Measuring something as intangible as “cognitive fatigue” is no small feat. Varesco drew inspiration from muscle physiology, where fatigue is quantified by observing performance decline over time—for instance, comparing output before and after exertion.
“Imagine a sprinter running 400 metres at full speed,” said Varesco. “They hit a certain velocity at the start, and then it gradually drops. This decrease is an indicator of fatigue.”
The same logic can be applied to cognition, but with some reservations. The brain is far more complex than a muscle. When a person responds to a visual or auditory cue, a cascade of processes unfolds between perception and the final response. Researchers can capture only a fragment of this intricate chain.
An important metric
Ultimately, the results of this study could pave the way for incorporating cognitive assessments into routine athlete monitoring. Coaches could then better detect early signs of overtraining or altitude-related strain, which can increase the risk of technical errors and injury.
“The brain is also a key factor in athletic performance,” said Varesco. “Even in sports that seem primarily physical, athletes must constantly make decisions: adjusting pace, reading the environment, reacting to the unexpected or following their coach’s instructions. In mogul skiing, where movements follow one another at high speed, a split-second lapse in attention can have serious consequences.”
A reliable, rapid cognitive test could allow coaches to gauge an athlete’s cognitive readiness before or even during a training session, helping them decide when to dial back the intensity or steer clear of high-risk situations.
A training high
In Tignes, athletes sleep at 2,000 metres and train at elevations up to 3,400 metres. While these are not considered extreme altitudes, they are enough to trigger a series of physiological adaptations.
The rarefied atmosphere is the obvious culprit, but according to Varesco, the story is more complicated than that. The body is reacting to more than just reduced oxygen supply to the brain.
Upon arrival at high altitude, the body activates a host of adaptive mechanisms, particularly in the cardiovascular and respiratory systems. Changes also occur in brain function and neurotransmitter regulation. All of these adjustments can affect sleep, performance and cognitive function.
“During some phases of sleep, breathing can become less regular and blood oxygen levels can fluctuate more,” said Varesco. “We’ve observed that these fluctuations are more pronounced at the beginning of stays at high altitude, before the body gradually acclimatizes.”
Poor sleep quality, in turn, impacts the next day’s performance. Fatigue at altitude is rarely due to a single factor. Altitude, travel, jet lag, stress and the accumulation of training sessions can all contribute.
