The Mechanics of Breathing during Swimming
Link to research paper
What are the differences between land-based sports (cycling, running, etc.) and swimming?
Swimming is quite an interesting activity as it requires one to synchronize their breathing with the cyclical nature of their swim stroke. During running, cycling, and other land-based activities, one can inhale and exhale freely without having to worry about sucking in water. The constraints of the swimming environment (regardless of pool or open water), one has to time their breath cycle right and become efficient at working with that breathing pattern. These constraints imposed upon the swimmer along with the unique body position (horizontal, face down) and pressures on the chest wall from the surrounding water are hypothesized to affect the breathing mechanics of well-trained swimmers. These unique breathing differences between swimming and land-based sports are important to understand and take into account, for both athletes and coaches alike. The study discussed here today helps shed some light on these unique effects of swimming on the mechanics of breathing.
What did the researchers study?
Researchers enlisted 8 collegiate swimmers and had them perform the following tests across multiple days:
1. Graded, maximal swim test to determine VO2 Peak and breathing mechanics of swimming
2. Graded, maximal cycling test to determine VO2 Peak and breathing mechanics of a land-based sport
Researchers then compared the test results across all participants for differences in breathing patterns and physiological responses.
What are the major findings?
The three most important findings stemming from this study are as follows:
1. Peak heart rate was significantly lower during swimming (164±19 bpm) when compared to cycling (183±8 bpm).
2. The work of breathing was higher in swimming compared to cycling.
3. There was interbreath apnea present while swimming that does not exist in cycling.
What do these findings mean to YOU as an endurance athlete or coach?
Let’s put these findings into context.
First, let’s think about the lower heart rate elicited by a maximal swim test when compared to a maximal cycling test. Why is this so? Well, turns out this is pretty typical and what we would expect to see. An athlete’s true maximal heart rate is going to be best measured by having them perform a maximal running test as this type of activity involves the greatest amount of muscle mass, particularly when compared to cycling and swimming. Cycling tests will typically elicit a slight lower peak heart rate when compared to a maximal run test, but a higher peak heart rate when compared to a maximal swim test. What’s the take-home here? Know that peak/max heart rate is activity-dependent. True maximal heart rate is that elicited by way of a run test, whereas swimming, even at a maximal effort, will elicit a much lower peak heart rate, possibly in the realm of ~15 bpm lower than peak run heart rate and ~10 bpm lower than peak cycling heart rate. This is a VERY important consideration for the multisport athlete that is determining training zones as heart rate training zones MUST be established for each individual sport.
Second, it was found that the work of breathing was higher in swimming when compared to cycling. This makes sense when you consider the pressures being exerted on the chest from the surrounding water. The horizontal body position and hydrostatic pressure from the water increase airflow resistance into and out of the lungs as well as increase the elastic forces placed on the lungs. Both of these factors make it more difficult to get air into and out of the lungs, thereby placing a greater demand on the lungs and the muscles used during breathing (i.e., greater work of breathing). This is an interesting concept as there is some research to demonstrate that well-trained swimmers have greater lung volumes and respiratory muscle endurance due to the demands placed on these tissues during swimming. These adaptations would help improve swimmers’ performances in the water.
Finally, this study was the first of its kind to demonstrate the interbreath apnea that is present while swimming. What does this mean? It means that swimmers will inhale while their face is out of the water, hold their breath briefly (in this study breath holding ranged from 0.13-2.07 seconds), and then exhale before repeating this cycle. This is quite different from land-based sports where one is either inhaling or exhaling. Athletes will usually not hold their breath at any point in time during land-based activities as there is no need to hold ones breath. However, in swimming, the constraints of the environment force the athlete to inhale forcefully during the brief moment their face is out of the water, hold it in briefly, and then finally exhale once their face returns to the water. The key take-home here would be to understand that a short period of breath holding during swimming is normal, and swimmers should NOT be encouraged to immediately exhale as soon as they complete their inhale. Swimmers should be encouraged to exhale slowly while their face is submerged in the water if there is a large period of time within which the swimmer is holding their breath under water, but perhaps more importantly the swimmer should work to time the inhaling and exhaling of air with their stroke cycle, which is entirely unique to each individual.
I found this research particularly interesting, and I hope you did too. There are some great takeaways from this study, and I hope you now have a better understanding of some of the key differences in breathing mechanics of swimming when compared to land-based sports!
Happy training and racing!
-Ryan Eckert, MS, CSCS