Thermoregulatory effects of caffeine ingestion during submaximal exercise in men.
BACKGROUND
The exclusive effect of caffeine ingestion on exercise thermoregulation is unclear; data indicate that caffeine may have a positive effect, a negative effect, or no effect.


METHODS
Rectal (TRE) and mean skin (TSK) temperatures, skin heat conductance (HSK), and sweat rate (MSW) were measured during 30 min of rest and subsequent 70 min of submaximal cycle-ergometer exercise (67% VO2PEAK) in 11 aerobically conditioned men (mean +/- SD 29 +/- 6 yr, 49 +/- 6 mL x min(-1) x kg(-1) VO2PEAK) under two conditions: a caffeine (10 mg x kg(-1) ingestion (CI) session and a noncaffeine ingestion (NCI) control session.


RESULTS
There were no significant differences in physiological or thermoregulatory parameters during exercise: X (+/-SE) end exercise levels for the NCI and CI sessions, respectively, were VO2 = 2.50 +/- 0.09 vs. 2.55 +/- 0.09 L x min(-1); heart rate = 145 +/- 7 vs. 145 +/- 5 bpm; HSK = 30 +/- 3 vs. 28 +/- 3 kcal x m(-2) x h(-1) x degrees C(-1); MSW = 393 +/- 35 vs. 378 +/- 36 g x m(-2) x h(-1); and TRE = 38.3 +/- 0.2 vs. 38.4 +/- 0.1 degrees C. Control TSK was lower than that for CI by 0.4 to 0.5 degrees C at rest and during exercise.


CONCLUSIONS
Ingestion of a high level (10 mg x kg(-1) of caffeine has no effect on skin heat conductance, sweating, or the rate of increase and final level of rectal temperature during moderate, submaximal leg exercise.
Dunagan
N
N
Exercise Physiology Laboratory, San Jose State University, CA, USA.
Greenleaf
J E
JE
Cisar
C J
CJ
D000328:Adult; D001831:Body Temperature / Q000187:drug effects; D001833:Body Temperature Regulation / Q000187:drug effects* / Q000502:physiology*; D001835:Body Weight / Q000502:physiology; D002110:Caffeine / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D012007:Rectum / Q000502:physiology; D012146:Rest / Q000502:physiology; D012881:Skin Temperature / Q000187:drug effects; D013546:Sweating / Q000187:drug effects
D000697:Central Nervous System Stimulants; D002110:Caffeine