European Journal of Applied Physiology

, Volume 119, Issue 11–12, pp 2567–2578 | Cite as

Acute glutamine supplementation does not improve 20-km self-paced cycling performance in the heat

  • John O. OsborneEmail author
  • Ian B. Stewart
  • Kenneth W. Beagley
  • David N. Borg
  • Geoffrey M. Minett
Original Article



The premise of this study was to investigate the effect of acute glutamine supplementation on 20 km time trial cycling performance in the heat, neuromuscular function, inflammation and endotoxemia.


Twelve cyclists completed two, 20-km time trials (20TT) in 35 °C (50% relative humidity). Participants ingested either glutamine (GLUT; 0.9 g kg−1 fat-free mass) or a placebo (CON) 60 min before each 20TT. Physiological and perceptual measures were recorded during each 20TT, and neuromuscular function assessed pre- and post-exercise. Venous blood was analysed for endotoxins, markers of gut damage (inflammatory fatty acid binding protein; I-FABP) and inflammatory cytokines (interleukin-6, IL-6; tumour necrosis factor-alpha, TNF-α). Data were analysed using linear mixed models in a Bayesian framework.


20TT in the heat increased I-FABP and elevated inflammatory cytokines (IL-6 and TNF-α) compared to pre-exercise values but did not result in endotoxemia. Completion time was not statistically different between conditions (mean difference [95% credible interval] = 11 s [− 23, 44]). Relative to CON, GLUT did not alter any physiological or perceptual measures during the 20TT.


Glutamine supplementation does not improve 20TT performance in the heat or preserve neuromuscular function when compared to a placebo. These findings suggest that glutamine is not an ergogenic aid or prophylactic intervention for heat-induced gut damage during short-duration self-paced exercise in hot environments.


Glutamine Exercise Endotoxemia Hyperthermia Inflammation 


½ RT

Half relaxation time


20 km time trial


Contraction duration


Credible interval




Central nervous system


Coefficient of variation


Enzyme-linked immunosorbent assay








Heart rate


Intraclass correlation


Intestinal fatty acid binding protein


Interleukin 6


Markov chain Monte Carlo


Mean difference


Maximum voluntary contraction


Profile of mood states


Peak torque




Rating of perceived exertion


Rate of relaxation


Rate of torque development


Smallest effect size of interest


Core (rectal) temperature


Tumour necrosis factor alpha


Time to peak torque


Mean skin temperature


Urine specific gravity


Voluntary activation


vastus lateralis


Vastus medialis

VO2 max

maximal aerobic capacity



The authors sincerely thank Mr Logan Trim (Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia) for his technical assistance with the immunoassay analysis.

Author contributions

Study conception and design: JOO, IBS, GMM. Data collection: JOO. Data analysis: JOO, IBS, DNB, GMM. Contributed reagents/materials/analysis tools: IBS, KWB, GMM. Manuscript development: JOO, IBS, KWB, DNB, GMM.


None declared.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no competing interests.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.School of Exercise and Nutrition SciencesQueensland University of Technology (QUT), Kelvin GroveBrisbaneAustralia
  2. 2.Institute of Health and Biomedical InnovationQueensland University of Technology (QUT)BrisbaneAustralia
  3. 3.School of Biomedical SciencesQueensland University of Technology (QUT)BrisbaneAustralia
  4. 4.The Hopkins Centre, Menzies Health Institute Queensland, Griffith UniversityBrisbaneAustralia

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