Carbohydrate dependence during prolonged simulated cycling time trials.
Eur J Appl Physiol
; 116(4): 781-90, 2016 Apr.
Article
em En
| MEDLINE
| ID: mdl-26850449
ABSTRACT
PURPOSE:
We determined the effect of suppressing lipolysis via administration of Nicotinic acid (NA) and pre-exercise feeding on rates of whole-body substrate utilisation and cycling time trial (TT) performance.METHODS:
In a randomised, single-blind, crossover design, eight trained male cyclists/triathletes completed two series of TTs in which they performed a predetermined amount of work calculated to last ~60, 90 and 120 min. TTs were undertaken after a standardised breakfast (2 g kg(-1) BM of carbohydrate (CHO)) and ingestion of capsules containing either NA or placebo (PL).RESULTS:
Plasma [free fatty acids] were suppressed with NA, but increased in the later stages of TT90 and TT120 with PL (p < 0.05). There was no treatment effect on time to complete TT60 (60.4 ± 4.1 vs. 59.3 ± 3.4 min) or TT90 (90.4 ± 9.1 vs. 89.5 ± 6.6 min) for NA and PL, respectively. However, TT120 was slower with NA (123.1 ± 5.7 vs. 120.1 ± 8.7 min, p < 0.001), which coincided with a decline in plasma [glucose] during the later stages of this ride (p < 0.05). For TTs of the same duration, the rates of whole-body CHO oxidation were unaffected by NA, but decreased with increasing TT time (p < 0.05). CHO was the predominant substrate for all TTs contributing between 83 and 94 % to total energy expenditure, although there was a small use of lipid-based fuels for all rides.CONCLUSION:
(1) NA impaired cycling TT performance lasting 120 min, (2) cycling TTs lasting from 60 to 120 min are CHO dependent, and (3) there is an obligatory use of lipid-based fuels in TTs lasting 1-2 h.Palavras-chave
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Complexo Vitamínico B
/
Carboidratos da Dieta
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Exercício Físico
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Desempenho Atlético
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Niacina
Tipo de estudo:
Clinical_trials
Limite:
Adolescent
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Adult
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Humans
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Male
Idioma:
En
Ano de publicação:
2016
Tipo de documento:
Article