Reading research: Comparison of lung volume between swimmers and land based athletes

There are many intriguing ideas kicking around in sports science.  Some of them appear to be myths and some of them are true.

What am I talking about?  Well, a good example might be the idea that Olympic weightlifters are better jumpers than triple jump or long jump athletes.  That pops up relatively frequently on forums.  If you are uncertain about whether this is a myth or true, read Zatsiorsky (affiliate links: UK, US).

Another idea that I am particularly fond of is the idea that swimmers have greater lung volumes than other athletes.  Let’s look at a study that does an experiment to find out whether it is true.

Swimmer (photo courtesy of the talented Jim Bahn)

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What’s the study?

The study is called, Comparison of lung volume in Greek swimmers, land based athletes, and sedentary controls using allometrics caling, by Doherty and Dimitriou, British Journal of Sports Medicine, 1997.

The purpose of the study was to compare lung volumes in a large cross-sectional sample of Greek swimmers, land-based athletes and sedentary controls by means of allometric scaling.

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Why is lung volume important for swimmers?

The study notes that many preceding works have shown that the pulmonary system (lungs and muscles associated with breathing) is not a limiting factor for land-based athletes.  If land-based athletes improve their cardiovascular fitness, it doesn’t come from being able to breath more air.  However, for swimmers, it appears more important.  Why is this?

Well, the fact that swimmers are partially immersed in water makes breathing more challenging.  Why is this?  Well, there is more pressure on the breathing muscles because of the water surrounding them.  In addition, being able to breathe more air with each breath makes it easier to swim more economically, as a breathing stroke is often less efficient than a non-breathing stroke.  Finally, having more air on board makes the body more buoyant.

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How do you measure lung volume?

If you recall, Total Lung Capacity (TLC) can be divided into Vital Capacity (VC) and Residual Volume (RV).  VC is the maximum volume of expired air after a maximum inspiration and RV is the remaining volume after this maximum expiration.  This experiment set out to measure the VC.

The researchers used a spirometer for measuring the maximum exhalation of the lungs by each of the subjects.

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What is allometric scaling?

Allometric scaling is basically a mathematical treatment of the data, which allows the researchers to compare the absolute data about lung volumes between subjects of different sizes.

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So what were the results?

The researchers report that the results were that both male and female swimmers had superior VC than both land-based athletes and sedentary controls.

The average male VC was: swimmers – 4.5L, land-based athletes – 3.9L and sedentary controls – 3.5L.  The average female VC was swimmers – 3.5L, land-based athletes – 3.3L and sedentary controls – 2.9L.

The researchers also isolated the data for national-standard vs. non-national standard swimmers and found that they were at the higher end for VC measurements.  Some of this increased capacity was found to be correlated with length of time spent training.

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So how do you increase lung volume?

The interesting question, of course, which is not answerable by this study, is whether swimmers are born with extra lung volume or whether they develop it through specific training.

Many researchers hold that it is more likely genetically determined but others remain convinced that the training effects of breathing under difficult conditions trains the respiratory muscles and permits a greater lung volume to be developed.

What do I think?  Well, I suspect both factors are involved.  However, I wonder whether introducing some of the training ideas used by freedivers would have a beneficial effect on lung volumes in swimmers?