title: Strategies of dietary carbohydrate manipulation and their effects on performance in cycling time trials.
abstract: The relationship between carbohydrate (CHO) availability and exercise performance has been thoroughly discussed. CHO improves performance in both prolonged, low-intensity and short, high-intensity exercises. Most studies have focused on the effects of CHO supplementation on the performance of constant-load, time-to-exhaustion exercises. Nevertheless, in the last 20 years, there has been a consistent increase in research on the effects of different forms of CHO supplementation (e.g., diet manipulation, CHO supplementation before or during exercise) on performance during closed-loop exercises, such as cycling time trials (TTs). A TT is a highly reproducible exercise and reflects a more realistic scenario of competition compared with the time-to-exhaustion test. CHO manipulation has been performed in various time periods, such as days before, minutes before, during a TT or in a matched manner (e.g. before and during a TT). The purpose of this review is to address the possible effects of these different forms of CHO manipulation on the performance during a cycling TT. Previous data suggest that when a high-CHO diet (~70% of CHO) is consumed before a TT (24-72 h before), the mean power output increases and reduces the TT time. When participants are supplemented with CHO (from 45 to 400 g) prior to a TT (from 2 min to 6 h before the TT), mean power output and time seem to improve due to an increase in CHO oxidation. Similarly, this performance also seems to increase when participants ingest CHO during a TT because such consumption maintains plasma glucose levels. A CHO mouth rinse also improves performance by activating several brain areas related to reward and motor control through CHO receptors in the oral cavity. However, some studies reported controversial results concerning the benefits of CHO on TT performance. Methodological issues such as time of supplementation, quantity, concentration and type of CHO ingested, as well as the TT duration and intensity, should be considered in future studies because small variations in any of these factors may have beneficial or adverse effects on TT performance.
authors: Sports Science Research Group, Faculty of Nutrition, Federal University of Alagoas, Lorival Melo Mota Avenue, S/N, Tabuleiro do Martins, Maceio, AL 57072970, Brazil.
authors: Carlos Rafaell
authors: CR
authors: Correia-Oliveira
authors: Romulo
authors: R
authors: Bertuzzi
authors: Maria Augusta Peduti
authors: MA
authors: Dal'Molin Kiss
authors: Adriano Eduardo
authors: AE
authors: Lima-Silva
mesh_terms: D054874:Athletic Performance / Q000502:physiology*; D001642:Bicycling / Q000502:physiology*; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D006801:Humans; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000187:drug effects*; D017410:Practice Guidelines as Topic
chemical_list: D004040:Dietary Carbohydrates
references: J Physiol. 2009 Apr 15;587(Pt 8):1779-94
references: 19237430
references: Med Sci Sports Exerc. 1989 Feb;21(1):59-65
references: 2927302
references: Int J Sport Nutr Exerc Metab. 2001 Dec;11(4):490-502
references: 11915783
references: Int J Sports Med. 1998 Aug;19(6):415-8
references: 9774209
references: Med Sci Sports Exerc. 2007 Aug;39(8):1374-9
references: 17762371
references: Int J Sport Nutr Exerc Metab. 2009 Jun;19(3):275-84
references: 19574614
references: Med Sci Sports Exerc. 2004 Dec;36(12):2107-11
references: 15570147
references: Med Sci Sports Exerc. 2002 Sep;34(9):1492-8
references: 12218744
references: J Appl Physiol (1985). 1996 Dec;81(6):2644-50
references: 9018517
references: Eur J Appl Physiol Occup Physiol. 1994;69(4):287-93
references: 7851362
references: Int J Sport Nutr Exerc Metab. 2003 Dec;13(4):489-503
