Double blind carbohydrate ingestion does not improve exercise duration in warm humid conditions

Camila Nassif, Ana Paula Araujo Ferreira, Aline Regina Gomes, Luciana De Martin Silva, Emerson Silami Garcia, Frank E. Marino

Research output: Contribution to journalJournal Articlepeer-review

11 Citations (Scopus)


The positive effects of carbohydrate (CHO) supplementation on endurance exercise are well documented but the placebo (PLAc) effect can make the ergogenic qualities of substances more difficult to determine. Therefore, this study tested the effect of double blind ingestion of PLAcand CHOcin capsules versus known capsule (CHOk) ingestion on prolonged exercise heat stress. Nine well trained male volunteers (mean ± S.D.: 23 ± 3 years; 62.4 ± 6.5 kg and 65.8 ± 5.2 mL kg-1min-1peak oxygen consumption) exercised at 60% of maximum power output until volitional exhaustion (TTE) in the three different conditions. Capsules were ingested with 252 ± 39 mL of water. Blood glucose in CHOcand CHOkwas similar but higher (p <0.05) than PLAcfrom 45 min to end of exercise. There were no differences in TTE between PLAc(125.2 ± 37.1 min) or CHOc(138.8 ± 47.0 min) or between CHOcand CHOk(155.8 ± 54.2 min). Time to volitional exhaustion was different between PLAcand CHOk(p <0.05). Increased TTE resulted when participants and researchers knew the capsule content, but not in the double blind condition. The difference could be related to a combined effect of CHO ingestion and knowledge of what was ingested possibly acting as a potent psychological motivator. © 2007 Sports Medicine Australia.
Original languageEnglish
Pages (from-to)72-79
Number of pages8
JournalJournal of Science and Medicine in Sport
Issue number1
Publication statusPublished - Jan 2008
Externally publishedYes


  • Carbohydrate
  • Exercise
  • Heat stress
  • Metabolism
  • Placebo
  • Rectal temperature


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