Thermal Regulation in the Heat During Exercise After Caffeine and Ephedrine Ingestion

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Authors
  1. Bell, D.G.
  2. Jacobs, I.
  3. McLellan, T.M.
  4. Miyazaki, M.
  5. Sabiston, C.M.
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN)
Abstract
Ingesting a combination of caffeine and ephedrine (C+E) has been shown to raise metabolic heat production and body temperature. This side effect of C+E ingestion may be positive during a cold stress scenario, however, during heat stress it could prove to be detrimental. Thus, the purpose of this study was to clarify the effect of C+E ingestion on body temperature regulation during moderate exercise in a hot dry environment. Ten, healthy, non heat acclimated, males exercised at 50% V02peak in a 40C and 30% RH environment until rectal temperature reached 39.3C; heart rate (HR) remained at 95% of peak value or greater for 3 min, dizziness or nausea precluded further exercise, or 3 h had elapsed. They did this four times at weekly intervals: familiarization (Fam), control (Cont), placebo, and C+E (5 mg-kg1(-) caffeinge + 1 mg-kg(-) ephedrine) trials. The Fam and Cont treatments were done first and sequentially while the placebo and C+E treatnebts were balanced and double-blind. Tolerance times, mean skin temperature (Tsk), rectal temperature (Tre), Vo2, Vco2, VE, sweat rate (SR), HR, and sensation of thermal confort were measured. Tolerance times (mean + or - SD in minutes) were similar for the placebo (120.0 + or - 28.4) and C+E (121.3 + or - 33.9) trials and both times were significantly longer than Cont (106.6 + or - 24.0) trial. C+E did not affect Tsk, initial Tre, increment Tre, SR or the sensation of thermal conform.
Keywords
Ergogenic aids;Physical training;Human performance;Methylxanthine;Sympathomimetic
Report Number
DCIEM-98-P-39 — Reprint
Date of publication
01 Mar 1998
Number of Pages
9
Reprinted from
Aviation, Space, and Environmental Medicine, Vol 70, no 6, 1999, p 583-588
DSTKIM No
99-01857
CANDIS No
511937
Format(s):
Hardcopy;Document Image stored on Optical Disk

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