title: Tyrosine supplementation does not influence the capacity to perform prolonged exercise in a warm environment.
abstract: Eight young men were recruited to a study designed to examine the effect of tyrosine (TYR) supplementation on the capacity to perform prolonged exercise in a warm environment. Subjects entered the laboratory in the morning and remained seated for 1 hr before cycling to exhaustion at 70% VO2peak. Two 250-ml aliquots of a placebo (PLA ) or a TYR solution were ingested at 30-min intervals before exercise, with an additional 150 ml consumed every 15 min throughout exercise (total TYR dose: 150 mg/kg BM). Cognitive function was assessed before drink ingestion, at the end of the rest period, and at exhaustion. TYR ingestion had no effect on exercise capacity (PLA 61.4 ± 13.7 min, TYR 60.2 ± 15.4 min; p = .505). No differences in heart rate (p = .380), core temperature (p = .554), or weighted mean skin temperature (p = .167) were apparent between trials. Ingestion of TYR produced a marked increase in serum TYR concentrations (+236 ± 46 μmol/L; p < .001), with this difference maintained throughout exercise. No change was apparent during the PLA trial (p = .924). Exercise caused an increase in error rate during the complex component of the Stroop test (p = .034), but this response was not influenced by the drink ingested. No other component of cognitive function was altered by the protocol (all p > .05). Ingestion of a TYR solution did not influence time to exhaustion or several aspects of cognitive function when exercise was undertaken in a warm environment.
authors.affiliation: School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, UK.
authors.forename: Phillip
authors.initials: P
authors.lastname: Watson
authors.forename: Sophie
authors.initials: S
authors.lastname: Enever
authors.forename: Andrew
authors.initials: A
authors.lastname: Page
authors.forename: Jenna
authors.initials: J
authors.lastname: Stockwell
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Maughan
mesh_terms: D015444:Exercise; D017079:Exercise Tolerance; D006358:Hot Temperature; D006801:Humans; D012881:Skin Temperature; D014443:Tyrosine
chemical_list: D014443:Tyrosine