There are a few important points to consider when interpreting the results of this study. First, the magnitude of improvement in exercise performance was trivial, so for the vast majority of people, the payoff of this intervention probably isn’t worth the effort it requires.

Second, the researchers conducted a pilot study to evaluate the test/retest reliability of the time-to-exhaustion test they used, and they found a coefficient of variation of 1.9%, which represents the average fluctuation in performance between 2 tests. The change in performance induced by the breath-holding intervention was 0.76%, a value well within the coefficient of variation, so it cannot be said with high certainty that the intervention actually improved performance. It’s possible that the superior exercise performance in the breath-holding condition was a product of random chance. It could also have been due to the placebo effect because a sham intervention was not used in the control condition.

For these reasons, it’s not clear whether the breath-holding intervention provided a genuine ergogenic effect in this study. However, there is other evidence to consider on the topic.

Mechanistically, repeated breath holding with face immersion in cold water causes spleen contractions, which results in an increase in red blood cell count.^[2]^[3] This increase in blood volume could theoretically enhance oxygen transport and uptake in skeletal muscle, thus improving aerobic exercise performance.^[4]

Accordingly, “blood doping” — or increasing red blood cell volume artificially by either infusing previously stored red blood cells or by taking the drug erythropoietin — improves aerobic exercise performance.^[5] Moreover, blood loss has been shown to impair aerobic exercise performance.^[6]

Although the reported improvement in performance in the breath-holding condition was underwhelming, there were changes in hematological outcomes, which provides support for the potential utility of this intervention. Immediately before the exercise test, hematocrit, hemoglobin, and red blood cell count were all higher in the breath-holding condition than the control condition. Additionally, blood lactate was lower in the breath-holding condition.

During the exercise test, oxygen uptake was lower in the breath-holding condition, which indicates improved exercise economy (i.e., reduced oxygen cost of movement). Also, there was a delay in the time it took to reach the second ventilatory threshold, which indicates a postponement of the transition from predominantly aerobic to anaerobic metabolism. In combination, these physiological alterations enable the ability to exercise at a higher proportion of maximal aerobic capacity for a longer amount of time.

After the exercise test, blood lactate was lower in the breath-holding condition. Increases in blood lactate are associated with the onset of fatigue during exercise, although lactate does not cause fatigue,^[7] and the ability to maintain a given exercise intensity with lower blood lactate levels is an important predictor of aerobic exercise performance.^[8]

Collectively, these data provide supportive mechanistic evidence that shows how combining breath holding with face immersion in cold water could improve exercise performance.

A couple of other studies have investigated the efficacy of breath holding alone for improving aerobic exercise performance, and no apparent benefits were found.^[9]^[10] This is because combining breath holding with face immersion in cold water is needed to induce the diving response, a suite of physiological changes that conserve oxygen and prioritize blood flow to vital organs.^[11]^[12]

Another study, which was published in 2021 and used the same intervention as the summarized study, found that breath holding plus face immersion in cold water improved performance on a time to exhaustion test by approximately 11%.^[1] The larger magnitude of effect reported in this study than in the summarized study could be related to the use of a different exercise test.

The time-to-exhaustion test involved cycling at 150% of peak power output, and the breath-holding intervention increased the time to exhaustion from approximately 45 seconds to 49 seconds. As such, the average intensity of exercise in this study was much higher, and consequently, the duration of exercise was much shorter.

Can breath holding before exercise improve performance? Original paper