Breath control training: how hypoventilation can boost endurance performance

Since it was announced that the 1968 Olympics would take place at elevation in Mexico City, the sporting community has been fascinated with the potential benefits of altitude training. As time passed, coaches, athletes and scientists began to explore different ways to take advantage of manipulations in oxygen availability.

Dr James Counsilman, a renowned swimming coach, developed a training method that consisted of restricting the frequency of breathing to recreate a hypoxic effect for his swimmers who were unable to train at altitude. His goal was to facilitate ‘training at altitude’ while still remaining at sea level. While this type of training has become a common practice in swimming, and may very well have benefits due to respiratory adaptations^{J Strength Cond Res. 2017 May;31(5):1273-1281 Scand J Med Sci Sports. 2015 Feb;25(1):16-24}, it doesn’t create the hypoxic environment that you see at altitude^{Med Sci Sports Exerc. 1980 Spring;12(1):20-3 Scand J Sports Sci. 1980;2(1):1-6}.

However, the lure of altitude training is still very appealing, and continued attempts have been made to create hypoxic environments at sea-level. Traditional respiration restriction - known as ‘hypoventilation training’ - has recently been updated with a novel twist, and the results are promising. In this article, I’ll explain what that twist is, the effects it has on your physiology and your performance, and how to incorporate this novel strategy seamlessly into your current training regimen.

A simple change

Counsilman was not the only famous coach to advocate hypoventilation training. Other coaches and athletes such as Emil Zatopek have experimented with this idea while attempting to improve performance. Traditional execution of hypoventilation training consists of taking a breath, holding it for a prescribed time or number of strokes, steps, or pedals, exhaling, and then repeating the process.

It was Dr Xavier Woorons, a French physiologist, who challenged conventional wisdom. Woorons hypothesised that hypoventilation could be improved by requiring an exhalation immediately after inhalation and then holding the breath. With a traditional approach, most of the training was performed at relatively high lung (pulmonary) volumes. In contrast, Woorons’ new paradigm consisted of training with low pulmonary volumes.

Does it work?

Theories are one thing, but Dr Woorons needed to see how human physiology responded when the training was actually performed. In a landmark study, ten triathletes cycled for five minutes at 70% of their individually determined VO2max (moderately hard) on two separate occasions^{Respir Physiol Neurobiol. 2007 Aug 15;158(1):75-82}. During one test, they did so with normal breathing. During a second testing session, the cyclists included a prolonged exhalation that commenced at the conclusion of each inhalation. This addition served to reduce ventilation frequency and reduce average pulmonary volumes. The results? Cycling with a prolonged exhalation led to severe hypoxemia, or blood oxygen levels (see figure 1).

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FIGURE 1: BLOOD OXYGENATION – NORMAL VS. HYPOXIC BREATHING

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These results have been confirmed in subsequent studies^{Respir Physiol Neurobiol. 2014 Jan 1;190:33-9 Int J Sports Med. 2011 Jun;32(6):438-45 Eur J Appl Physiol. 2010 Sep;110(2):367-77}. Importantly, these studies have also compared the degree of hypoxemia experienced during exercise with prolonged expiration hypoventilation with exercise performed in an actual hypoxic environment. The results were indistinguishable – ie this mode of hypoxic breathing really does result in low blood oxygenation as occurs at altitude. Thus, it appears that Dr. Woorons was right in his hypothesis. Of course, being able to create hypoxic conditions is only part of the answer for aspiring athletes. We need to know if training in this state actually improves performance. Fortunately, Dr. Woorons and his lab examined that very question.

Hypoxic breathing and performance

A recent study looked at triathletes, and examined whether hypoventilation swim training conducted at supramaximal intensity can impact swimming performance^{Med Sci Sports Exerc. 2016 Jun;48(6):1119-28}. Sixteen competitive triathletes participated in the study. Importantly, all subjects were training at least eight hours per week prior to beginning the study, including 1-2 intense swimming sessions per week.

The triathletes performed 12-20 repetitions of 25-metre swims twice per week, in addition to their regular training. The number of repetitions was increased over the course of the training programme and each repetition was performed on a 30 or 35-second send off, thus allowing each swimmer to get 10-15-seconds rest. This allowed each swimmer to complete the session at velocities that were greater than the 200m race velocity, hence the term ‘supramaximal’ training stimulus.

The control group performed these 25m swim repetitions using normal breathing, while the experimental group performed hypoventilation training. Each session was comprised of an hour of swimming, including 30 minutes of traditional aerobic training, all of which was performed with regular breathing. Before and after the training intervention, both groups performed 100m, 200m, and 400m time trials.

