Muscular and Cerebral Adaptation to Hypoxia

Hello, underwater lovers!

What you’re about to read is a doorway—a glimpse into the ocean of thoughts, lessons, and wild experiences that make up The Depth Collector series.

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This isn’t a polished pitch or a neatly packaged summary. It’s straight from the pages of The Depth Collector Book One, raw and real—just like freediving. Here’s a glimpse into pages 111 to 116.

So, grab your noseclip, take a deep breath, and let’s dive into Muscular and Cerebral adaptation to Hypoxia.

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depth Collector Book One

Page 111 to 116

Free immersion dive in Dean's Blue Hole, Bahamas, 2023.

Muscular Adaptation to Hypoxia

Muscular hypoxic adaptation involves training your muscles to perform optimally in an environment deprived of oxygen. During a dive, vasoconstriction and blood shift are draining the blood from your legs. Without blood, there's no oxygen delivery. Training them to function more efficiently under these conditions could be beneficial, but replicating the exact conditions of a dive on land is impossible. The pressure we experience at depth triggers a host of very specific physiological reflexes, starting with the mammalian diving reflex, and it's simply impossible to reproduce all of them during dry training.

Many theories are floating around about training different types of muscle fibers (fast and slow twitch) and which ones are better for freediving. I've explored many of them personally, but none have been definitively proven effective for the specific demands of deep diving. 

Honestly, training a specific type of muscle fiber is a long process, and when even marine mammals disagree on that point, it seems a waste of time (in my humble opinion, of course).

So, I'm sorry to say, but engaging in crazy apnea walks with jump squats or other insane exercises until you pee yourself won't train your muscles to endure low oxygen levels. Nope! Your body has the remarkable capacity to find a way to deliver oxygen to your muscles—so good luck simulating  on land the same muscle oxygen desaturation you encounter during a dive. The only viable method I see is attempting to reproduce vasoconstriction.

In our discussion on myoglobin, we explored a method by Eric Fattah involving an ice bath. He immerses his legs in icy water before engaging in DYNB. The cold from the ice bath triggers vasoconstriction. This idea is intriguing and opens the door to many imaginative training exercises. For example, why not adapt this ice bath strategy for monofin or no-fin disciplines? Or consider an ice bath followed by a series of apnea squats.

I did not find any proof these methods work, but that's precisely why I love freediving so much. It's about trying out unconventional experiments, which makes the sport so fascinating to me.  Freediving is such a niche sport that financed scientific studies are rare, and even if we could, how would we test a diver at 90m with limited time?

Detailed anatomy of skeletal muscle structure,

Before starting any new training approach, it's crucial to ask yourself: Is this training method necessary and beneficial for you at your current level? Could your time be more effectively spent improving your CO2 tolerance or refining your technique? The first step to efficient hypoxic resistance training is mastering the freediving movements to avoid wasting oxygen. I raise this question to highlight an important consideration. Remember that engaging in these extreme exercises carries a notable risk—the potential of developing a mental block. This concern brings us back to a fundamental principle: Consistency is always more valuable than extreme intensity. 

I trained my muscles through specific periodization and endurance training. Still, this regimen does not include breath-holding workouts. But who knows, I will maybe change my mind soon.

Cerebral Adaptation to Hypoxia

The cerebral adaptation to hypoxia involves conditioning your brain to tolerate lower oxygen levels and delay the survival reflex that leads to loss of consciousness. This process can be viewed as training the brain to recognize that what it previously perceived as dangerous is no longer a threat. 

However, the adaptation process doesn't stop there; the brain must also adjust to the decrease in oxygen's partial pressure within the lungs during ascent. As you may know, the most significant pressure drop occurs between 10m and the surface, where the partial pressure of oxygen is effectively divided by two. This rapid drop represents a different shock to the brain. 

Brain illustration highlighting the amygdala, key to emotion and stress response.

Training to adapt to low oxygen levels becomes crucial as we dive deeper. There are effective ways to practice and train for this on land. The best method is to hold our breath on functional residual capacity (FRC) or residual volume (RV), simply because it's easier to desaturate our oxygen levels with 'half' empty or empty lungs. Your oxygen levels will gradually decrease during your breath-hold—graduality is the key concept here. However, this only covers part of the requirements for deep diving. 

We must also get used to the sharp drop in oxygen levels during the last part of the dive. This can be trained by performing hangs at the depth of residual volume. These two training methods—on land for a slow oxygen decrease and in the ocean for sudden drops—are two sides of the same coin, and both should be considered essential in your preparation.

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To be continued…

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