross-trainings described in this book are also novel and very effective. No more Wonka tables or simple static tables. Some of Eric’s dry static tables are done with the help of pure O2 and an oximeter. Other tables incorporate exhale statics and hyperventilation. They are intense, but extremely effective. Within three weeks of doing one cycle of static trainings weekly I managed to do a 3 min 45 breathhold on an exhale. My personal best before that? One minute forty seconds.

The price of the product [95 USD] is proportional to the lifetime of secrets it contains and the extraordinary tribulations I went through to discover them – Eric Fattah

Holistic Freediving by Eric Fattah sample

Mouthfill equalization by Eric Fattah

Ask Eric for a copy below: