A study of athletes competing in ultramarathons has found that spatial cognition improved under conditions of energetic stress (after a multi-day race, when the participants were tired). Energetic stress did not affect participants’ reaction times (psychomotor speed), while the ability to recall information about specific events (episodic memory performance) was adversely affected in female athletes. The study was published in the American Journal of Biological Anthropology.
Energetic stress is a condition that arises when the body is in a situation that requires it to expend more energy than usual for a prolonged period. Similar to how disruptions in the social and physical environments can cause social or mechanical stress, researchers have proposed that changes in the energy demands of the body can cause energetic stress. Theorists propose that, when such stress happens, our body might engage in various trade-offs in allocation of energy to various body and cognitive functions in order to be more efficient at what it is doing.
For example, studies have shown that bees can have two different strategies of collecting pollen – an accurate, but slow, and a fast, but inaccurate strategy. Some studies indicate that the fast but inaccurate strategy, one in which a bee visits many flowers but does not search them thoroughly might result in more pollen being collected compared to the slow, but accurate one.
It is possible that similar trade-offs exist in humans as well. This might particularly be the case with various cognitive functions as the brain is an organ that requires lots of energy and making tradeoffs in allocating energy to different functions could very-well improve the body’s energy expenditure, particularly when energy demands are high.
To examine the possibility of these trade-offs and to gauge human cognitive adaptability during energy deficits, study author Daniel P. Longman and his colleagues conducted a study in which they evaluated changes in spatial working memory, episodic memory, and psychomotor speed of athletes after an ultramarathon.
An ultramarathon, often simply referred to as an “ultra,” is a long-distance running race that goes beyond the traditional marathon distance of 26.2 miles (42.195 kilometers). Ultramarathons can vary significantly in distance, ranging from 50 kilometers (31 miles) to several hundred kilometers or even longer. These races are known for their extreme physical and mental challenges, and they often take place on varied terrains, including trails, mountains, deserts, and roads.
The study focused on 48 athletes who participated either in the 2018 Jordan Ultra or the 2019 Sri Lanka Ultra; 29 of these participants were male. Both events were competitive 5-day races held under extreme climatic conditions, with temperatures reaching 28–35°C in Jordan and slightly lower in Sri Lanka, coupled with 60%-80% humidity in Sri Lanka.
All participants underwent assessments both before the race and on its fourth day, by which time they had covered between 150-160 km. The pre-race evaluations served as baseline measurements, whereas the fourth-day assessments gauged conditions of energetic stress. The researchers surmised that after running 40 km daily for four consecutive days and with another race day looming, the athletes would undoubtedly be undergoing energetic stress. The team also recorded participants’ body mass during both occasions.
Using a tablet, participants engaged in a series of tests from the Cambridge Neuropsychological Test Battery (CANTAB). These tests measured various cognitive functions, ranging from spatial working memory, which pertains to retaining and using spatial information to guide decision-making, to episodic memory and psychomotor speed.
Findings indicated no significant differences among athletes from the two races concerning age, height, weight, or body mass index. Notably, participants from the Jordan Ultra lost an average of 2 kg during the race, whereas those from the Sri Lanka Ultra did not. The researchers interpreted this weight loss as a sign of increased energy demands and therefore, heightened energetic stress. When contrasting the two races, it emerged that average cognitive performance altered only during the Jordan Ultra, where weight loss was evident.
On the whole, those who shed more weight during a race exhibited enhanced spatial working memory compared to their baseline scores. Yet, they also displayed weaker performance in one of the episodic memory metrics. Both male and female athletes showcased this association between weight loss and improved spatial working memory. However, only female athletes evidenced the decline in episodic memory.
“It is likely that loss of body mass, representative of a breakdown of adipose/muscle tissue (as opposed to dehydration—the athletes had the opportunity to rehydrate prior to mid-race weighing and cognitive testing), was responsible for the observed cognitive plasticity,” the study authors concluded. “Consequently, limitations in circulating substrate, and subsequent reduced availability of metabolic resources, are expected to have played a central role in the observed trade-off.”
“It is acknowledged, however, that dehydration could limit the body’s ability to delivery substrate to metabolically active tissues. We propose that prioritization of spatial working memory performance during conditions of negative energy balance represents an adaptive response due to its role in facilitating calorie acquisition.”
The study makes an important contribution to the scientific understanding of how body optimizes the use of resources under conditions of high demand. However, it also has limitations that need to be taken into account. Notably, the study sample was small and consisted solely of individuals capable of enduring a 250 km race in 5 days. That is the level of physical training and condition way outside the physical capacities of an average individual. Results of studies of groups more representative of the general population and on larger samples might not be the same.
The study, “Human energetic stress associated with upregulation of spatial cognition”, was authored by Daniel P. Longman, Jonathan C. K. Wells, and Jay T. Stock.
