In traditional medicine, a sufficient oxygen supply for the human body is vital in various physiological processes, medical techniques, and recovery.
However, in modern sports medicine, specialized equipment and techniques to limit the amount of oxygen a person consumes have been around for years to biohack or enhance physical and cognitive performance.
How does “holding breath” trick our bodies and significantly improve our health? A recent study published by the journal of Frontiers in Neuroscience has shown that exercising when oxygen is inadequate – a technique officially known as intermittent hypoxic training – can increase human brain capacity.
Intermittent Hypoxic Training: How Holding Breath Promotes Neuroprotection
What Is Intermittent Hypoxic Training?
Intermittent hypoxic training (also known as interval-hypoxic training or IHT) is a technique that reduces the amount of oxygen a person consumes (from 21% in atmospheric air to below 16%) when exercising in an interspersed manner.
The term ‘hypoxia’ from ‘hypoxic training’ refers to inadequate oxygen, whereas the average oxygen level (comparable to atmospheric oxygen levels) is known as ‘normoxia.’
Like fasting – when a person completely abstains from food for a specific time – hypoxic training takes away a fundamental need of a living organism – oxygen. That’s why this training technique is only conducted intermittently not to hurt the body and avoid the detrimental effects in case of excessive implementation.
Depending on the intensity level, the duration and the amount of oxygen in intermittent hypoxic training can vary greatly. Two fundamental techniques are:
- Brief (1-10 min) hypoxia interspersed with 1-20 min normoxia
- Prolonged daily hypoxia (1-12 h) over durations of 2-90 days
However, while each variation of intermittent hypoxic training offers different outcomes, it has been shown that short and frequent hypoxic episodes may result in more benefits.
How Does Intermittent Hypoxic Training Work?
Increase Adaptability and Endurance
Research suggests that intermittent hypoxia, a potent stressor, can cause various changes to the physiological reactions of the human body. These changes can benefit the body’s capacity to become more adaptable and resilient if reoxygenation is allowed.
One of the underlying mechanisms of intermittent hypoxic training is that it improves the chance of survival in severe hypoxic conditions. In other words, the body can survive longer even if less oxygen is available. Scientists explained this mechanism by suggesting that when the body adapts to one stressor, it becomes more resistant to others.
Another mechanism is that it helps increase the respiratory system’s efficiency and energy metabolism. When the body produces energy for exercise, it requires much more oxygen than at rest. During hypoxia, the body increases the efficiency of how it takes in and uses oxygen to maintain the same energy levels even when less oxygen is available.
Increase Blood Flow to the Brain
Intermittent hypoxic training can increase blood flow to the brain by stimulating the production of vascular endothelial growth factor (VEGF), a protein that promotes the growth of blood vessels. This increased blood flow can improve the delivery of nutrients and oxygen to the brain, leading to enhanced cognitive function and memory.
Also, hypoxic training can protect cerebrovascular function by increasing the production of nitric oxide (NO), a compound that reduces inflammation. Indeed, it has been demonstrated that low-intensity exercise combined with hypoxic training helps modify inflammatory and immunological markers, including nitric oxide synthase activity.
Finally, hypoxic training can strengthen brain connectivity by promoting the growth of new neurons and synapses. As a result, increased brain connectivity can improve cognitive function, including memory, attention, and learning, while reducing the risk of cerebrovascular diseases like stroke and dementia.
Neuroprotective Benefits of Intermittent Hypoxic Training
Improve Cognitive Functions
As mentioned before, once the body has fully adapted to intermittent hypoxia, the increased blood flow can enhance the levels of nutrients and oxygen reaching the brain, leading to improved cognitive functions, such as memory, attention, and learning.
Specifically, adequate levels of oxygen and nutrients are essential for maintaining brain health and memory function. Such improved delivery can also enhance memory consolidation and retrieval. Meanwhile, hypoxic training enhances attention and concentration, allowing individuals to focus better on tasks.
Moreover, oxygen and nutrients are vital for brain plasticity, the ability of the brain to adapt to new information. Therefore, hypoxic training can enhance how the brain strengthens neural connections, facilitating learning. Finally, the technique can improve executive function, leading to better planning, decision-making, and problem-solving skills.
Prevent Dementia and Neurodegeneration
Research has shown that 40% of people with cognitive decline suffer from increased chronic inflammation. Also, individuals with high levels of chronic inflammation in midlife are more susceptible to memory loss and mental issues later in life.
This prevalence suggests that many dementia and Alzheimer’s cases can be brought on by persistent neuroinflammation. By adapting to hypoxia, the body reduces inflammation in the brain and the central nervous system. This reduction in neuroinflammation may subsequently protect against dementia and neurodegenerative diseases.
Also, hypoxic training can protect the brain from the accumulation of amyloid β, a protein associated with Alzheimer’s disease. Hypoxic training can do this because it protects the brain from oxidative stress, a phenomenon interconnected with amyloid β. While amyloid β causes oxidative stress, the latter increases the deposition of the former.
By helping with the clearance of amyloid β from the brain, intermittent hypoxia prevents its accumulation and reduces the risk of Alzheimer’s disease.
Risks of Improper Intermittent Hypoxic Training
Intermittent hypoxic training is generally safe when performed under appropriate supervision and with the proper equipment. However, as with any exercise, some potential side effects are associated with hypoxic training, including:
- Shortness of breath
- Dizziness and lightheadedness
- Headache and fatigue
- Nausea and vomiting
- Increased risk of injury
- Exacerbation of certain medical conditions
It’s essential to consult a healthcare professional before starting any exercise program, including hypoxic training, especially if you have any underlying medical conditions.
How to Start Intermittent Hypoxic Training
Conduct a Hypoxic Test
Technically, a person can achieve hypoxia by breathing gas-hypoxic mixtures (GHM) through special equipment (called rebreathers) based on the principle of return breathing.
A hypoxic test involves the person breathing GHM containing down to 5% oxygen interspersed with atmospheric air for up to 100 minutes to determine the safe and well-tolerated hypoxic threshold.
This test is critical to hypoxic training’s efficacy and safety as it characterizes individual tolerance to hypoxia and personalizes the best regimen for each condition.
Consider the Efficacy and Safety
The balance between its efficacy and safety is crucial in choosing the proper intermittent hypoxic training regimen. Research suggests moderate hypoxic training can be an efficient and safe technique with much therapeutic potential in clinical settings.
In contrast to severe hypoxia (2-8% oxygen) with more episodes per day (48-2,400 per day), which may cause adverse side effects, training under moderate hypoxia (9-16% oxygen) and low frequency (3-15 episodes per day) result in a more positive impact.
Implement the Technique
To start intermittent hypoxic training, you can use a hypoxic mask restricting the amount of oxygen you breathe. The training can be done while exercising, such as during a cardio or weightlifting workout.
The duration and intensity of the hypoxic training can be gradually increased over time to allow your body to adapt to the reduced oxygen levels. Below is the optimal and best-studied regimen for intermittent hypoxic training:
- Oxygen Levels: 9-16%
- Episodes: 3-15 per day
- Duration: 1-10 min hypoxia interspersed with 1-20 min normoxia
Rybnikova E. et al. (2022). Intermittent Hypoxia as an Effective Tool for Increasing the Adaptive Potential, Endurance and Working Capacity of the Brain. Frontiers in Neuroscience.
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