Purpose: We tested the hypothesis that marathon racing reduces working memory performance and increases frontal theta activity in trained female endurance athletes. We further examined whether changes in cognitive performance or brain activity were associated with either acute and/or chronic risk of low energy availability. Methods: Sixteen female Tier 2 runners (42 ± 9 yr; VO2max 45.6 ± 6 mL·kg-¹·min-¹) underwent VO2max testing and the Low Energy Availability in Females Questionnaire (LEAF-Q) 7-14 d before a marathon. Participants completed 1-back (low-load) and 3-back (high-load) working memory tasks during electroencephalogram recordings, performed before and immediately after the race (<10 min). Accuracy and reaction time measured cognitive performance, and frontal theta power measured cognitive effort. Results: Sixteen runners completed the marathon in 4:16 ± 37 min (70 ± 6% VO2max), with a mean carbohydrate intake of 28 ± 14 g·h-1. Six athletes exceeded the LEAF-Q threshold (=8) and eight reported menstrual dysfunction. Postrace, 3-back accuracy declined (-18.8%, P = 0.003) while reaction time shortened for both task versions (5.3%-6.6%, P = 0.002). Frontal theta increased postrace (1-back: +26.8%; 3-back: +29.6%, P < 0.001). Regression models showed that 3-back accuracy changes were predicted by LEAF-Q score (ß = 0.494, P = 0.016). In contrast, theta increases were predicted by a combination of lower carbohydrate intake (ß = -0.025, P = 0.005), longer race time (ß = 0.008, P = 0.005), and higher LEAF-Q score (ß = 0.121, P < 0.001). Conclusions: Working memory performance is reduced and cognitive effort is increased after marathon racing in trained female athletes. These effects are linked to both acute and chronic risk of low energy availability, emphasizing the need for individualized fueling strategies to preserve cognitive performance during endurance events.
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