European Journal of Applied Physiology

, Volume 116, Issue 4, pp 781–790 | Cite as

Carbohydrate dependence during prolonged simulated cycling time trials

  • Samuel L. Torrens
  • José L. Areta
  • Evelyn B. Parr
  • John A. Hawley
Original Article



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.


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).


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.


(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.


Fat High-intensity cycling Nicotinic acid Substrate utilisation Performance 



Body mass




Fatty acid


Free fatty acids


Heart rate


Intramuscular triglyceride


Linear mixed model


Nicotinic acid




Peak power output


Respiratory exchange ratio


Rating of perceived exertion




Time trial

\({\dot V}\)O2max

Maximal oxygen consumption




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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Samuel L. Torrens
    • 1
  • José L. Areta
    • 2
  • Evelyn B. Parr
    • 1
  • John A. Hawley
    • 1
    • 3
  1. 1.Mary MacKillop Institute for Health Research, Centre for Exercise and NutritionAustralian Catholic UniversityMelbourneAustralia
  2. 2.Department of Physical PerformanceNorwegian School of Sport SciencesOsloNorway
  3. 3.Research Institute for Sport and Exercise SciencesLiverpool John Moores UniversityLiverpoolUK

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