title: Effect of ambient temperature on cardiovascular drift and maximal oxygen uptake.
abstract: OBJECTIVE
  This study tested the hypothesis that the magnitude of cardiovascular (CV) drift and decrease in maximal oxygen uptake (V[spacing dot above]O2max) would be greater at 35 degrees C than at 22 degrees C.
  
  
  METHODS
  The increase in HR and decrease in stroke volume (SV) between 15 and 45 min of cycling at 59.2 +/- 1.9% V[spacing dot above]O2max (CV drift) was measured in hot (HEAT, 35 degrees C) and cool (COOL, 22 degrees C) ambient temperatures in 10 endurance-trained men (age = 23 +/- 3 yr, V[spacing dot above]O2max = 64.7 +/- 8.7 mL.kg.min). V[spacing dot above]O2max was measured immediately after the 45 min of cycling and again under both ambient temperature conditions on separate days after 15 min of cycling. This design permitted assessment of V[spacing dot above]O2max between the same time points that CV drift occurred. Fluid to replace sweat losses was provided during all trials.
  
  
  RESULTS
  CV drift and the associated decrease in V[spacing dot above]O2max was greater (P < 0.05) in HEAT versus COOL. HR increased 11% (P < 0.05), SV decreased 11% (P < 0.05), and V[spacing dot above]O2max fell 15% (P < 0.05) between 15 and 45 min in HEAT, whereas HR and SV changed less (+2% and -2% for HR and SV, respectively, P < 0.05), and there was no significant decrease in V[spacing dot above]O2max (5%, P > 0.05) between 15 and 45 min in COOL.
  
  
  CONCLUSIONS
  These data demonstrate the magnitude of CV drift during prolonged submaximal exercise, and the accompanying decrease in V[spacing dot above]O2max measured immediately thereafter is greater in a hot than in a cool environment.
authors.affiliation: Department of Biology, University of Portland, Portland, OR, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Lafrenz
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Wingo
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Ganio
authors.forename: Kirk J
authors.initials: KJ
authors.lastname: Cureton
mesh_terms: D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology; D018882:Heat Stress Disorders / Q000503:physiopathology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology