Energy Systems and How to Breathe to Swim Faster

breathing technique

Physiology 102: Why your swimming breathing technique matters

Swimming fast involves proper breathing technique and building robust energy systems. In a previous physiology article, we discussed the three different systems that humans have available to produce energy for bodily functions, including muscle contraction in swimming. They are aerobic (requiring oxygen), anaerobic (not requiring oxygen) and stored energy. The aerobic and anaerobic energy systems produce energy in the form of adenosine triphosphate (ATP) while we store energy in our muscles in the form of ATP and Creatine Phosphate (CP).
To reduce frontal drag while swimming faster and to maximize the efficient use of our energy systems, it is vital that we learn proper swimming breathing techniques, particularly the breathing techniques of a faster freestyle and butterfly. This week, in Lanes 2, 3, and 4 in our subscription service,  you will find the first of a series of webisodes on swimming breathing technique. This webisode will help teach you how to breathe when swimming properly in faster freestyle.
While it may sound as if the aerobic system is more efficient than the anaerobic system, producing 18 times more ATP for each molecule of glucose (36 vs 2), it really isn’t. The anaerobic system works 200 times faster than the aerobic system. In other words, in the same amount of time it took the aerobic system to produce 36 molecules of ATP, the anaerobic system churned out 400 molecules of ATP, eleven times more energy. However, it also used 200 times the amount of glucose to produce that energy. In some endurance racing, like a 25k open water swimming race, we simply run out of available glucose, which is called bonking.
The problem with the anaerobic system isn’t efficiency, it’s the byproduct which lowers the pH of the body. All human organs and systems, including muscular contraction in swimmers, perform well within a very narrow range of pH and temperature. If the body’s pH or temperature goes too low or too high, the swimmer’s muscular contractions (and other bodily functions) begin to fail. Those of us that have competed in any sport, including swimming, know this feeling all too well.

The Anaerobic Threshold

In my simple mind, I picture a little man or woman sitting on a chair inside our body somewhere. Their job is to keep us alive. To do so they watch two meters that are in front of them; one for pH and the other for temperature. When either meter indicator goes too high or low, but before it gets to a red line on the meter, they stand up and pull a big red lever down on the wall, shutting down all systems. By shutting down the systems, or at least slowing them down, they may keep us alive, but they wreak havoc on our ability to swim fast. While racing in the sport of swimming, we want to keep them in that chair.
The best way to keep the little man or woman sitting down when we are racing is by developing a more robust aerobic system. That is what we do when we train swimmers aerobically. We improve their swimming breathing technique and other systems to deliver oxygen to the muscles (heart, lungs, blood, transport systems, respiratory rate, etc) and to produce ATP at the cellular level (mitochondria) more efficiently.
By pushing our swimmers harder in practice, into what is called the anaerobic threshold (around 20 beats/min less than maximal heart rate, or what Jon Urbanchek refers to as the blue zone), where they begin to produce lactate from the increased energy demands, we prepare them for racing in another way. Their bodies become better at buffering or neutralizing the pH. If we can get increased ATP production from the more efficient anaerobic system, yet buffer the pH, we will be able to sustain our speed better, so long as we don’t run out of glucose. This type of adaptation is called lactate training.
By training swimmers for short 5-10 second maximum bursts of speed, we may also be able to increase the quantity of stored energy available for sprinting. This is called alactic training.
Therefore, we have the ability to improve our aerobic energy systems, increase our ability to buffer the acid from the anaerobic system and increased stored energy. Yet all three require substantially different types of training.

Swim Training

The way in which we train our swimmers is complicated by having these three different sources of energy that produce or deliver ATP or CP at different rates and at different levels of efficiency. For example, in 50-meter sprints, which involve 20-30 seconds of all out exertion, around 95% of the energy will come from stored and the anaerobic system. Consequently, there is no good rationale for breathing much in 50-meter freestyle or fly sprints for mature swimmers, which only slow the athlete down.
In the 200 meters or longer events, requiring about 2 minutes or more of exertion, the majority of energy will come from the aerobic system. The longer the event, the greater contribution of energy comes from the aerobic system, so long as we breathe sufficiently. In these events, oxygen needs to be delivered at the most efficient rate possible. In land sports over this same duration, the respiratory rate is in the range of 50-60 breaths per minute. The respiratory rate should be similar while swimming these longer events.
The 100 is an interesting race, as it takes place over approximately one minute of exertion. About half (mostly first half) of the energy needed for the race will come from the anaerobic and stored systems and the other half of the energy (mostly second half), will come from the aerobic system. However, since the aerobic system gets activated from the start of the race, we need to breath fairly often on the first half of the race, even though we may not feel as if we need the oxygen.  If we don’t breathe often enough early in the race, we build up a huge oxygen debt, the pH goes down and the little man or woman will get off the chair toward the end of the race and shut down the systems.
At the elite level of swimming, the respiratory rates of females are typically less than of males in the 100-meter freestyle and butterfly events. While there are theories about why this is, and I have some, I am not certain we know all of the reasons for this. Perhaps the physiologists that are reading this article can offer their opinion.
In summary, how we train and how often we breathe determine, to a large extent, how much energy we can produce for our muscles and from which systems we will get that energy. First, check out our latest webisode in Lane 2, 3 or 4 on our website,, to find out the best swimming breathing technique for a faster freestyle.
Yours in swimming,
Gary Sr.

Special thanks to David Costill, PhD, for his contributions to this article.

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