PMID- 17277597
OWN - NLM
STAT- MEDLINE
DCOM- 20070410
LR  - 20070205
IS  - 0195-9131 (Print)
IS  - 0195-9131 (Linking)
VI  - 39
IP  - 2
DP  - 2007 Feb
TI  - Influence of hydration status on thermoregulation and cycling hill climbing.
PG  - 323-9
AB  - PURPOSE: Although dehydration can impair endurance performance, a reduced body 
      mass may benefit uphill cycling by increasing the power-to-mass ratio. This study 
      examined the effects of a reduction in body mass attributable to unreplaced sweat 
      losses on simulated cycling hill-climbing performance in the heat. METHODS: Eight 
      well-trained male cyclists (mean +/- SD: 28.4 +/- 5.7 yr; 71.0 +/- 5.9 kg; 176.7 
      +/- 4.7 cm; VO2peak: 66.2 +/- 5.8 mL x kg(-1) x min(-1)) completed a maximal 
      graded cycling test on a stationary ergometer to determine maximal aerobic power 
      (MAP). In a randomized crossover design, cyclists performed a 2-h ride at 53% MAP 
      on a stationary ergometer, immediately followed by a cycling hill-climb 
      time-to-exhaustion trial (88% MAP) on their own bicycle on an inclined treadmill 
      (8%) at approximately 30 degrees C. During the 2-h ride, they consumed either 2.4 
      L of a 7% carbohydrate (CHO) drink (HIGH) or 0.4 L of water (LOW) with sport gels 
      to match for CHO content. RESULTS: After the 2-h ride and before the hill climb, 
      drinking strategies influenced body mass (LOW -2.5 +/- 0.5% vs HIGH 0.3 +/- 0.4%; 
      P < 0.001), HR (LOW 158 +/- 15 vs HIGH 146 +/- 15 bpm; P = 0.03), and rectal 
      temperature (T(re): LOW 38.9 +/- 0.2 vs HIGH 38.3 +/- 0.2 degrees C; P = 0.001). 
      Despite being approximately 1.9 kg lighter, time to exhaustion was significantly 
      reduced by 28.6 +/- 13.8% in the LOW treatment (LOW 13.9 +/- 5.5 vs HIGH 19.5 +/- 
      6.0 min, P = 0.002), as was the power output for a fixed speed (LOW 308 +/- 28 vs 
      HIGH 313 +/- 28 W, P = 0.003). At exhaustion, T(re) was higher in the LOW 
      treatment (39.5 vs HIGH 39.1 degrees C; P < 0.001), yet peak HR, blood lactate, 
      and glucose were similar. CONCLUSION: Exercise-induced dehydration in a warm 
      environment is detrimental to laboratory cycling hill-climbing performance 
      despite reducing the power output required for a given speed.
FAU - Ebert, Tammie R
AU  - Ebert TR
AD  - Department of Physiology, Australian Institute of Sport, Canberra, Australia. 
      tammie.ebert@ausport.gov.au
FAU - Martin, David T
AU  - Martin DT
FAU - Bullock, Nicola
AU  - Bullock N
FAU - Mujika, Inigo
AU  - Mujika I
FAU - Quod, Marc J
AU  - Quod MJ
FAU - Farthing, Lesley A
AU  - Farthing LA
FAU - Burke, Louise M
AU  - Burke LM
FAU - Withers, Robert T
AU  - Withers RT
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Med Sci Sports Exerc
JT  - Medicine and science in sports and exercise
JID - 8005433
SB  - IM
MH  - Adult
MH  - *Altitude
MH  - Bicycling/*physiology
MH  - Body Mass Index
MH  - *Body Temperature Regulation
MH  - *Dehydration
MH  - Exercise Test
MH  - Fatigue/complications/physiopathology
MH  - *Health Status
MH  - Heart Rate
MH  - Humans
MH  - Male
MH  - Physical Endurance/*physiology
MH  - Prospective Studies
EDAT- 2007/02/06 09:00
MHDA- 2007/04/11 09:00
CRDT- 2007/02/06 09:00
PHST- 2007/02/06 09:00 [pubmed]
PHST- 2007/04/11 09:00 [medline]
PHST- 2007/02/06 09:00 [entrez]
AID - 00005768-200702000-00015 [pii]
AID - 10.1249/01.mss.0000247000.86847.de [doi]
PST - ppublish
SO  - Med Sci Sports Exerc. 2007 Feb;39(2):323-9. doi: 
      10.1249/01.mss.0000247000.86847.de.