title: Influence of caffeine, cold and exercise on multiple choice reaction time.
abstract: BACKGROUND
  The effects of caffeine on psychomotor performance have been evaluated under resting conditions and in a thermoneutral environment. Our hypothesis was that these effects could be modified by factors enhancing the level of alertness, such as exercise and cold exposure.
  
  
  OBJECTIVE
  The purpose of this study was to follow up changes in the multiple choice reaction time (RT) during exercise at room and low ambient temperatures after caffeine or placebo administered in a double blind manner.
  
  
  METHODS
  Nine soccer players performed multistage, incremental exercise until volitional exhaustion on a bicycle ergometer at 22 degrees C or 4 degrees C, 1 h after ingestion of coffee with caffeine (CAF) or without it (PL). Immediately before exercise and at the end of each workload, RT and blood lactate (LA) were measured. Oxygen uptake (VO2) and heart rate (HR) were recorded continuously. Blood LA threshold and the workload associated with the shortest RT were determined.
  
  
  RESULTS
  During exercise at 22 degrees C, RT was significantly shorter in CAF than in the PL test, while at 4 degrees C there were no differences in RT between CAF and PL trials. Cold exposure did not affect RT either at rest or during exercise. Neither caffeine nor cold exposure influenced the maximal VO2, the maximal HR and LA threshold.
  
  
  CONCLUSIONS
  In the thermoneutral environment, caffeine ingestion improved psychomotor performance during exercise, whilst at low ambient temperature this effect was blunted. These findings suggest that the stimulating action of caffeine depends on the level and source of arousal.
authors.affiliation: Department of Applied Physiology, MRC, Polish Academy of Sciences, Warsaw. kruk@cmdik.pan.pl
authors.forename: B
authors.initials: B
authors.lastname: Kruk
authors.forename: J
authors.initials: J
authors.lastname: Chmura
authors.forename: K
authors.initials: K
authors.lastname: Krzeminski
authors.forename: A W
authors.initials: AW
authors.lastname: Ziemba
authors.forename: K
authors.initials: K
authors.lastname: Nazar
authors.forename: H
authors.initials: H
authors.lastname: Pekkarinen
authors.forename: H
authors.initials: H
authors.lastname: Kaciuba-Uscilko
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D002110:Caffeine / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003080:Cold Temperature; D004311:Double-Blind Method; D005080:Exercise Test / Q000187:drug effects; D006801:Humans; D008297:Male; D005082:Physical Exertion / Q000187:drug effects* / Q000502:physiology*; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology; D011930:Reaction Time / Q000187:drug effects* / Q000502:physiology*
chemical_list: D000697:Central Nervous System Stimulants; D002110:Caffeine