Published in 2019, this review study included 55 clinical and preclinical studies (44 original studies and 11 literature reviews) that investigated the impacts of L-glutamine supplementation on delaying fatigue markers and improving performance in the context of physical exercise. Studies included observed both trained and untrained athletes, endurance and power exercises as well as various durations and doses of glutamine supplements.
Coqueiro AY, Rogero MM, Tirapegui J. Glutamine as an Anti-Fatigue Amino Acid in Sports Nutrition. Nutrients. 2019 Apr 17;11(4):863. doi: 10.3390/nu11040863. PMID: 30999561; PMCID: PMC6520936.