Brain serotonin and dopamine modulators, perceptual responses and endurance performance during exercise in the heat following creatine supplementation

Hadjicharalambous, M., Kilduff, L. and Pitsiladis, Y.P. (2008) Brain serotonin and dopamine modulators, perceptual responses and endurance performance during exercise in the heat following creatine supplementation. Journal of the International Society of Sports Nutrition, 5(14), (doi: 10.1186/1550-2783-5-14)

Abstract

Background:The present experiment examined the responses of peripheral modulators and indices of brain serotonin (5-HT) and dopamine (DA) function and their association with perception of effort during prolonged exercise in the heat after creatine (Cr) supplementation. Methods:Twenty one endurance-trained males performed, in a double-blind fashion, two constant-load exercise tests to exhaustion at 63 ± 5% V O2 max in the heat (ambient temperature: 30.3 ± 0.5°C, relative humidity: 70 ± 2%) before and after 7 days of Cr (20 g·d^-1 Cr + 140 g·d^-1 glucose polymer) or placebo (Plc) (160 g·d^-1 glucose polymer) supplementation.Results:3-way interaction has shown that Cr supplementation reduced rectal temperature, heart rate, ratings of perceived leg fatigue (P < 0.05), plasma free-tryptophan (Trp) (P < 0.01) and free-Trp:tyrosine ratio (P < 0.01) but did not influence the ratio of free-Trp:large neutral amino acids or contribute in improving endurance performance (Plc group, n = 10: 50.4 ± 8.4 min vs. 51.2 ± 8.0 min, P > 0.05; Cr group, n = 11: 47.0 ± 4.7 min vs. 49.7 ± 7.5 min, P > 0.05). However, after dividing the participants into "responders" and "non-responders" to Cr, based on their intramuscular Cr uptake, performance was higher in the "responders" relative to "non-responders" group (51.7 ± 7.4 min vs.47.3 ± 4.9 min, p < 0.05).Conclusion:although Cr influenced key modulators of brain 5-HT and DA function and reduced various thermophysiological parameters which all may have contributed to the reduced effort perception during exercise in the heat, performance was improved only in the "responders" to Cr supplementation. The present results may also suggest the demanding of the pre-experimental identification of the participants into "responders" and "non-responders" to Cr supplementation before performing the main experimentation. Otherwise, the possibility of the type II error may be enhanced

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Pitsiladis, Dr Yannis
• Authors: Hadjicharalambous, M., Kilduff, L., and Pitsiladis, Y.P.
• Subjects: R Medicine > RC Internal medicine > RC1200 Sports Medicine
• College/School: College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health; College of Medical Veterinary and Life Sciences
• Journal Name: Journal of the International Society of Sports Nutrition
• Publisher: BioMed Central
• ISSN: 1550-2783
• Copyright Holders: Copyright © 2008 Hadjicharalambous et al; licensee BioMed Central Ltd.
• First Published: First published in Journal of the International Society of Sports Nutrition 5(14)
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher