Hypoxic Work in the Pool

Question:

In doing hypoxic work in the pool (i.e., 25 meters under water in only one breath, up at the wall to take one breath to begin 25 meters freestyle return, aggressively taking as many breaths as needed) would a 6' 5'' 225 pound person require more as a recovery interval than a 5'6'' 125 pound person? I was setting the recovery time as one minute between sets for each. I only pose this question because it was asked of me. I thought that because each individual has a heart and lungs in proportion to his or her own body size, their individual sizes should not matter.

Answer:

Judging from the training parameters you described, I am going to assume you mean the traditional hypoxic training involving forced breath holding (a technique credited to a coach from Indiana University, Dr. James Councilman) which when doing research should not be confused with another form of hypoxic training (Intermittent Hypoxic Training), which involves training in a hypoxic air (approximately 10 percent oxygen) environment. With this in mind, some coaches are now preferring the term "anoxic" training or more simply "low-frequency breathing."

Back to your question. It is important to remember that while size and weight may provide some basic frameworks to help set training parameters, they do not account for numerous key anatomical and physiological factors. The easiest way to approach tissue oxygenation is in stages, these being uptake, transportation and utilization.

Firstly, to address uptake. Lung size, while having a relative significance, is not the key to uptake. Two athletes with the same sized lungs may have different breathing volumes (e.g., Tidal Volume¹ and Inspiratory Reserve Volume²) and capacities (Inspriratory Capacity³ and Total Lung Capacity⁴). While several factors can have an influence on lung volumes and reserves, two more notable factors are age (lung capacity decreases with age) and disease (obstructive lung diseases like Emphysema). Part of uptake is also the transfer of the uptaken oxygen across into the alveoli of the lungs. This transfer is subject to Fick’s Laws of Diffusion (These are 1. The greater the surface area across which diffusion can take place the greater the rate of diffusion and 2. The shorter the distance through which diffusion must take place, the greater the rate of diffusion) and are therefore impacted on by factors that impact on these laws such as changed surface area of lung tissue (i.e., Emphysema) and increased distance through which diffusion takes place (i.e., tar from cigarettes).

Next comes the transportation. Here individual differences in the heart output (e.g., stroke volume and heart rate, which both change with fitness) and blood haemoglobin come into effect.

Finally comes utilization, that is the ability to actually use the oxygen for oxidization. Key enzymes (e.g., those found in the TCA/Kreb’s cycle) and co-enzymes (e.g., nicotinamide adenine dinucleotide and flavin adenine dinucleotide) impact on how and how much of the oxygen is used.

A further consideration to this equation is the technique of both swimmers. The more technical the swimmer, the more efficient the stroke, the lower the muscular workload and therefore the lower the oxidative requirement over the same distance. Thus even two swimmers with the same anatomical and physiological characteristics will still require different training and recovery parameters.

What all this means is that numerous anatomical, physiological and technical factors will influence the training and recovery intervals for each individual. In a nutshell, you are right in that generally individual sizes are not the key factors in determining effective training intervals. 

So, with these differences discussed, we must now consider why your client is/will be performing hypoxic training.

While some coaches hoped that this form of training simulated high altitude training, research has not found any direct physiological correlation (e.g., increased haemoglobin count, increased erythropoietin, etc). This may be due to the fact that at altitude, you have less actual oxygen transferring into the alveoli with each breath due to a shift in pressure gradients (and may lead to carbon dioxide "washing out" or respiratory alkalosis) whereas with hypoxic training, the amount of oxygen transferring across the membranes with each breath is normal - you simply have fewer breaths (and may lead to respiratory acidosis). Then there is the question of duration. For the benefits of high altitude, athletes typically are immersed into the environment for a sustained period (typically two to three weeks).

However, on the plus side, the restriction of oxygen supply in blood and tissues during exercise may improve the body’s buffering⁵ capacity as glycolysis becomes anaerobic and lactic acid is produced (although there are numerous safer and more effective ways of training buffering capacity).

The most agreed upon value of hypoxic styled training is technical rather than physiological as there is an expected gain to swimming efficiency by way of technique. By rolling to breathe, the streamline position is altered and drag is usually increased; therefore, fewer breaths means a more efficient position can be maintained. This can be vital in a sprint finish or when preparing for a turn. So by training to take fewer breaths at key points in a race, speed would increase as a streamline position is maintained.

Let's put this all together. For hypoxic training, consider the following points. First, is it safe for my client to perform hypoxic training? Second, why is the hypoxic training going to be performed, and what is needed (improved turns, faster finishes, bursts of speed)? Finally, consider your client's anatomical/physiological profile (without lab equipment, this would mean looking at how your client responds to the set training parameters, starting conservatively with the frequency and recovery).

Good luck!

Glossary of Terms:

1. Tidal Volume (TV) - Amount of air inhaled or exhaled with each breath under resting conditions (ave = 500ml).
2. Inspiratory Reserve Volume (IRV) -  Amount of air that can be forcefully inhaled after a normal TV inhalation (ave= 3000ml).
3. Inspiratory Capacity (IC) - Maximal Volume of air that can be inspired after normal quiet expiration. IC = TV + IRV (ave = 3500ml).
4. Total Lung Capacity (TLC) - Maximal amount of air contained in lungs after maximal inspiratory effort (ave = 5700ml).
5. The role of a buffer is to convert a stronger acid into a weaker one. As lactic acid increases, sodium bicarbonate is released to act as a buffer, and carbonic acid is formed. Carbonic acid is then broken down into water and carbon dioxide. This carbon dioxide is then exhaled with the carbon dioxide produced via the carbon oxidation of fuel.