With advances in technology and the relentless quest to break sports records, scientists and coaches are working hard to develop techniques to optimize performance and push the limits of the human body. Among the possible avenues, adding physiological stress to training may lead to overcompensation and, thus, better performance on D-Day. One of the first options that come to mind is altitude training, which causes hypoxic stress and lower inspired oxygen saturation, resulting in a lower arterial saturation (SpO2).

This decrease in SpO2 combined with training allows for many adaptations, including an increased concentration of red blood cells, which are essential for transporting and supplying oxygen to the muscles. However, it remains largely unpopular even though most trainers know the benefits of adding hypoxia to training. In fact, only professional teams can afford mountain training camps or purchase equipment that can generate a hypoxic environment, leaving all other athletes without this attractive training modality.

To get around this problem, it is only necessary to block the oxygen supply by stopping to breathe during the effort in an attempt to decrease SpO2. The greater the intensity of the effort, the greater the hypoxemia. This technique is called voluntary hypoventilation with reduced lung volume (VHL). This article will describe how to integrate this innovative technique into training and its benefits.

Adding VHL to training

As mentioned previously, the objective is to generate the most severe hypoxia possible. To do this, the oxygen supply must be blocked during the effort, and work must be done at high intensity. First, it would be useless to breathing block while the lungs are full of oxygen, that is to say, after a deep breath. Before the effort, it is thus necessary to exhale normally to evacuate the air from the lungs. Then the effort has to be made without a breathing block (Woorons et al., 2007, 2010).

Second, it is necessary to do an activity that allows for intense effort (running sprint, bike sprint, rower sprint, etc.) It is important to sequence periods of effort to accumulate the longest period of total hypoxemia. According to a few researchers on the subject, a sequence of 8 intervals of 6 seconds of VHL sprints with 24 to 30 seconds of recovery would be a sufficient ratio to generate a decrease in SpO2 (Woorons et al., 2019).

In order to expect a long-term adaptation, a total of 3 series should be done in the session twice a week over a period of 4 weeks. Usually, physical trainers are already familiar with this type of training, i.e. repeated-sprints ability (RSA).

However, before adding VHL to sessions, it is important to familiarize yourself with the technique by performing increasingly intense interval sprints. In addition, if you are administering this technique to a training group, pay attention to symptoms such as headaches, dizziness, and poor breathing patterns during recovery. Do not hesitate to adjust your training accordingly.

VHL and hypoxic masks

Many of you have probably already seen the so-called “hypoxic” masks selling the benefits of creating hypoxemia on the internet. These masks are equipped with a filter that reduces the volume of air breathed.

However, it is important to remember that in order to have hypoxia, it is important to have a decrease in SpO2. However, even if the volume of air is lower, the fraction of oxygen inhaled remains the same, at 21 %. Thus, no hypoxia is generated compared to the VHL, where complete respiratory blockade allows a decrease in SpO2.

Are these masks then completely useless? Not if the objective is to work the respiratory muscles because the filter creates resistance that muscles must overcome in order to have a sufficient volume of air.

Benefits of VHL

RSA training is very relevant for team sports athletes subjected to intense and intermittent effort with few recovery periods. These parameters lead to a high level of fatigue that accumulates and directly affects end-game performance. In these final critical moments, simple possession of the ball can change the outcome of the game. For this reason, RSA training has seen a great expansion in recent years and, as with all training modalities, has been optimized.

The addition of VHL during repeated sprint sessions allows a 23% to 30% increase in performance compared to training with normal breathing (Lapointe et al., 2020; Woorons et al., 2019, 2020). The research project I conducted in the last year of my Master’s degree in Kinesiology may help you better understand this data. We compared the results of a test of 12 20-meter sprints (with 30 seconds of semi-active recovery between sprints) before and after 8 sessions of repeated interval sprints under two conditions, control and VHL.

The participants were university-level basketball players and followed a training protocol similar to the one explained in the previous section. Unsurprisingly, we observed an increase in the time to complete the interval sprints with the sequence of repetitions. However, the increase in sprint time was much less pronounced for participants who trained with the VHL technique. This was observed in the performance deterioration score calculation, which was 23% lower and statistically significant.

Key Message

The addition of the VHL technique to repeated sprint training significantly impacts team sports athletes. Sprint speed is better maintained with it, even with the accumulation of fatigue due to maximal effort. This is particularly interesting at the end of the game when the team’s success is at stake. With the democratization of access to hypoxic stress, it thus becomes straightforward to improve training.