RandoRaids are competitions that can be considered a mix between the so-called “Chemin Solidaires,” the “Grandes Randonnées” and the Non-Stop Raid Nature, often conducted in semi-self-sufficiency and run for extremely long distances. Differently from ultra-trail marathons, RandoRaids are largely conducted in independence by the raiders, and cover longer distances.

Often completed in times that are somewhat similar to the ultra-trail marathon [the minimum average speed to complete the Tor des Géants ultra-trail (330 Km) is 2.2 km/h, while this value is set to 2.165 km/h for the Transpyrénéa RandoRaid (866 Km)], it is reasonable to think that effects on the health status of competitors would be similar to those experienced by the ultra-trailers. To date, various evidence for significant effects on physical (Vitiello et al., 2013) and cognitive functions (Tomporowski, 2002; Cona et al., 2015; Hurdiel et al., 2015; Tonacci et al., 2016) of ultra-trailers has already been observed, mainly caused by a mix of high altitude exposure (Yan, 2014), environmental conditions (Lefferts et al., 2016; Taylor et al., 2016)—including cold, heat and hypoxia—muscular fatigue, dehydration (Cian et al., 2000), and sleep deprivation (Davis et al., 2014; Fullagar et al., 2015).

According to Hurdiel et al. (2015), ultra-trailers experience a wide range of symptoms, ranging from response lags to cognitive tasks to serious symptoms such as visual hallucinations, regardless of rest duration, and time in race. In addition, neurosensory features appear to be affected by a mix of strenuous physical effort and sleep restriction/deprivation, as demonstrated in a recent study held during the Tor des Géants ultra-trail (Tonacci et al., 2016).

Cognitive reserve also turns out to be linked to physical performances, as demonstrated by Cona et al. (2015), which found the correlation between ultra-trailers' physical performances and their neurocognitive functioning, including superior inhibitory control for motor response and for processing of irrelevant information (i.e., emotional stimuli). Such findings are somehow in line with results achieved by Del Percio et al. (2009), which hypothesized a mechanism of neural efficiency ruling the performances of elite athletes also in different sport activities.

However, the cognitive abilities of athletes performing ultra-long distances—and RandoRaids in particular—are not well-explored in scientific literature, and thus present an interesting challenge to be investigated by studies conducted in naturalistic settings.

In particular, focusing on cognitive and neurosensory features, such domains are normally studied via exhaustive tests that take time to administer, so are unsuitable for longitudinal administration during the execution of a competition. However, thanks to surrogate biomarkers and quick-to-administer testing methods, it is possible to retrieve interesting information regarding the cognitive and sensory status of an athlete, even during a strenuous competition such as an ultra-long RandoRaid. The aim of our study was to evaluate the cognitive and neurosensory effects on ultra-endurance RandoRaid athletes during the Transpyrénéa race.

The Transpyrénéa first took place in the summer of 2016 on the French side of the Pyrenees, covering an overall distance of 866 km with 65,000 meters of positive slope throughout the race. The race started near the Mediterranean Sea, in Le Perthus, and ended in Hendaye, on the Atlantic Ocean, following the Grande Randonnée path called GR10. The maximum time to complete the race was set to 400 h, with 22 checkpoints (CPs) and three life bases (LBs, 166, 418, 678 km) along the path.

Of the 40 athletes initially enrolled, 28 subjects (25 males; age 43.5 ± 8.5 years) reached Mérens-les-Vals (after an average of 60.0 ± 21.3 h) and were re-evaluated. Twenty of them (17 males, age 44.8 ± 8.7 years) successfully reached Bagnères-de-Luchon after 185.9 ± 23.7 h and were re-assessed, while 13 (11 males; age 43.8 ± 7.6 years) completed the competition in 363.3 ± 33.1 h (Table 2).

All the athletes entering the life bases for testing decided to undergo both the olfactory and cognitive assessments. The mean time for the complete test battery administration was 9.5 ± 3.5 min at T0, 7.5 ± 2.3 min at T1 and T2, 9.5 ± 2.4 min at T3.

