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Effect of Repeated Caffeine Ingestion on Repeated Exhaustive Exercise Endurance

BELL, DOUGLAS G.; MCLELLAN, TOM M.

Medicine & Science in Sports & Exercise: August 2003 - Volume 35 - Issue 8 - p 1348-1354
doi: 10.1249/01.MSS.0000079071.92647.F2
BASIC SCIENCES: Original Investigations

BELL, D. G., and T. M. MCLELLAN. Effect of Repeated Caffeine Ingestion on Repeated Exhaustive Exercise Endurance. Med. Sci. Sports Exerc., Vol. 35, No. 8, pp. 1348–1354, 2003.

Purpose The purpose of this study was to examine the effect of repeated doses of caffeine on repeated exercise endurance.

Methods Nine male caffeine users performed exercise rides (ER) to exhaustion at 80% V̇O2max after ingesting a placebo, 5 mg·kg−1 of caffeine, or 2.5 mg·kg−1 of caffeine 1 h before the ER. Two ER were performed weekly on the same day once in the morning (AM) and 5 h later in the afternoon (PM). There were four treatments containing either caffeine or placebo, i.e., trial A representing 5-mg·kg−1 caffeine in the AM and 2.5-mg·kg−1 caffeine in the PM; trial B, which was placebo in both AM and PM; trial C representing 5-mg·kg−1 caffeine in the AM and placebo in the PM; and trial D representing a placebo in the AM and 5-mg·kg−1 caffeine in the PM. The order of the treatment trials was double blind and randomized.

Results Caffeine ingestion significantly increased exercise time to exhaustion in the AM (trial A 24.9 ± 10.2 min and trial C 21.8 ± 4.9 vs trial B 18.0 ± 6.4 min and D 17.7 ± 4.3 min). This effect was maintained in the PM and greater than placebo (B 18.3 ± 4.8 min) regardless of whether redosing (trial A 21.5 ± 8.6 min) or placebo (trial C 21.0 ± 6.8) followed the initial morning dose. Caffeine dosing in the PM (trial D 22.4 ± 7.2 min) also increased ER after placebo trial D in the AM.

Conclusions It was concluded that redosing with caffeine after exhaustive exercise in the AM was not necessary to maintain the ergogenic effect of the drug during subsequent exercise 6 h later.

Operational Medicine Section, Defence R&D Canada–Toronto, Ontario, CANADA

Address for correspondence: D. G. Bell, Defence R&D Canada–Toronto, 1133 Sheppard Avenue West, P. O. Box 2000, Toronto, Ontario, Canada, M3M 3B9; E-mail: doug.bell@drdc-rddc.gc.ca.

Submitted for publication December 2002.

Accepted for publication April 2003.

©2003The American College of Sports Medicine