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Articles in PresS, published online ahead of print February 1, 2002
J Appl Physiol, 10.1152/jap.01065.2001
Submitted on October 23, 2001
Accepted on January 25, 2002
1 Department of Exercise and Sport Science, Manchester Metropolitan University, Alsager, United Kingdom
2 School of Sport, Exercise and Leisure, University of Surrey Roehampton, London, United Kingdom
3 University Department of Anaesthesia, Withington Hospital, Manchester, United Kingdom
* To whom correspondence should be addressed. E-mail: A.M.Jones{at}mmu.ac.uk.
The purpose of this study was to test the effect of oral creatine (Cr) supplementation on oxygen uptake (VO2) kinetics during moderate (below the ventilatory threshold, VT) and heavy (above the VT) submaximal exercise. Nine subjects (7 males; mean ± S.D. age 28 ± 3 years, body mass 73.2 ± 5.6 kg, VO2 max 46.4 ± 8.0 ml.kg-1.min-1) volunteered to participate in this study. The subjects performed transitions of 6 min duration from unloaded cycling to moderate exercise (80 % VT; 8-12 repeats) and heavy exercise (50 % 
; i.e. half-way between VT and VO2 max; 4-6 repeats) both in the control condition and following Cr loading, in a crossover design. The Cr loading regimen involved the oral consumption of 20 g per day of creatine monohydrate for 5 days, followed by a maintenance dose of 5 g per day thereafter. The VO2 was measured breath-by-breath and modelled using two (moderate) or three (heavy) exponential terms. For moderate exercise, there were no differences in the parameters of the VO2 kinetic response between the control and Cr-loaded conditions. For heavy exercise, the time-based parameters of the VO2 response were unchanged but the amplitude of the primary component was significantly reduced with Cr loading (mean ± SEM, control: 2.00 ± 0.12; Cr-loaded: 1.92 ± 0.10 l.min-1; P<0.05) as was the end-exercise VO2 (control: 2.19 ± 0.13; Cr-loaded: 2.12 ± 0.14 l.min-1; P<0.05). The magnitude of the reduction in submaximal VO2 with Cr loading was significantly correlated with the % of type II fibres in the m. vastus lateralis (r = 0.87; P<0.01; n = 7), indicating that the effect might be related to changes in motor unit recruitment patterns or the volume of muscle activated.
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