title: Effect of timing of protein and carbohydrate intake after resistance exercise on nitrogen balance in trained and untrained young men.
abstract: BACKGROUND
  Resistance exercise alters the post-exercise response of anabolic and catabolic hormones. A previous study indicated that the turnover of muscle protein in trained individuals is reduced due to alterations in endocrine factors caused by resistance training, and that muscle protein accumulation varies between trained and untrained individuals due to differences in the timing of protein and carbohydrate intake. We investigated the effect of the timing of protein and carbohydrate intake after resistance exercise on nitrogen balance in trained and untrained young men.
  
  
  METHODS
  Subjects were 10 trained healthy men (mean age, 23 ± 4 years; height, 173.8 ± 3.1 cm; weight, 72.3 ± 4.3 kg) and 10 untrained healthy men (mean age, 23 ± 1 years; height, 171.8 ± 5.0 cm; weight, 64.5 ± 5.0 kg). All subjects performed four sets of 8 to 10 repetitions of a resistance exercise (comprising bench press, shoulder press, triceps pushdown, leg extension, leg press, leg curl, lat pulldown, rowing, and biceps curl) at 80% one-repetition maximum. After each resistance exercise session, subjects were randomly divided into two groups with respect to intake of protein (0.3 g/kg body weight) and carbohydrate (0.8 g/kg body weight) immediately after (P0) or 6 h (P6) after the session. All subjects were on an experimental diet that met their individual total energy requirement. We assessed whole-body protein metabolism by measuring nitrogen balance at P0 and P6 on the last 3 days of exercise training.
  
  
  RESULTS
  The nitrogen balance was significantly lower in the trained men than in the untrained men at both P0 (P <0.05) and P6 (P <0.01). The nitrogen balance in trained men was significantly higher at P0 than at P6 (P <0.01), whereas that in the untrained men was not significantly different between the two periods.
  
  
  CONCLUSIONS
  The timing of protein and carbohydrate intake after resistance exercise influences nitrogen balance differently in trained and untrained young men.
authors.affiliation: Faculty of Health Science, Department of Nutrition Management, Hyogo University, 2301 Arazaike, 675-0195 Hiraoka-cho, Kakogawa City, Hyogo, Japan. h-mori@hyogo-dai.ac.jp.
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Mori
mesh_terms: D000328:Adult; D056352:Athletes; D004040:Dietary Carbohydrates / Q000378:metabolism*; D004044:Dietary Proteins / Q000378:metabolism*; D002149:Energy Intake / Q000502:physiology*; D006801:Humans; D008297:Male; D009584:Nitrogen / Q000378:metabolism* / Q000652:urine; D055070:Resistance Training; D013997:Time Factors; D014891:Weight Lifting / Q000502:physiology*; D055815:Young Adult
chemical_list: D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D009584:Nitrogen
references.citation: Am J Physiol Endocrinol Metab. 2002 Oct;283(4):E648-57
references.pmid: 12217881
references.citation: Metabolism. 1998 Nov;47(11):1303-7
references.pmid: 9826204
references.citation: Med Sci Sports Exerc. 2003 Mar;35(3):449-55
references.pmid: 12618575
references.citation: J Appl Physiol (1985). 1997 Jun;82(6):1882-8
references.pmid: 9173954
references.citation: J Appl Physiol (1985). 2009 May;106(5):1692-701
references.pmid: 19036897
references.citation: J Appl Physiol (1985). 2004 Feb;96(2):674-8
references.pmid: 14594866
references.citation: J Appl Physiol (1985). 1992 May;72(5):1854-9
references.pmid: 1601794
references.citation: Proc Natl Acad Sci U S A. 1997 Dec 23;94(26):14930-5
references.pmid: 9405716
references.citation: J Strength Cond Res. 2008 Sep;22(5):1617-24
references.pmid: 18714223
references.citation: J Appl Physiol (1985). 2000 Feb;88(2):386-92
references.pmid: 10658002
references.citation: Am J Physiol Regul Integr Comp Physiol. 2008 Jan;294(1):R172-8
references.pmid: 18032468
references.citation: Can J Appl Physiol. 1995 Dec;20(4):480-6
references.pmid: 8563679
references.citation: Metabolism. 2006 May;55(5):570-7
references.pmid: 16631431
references.citation: Int J Sport Nutr Exerc Metab. 2009 Apr;19(2):172-85
references.pmid: 19478342
references.citation: J Appl Physiol (1985). 1992 Oct;73(4):1383-8
references.pmid: 1280254
references.citation: J Nutr. 2007 Apr;137(4):985-91
references.pmid: 17374665
references.citation: Am J Physiol. 1997 Jul;273(1 Pt 1):E99-107
references.pmid: 9252485
references.citation: J Gerontol A Biol Sci Med Sci. 2010 Oct;65(10):1068-76
references.pmid: 20622139