Tyrosine and its effect on cognitive function and load-carriage performance in the heat

2.50
Hdl Handle:
http://hdl.handle.net/10547/595702
Title:
Tyrosine and its effect on cognitive function and load-carriage performance in the heat
Authors:
Coull, Nicole
Abstract:
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. Acute ingestion of tyrosine (TYR), a catecholamine precursor, has been shown to improve aspects of cognitive function and mood during exposure to stressful environments, in military and sport specific settings. Currently, there is limited research exploring the optimal dose of TYR relative to blood values, to prescribe pre-exercise or before exposure to a stressor. Therefore, the purpose of experimental chapter 1 was to investigate the effects of acute TYR ingestion strategies (0, 150 and 300 mg.kg body mass-1 TYR administered in 2 equal doses, 4 h apart) on serum TYR concentrations at rest. Twenty-one healthy males were randomly allocated to one of three groups (n = 7 per group); HIGH (300 mg.kg body mass-1 TYR in total), LOW (150 mg.kg body mass-1 TYR in total) and CON (sugar free squash placebo). Ingestion of TYR was double blinded and was administered in a drink form (dissolved in 250 mL sugar free squash) in two separate doses at both 0900 and 1300. Participants consumed a standardized breakfast (0800) and lunch (1200) prior to consumption of TYR and remained in the laboratory from 0900-1700 having blood drawn every hour from a cannula. Measures of gastric discomfort were also recorded. Significant differences in serum TYR concentrations were observed between groups (p < 0.001), with the HIGH dose (399 ± 69 μmol/L) resulting in the largest elevation compared to the LOW dose (279 ± 76 μmol/L) and CON (64 ± 11 μmol/L). Ingesting TYR as a double-dose did not significantly increase the peak in serum TYR compared to the first dose in both groups; LOW (221 vs 279 μmol/L) and HIGH dose (350 vs 399 μmol/L) (p > 0.05). No significant differences in gastric discomfort were observed between groups (p > 0.05). This study demonstrates that ingestion of a single dose of 150 mg.kg body mass-1 TYR may be sufficient to elevate serum TYR concentrations and that the peak in TYR concentration typically occurs 2 h post ingestion (without the need for a second identical dose 4 h later). Experimental chapter 2 was designed to investigate the effects of TYR ingestion on steady state exercise, cognitive function and time-trial performance in the heat, utilising the identified dose from the findings of experimental chapter 1. Eight recreationally active, healthy males 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 TYR (same as PLA plus 150 mg.kg body mass-1 TYR powder) 1 h pre-exercise. Participants completed a 60 min walk at 6.5 km.h, followed by a 2.4 km time-trial carrying a 25 kg backpack in 40°C; 30% RH. Cognitive function (vigilance, dual-task and simple reaction time) was assessed at 5 time-points; pre-ingestion, pre-exercise, 30 min into exercise, post 60 min exercise and post time-trial. Traditional physiological (HR), perceptual (RPE, TSS) and temperature (rectal and skin temperature) measures were recorded throughout exercise. A significant increase from pre-post 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, perceptual or temperature measures between conditions (p > 0.05). The main findings presented within this thesis indicate that although it was identified that a single dose of 150 mg.kg body mass-1 was sufficient to significantly elevate serum TYR concentrations, ingestion of this dose did not influence cognitive function or time-trial performance in the heat. This is surprising since ingestion of similar doses have significantly improved aspects of cognitive function previously during exercise-heat-stress. In conclusion it appears that under the conditions of the present study, TYR is not a useful ergogenic aid. Future research should aim to elucidate the central effects of TYR to enable a better understanding of its mechanistic properties. Key words: Heat-stress; central fatigue; tyrosine; cognitive function
Citation:
Coull, N. (2015) 'Tyrosine and its Effect on Cognitive Function and Load-carriage Performance in the Heat'. MSC by research thesis. University of Bedfordshire
Publisher:
University of Bedfordshire
Issue Date:
Dec-2015
URI:
http://hdl.handle.net/10547/595702
Type:
Thesis or dissertation
Language:
en
Description:
A thesis submitted to the University of Bedfordshire in partial fulfilment of the requirements for the degree of Masters of Science by Research
Appears in Collections:
Masters e-theses

