caa a22 4500 469054190 CHVBK 20180323132838.0 cr unu---uuuuu 170328e19921101xx s 000 0 eng 10.1007/BF00602357 doi (NATIONALLICENCE)springer-10.1007/BF00602357 Effects of carbohydrate feedings on plasma free tryptophan and branched-chain amino acids during prolonged cycling [Elektronische Daten] [J. Davis, Stephen Bailey, Jeffrey Woods, Floyd Galiano, Marc Hamilton, William Bartoli] Summary: Brain serotonin (5-hydroxytryptamine, 5-HT) has been suggested to be involved in central fatigue during prolonged exercise. Changes in the ratio of plasma free tryptophan (free Trp) to branched-chain amino acids (BCAA) are associated with altered brain 5-HT synthesis. The purposes of this study were to describe systematically the effects of prolonged exercise on changes in plasma free Trp and BCAA and to examine the effects of carbohydrate (CHO) feedings on these same variables. Eight well-trained men [ $$\dot V{\text{O}}_{\text{2}} $$ max = 57.8 (SE 4.1) ml kg−1 min−1] cycled for up to 255 min at a power output corresponding toVO2 at lactate threshold (approximately 68%VO2max) on three occasions separated by at least 1 week. Subjects drank 5 ml kg−1 body wt−1 of either a water placebo, or a liquid beverage containing a moderate (6% CHO) or high (12% CHO) concentration of carbohydrate beginning at min 14 of exercise and every 30 min thereafter. Exercise time to fatigue was shorter in subjects receiving placebo [190 (SE 4) min] as compared to 6% CHO [235 (SE 10) min] and 12% CHO [234 (SE 9) min] (P<0.05). Glucose and insulin decreased in the placebo group, and free Trp, free-Trp/BCAA, and free fatty acids increased approximately five- to sevenfold (P < 0.05). These changes were attenuated in a dose-related manner by the carbohydrate drinks. Plasma free Trp and plasma free fatty acids were highly correlated (r=0.86,P<0.001). Plasma BCAA did not change in the placebo group, but decreased slightly in those receiving 6% CHO and 12% CHO (P<0.05). No differences in heart rate, $$\dot V{\text{O}}_{\text{2}} $$ , plasma volume and respiratory exchange ratio were found. The results indicate that free Trp and free Trp/BCAA increase progressively during prolonged cycling to fatigue. This response was attenuated by CHO feedings. Changes in plasma free fatty acids probably play a prominent role in these responses. Springer-Verlag, 1992 Amino acids nationallicence Carbohydrate feedings nationallicence Free fatty acids nationallicence Fatigue nationallicence Serotonin nationallicence Davis J. Department of Exercise Science, School of Public Health, University of South Carolina, 29208, Columbia, SC, USA aut Bailey Stephen Department of Exercise Science, School of Public Health, University of South Carolina, 29208, Columbia, SC, USA aut Woods Jeffrey Department of Exercise Science, School of Public Health, University of South Carolina, 29208, Columbia, SC, USA aut Galiano Floyd Department of Exercise Science, School of Public Health, University of South Carolina, 29208, Columbia, SC, USA aut Hamilton Marc Department of Exercise Science, School of Public Health, University of South Carolina, 29208, Columbia, SC, USA aut Bartoli William Department of Exercise Science, School of Public Health, University of South Carolina, 29208, Columbia, SC, USA aut European Journal of Applied Physiology and Occupational Physiology Springer-Verlag 65/6(1992-11-01), 513-519 0301-5548 65:6<513 1992 65 421 https://doi.org/10.1007/BF00602357 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00602357 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Davis J. Department of Exercise Science, School of Public Health, University of South Carolina, 29208, Columbia, SC, USA aut NATIONALLICENCE 700 1- Bailey Stephen Department of Exercise Science, School of Public Health, University of South Carolina, 29208, Columbia, SC, USA aut NATIONALLICENCE 700 1- Woods Jeffrey Department of Exercise Science, School of Public Health, University of South Carolina, 29208, Columbia, SC, USA aut NATIONALLICENCE 700 1- Galiano Floyd Department of Exercise Science, School of Public Health, University of South Carolina, 29208, Columbia, SC, USA aut NATIONALLICENCE 700 1- Hamilton Marc Department of Exercise Science, School of Public Health, University of South Carolina, 29208, Columbia, SC, USA aut NATIONALLICENCE 700 1- Bartoli William Department of Exercise Science, School of Public Health, University of South Carolina, 29208, Columbia, SC, USA aut NATIONALLICENCE 773 0- European Journal of Applied Physiology and Occupational Physiology Springer-Verlag 65/6(1992-11-01), 513-519 0301-5548 65:6<513 1992 65 421 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer