No Influence of Low-, Medium-, or High-Dose Tyrosine on Exercise in a Warm Environment

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No Influence of Low-, Medium-, or High-Dose Tyrosine on Exercise in a Warm Environment. / Tumilty, Les; Gregory, Nicholas; Beckmann, Manfred; Thatcher, Rhys.

In: Medicine and Science in Sports and Exercise, Vol. 52, No. 6, 01.06.2020, p. 1404-1413.

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Tumilty, Les ; Gregory, Nicholas ; Beckmann, Manfred ; Thatcher, Rhys. / No Influence of Low-, Medium-, or High-Dose Tyrosine on Exercise in a Warm Environment. In: Medicine and Science in Sports and Exercise. 2020 ; Vol. 52, No. 6. pp. 1404-1413.

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@article{852625977ad544159662b1c3d5150bce,
title = "No Influence of Low-, Medium-, or High-Dose Tyrosine on Exercise in a Warm Environment",
abstract = "PURPOSE: Tyrosine administration may counter exercise fatigue in a warm environment, but the typical dose is inconclusive, with little known about higher doses. We explored how three tyrosine doses influenced the circulating ratio of tyrosine/amino acids competing for brain uptake and hypothesized that a medium and high dose would enhance exercise performance in a warm environment. METHODS: Eight recreationally trained, non-heat-acclimated male individuals (mean ± SD age, 23 ± 4 yr; stature, 181 ± 7 cm; body mass, 76.1 ± 5.9 kg; peak oxygen uptake, 4.1 ± 0.5 L·min) performed a peak oxygen uptake test, two familiarization trials, then four experimental trials in a randomized order separated by 7 d. Before exercise, subjects drank 2 × 300 mL sugar-free drinks delivering 0 (PLA), 150 (LOW), 300 (MED), or 400 (HIGH) mg·kg body mass tyrosine in a double-blind fashion. Subjects performed a 60-min constant intensity cycling then a simulated time trial in 30°C and 60% relative humidity. RESULTS: Time trial performance (P = 0.579) was not influenced by tyrosine ingestion. The plasma ratio of tyrosine/∑(free-tryptophan, leucine, isoleucine, valine, phenylalanine, methionine), a key determinant of brain tyrosine influx, increased relative to PLA (P < 0.001). The increase was similar (P > 0.05) in MED (7.7-fold) and HIGH (8.2-fold), and greater than that in LOW (5.3-fold; P < 0.05). No differences existed between trials in core and skin temperature, heart rate, RPE, or thermal sensation (P > 0.05). CONCLUSION: Exercise performance in a warm environment was not influenced by tyrosine availability in recreationally trained male individuals. The results provide novel data informing future studies, on the tyrosine dose maximizing the circulating ratio of tyrosine/amino acids competing for brain uptake.",
author = "Les Tumilty and Nicholas Gregory and Manfred Beckmann and Rhys Thatcher",
year = "2020",
month = jun,
day = "1",
doi = "10.1249/MSS.0000000000002245",
language = "English",
volume = "52",
pages = "1404--1413",
journal = "Medicine and Science in Sports and Exercise",
issn = "0195-9131",
publisher = "Lippincott Williams & Wilkins",
number = "6",

}

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TY - JOUR

T1 - No Influence of Low-, Medium-, or High-Dose Tyrosine on Exercise in a Warm Environment

AU - Tumilty, Les

AU - Gregory, Nicholas

AU - Beckmann, Manfred

AU - Thatcher, Rhys

PY - 2020/6/1

Y1 - 2020/6/1

N2 - PURPOSE: Tyrosine administration may counter exercise fatigue in a warm environment, but the typical dose is inconclusive, with little known about higher doses. We explored how three tyrosine doses influenced the circulating ratio of tyrosine/amino acids competing for brain uptake and hypothesized that a medium and high dose would enhance exercise performance in a warm environment. METHODS: Eight recreationally trained, non-heat-acclimated male individuals (mean ± SD age, 23 ± 4 yr; stature, 181 ± 7 cm; body mass, 76.1 ± 5.9 kg; peak oxygen uptake, 4.1 ± 0.5 L·min) performed a peak oxygen uptake test, two familiarization trials, then four experimental trials in a randomized order separated by 7 d. Before exercise, subjects drank 2 × 300 mL sugar-free drinks delivering 0 (PLA), 150 (LOW), 300 (MED), or 400 (HIGH) mg·kg body mass tyrosine in a double-blind fashion. Subjects performed a 60-min constant intensity cycling then a simulated time trial in 30°C and 60% relative humidity. RESULTS: Time trial performance (P = 0.579) was not influenced by tyrosine ingestion. The plasma ratio of tyrosine/∑(free-tryptophan, leucine, isoleucine, valine, phenylalanine, methionine), a key determinant of brain tyrosine influx, increased relative to PLA (P < 0.001). The increase was similar (P > 0.05) in MED (7.7-fold) and HIGH (8.2-fold), and greater than that in LOW (5.3-fold; P < 0.05). No differences existed between trials in core and skin temperature, heart rate, RPE, or thermal sensation (P > 0.05). CONCLUSION: Exercise performance in a warm environment was not influenced by tyrosine availability in recreationally trained male individuals. The results provide novel data informing future studies, on the tyrosine dose maximizing the circulating ratio of tyrosine/amino acids competing for brain uptake.

AB - PURPOSE: Tyrosine administration may counter exercise fatigue in a warm environment, but the typical dose is inconclusive, with little known about higher doses. We explored how three tyrosine doses influenced the circulating ratio of tyrosine/amino acids competing for brain uptake and hypothesized that a medium and high dose would enhance exercise performance in a warm environment. METHODS: Eight recreationally trained, non-heat-acclimated male individuals (mean ± SD age, 23 ± 4 yr; stature, 181 ± 7 cm; body mass, 76.1 ± 5.9 kg; peak oxygen uptake, 4.1 ± 0.5 L·min) performed a peak oxygen uptake test, two familiarization trials, then four experimental trials in a randomized order separated by 7 d. Before exercise, subjects drank 2 × 300 mL sugar-free drinks delivering 0 (PLA), 150 (LOW), 300 (MED), or 400 (HIGH) mg·kg body mass tyrosine in a double-blind fashion. Subjects performed a 60-min constant intensity cycling then a simulated time trial in 30°C and 60% relative humidity. RESULTS: Time trial performance (P = 0.579) was not influenced by tyrosine ingestion. The plasma ratio of tyrosine/∑(free-tryptophan, leucine, isoleucine, valine, phenylalanine, methionine), a key determinant of brain tyrosine influx, increased relative to PLA (P < 0.001). The increase was similar (P > 0.05) in MED (7.7-fold) and HIGH (8.2-fold), and greater than that in LOW (5.3-fold; P < 0.05). No differences existed between trials in core and skin temperature, heart rate, RPE, or thermal sensation (P > 0.05). CONCLUSION: Exercise performance in a warm environment was not influenced by tyrosine availability in recreationally trained male individuals. The results provide novel data informing future studies, on the tyrosine dose maximizing the circulating ratio of tyrosine/amino acids competing for brain uptake.

UR - http://www.scopus.com/inward/record.url?scp=85085229990&partnerID=8YFLogxK

U2 - 10.1249/MSS.0000000000002245

DO - 10.1249/MSS.0000000000002245

M3 - Article

C2 - 31834099

AN - SCOPUS:85085229990

VL - 52

SP - 1404

EP - 1413

JO - Medicine and Science in Sports and Exercise

JF - Medicine and Science in Sports and Exercise

SN - 0195-9131

IS - 6

ER -

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