Effect of oral creatine ingestion on parameters of the work rate-time relationship and time to exhaustion in high-intensity cycling

J C Smith, D P Stephens, E L Hall, A W Jackson, Conrad P Earnest

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The relationship between work rate (overhead dot W) and time to exhaustion (t) during intense exercise is commonly described by either a hyperbolic function (NLin), t = W'/( overhead dot W - overhead dot W-cp), or by its linear equivalent (LinW) W-lim = W' + overhead dot Q-cp(t). The parameter overhead dot W-cp (critical power) has been described as an inherent characteristic of the aerobic energy system, while W' has been shown to be a rapid estimate of anaerobic work capacity. Recent studies have demonstrated that oral supplementation of creatine monohydrate (CrH-2O) increases total muscle creatine stores, and have linked these increases to improved performances in intense intermittent exercise. This study was conducted to determine the effect of CrH-2O supplementation on estimates of W' and overhead dot W-cp derived from the NLin and LinW equations, and to determine the effect of CrH-2O on t in exhaustive constant power exercise of different intensities. Fifteen active but untrained university students completed three phases of testing on a cycle ergometer: (1) familiarization, three learning trials, (2) baseline determination of W' and overhead dot W-cp, four bouts performed at a overhead dot W selected to elicit fatigue in 90-600 s, and (3) experimental determination of W' and overhead dot W-cp, four bouts performed at the same overhead dot Q as baseline, but performed after 5 days of ingesting either a placebo (4 times 6 g of glucose/day) or CrH-2O (4 times 5 g of CrH-2O and 1 g glucose/day). Testing was administered in a double-blind manner. Analyses of covariance revealed a significant effect for CrH-2O on both estimates of W' (NLin, P = 0.04; LinW, P lt 0.0 1), but not on estimates of overhead dot W-cp (NLin, P = 0.37; LinW; P = 0.30). Within groups, t was significantly different for only CrH-2O at the two highest overhead dot Ws (P = 0.04). It is concluded that oral ingestion of CrH-2O increases estimates of W' due to an improved t at the shorter, more intense exercise bouts.
Original languageEnglish
Pages (from-to)360-365
Number of pages6
JournalEuropean Journal of Applied Physiology
Issue number4
Publication statusPublished - 1998



  • Critical Power
  • Animals
  • Sports Medicine
  • (Metabolism--Energy and Respiratory Metabolism)
  • General and Miscellaneous--General)
  • General and Miscellaneous--Exercise and Physical Therapy (1970- ))
  • Mammals
  • Human
  • Humans
  • Time To Exhaustion
  • High-Intensity Cycling
  • Chordates
  • Aerobic Capacity
  • Creatine
  • Oral Ingestion
  • Peptides and Amino Acids (1972- ))
  • Primates
  • (Nutrition--Proteins
  • Vertebrates
  • Research Article
  • (Physiology
  • Work Rate-Time Relationship

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