Tumilty, Les, Davison, Glen, Beckmann, Manfred, Thatcher, Rhys (2014) Failure of oral tyrosine supplementation to improve exercise performance in the heat. Medicine and science in sports and exercise, 46 (7). pp. 1417-1425. ISSN 1530-0315. (doi:10.1249/MSS.0000000000000243) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:43304)
The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided. | |
Official URL: http://dx.doi.org/10.1249/MSS.0000000000000243 |
Abstract
PURPOSE
Acute oral tyrosine administration has been associated with increased constant-load, submaximal exercise capacity in the heat. This study sought to determine whether self-paced exercise performance in the heat is enhanced with the same tyrosine dosage.
METHODS
After familiarization, seven male endurance-trained volunteers, unacclimated to exercise in the heat, performed two experimental trials in 30°C (60% relative humidity) in a crossover fashion separated by at least 7 d. Subjects ingested 150 mg·kg(-1) body mass tyrosine (TYR) or an isocaloric quantity of whey powder (PLA) in 500 mL of sugar-free flavored water in a randomized, double-blind fashion. Sixty minutes after drink ingestion, the subjects cycled for 60 min at 57% ± 4% peak oxygen uptake (VO2peak) and then performed a simulated cycling time trial requiring completion of an individualized target work quantity (393.1 ± 39.8 kJ).
RESULTS
The ratio of plasma tyrosine plus phenylalanine (tyrosine precursor) to amino acids competing for brain uptake (free-tryptophan, leucine, isoleucine, valine, methionine, threonine, and lysine) increased 2.5-fold from rest in TYR and remained elevated throughout exercise (P < 0.001), whereas it declined in PLA from rest to preexercise (P = 0.004). Time-trial power output (P = 0.869) and performance (34.8 ± 6.5 and 35.2 ± 8.3 min in TYR and PLA, respectively; P = 0.4167) were similar between trials. Thermal sensation (P > 0.05), RPE (P > 0.05), core temperature (P = 0.860), skin temperature (P = 0.822), and heart rate (P = 0.314) did not differ between trials.
CONCLUSIONS
These data indicate that acute tyrosine administration did not influence self-paced endurance exercise performance in the heat. Plasma tyrosine availability is apparently not a key determinant of fatigue processes under these conditions.
Item Type: | Article |
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DOI/Identification number: | 10.1249/MSS.0000000000000243 |
Subjects: | Q Science |
Divisions: | Divisions > Division of Natural Sciences > Physics and Astronomy |
Depositing User: | Glen Davison |
Date Deposited: | 13 Oct 2014 14:36 UTC |
Last Modified: | 05 Nov 2024 10:27 UTC |
Resource URI: | https://kar.kent.ac.uk/id/eprint/43304 (The current URI for this page, for reference purposes) |
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