title: Thermal and Cardiovascular Strain Mitigate the Potential Benefit of Carbohydrate Mouth Rinse During Self-Paced Exercise in the Heat.
abstract: OBJECTIVE
  To determine whether a carbohydrate mouth rinse can alter self-paced exercise performance independently of a high degree of thermal and cardiovascular strain.
  
  
  METHODS
  Eight endurance-trained males performed two 40-km cycling time trials in 35°C, 60% RH while swilling a 20-ml bolus of 6.5% maltodextrin (CHO) or a color- and taste-matched placebo (PLA) every 5 km. Heart rate, power output, rectal temperature (Tre), and mean skin temperature (Tsk) were recorded continuously; cardiac output, oxygen uptake (VO2), mean arterial pressure (MAP), and perceived exertion (RPE) were measured every 10 min.
  
  
  RESULTS
  Performance time and mean power output were similar between treatments, averaging 63.9 ± 3.2 and 64.3 ± 2.8 min, and 251 ± 23 and 242 ± 18 W in CHO and PLA, respectively. Power output, stroke volume, cardiac output, MAP, and VO2 decreased during both trials, increasing slightly or remaining stable during a final 2-km end-spurt. Tre, Tsk, heart rate, and RPE increased throughout exercise similarly with both treatments. Changes in RPE correlated with those in Tre (P < 0.005) and heart rate (P < 0.001).
  
  
  CONCLUSIONS
  These findings suggest that carbohydrate mouth rinsing does not improve ~1-h time trial performance in hot-humid conditions, possibly due to a failure in down-regulating RPE, which may be influenced more by severe thermal and cardiovascular strain.
authors.affiliation: School of Human Kinetics, Faculty of Health Sciences, University of Ottawa Ottawa, ON, Canada ; Discipline of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney Lidcombe, NSW, Australia.
authors.forename: Matthew N
authors.initials: MN
authors.lastname: Cramer
authors.affiliation: Discipline of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney Lidcombe, NSW, Australia.
authors.forename: Martin W
authors.initials: MW
authors.lastname: Thompson
authors.affiliation: Discipline of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney Lidcombe, NSW, Australia ; Athlete Health and Performance Research Centre, Aspetar Orthopaedic and Sports Medicine Hospital Doha, Qatar.
authors.forename: Julien D
authors.initials: JD
authors.lastname: Périard
keywords: cycling; exercise performance; fatigue; hyperthermia; perceived exertion; time trial