Skip to main content
  • Meeting abstract
  • Open access
  • Published:

Effect of tyrosine ingestion on cognitive function and load carriage performance in the heat

Introduction

Prolonged exercise-heat-stress impairs both exercise performance and cognitive function. Military based operations are often performed in hot environmental conditions and thus performance and safety may be compromised which could be potentially life threatening. Ingestion of tyrosine (TYR), a catecholamine precursor has been shown to improve exercise performance [1] and cognitive function [2] in hot environments, but no study has assessed the effects of TYR in a simulated military setting in the heat simultaneously assessing steady sate exercise performance, time-trial performance and alterations in various facets of cognitive function. Therefore, the aim of this study was to investigate the effect of 150 mg.kg TYR on steady state exercise, cognitive function and time-trial performance in the heat.

Methods

Eight recreationally active, healthy males [age 23(1) y, height 176.4(5.9) cm, body mass 79(11.5) kg] visited the laboratory on four occasions (two familiarisation and two experimental conditions). In a double-blind, counter-balanced, crossover design participants ingested a placebo [PLA (250 mL sugar free squash)] or tyrosine [TYR (same as PLA plus 150 mg.kg TYR powder)] 1 h pre-exercise. Participants completed a 60 min walk at 6.5 km.h-1, followed by a 2.4 km time-trial carrying a 25 kg backpack in 40 °C and 30 % rh. Aspects of cognitive function were assessed using the PsychE software package, including number vigilance (identification of a duplicate number), dual-task (tracking and stimuli response) and simple reaction time (stimuli response - thinking and movement time) at 5 time-points; pre-ingestion, pre-exercise, 30 min into exercise, post 60 min exercise and post time-trial. Measures of heart rate (HR), rating of perceived exertion (RPE), thermal sensation (TSS) and rectal (Tre) and skin temperature (Tsk) were recorded throughout the exercise and rest period.

Results

A significant increase from pre-exercise to post 60 min exercise (p < 0.01) was observed for vigilance and dual-task FALSE scores, and for reaction time in both conditions. However, no significant difference was observed between TYR and PLA conditions in any of the cognitive tests measured (p > 0.05). Furthermore, no significant difference was observed in time-trial completion time (F1,14 = 547.9, p = 0.74) between TYR [19.78(3.44) min] and PLA [20.29(3.55) min]. No significant differences were observed in any of the physiological (HR), perceptual (RPE, TSS) or temperature measures between conditions (p > 0.05).

Discussion

During TYR and PLA conditions, vigilance, dual task and reaction time cognitive processes declined pre to post exercise. This is surprising since increasing the provision of TYR (a catecholamine precursor), through oral ingestion is suggested to maintain catecholamine synthesis and thus alleviate stress-related decrements in performance; as shown elsewhere during soccer specific exercise [2].

Conclusion

Ingestion of 150 mg.kg TYR did not influence cognitive function or any outcome variable associated with steady state exercise or time-trial performance after load carriage (25 kg) in a hot environment (40 °C).

References

  1. Tumilty L, Davison G, Beckmann M, Thatcher R: Oral tyrosine supplementation improves exercise capacity in the heat. Eur J Appl Physiol. 2011, 111: 2941-2950. 10.1007/s00421-011-1921-4. doi:10.1007/s00421-011-1921-4

    Article  CAS  PubMed  Google Scholar 

  2. Coully NA, Watkins SL, Aldous JW, Warren LK, Chrismas BC, Dascombe B, Mauger AR, Abt G, Taylor L: Effect of tyrosine ingestion on cognitive and physical performance utilising an intermittent soccer performance test (iSPT) in a warm environment. Eur J Appl Physiol. 2015, 2: 373-386. doi:10.1007/s00421-014-3022-7

    Article  Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Lee Taylor.

Rights and permissions

Open Access  This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.

The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/.

The Creative Commons Public Domain Dedication waiver (https://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Coull, N., Foster, J., Chrismas, B. et al. Effect of tyrosine ingestion on cognitive function and load carriage performance in the heat. Extrem Physiol Med 4 (Suppl 1), A148 (2015). https://doi.org/10.1186/2046-7648-4-S1-A148

Download citation

  • Published:

  • DOI: https://doi.org/10.1186/2046-7648-4-S1-A148

Keywords