title: Mild dehydration and cycling performance during 5-kilometer hill climbing.
abstract: BACKGROUND
  Hydration has been shown to be an important factor in performance; however, the effects of mild dehydration during intense cycling are not clear.
  
  
  OBJECTIVE
  To determine the influence of mild dehydration on cycling performance during an outdoor climbing trial in the heat (ambient temperature = 29.0°C ± 2.2°C).
  
  
  METHODS
  Crossover study.
  
  
  METHODS
  Outdoor.
  
  
  METHODS
  Ten well-trained, male endurance cyclists (age = 28 ± 5 years, height = 182 ± 0.4 cm, mass = 73 ± 4 kg, maximal oxygen uptake = 56 ± 9 mL·min(-1)·kg(-1), body fat = 23% ± 2%, maximal power = 354 ± 48 W).
  
  
  METHODS
  Participants completed 1 hour of steady-state cycling with or without drinking to achieve the desired pre-exercise hydration level before 5-km hill-climbing cycling. Participants started the 5-km ride either euhydrated (EUH) or dehydrated by -1% of body mass (DEH).
  
  
  METHODS
  Performance time, core temperature, sweat rate, sweat sensitivity, and rating of perceived exertion (RPE).
  
  
  RESULTS
  Participants completed the 5-km ride 5.8% faster in the EUH (16.6 ± 2.3 minutes) than DEH (17.6 ± 2.9 minutes) trial (t1 = 10.221, P = .001). Postexercise body mass was -1.4% ± 0.3% for the EUH trial and -2.2% ± 0.2% for the DEH trial (t1 = 191.384, P < .001). Core temperature after the climb was greater during the DEH (39.2°C ± 0.3°C) than EUH (38.8°C ± 0.2°C) trial (t1 = 8.04, P = .005). Sweat rate was lower during the DEH (0.44 ± 0.16 mg·m(-2)·s(-1)) than EUH (0.51 ± 0.16 mg·m(-2)·s(-1)) trial (t8 = 2.703, P = .03). Sweat sensitivity was lower during the DEH (72.6 ± 32 g·°C(-1)·min(-1)) than EUH (102.6 ± 54.2 g·°C(-1)·min(-1)) trial (t8 = 3.072, P = .02). Lastly, RPE after the exercise performance test was higher for the DEH (19.0 ± 1.0) than EUH (17.0 ± 1.0) participants (t9 = -3.36, P = .008).
  
  
  CONCLUSIONS
  We found mild dehydration decreased cycling performance during a 5-km outdoor hill course, probably due to greater heat strain and greater perceived intensity.
authors: Department of Nutrition and Dietetics, Harokopio University, Athens, Greece.
authors: Costas N
authors: CN
authors: Bardis
authors: Stavros A
authors: SA
authors: Kavouras
authors: Giannis
authors: G
authors: Arnaoutis
authors: Demosthenes B
authors: DB
authors: Panagiotakos
authors: Labros S
authors: LS
authors: Sidossis
mesh_terms: D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D001642:Bicycling / Q000502:physiology*; D015992:Body Mass Index; D001831:Body Temperature; D018592:Cross-Over Studies; D003681:Dehydration; D004326:Drinking; D005080:Exercise Test / Q000379:methods*; D005334:Fever; D006339:Heart Rate; D006358:Hot Temperature; D006801:Humans; D008297:Male; D010100:Oxygen / Q000378:metabolism; D010807:Physical Endurance / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology; D013546:Sweating
chemical_list: D010100:Oxygen
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