This study investigated olfactory and cognitive modifications occurring during the first-ever edition of the toughest RandoRaid competition in Europe, Transpyrénéa, organized in the French Pyrenees in summer 2016. The study is a completion of a research previously published about the Tor des Géants® mountain ultra-trail marathon (Borghini et al., 2015; Mrakic-Sposta et al., 2015; Tonacci et al., 2016), adding to the referenced studies a deeper insight into cognition and the use of minimally obtrusive methods, shown to be employable in a naturalistic setting, in a completely different competition. In fact, Transpyrénéa is a much longer competition (866 vs. 330 kms) than the previous one, and therefore requires a dissimilar race management concerning sleep/wake cycles, feeding and so forth. Furthermore, environmental conditions and altimetry profiles are not comparable between the two races, thus representing completely different models to be studied.

Focusing in particular on the cognitive and sensory effects that a similar effort could have on athletes' health, several variables should be taken into account. At first, the effort itself should be considered, since prolonged strenuous physical activity could possibly bring on consequences for health, and specifically cognition and sensoriality, in athletes (Tonacci et al., 2016). Second, mechanisms of sleep deprivation or even sleep restriction are likely to deeply impact, possibly in a transient way, the cognitive and sensory features of a person (Fullagar et al., 2015). Such effects seem to be more dramatic when sleep deprivation is combined with a massive physical effort, as occurs in these events (Davis et al., 2014; Hurdiel et al., 2015), also carrying on serious symptoms, including visual hallucination, possibly impacting the safety of athletes.

Third, feeding and all mechanisms of dehydration and missed/unbalanced supply of nutrients (Murray et al., 2009) that could occur in a similar event could possibly be related to a short-term cognitive deficiency. Fourth, altitude (Yan, 2014), hypoxia, heat and cold stress, known to be both task- and severity-dependent, are probably linked to the cognitive and sensory status of an athlete (Ruffini et al., 2015; Taylor et al., 2016) and are experienced by RandoRaid and ultra-trail athletes competing in a race like the Transpyrénéa.

Therefore, this study employed olfactory testing, a minimally obtrusive, quick, user-friendly surrogate of overall cognitive function and a reliable method for assessing a specific sensory domain, along with specific cognitive testing methods to assess the cognition states of 40 athletes competing in the Transpyrénéa.

Four testing sessions were set up, at the departure (T0), after 166 (T1) and 418 kms (T2) and at the finish line (T3). To avoid particular annoyance for the athletes, a complete testing battery was administered at T0 and T3, whereas at T1 and T2 only olfactory testing and COWAT testing for verbal fluency were performed, with the computer version of TMT performed by athletes only at T0 and T3.

Olfaction—at pre-race assessment slightly related to the age of athletes, as already demonstrated (Kobal et al., 2000)—was seen as slightly decreased throughout the race, similarly to that which occurred in athletes at the Tor des Géants® (Tonacci et al., 2016), where a mix of strenuous physical effort and sleep restriction/deprivation negatively affected the olfactory function. Among the possible causes of the abovementioned sensory-cognitive detriment, sleep deprivation (or sleep restriction) was seen to be correlated with the “delta” of olfactory decrease between pre-race and post-race assessment. On the other hand, no particular effects for body composition variables were seen on cognitive domains, probably masked by other, predominant contributions, similarly to what reported during the Tor des Géants (Tonacci et al., 2016). This particular comparison was rarely performed among athletes, even though it was demonstrated that exercise-induced dehydration severely affects cognitive function (Cian et al., 2000). The findings reported by Cian et al. (2000) were referring, however, to dehydrated athletes, while none of our athletes had experienced dehydration as showed by the TBW composition.