What happened? For the control group, not much. There was no change in performance in any of the time trials. For the hypoventilation group however, performance was improved significantly over 100m (4.4%), 200m (3.6%) and 400m (3.5%) (see figures 2a and 2b). Not bad for ten training sessions performed over five weeks, with only 10-15 minutes of intense work per session! Another interesting finding was that the lactate response was significantly improved in the hypoventilation group, but not in the control group. This indicates that hypoventilation training conducted at supramaximal intensity can also improve aspects of anaerobic performance. While the benefits are obvious for swimmers (faster times!), this indicates that hypoventilation training could help cyclists, runners, or triathletes with their kick at the end of their race, as well as during any other high intensity effort required during a race.

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FIGS 2A & 2B: SWIMMING PERFORMANCES AT 200M & 400M (GREY BARS = BEFORE TRAINING; BLACK BARS = AFTER TRAINING)

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Getting practical

Hopefully, these findings have convinced you that hypoventilation training can have an impact on your performance, and is well worth considering when you’re training for next season’s competitions. If you feel you need a boost in performance, or just a good challenge, hypoventilation training could be the right fit for you. The technique for executing hypoventilation training has been described in the cited studies, as well as in a book written about hypoventilation^{Hypoventilation Training. Woorons, X. ARPEH, 2014}. While the technique is relatively simple, executing it accurately is critical for the full effects to be realised. The information in panel 1 provides further details. The most important idea is to consider the balance between restricting oxygen and maintaining exercise intensity. At one extreme, if you don’t breathe you won’t be able to keep exercising! At the other extreme, if you don’t restrict your breathing there won’t be any additional benefits. If you’re questioning whether you’re doing it right, just make sure you’re challenging yourself while maintaining exercise intensity.

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Panel 1: HYPOVENTILATION TECHNIQUE

*Inhalation

Inhalations should be natural - as one would normally breathe. Due to the nature of the training, this inhalation will be deeper than normal (ie at rest), but not intentionally so.

*Exhalation

• An initial exhalation should be performed in a natural fashion immediately after inhalation. In swimming, the exhalation will have to be more forceful due to the resistance of the water. It is important to note that while you are trying to exhale, there should still be some air left. You’re not trying to get all the air out.
• The hold - Following exhalation, the breath must be held for several seconds. The duration will be a little bit shorter for more intense exercise and a little bit longer for less intense exercise. It should not be a maximum hold as this will not allow for exercise to be maintained. The hold should be 3-5 seconds long. Start with a shorter hold and you can increase the duration to increase the challenge later.
• The second exhalation - Once you need to breathe, perform a sharp exhalation. This should be quick and powerful - you’ll feel like you’ve really evacuated your lungs. The purpose of this manoeuver is get rid of the carbon dioxide that has built up in your lungs. This allows exercise intensity to be maintained

Note: Following the basics is more important than being concerned about exhaling the exact amount of air or holding for the perfect amount of time. Stay true to the principles and you’ll be fine! During rest intervals between repetitions, breathing should be conducted normally. You’ll need to!

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Sample training sessions

As hypoventilation training is an intensification technique, it makes sense to incorporate this type of training later on during a training period, when you are already planning on including high-intensity training. For those accustomed to high-intensity interval training, you can simply replace a portion of your previously planned interval work with hypoventilation training. However, if you haven’t been doing high-intensity interval training, it’s best to start with a more basic approach as the added challenge of hypoventilation training will likely be counterproductive.

In table 1, some specific training parameters for swimming are outlined (in line with the study - as well as those recommended by Dr. Woorons)^{Hypoventilation Training. Woorons, X. ARPEH, 2014}. Of course, these parameters are just a guideline; you are free to adapt and/ or modify the sessions as needed or desired. One tip that we have found works well for our swimmers, and which is an easy way to control your breathing, is to exhale over two strokes and then hold your breath for three to four strokes.

TABLE 1 SUPRAMAXIMAL INTENSITY HYPOVENTILATION SWIMMING SESSIONS 2022 10 04

Option #1	Option #2
Repetition numbers: 12-20	Repetition numbers: 6-16
Repetition distance: 25m	Repetition distance: 50m
Rest: 10-20 seconds passive rest with normal breathing	Rest: 10-20 seconds passive rest with normal breathing
Intensity*: slightly above 200m race velocity	Intensity*: 400m race velocity
Number of sets: 1-3	Number of sets: 1-3
Rest between sets: 1-3 minutes passive rest with normal breathing	Rest between sets: 1-3 minutes passive rest with normal breathing

*If you’re not sure what your race velocity is, you have two options. The first is to conduct a time trial for the specific distance and use that number. If you choose this option, make sure you treat the time trial like a proper race to get accurate information. The second option is to perform the repetitions as fast as possible, making sure you can finish as fast as you start. It is best to be conservative to begin with, and increase the speed as you experience success.

*Progression - Start at the low end of the repetition scale, total volume, and use more recovery. As you feel comfortable, and as your fitness improves, gradually increase the challenge, altering one variable at a time. You can also increase the repetition distance to 100m, while slightly reducing the speed and repetition numbers. Upon subsequent training cycles, you can start out at a more advanced level.

