Exercise Induced Fatigue to Cause Low Oxygen Supply that impairs Judgement

Certain physically demanding activities are performed at high altitude or in other low-oxygen environments, excellent coordination, judgment, and decision-making are important. In some cases, such as when mountaineering, these capabilities may be the difference between life and death.

Low blood-oxygen levels were found to be the distinguishing factor that affected executive control-related neural activity and cognitive performance when exercise was performed in low-oxygen conditions. In a study published this month inScientific Reports, researchers at the University of Tsukuba showed that reductions in neural activity in brain regions responsible for executive control-related cognitive functions and cognitive performance during exercise in low-oxygen conditions could be prevented by maintaining oxygen saturation.

Researchers demonstrated causality that the decreases in neural activity and performance are caused by low oxygen availability to brain tissue it was not straightforward because of the complexity exhibited by the brain and all its functions. Researchers compared the effects of hypoxic conditions in which blood oxygen levels is reduced with those in which blood oxygen levels remains stable during exercise. By doing this, they isolated low oxygen saturation as a factor for decreased neural activity and decreased performance.

Neural activity in the prefrontal cortex was measured with functional near-infrared spectroscopy to show change in oxygenated hemoglobin (i.e., oxygen usage from regional blood supply). Cognitive performance was assessed using Stroop interference, which is the difference in completion time (or number of errors) between neutral and incongruent trials. In incongruent trials, the color of the text must be identified when, for example, the word red is written in green. In neutral trials, only the color of a swatch must be identified.

The study suggests that oxygen supply is important for maintaining cognitive function during exercise in low-oxygen environments. Furthermore, regions of the brain with newer (from an evolutionary point of view), less critical functions may be lower priority than those responsible for functions that keep us alive. Thus, the effects of cognitive fatigue must be taken into account when physical activities that require judgment and critical thinking are performed in low-oxygen environments.

Reference: "Cognitive fatigue due to exercise under normobaric hypoxia is related to hypoxemia during exercise," was published in Scientific Reports at DOI: 10.1038/s41598-022-14146-5.