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Acute tryptophan depletion does not improve endurance cycling capacity in a warm environment.
MedLine Citation:
PMID:  23179087     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Newsholme's theory of central fatigue suggests that acute tryptophan depletion should improve endurance exercise capacity in a warm environment by reducing serotonergic activity in the brain. Eight males cycled to volitional exhaustion at 55 % [Formula: see text] peak in 30.1 ± 0.5 °C and 30 ± 7 % relative humidity on two separate occasions, after consuming either an amino acid load to deplete their circulating tryptophan concentration (TD), or a control amino acid load (CON). Blood samples were taken before ingesting the amino acids, before the start of exercise, every 15 min during exercise and at the point of exhaustion. Heart rate (HR), core (Tc) and skin (Tsk) temperatures and ratings of perceived exertion (RPE) and thermal comfort (TC) were also monitored every 10 min during exercise. Plasma tryptophan (P = 0.003) and free tryptophan (P < 0.001) concentrations, and the free tryptophan to branched-chain amino acid ratio (P = 0.004) were all lower on the TD trial than on the CON trial. There was no difference in endurance exercise capacity (TD 99.2 ± 24.4 min as compared to CON 108.4 ± 21.6 min; P = 0.088). There was a tendency for HR (P = 0.053) and Tc (P = 0.069) to be higher on the TD trials. There were no differences for any of the other parameters. Endurance cycling capacity in a warm environment is not improved by acute tryptophan depletion, suggesting tryptophan availability is not a significant factor in the development of fatigue in such situations.
Authors:
Ruth M Hobson; Phillip Watson; Ronald J Maughan
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-11-21
Journal Detail:
Title:  Amino acids     Volume:  -     ISSN:  1438-2199     ISO Abbreviation:  Amino Acids     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-26     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9200312     Medline TA:  Amino Acids     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
School of Science and Technology, Nottingham Trent University, Nottingham, NG11 8NS, UK, ruth.hobson@ntu.ac.uk.
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