Circulating Endocannabinoids Are Associated with Mental Alertness During Ultra-Endurance Exercise

Introduction: Ultra-endurance exercise events result in central fatigue, impacting on mental alertness and decision making. Endocannabinoids are typically elevated during endurance exercise and have been implicated in central processes such as learning and memory, but their role in central fatigue has never been studied. Materials and Methods: Twenty-four recreational male ultrarunners participated in a 100-km trail run, and 18 of them completed at least 60 km and were included in the analyses. A cognitive test battery to assess median reaction time (MRT) and median movement time during a reaction time task and median response latency during a rapid visual information processing task was completed prior to and immediately after the trail. Blood serum samples pre- and postexercise were analyzed for endocannabinoids and related lipids (anadamide: AEA; 2-arachidonoylglycerol: 2-AG; palmitoylethanolamide: PEA; oleoylethanolamide: OEA; stearoylethanolamine: SEA) via liquid chromatography-mass spectrometry. Results: Ultra-endurance exercise worsened all cognitive parameters and increased abundance of AEA, PEA, OEA, and SEA but not 2-AG. Interestingly, the exercise-induced change in MRT showed moderate, positive correlations with the change in different endocannabinoids, that is, AEA (r = 0.5164, p = 0.0338), PEA (r = 0.5466, p = 0.0251), and OEA (r = 0.5442, p = 0.0239). Conclusion: These results indicate a potential role of endocannabinoids on mental alertness following ultra-endurance exercise.