Another cognitive domain, language fluency, was otherwise clearly improved during the race, with a similar—and opposite—dynamic when compared to olfaction. Interestingly, the cognitive domains studied with TMT—in particular those more related to the TMT-B score—and not different from each other between pre- and post-race assessment, were correlated with the COWAT score at the post-race assessment.

This different response detected with olfactory and cognitive testing is probably related to a differential activation of several cortical areas in response to stimuli. In fact, it could be stated that during the physical effort of the Transpyrénéa race, some cortical areas are more largely activated by the tasks required of the athlete in order to succeed in the competition, due to the so-called “neural efficiency” hypothesis (Vernon, 1993; Del Percio et al., 2009; Nakata et al., 2010).

This theory is based on psychometric considerations, and was strengthened by several neuroimaging studies using both ionizing radiation- (PET, SPECT) and non-ionizing radiation (fMRI)-based methods. Such research found that the subjects scoring highest on tests such as intelligence quotient, word fluency, spatial skills, and working memory show weaker fronto-parietal activation during cognitive tasks (Haier et al., 1988, 1992, 2004; Parks et al., 1988; Charlot et al., 1992; Rypma and D'Esposito, 1999; Rypma et al., 2002, 2005; Ruff et al., 2003).

Indeed, it is well-known that the cortical structures involved in olfactory identification processing (piriform and entorhinal cortex, amygdala, orbitofrontal cortex, anterior olfactory nucleus) are quite different when compared to the cortical structures called upon by COWAT for language fluency and execution (prefrontal cortex, caudate and subthalamic nuclei) and from the structures involved in tasks such as processing speed and attention (TMT-A) or visuomotor tracking, sequencing and cognitive flexibility (TMT-B).

During ultra-trail marathons or similar competitions, the athlete is called upon to process a number of stimuli that arise from the peculiarities of the race. It can be stated that ability in executing tasks, attention and visuomotor tracking is crucial for the good outcome of several sports activities (Abernethy, 1990; Ferrari and Rizzolatti, 2015), including walking, running or similar activities (Drew et al., 2008), in both good and bad visibility conditions (Durgin and Pelah, 1999). This could be the main reason why TMT and COWAT scores do not decrease throughout the race, and indeed are in some cases enhanced as seen with language fluency, whereas a cognitive pathway related to sensory stimuli, such as the olfactory path, could be somehow sacrificed for the advantage of more important cortical circuitries.

It can be hypothesized that this “double nature” of increasing the activity of some cortical parts while decreasing others that are less useful for the primary task to be accomplished (the competition in this case), could be related to some compensatory mechanisms of the brain, which occur in a wide number of disorders or sports injuries but to date have been reported in only a few studies on healthy athletes (Laurienti et al., 2002; Kudo et al., 2004). This could also be the reason why a correlation between cognitive parameters and sleep restriction was not found, contradicting some literature findings (Fullagar et al., 2015).

The study protocol was approved by the institutional Ethics Committee of the Aosta Valley Hospital (n. 895; 31/8/2015) and followed the guidelines of the Helsinki Declaration. All volunteers were informed regarding the design and purposes of the study and gave written informed consent.

AT contributed substantially to the conception and design of the work, participated in data acquisition and analysis, as well as in the interpretation of results, drafted the work and approved its version to be submitted. SM contributed substantially to the conception and design of the work, participated in data acquisition and analysis, critically revised the work and approved its version to be submitted. KU contributed substantially to the design of the work, critically revised the work and approved its version to be submitted. FS contributed substantially to the conception of the work, critically revised the work and approved its version to be submitted. AF contributed substantially to the conception and design of the work, participated in data acquisition, critically revised the work and approved its version to be submitted. GG contributed substantially to the conception of the work, critically revised the work and approved its version to be submitted. RC contributed substantially to the conception of the work, critically revised the work and approved its version to be submitted. LP contributed substantially to the conception and design of the work, participated in data acquisition and analysis, as well as in the interpretation of results, drafted and critically revised the work, and approved its version to be submitted. All the authors agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.