| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Department of Human Biology, Nutrition Research Institute Maastricht, Maastricht University, 6200 MD Maastricht, The Netherlands
Submitted 1 December 2003 ; accepted in final form 25 May 2004
The aims of this study were to compare different tracer methods to assess whole body protein turnover during 6 h of prolonged endurance exercise when carbohydrate was ingested throughout the exercise period and to investigate whether addition of protein can improve protein balance. Eight endurance-trained athletes were studied on two different occasions at rest (4 h), during 6 h of exercise at 50% of maximal O2 uptake (in sequential order: 2.5 h of cycling, 1 h of running, and 2.5 h of cycling), and during subsequent recovery (4 h). Subjects ingested carbohydrate (CHO trial; 0.7 g CHO·kg–1·h–1) or carbohydrate/protein beverages (CHO + PRO trial; 0.7 g CHO·kg–1·h–1 and 0.25 g PRO·kg–1·h–1) at 30-min intervals during the entire study. Whole body protein metabolism was determined by infusion of L-[1-13C]leucine, L-[2H5]phenylalanine, and [15N2]urea tracers with sampling of blood and expired breath. Leucine oxidation increased from rest to exercise [27 ± 2.5 vs. 74 ± 8.8 (CHO) and 85 ± 9.5 vs. 200 ± 16.3 mg protein·kg–1·h–1 (CHO + PRO), P < 0.05], whereas phenylalanine oxidation and urea production did not increase with exercise. Whole body protein balance during exercise with carbohydrate ingestion was negative (–74 ± 8.8, –17 ± 1.1, and –72 ± 5.7 mg protein·kg–1·h–1) when L-[1-13C]leucine, L-[2H5]phenylalanine, and [15N2]urea, respectively, were used as tracers. Addition of protein to the carbohydrate drinks resulted in a positive or less-negative protein balance (–32 ± 16.3, 165 ± 4.6, and 151 ± 13.4 mg protein·kg–1·h–1) when L-[1-13C]leucine, L-[2H5]phenylalanine, and [15N2]urea, respectively, were used as tracers. We conclude that, even during 6 h of exhaustive exercise in trained athletes using carbohydrate supplements, net protein oxidation does not increase compared with the resting state and/or postexercise recovery. Combined ingestion of protein and carbohydrate improves net protein balance at rest as well as during exercise and postexercise recovery.
protein metabolism; dietary supplements; protein intake
This article has been cited by other articles:
|
|
 |
|
  M. Beelen, R. Koopman, A. P. Gijsen, H. Vandereyt, A. K. Kies, H. Kuipers, W. H. M. Saris, and L. J. C. van Loon Protein coingestion stimulates muscle protein synthesis during resistance-type exercise Am J Physiol Endocrinol Metab, July 1, 2008; 295(1): E70 - E77. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. J. Manders, R. Koopman, M. Beelen, A. P. Gijsen, W. K. Wodzig, W. H. Saris, and L. J. van Loon The Muscle Protein Synthetic Response to Carbohydrate and Protein Ingestion Is Not Impaired in Men with Longstanding Type 2 Diabetes J. Nutr., June 1, 2008; 138(6): 1079 - 1085. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Koopman, B. Pennings, A. H. G. Zorenc, and L. J. C. van Loon Protein Ingestion Further Augments S6K1 Phosphorylation in Skeletal Muscle Following Resistance Type Exercise in Males J. Nutr., August 1, 2007; 137(8): 1880 - 1886. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Koopman, A. J. M. Wagenmakers, R. J. F. Manders, A. H. G. Zorenc, J. M. G. Senden, M. Gorselink, H. A. Keizer, and L. J. C. van Loon Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects Am J Physiol Endocrinol Metab, April 1, 2005; 288(4): E645 - E653. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