Full metadata record

DC FieldValue Language
dc.contributor.authorCoull, Nicoleen
dc.date.accessioned2016-02-05T11:50:22Zen
dc.date.available2016-02-05T11:50:22Zen
dc.date.issued2015-12en
dc.identifier.citationCoull, N. (2015) 'Tyrosine and its Effect on Cognitive Function and Load-carriage Performance in the Heat'. MSC by research thesis. University of Bedfordshireen
dc.identifier.urihttp://hdl.handle.net/10547/595702en
dc.descriptionA thesis submitted to the University of Bedfordshire in partial fulfilment of the requirements for the degree of Masters of Science by Researchen
dc.description.abstractProlonged 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. Acute ingestion of tyrosine (TYR), a catecholamine precursor, has been shown to improve aspects of cognitive function and mood during exposure to stressful environments, in military and sport specific settings. Currently, there is limited research exploring the optimal dose of TYR relative to blood values, to prescribe pre-exercise or before exposure to a stressor. Therefore, the purpose of experimental chapter 1 was to investigate the effects of acute TYR ingestion strategies (0, 150 and 300 mg.kg body mass-1 TYR administered in 2 equal doses, 4 h apart) on serum TYR concentrations at rest. Twenty-one healthy males were randomly allocated to one of three groups (n = 7 per group); HIGH (300 mg.kg body mass-1 TYR in total), LOW (150 mg.kg body mass-1 TYR in total) and CON (sugar free squash placebo). Ingestion of TYR was double blinded and was administered in a drink form (dissolved in 250 mL sugar free squash) in two separate doses at both 0900 and 1300. Participants consumed a standardized breakfast (0800) and lunch (1200) prior to consumption of TYR and remained in the laboratory from 0900-1700 having blood drawn every hour from a cannula. Measures of gastric discomfort were also recorded. Significant differences in serum TYR concentrations were observed between groups (p < 0.001), with the HIGH dose (399 ± 69 μmol/L) resulting in the largest elevation compared to the LOW dose (279 ± 76 μmol/L) and CON (64 ± 11 μmol/L). Ingesting TYR as a double-dose did not significantly increase the peak in serum TYR compared to the first dose in both groups; LOW (221 vs 279 μmol/L) and HIGH dose (350 vs 399 μmol/L) (p > 0.05). No significant differences in gastric discomfort were observed between groups (p > 0.05). This study demonstrates that ingestion of a single dose of 150 mg.kg body mass-1 TYR may be sufficient to elevate serum TYR concentrations and that the peak in TYR concentration typically occurs 2 h post ingestion (without the need for a second identical dose 4 h later). Experimental chapter 2 was designed to investigate the effects of TYR ingestion on steady state exercise, cognitive function and time-trial performance in the heat, utilising the identified dose from the findings of experimental chapter 1. Eight recreationally active, healthy males 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 TYR (same as PLA plus 150 mg.kg body mass-1 TYR powder) 1 h pre-exercise. Participants completed a 60 min walk at 6.5 km.h, followed by a 2.4 km time-trial carrying a 25 kg backpack in 40°C; 30% RH. Cognitive function (vigilance, dual-task and simple reaction time) was assessed at 5 time-points; pre-ingestion, pre-exercise, 30 min into exercise, post 60 min exercise and post time-trial. Traditional physiological (HR), perceptual (RPE, TSS) and temperature (rectal and skin temperature) measures were recorded throughout exercise. A significant increase from pre-post 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, perceptual or temperature measures between conditions (p > 0.05). The main findings presented within this thesis indicate that although it was identified that a single dose of 150 mg.kg body mass-1 was sufficient to significantly elevate serum TYR concentrations, ingestion of this dose did not influence cognitive function or time-trial performance in the heat. This is surprising since ingestion of similar doses have significantly improved aspects of cognitive function previously during exercise-heat-stress. In conclusion it appears that under the conditions of the present study, TYR is not a useful ergogenic aid. Future research should aim to elucidate the central effects of TYR to enable a better understanding of its mechanistic properties. Key words: Heat-stress; central fatigue; tyrosine; cognitive functionen
dc.language.isoenen
dc.publisherUniversity of Bedfordshireen
dc.subjectheat-stressen
dc.subjectcentral fatigueen
dc.subjecttyrosineen
dc.subjectcognitive functionen
dc.subjectB120 Physiologyen
dc.subjectload carriage performanceen
dc.titleTyrosine and its effect on cognitive function and load-carriage performance in the heaten
dc.typeThesis or dissertationen
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