Original articles  BODY COMPOSITION, SPORT NUTRITION AND SUPPLEMENTATION 

The Journal of Sports Medicine and Physical Fitness 2002 September;42(3):320-9

Copyright © 2009 EDIZIONI MINERVA MEDICA

language: English

Pre-exercise oral creatine ingestion does not improve prolonged intermittent sprint exercise in humans

Preen D., Dawson B., Goodman C., Lawrence S. *, Beilby J. **, Ching S. **

From the Department of Human Movement and Exercise Science, The University of Western Australia, Crawley, Australia *Western Australian Institute of Sport, Challenge Stadium Mt Claremont, Australia **The Western Australian Centre for Pathology and Medical Research, QEII Medical Centre, Nedlands, Australia

Back­ground. ­This inves­ti­ga­tion deter­mined ­whether pre-exer­cise ­oral Cr inges­tion ­could ­enhance pro­longed inter­mit­tent ­sprint exer­cise per­for­mance.
­Methods. Experi­mental ­design: a ran­dom­ised, ­double-­blind cross­over ­design was ­employed. Set­ting: ­testing was per­formed at the ­Western Aus­tra­lian Insti­tute of ­Sport and par­tic­i­pants ­were mon­i­tored and ­treated by ­both sci­en­tific and med­ical per­sonnel. Par­tic­i­pants: ­eight ­active, but not ­well-­trained ­males ­with a back­ground in mul­tiple-­sprint ­based ­sports ­acted as sub­jects for ­this inves­ti­ga­tion. Inter­ven­tions: sub­jects ­ingested ­either 15 g Cr.H2O or pla­cebo 120 min and 60 min ­prior to the ­start of an 80-min max­imal ­sprint ­cycling ­task (10 ­sets of mul­tiple 6-sec ­sprints ­with var­ying ­active recov­eries). Sub­jects ­were ­retested 14 ­days ­later, ­being ­required to ­ingest the alter­nate sup­ple­ment and ­repeat the exer­cise ­test. Meas­ures: per­for­mance var­i­ables (­work ­done and ­peak ­power) ­were ­obtained ­throughout the exer­cise chal­lenge. ­Muscle biop­sies (­vastus lat­er­alis) ­were ­taken preexer­cise as ­well as imme­di­ately and 3 min ­post-exer­cise in ­order to deter­mine con­cen­tra­tions of ATP, PCr, Cr, La- and gly­cogen. ­Venous ­blood was ­drawn ­prior to and on ­four occa­sions ­during the exer­cise ­test, and ana­lysed for Cr, NH3+, La- and pH.
­Results. ­Serum Cr con­cen­tra­tions ­were ­raised to a ­peak of 2348±223 ­µmol·l-1 ­prior to the com­mence­ment of exer­cise ­after Cr inges­tion. ­There ­were no sig­nif­i­cant ­changes in any ­cycling per­for­mance param­e­ters fol­lowing Cr inges­tion, ­although ­blood La- was sig­nif­i­cantly ­lower (p<0.05) ­than pla­cebo at all ­time ­points ­during exer­cise, and ­plasma NH3+ accu­mu­la­tion was ­also sig­nif­i­cantly ­reduced (p<0.05) in the Cr con­di­tion, but ­only in the ­second ­half of the 80-min exer­cise ­test. ­Muscle ATP and TCr ­levels as ­well as post­ex­er­cise PCr replen­ish­ment ­were unaf­fected fol­lowing Cr admin­is­tra­tion.
Con­clu­sions. The ­data sug­gest ­that ­although the pre-exer­cise inges­tion of a ­large Cr ­dose was ­shown to ­have ­some ­impact on ­blood ­borne metab­olites, it ­does not ­improve max­imal pro­longed inter­mit­tent ­sprint exer­cise per­for­mance, pos­sibly due to an insuf­fi­cient ­time ­allowed for ­uptake of ­serum Cr by skel­etal ­muscle to ­occur. There­fore, ­this ­form of ­loading ­does not pro­vide an alter­na­tive ­method of Cr sup­ple­men­ta­tion to the tra­di­tional ­five-day sup­ple­men­ta­tion ­regimes estab­lished by pre­vious ­research.