references: 14967872
references: Eur J Appl Physiol. 2010 Apr;108(6):1133-40
references: 20091180
references: J Appl Physiol (1985). 1987 Dec;63(6):2388-95
references: 3325488
references: J Appl Physiol (1985). 1986 Jul;61(1):165-72
references: 3525502
references: Eur J Appl Physiol. 2003 Jan;88(4-5):444-52
references: 12527976
references: Med Sci Sports Exerc. 1995 Feb;27(2):200-10
references: 7723643
references: Eur J Appl Physiol. 2008 Nov;104(5):831-7
references: 18813941
references: Sports Med. 2007;37(8):647-67
references: 17645369
references: Med Sci Sports Exerc. 1995 Sep;27(9):1278-83
references: 8531626
references: J Appl Physiol (1985). 1987 Mar;62(3):983-8
references: 3571097
references: J Appl Physiol (1985). 2000 Apr;88(4):1284-90
references: 10749820
references: Med Sci Sports Exerc. 2000 Sep;32(9):1642-7
references: 10994918
references: Psychophysiology. 2011 Feb;48(2):277-84
references: 20624251
references: BMJ. 2012 Jul 18;345:e4848
references: 22810389
references: Int J Sport Nutr. 1995 Sep;5(3):215-24
references: 8547939
references: Int J Sport Nutr Exerc Metab. 2001 Dec;11(4):503-12
references: 11915784
references: BMJ. 2012 Jul 18;345:e4737
references: 22810386
references: Int J Sports Med. 1999 May;20(4):227-31
references: 10376478
references: Eur J Appl Physiol. 2006 Sep;98(1):62-70
references: 16799816
references: Sports Med. 2010 Sep 1;40(9):747-63
references: 20726621
references: Int J Sport Nutr. 1997 Sep;7(3):207-18
references: 9286744
references: Metabolism. 1983 Aug;32(8):769-76
references: 6865776
references: Scand J Med Sci Sports. 2010 Feb;20(1):105-11
references: 19000099
references: Int J Sport Nutr Exerc Metab. 2004 Oct;14(5):541-9
references: 15673100
references: J Appl Physiol Respir Environ Exerc Physiol. 1983 Jul;55(1 Pt 1):230-5
references: 6350247
references: J Appl Physiol (1985). 2003 Jun;94(6):2181-7
references: 12736189
references: Int J Sport Nutr Exerc Metab. 2009 Aug;19(4):400-9
references: 19827464
references: Int J Sports Med. 1997 Feb;18(2):125-9
references: 9081269
references: Int J Sport Nutr. 1994 Mar;4(1):46-53
references: 8167654
references: Eur J Appl Physiol Occup Physiol. 1997;75(5):407-12
references: 9189727
references: Appl Physiol Nutr Metab. 2008 Dec;33(6):1079-85
references: 19088765
references: BMJ. 2012 Jul 18;345:e4797
references: 22810388
references: Acta Physiol Scand. 1967 Oct-Nov;71(2):140-50
references: 5584523
references: Braz J Med Biol Res. 2009 May;42(5):404-12
references: 19377788
references: Med Sci Sports Exerc. 2008 Feb;40(2):275-81
references: 18202575
references: J Sports Sci. 2008 Feb 1;26(3):227-33
references: 18074296
references: Int J Sport Nutr. 1995 Mar;5(1):25-36
references: 7749423
references: Med Sci Sports Exerc. 1996 Feb;28(2):266-70
references: 8775164
references: J Sports Sci. 2004 Jan;22(1):39-55
references: 14971432
references: Metabolism. 1999 Dec;48(12):1509-17
references: 10599981
references: Med Sci Sports Exerc. 1989 Oct;21(5):598-604
references: 2691821
references: Br J Sports Med. 1994 Jun;28(2):105-9
references: 7921908
references: J Sports Sci. 1997 Apr;15(2):223-30
references: 9258853
references: Med Sci Sports Exerc. 2008 Dec;40(12):2096-104
references: 18981939
references: J Appl Physiol (1985). 1996 Aug;81(2):853-7
references: 8872656
references: Am J Clin Nutr. 1991 Nov;54(5):866-70
references: 1951158
references: Med Sci Sports Exerc. 2006 Aug;38(8):1476-83
references: 16888462
references: Appl Physiol Nutr Metab. 2012 Apr;37(2):276-83
references: 22436075
references: Br J Sports Med. 2005 Jan;39(1):34-8
references: 15618337
references: J Appl Physiol (1985). 2000 Jan;88(1):113-9
references: 10642370
references: BMJ. 2012 Jul 18;345:e4753
references: 22810387
references: Int J Sports Med. 1995 Oct;16(7):461-5
references: 8550255