title: Effects of acute supplementation of caffeine on cardiorespiratory responses during endurance running in a hot & humid climate.
abstract: OBJECTIVE
  Athletes in Malaysia need to perform in a hot and humid climate. Chronic supplementation of caffeine on endurance performance have been studied extensively in different populations. However, concurrent research on the effects of acute supplementation of caffeine on cardiorespiratory responses during endurance exercise in the Malaysian context especially in a hot and humid environment is unavailable.
  
  
  METHODS
  Nine heat adapted recreational Malaysian male runners (aged: 25.4+/-6.9 yr) who were nonusers of caffeine (23.7+/-12.6 mg per day) were recruited in this placebo--controlled double--blind randomized study. Caffeine (5 mg per kg of body weight) or placebo was ingested in the form of a capsule one hour prior to the running exercise trial at 70 per cent of VO2max on a motorised treadmill in a heat-controlled laboratory (31 degrees C, 70% relative humidity). Subjects drank 3 ml of cool water per kg of body weight every 20 min during the running trials to avoid the adverse effects of dehydration. Heart rate, core body temperature and rate of perceived exertion (RPE) were recorded at intervals of 10 min, while oxygen consumption was measured at intervals of 20 min.
  
  
  RESULTS
  Running time to exhaustion was significantly (P<0.05) higher in the caffeine trial compared to the placebo trial. Heart rate, core body temperature, oxygen uptake and RPE did not show any significant variation between the trials but it increased significantly during exercise from their respective resting values in both trials (P<0.001).
  
  
  CONCLUSIONS
  Our study showed that ingestion of 5 mg of caffeine per kg of body weight improved the endurance running performance but did not impose any significant effect on other individual cardiorespiratory parameters of heat-acclimated recreational runners in hot and humid conditions.
authors.affiliation: Sports Science Unit, School of Medical Sciences, Universiti Sains Malaysia, 16150, Kubang Kerian, Kelantan Malaysia.
authors.forename: Wong Chee
authors.initials: WC
authors.lastname: Ping
authors.forename: Chen Chee
authors.initials: CC
authors.lastname: Keong
authors.forename: Amit
authors.initials: A
authors.lastname: Bandyopadhyay
mesh_terms: D000328:Adult; D001823:Body Composition; D015992:Body Mass Index; D001831:Body Temperature; D002110:Caffeine / Q000494:pharmacology*; D004231:Diuresis / Q000187:drug effects*; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008296:Malaysia; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects*; D010101:Oxygen Consumption / Q000187:drug effects* / Q000502:physiology; D058573:Performance-Enhancing Substances / Q000494:pharmacology*
chemical_list: D058573:Performance-Enhancing Substances; D002110:Caffeine