Land-based training

Hypoventilation can also be applied to your training out of the water. Due to the greater effects of gravity on land, the intensity with which hypoventilation training can be performed needs to be reduced slightly. In his book^{Hypoventilation Training. Woorons, X. ARPEH, 2014}, Dr Woorons provides simple guidelines which are modified in table 2. When constructing training sessions for yourself, start at the low end of the ranges and increase one variable at a time as you adapt to the training.

These sessions need to reflect the typical demands of the sport, with each work bout alternating periods of hypoventilation and periods of normal breathing - all while exercising at the same speed. For instance, runners could perform three bouts of four minutes, resting two minutes between each bout. During each bout, a runner would train at a speed equal 70% of his/her best mile run, alternating 30 seconds of hypoventilation with 30 seconds of normal breathing. After four minutes, he/she would rest passively for two minutes and then repeat two more times.

It is also possible to use a more interval-based style of training similar to what is described in the sessions for swimmers above.

TABLE 2 TERRESTRIAL HYPOVENTILATION TRAINING 2022 10 04

Total duration of exercise	8-25 minutes
Duration of each work set	4-8 minutes
Duration of hypoventilation period	15-120 seconds
Duration of normal breathing period	10-30 seconds
Recovery between work sets	1-3 minutes
Intensity*	75-85% of maximum heart rate OR 65-75% of the velocity for your best mile run or 2-mile cycling time trial

*As with swimming, it is most important to be able to maintain exercise intensity throughout the training session. If you have access to velocity or power measurements, that can be useful. Otherwise, just try to be consistent with how far you go for a given time period. Any method of controlling intensity can be effective, as long as you’re consistent.

Special circumstances

As demonstrated in each study, hypoventilation training creates a greater activation of the glycolytic energy pathway, as indicated by increased lactate levels. Importantly, this greater activation occurs at lower speeds and intensities than normal. Why might this be a good thing? Well, hypoventilation training can be a great way to provide the cardiovascular system with a big training stimulus -but without really hitting the muscles too hard.

This is important; for those who are nursing injuries, or have a history of injury during intense training, hypoventilation training can be a great way to get the metabolic benefits of intense training, while limiting exposure to the higher forces associated with intense training. This approach can allow athletes to train intensely while staying healthy and injury free. Likewise, for individuals who want to limit the impact that intense training has on their muscular system, hypoventilation may be effective as well. If the muscular system is already under a high load, hypoventilation can spare the muscles a bit, while giving the cardiovascular system a major training stimulus.

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Case study: Northwestern University swim squad

In the sport of swimming, breath control is a big part of successful racing. This can occur in crawl swimmers who must limit their breathing to maintain speed, swimmers using underwater dolphin kicking, or breaststrokers who are executing underwater pullouts. Towards the end of races, controlling the breath and executing skills without air is a huge challenge. Of course, having the metabolic horsepower to finish races strong is a big deal, too!

Having read the research and recognised the potential value it had for my swimmers, I decided to implement a version of hypoventilation training with my squad in the two months leading up to our championship meet. Effective training should sometimes be more challenging than competition, so that swimmers are better able to handle the challenges competition presents. What I really liked about hypoventilation training is that it made the respiratory demands harder than those the swimmers would face during races.

Approximately two times per week, the squad performed 15-minute sets of high-intensity hypoventilation training at race velocities. We slowly increased the training stress by increasing the repetition distance and reducing the rest periods. The swimmers found the training difficult, but also exhilarating in the same way that motivated athletes find novel challenges to be exciting.

Over time, the respiratory demands of regular racing and high intensity training were much less daunting and they were more effective in maintaining their skills towards the end of races. The payoff was at our championship meet where many personal best times were achieved. As importantly, the swimmers were able to execute their skills under respiratory distress and finish their races strong.

For Masters swimmers who struggle to control their breathing at the end of tough races and finish strong, hypoventilation training can be a great way to improve the capacity to do so! The added benefit is that the time commitment is small.

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SUMMARY OF HYPOVENTILATION GUIDELINES

Hypoventilation training can be a great way to improve your endurance performance. If you choose to incorporate this method follow the guidelines below:

• *Be consistent with the hypoventilation technique. It is more important to choose volumes and intensities that allow you to execute the hypoventilation technique appropriately.
• *Remember, each breath is not a maximal breath hold! It must be sustainable and consistent across each session. If there is a big drop off in intensity during your session, you’re either holding too long or training too intensely for the technique.
• *Don’t worry if hypoventilation training requires you to slow down initially. As you adapt, you should be able to speed back up.
• *Slowly increase the challenge by increasing the volume or reducing the rest periods. Increasing the intensity is probably best reserved for your next hypoventilation training cycle.
• *Training cycles should include about 10-16 sessions depending on your experience. It is probably best to plan for the lower end, and increase the number with further experience. Hypoventilation training can be done 1-2 times per week and the number of weeks will depend on the number of sessions per week.
• *Plan more intense hypoventilation training towards the end of your training cycle, prior to your most important competition. Less intense hypoventilation can be included during the middle portion of your preparation.