The Question is Still Open: Is Supplemental Oxygen Enhancing Performance in Professional Athletes at High Altitude or Not?

Skiing Birds of Prey in Beaver Creek as a recreational skier may be challenging. You can see people stop after a few yards of monster moguls and gasp for air. Drug stores in the valley sell tourists canned supplemental oxygen to cope with the “high altitude” at Beaver Creek Ski Resort. The yearly Super G or giant slalom events at a starting altitude of 3483 m also challenge professionals and a shortage of oxygen is said to potentially influence their performance. In the giant slalom 2018, the German racer Stefan Luitz breathed supplemental oxygen before the race and between legs, aiming to mitigate the hypoxia-related detrimental effects. In the end, he won the race, yet was stripped of his medal and World Cup points after the FIS (International Ski Federation) decided by its rules that the supplemental oxygen was against doping rules. The German team argued that the World Anti-Doping Agency had excluded supplemental oxygen from its doping list because research could not show a substantial enhancement with oxygen in performance, except during the competition itself. The Germans appealed the FIS decision to the Court of Arbitration for Sport and won [1]. Stefan Luitz was given his win back and prize money and is now officially listed in the winners list. The Court of Arbitration for Sport and the World AntiDoping Agency most likely referred in their decision to several publications concluding that supplemental oxygen does not enhance several different types of muscular work. A recent publication regarding skiing at altitude and supplemental oxygen was designed and executed with members of our own working group as co-authors [2]. Tobias Dünnwald and colleagues gave individuals 100% oxygen versus hypoxic air for 15 min during recovery periods between five extreme flywheel sets of maximal exercise with eccentric and concentric movement performed at a simulated altitude of 3500 m. Concentric and eccentric peak performance were not different between groups. In addition, when 100% oxygen is given for 5 min before a single peak maximal performance of 60 s at a 3500-m simulated altitude, there was no difference in peak performance between oxygenated and ambient air [3]. Similar to peak performance, another study showed that breathing hyperoxic air at a simulated altitude of 3500 m before a balance test does not enhance balance [4]. Balance is next to peak muscle performance as one of the most important abilities for a successful ski race. Previous research conducted in cross-country skiers at intermediate altitude supports the findings of the Innsbruck research group [5, 6]. However, to be fair, there are those that propose that supplemental oxygen increases the performance of athletes at moderate-to-high altitudes. There are publications which report a positive effect of oxygen on performance at high altitude during training and competition [7, 8]. Although a higher muscle tissue oxygenation could not be found with breathing hyperoxic air between exercise intervals, it appeared to reduce the decline in power during maximal exercise in a hypoxic environment [9]. Second, muscles * Nikolaus C. Netzer Nikolaus.Netzer@Eurac.edu

Dear Editor, Skiing Birds of Prey in Beaver Creek as a recreational skier may be challenging. You can see people stop after a few yards of monster moguls and gasp for air. Drug stores in the valley sell tourists canned supplemental oxygen to cope with the "high altitude" at Beaver Creek Ski Resort. The yearly Super G or giant slalom events at a starting altitude of 3483 m also challenge professionals and a shortage of oxygen is said to potentially influence their performance.
In the giant slalom 2018, the German racer Stefan Luitz breathed supplemental oxygen before the race and between legs, aiming to mitigate the hypoxia-related detrimental effects. In the end, he won the race, yet was stripped of his medal and World Cup points after the FIS (International Ski Federation) decided by its rules that the supplemental oxygen was against doping rules. The German team argued that the World Anti-Doping Agency had excluded supplemental oxygen from its doping list because research could not show a substantial enhancement with oxygen in performance, except during the competition itself. The Germans appealed the FIS decision to the Court of Arbitration for Sport and won [1]. Stefan Luitz was given his win back and prize money and is now officially listed in the winners list.
The Court of Arbitration for Sport and the World Anti-Doping Agency most likely referred in their decision to several publications concluding that supplemental oxygen does not enhance several different types of muscular work. A recent publication regarding skiing at altitude and supplemental oxygen was designed and executed with members of our own working group as co-authors [2]. Tobias Dünnwald and colleagues gave individuals 100% oxygen versus hypoxic air for 15 min during recovery periods between five extreme flywheel sets of maximal exercise with eccentric and concentric movement performed at a simulated altitude of 3500 m. Concentric and eccentric peak performance were not different between groups. In addition, when 100% oxygen is given for 5 min before a single peak maximal performance of 60 s at a 3500-m simulated altitude, there was no difference in peak performance between oxygenated and ambient air [3]. Similar to peak performance, another study showed that breathing hyperoxic air at a simulated altitude of 3500 m before a balance test does not enhance balance [4]. Balance is next to peak muscle performance as one of the most important abilities for a successful ski race.
Previous research conducted in cross-country skiers at intermediate altitude supports the findings of the Innsbruck research group [5,6].
However, to be fair, there are those that propose that supplemental oxygen increases the performance of athletes at moderate-to-high altitudes. There are publications which report a positive effect of oxygen on performance at high altitude during training and competition [7,8].
Although a higher muscle tissue oxygenation could not be found with breathing hyperoxic air between exercise intervals, it appeared to reduce the decline in power during maximal exercise in a hypoxic environment [9]. Second, muscles and muscle performance are only one part of an athletically perfect race. Next to psychological mood, the cognitive functions of the brain, sensory reaction time, and the recognition and assessment of obstacles probably play an important role for an individual to win a race. Actual research shows how observations can be made on the function of the brain via an electroencephalogram in real and virtual ski races [10]. Although still speculative, future research might show how the recognition of an obstacle is associated with an elevated high alpha power in the electroencephalogram of a skier. Like muscles, some, but not all, parts of the brain increase their oxygen consumption substantially, in part to metabolize lactate as an energy substrate [11]. However, the brain will not react to a low oxygen supply exactly like the muscles.
As we were able to show, particularly if a challenging performance happens after a night at high altitude, motor reaction time is not substantially impaired but sensory reaction time is [12]. The reduced processing speed is especially observed in the first 24 h at altitude [13], which is important for an athlete at a ski World Cup. After more time, the brain may start to return towards better functioning.
Based on existing research on muscle performance, the World Anti-Doping Agency rules and regulations seem to be adequate. However, it could be that these regulations have to be reconsidered based on experiments addressing overall human performance and define and/or include an effect on brain function. Thus, we consider the question of what oxygen does for performance at high altitude as still open.
Funding Open Access funding enabled and organized by Projekt DEAL.
Data availability Not applicable.

Conflict of interest
The authors declare no to have no personal conflicts regarding the authorship of this article.
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