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AuthorCoull, Nicole
AuthorChrismas, Bryna
AuthorWatson, Phillip
AuthorHorsfall, Rachel
AuthorTaylor, Lee
Available date2017-02-09T07:38:04Z
Publication Date2016-02
Publication NameMedicine and Science in Sports and Exerciseen_US
CitationCOULL, NICOLE; CHRISMAS, BRYNA; WATSON, PHILLIP; HORSFALL, RACHEL; TAYLOR, LEE "Tyrosine Ingestion and Its Effects on Cognitive and Physical Performance in the Heat" Medicine and Science in Sports and Exercise (2016) volume 48, issue 2, pg. 277-286
AbstractPurpose: Ingestion of tyrosine (TYR), a catecholamine precursor, has previously improved aspects of cognitive function and mood during acute stress, although there is limited research exploring the optimal dose relative to blood values. The serum responses of two doses of TYR were investigated (study 1), with the identified ‘‘optimal’’ dose assessed relative to cognitive and physical performance during a military-based protocol in the heat (study 2). Methods: For study 1, 21 participants were assigned to one of the following three groups: HIGH (two doses of 150 mgIkgj1 body mass TYR), LOW (two doses of 75 mgIkgj1 body mass TYR), and CON (sugar-free drink). Participants ingested TYR in two separate doses (0900 and 1300 h) and remained in the laboratory from 0800 to 1700 h, having blood drawn every hour. For study 2, eight participants completed a military-based load carriage protocol composed of a 60-min walk (6.5 kmIhj1) followed by a 2.4-km time trial carrying a 25-kg backpack (40-C; relative humidity, 30%) on two occasions (TYR/placebo) in a double-blind counterbalanced crossover design. Cognitive function was assessed before, during, and after exercise. Results: Study 1 demonstrated that ingestion of a single dose of 150 mgIkgj1 body mass TYR was equally efficient at elevating serum TYR concentration relative to a double dose. In study 2, exercise heat stress impaired some aspects of cognitive function; however, TYR did not alleviate these decrements (P 9 0.05). Furthermore, no difference was observed in any physiological variable between conditions (P 9 0.05) or time trial completion time (P = 0.74) between TYR (19.78 T 3.44min) and placebo (20.29 T 3.55 min). Conclusions: Despite marked elevations in serum TYR concentration, ingestion of TYR did not influence cognitive function or physical performance during exercise heat stress
PublisherAmerican College of Sports Medicine
Subjectheat stress
Subjectcentral fatigue
Subjectamino acids
Subjectload carriage
TitleTyrosine Ingestion and Its Effects on Cognitive and Physical Performance in the Heat
Issue Number2
Volume Number48

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