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Failure of oral tyrosine supplementation to improve exercise performance in the heat

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. (Contact us about this Publication)
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
DOI/Identification number: 10.1249/MSS.0000000000000243
Subjects: Q Science
Divisions: Divisions > Division of Natural Sciences > School of Physical Sciences
Depositing User: Glen Davison
Date Deposited: 13 Oct 2014 14:36 UTC
Last Modified: 16 Feb 2021 12:56 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/43304 (The current URI for this page, for reference purposes)
Davison, Glen: https://orcid.org/0000-0003-4340-0074
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