Cognitive fatigue due to exercise under normobaric hypoxia is related to hypoxemia during exercise

Abstract

Abstract We previously found that a 10-min bout of moderate-intensity exercise (50% maximal oxygen uptake) under normobaric and hypoxic conditions (fraction of inspired oxygen [ $${{\text{F}}_\text{IO}}_{_{2}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:msub><mml:mtext>F</mml:mtext><mml:mtext>IO</mml:mtext></mml:msub></mml:mrow><mml:msub><mml:mrow/><mml:mn>2</mml:mn></mml:msub></mml:msub></mml:math> ] = 0.135) reduced executive performance and neural activity in the left dorsolateral prefrontal cortex (DLPFC). To examine whether this cognitive fatigue is due to a decrease in SpO 2 during exercise, we compared executive performance and related prefrontal activation between two experimental conditions, in which the participants inhaled normobaric hypoxic gas ( $${{\text{F}}_\text{IO}}_{_{2}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:msub><mml:mtext>F</mml:mtext><mml:mtext>IO</mml:mtext></mml:msub></mml:mrow><mml:msub><mml:mrow/><mml:mn>2</mml:mn></mml:msub></mml:msub></mml:math> = 0.135) (hypoxic exercise [HE]) or hypoxic gas adjusted so that SpO 2 during exercise remained at the resting level (milder hypoxic exercise [ME]). ME condition showed that reaction time in executive performance decreased ( t [13] = 2.228, P &lt; 0.05, d = 0.34, paired t -test) and left DLPFC activity increased ( t [13] = -2.376, P &lt; 0.05, d = 0.63, paired t -test) after exercise compared with HE condition. These results showed that the HE-induced reductions in the left DLPFC activity and executive performance were both suppressed in the ME condition, supporting the hypothesis that exercise-induced cognitive fatigue under hypoxic environment is due to hypoxemia during exercise. This may lead to the development of a method of coping with cognitive fatigue due to exercise that causes hypoxemia.

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