PMID- 15831802
OWN - NLM
STAT- MEDLINE
DCOM- 20051027
LR  - 20220409
IS  - 8750-7587 (Print)
IS  - 0161-7567 (Linking)
VI  - 99
IP  - 3
DP  - 2005 Sep
TI  - Caffeine increases exogenous carbohydrate oxidation during exercise.
PG  - 844-50
AB  - Both carbohydrate (CHO) and caffeine have been used as ergogenic aids during 
      exercise. It has been suggested that caffeine increases intestinal glucose 
      absorption, but there are also suggestions that it may decrease muscle glucose 
      uptake. The purpose of the study was to investigate the effect of caffeine on 
      exogenous CHO oxidation. In a randomized crossover design, eight male cyclists 
      (age 27 +/- 2 yr, body mass 71.2 +/- 2.3 kg, maximal oxygen uptake 65.7 +/- 2.2 
      ml x kg(-1) x min(-1)) exercised at 64 +/- 3% of maximal oxygen uptake for 120 
      min on three occasions. During exercise subjects ingested either a 5.8% glucose 
      solution (Glu; 48 g/h), glucose with caffeine (Glu+Caf, 48 g/h + 5 mg x kg(-1) x 
      h(-1)), or plain water (Wat). The glucose solution contained trace amounts of 
      [U-13C]glucose so that exogenous CHO oxidation could be calculated. CHO and fat 
      oxidation were measured by indirect calorimetry, and 13C appearance in the 
      expired gases was measured by continuous-flow IRMS. Average exogenous CHO 
      oxidation over the 90- to 120-min period was 26% higher (P < 0.05) in Glu+Caf 
      (0.72 +/- 0.04 g/min) compared with Glu (0.57 +/- 0.04 g/min). Total CHO 
      oxidation rates were higher (P < 0.05) in the CHO ingestion trials compared with 
      Wat, but they were highest when Glu+Caf was ingested (1.21 +/- 0.37, 1.84 +/- 
      0.14, and 2.47 +/- 0.23 g/min for Wat, Glu, and Glu+Caf, respectively; P < 0.05). 
      There was also a trend (P = 0.082) toward an increased endogenous CHO oxidation 
      with Glu+Caf (1.81 +/- 0.22 g/min vs. 1.27 +/- 0.13 g/min for Glu and 1.12 +/- 
      0.37 g/min for Wat). In conclusion, compared with glucose alone, 5 mg x kg(-1) x 
      h(-1) of caffeine coingested with glucose increases exogenous CHO oxidation, 
      possibly as a result of an enhanced intestinal absorption.
FAU - Yeo, Sophie E
AU  - Yeo SE
AD  - Human Performance Laboratory, School of Sport and Exercise Sciences, Univ. of 
      Birmingham, Edgbaston, Birmingham B15 2TT, UK.
FAU - Jentjens, Roy L P G
AU  - Jentjens RL
FAU - Wallis, Gareth A
AU  - Wallis GA
FAU - Jeukendrup, Asker E
AU  - Jeukendrup AE
LA  - eng
GR  - Wellcome Trust/United Kingdom
PT  - Clinical Trial
PT  - Journal Article
PT  - Randomized Controlled Trial
PT  - Research Support, Non-U.S. Gov't
DEP - 20050414
PL  - United States
TA  - J Appl Physiol (1985)
JT  - Journal of applied physiology (Bethesda, Md. : 1985)
JID - 8502536
RN  - 0 (Dietary Carbohydrates)
RN  - 0 (Drug Combinations)
RN  - 3G6A5W338E (Caffeine)
RN  - IY9XDZ35W2 (Glucose)
SB  - IM
MH  - Administration, Oral
MH  - Adult
MH  - Caffeine/*administration & dosage
MH  - Cross-Over Studies
MH  - Dietary Carbohydrates/*metabolism
MH  - Drug Combinations
MH  - Exercise Test
MH  - Glucose/*administration & dosage
MH  - Humans
MH  - Male
MH  - Metabolic Clearance Rate
MH  - Oxidation-Reduction/drug effects
MH  - Oxygen Consumption/*physiology
MH  - Physical Endurance/*physiology
MH  - Physical Exertion/*physiology
EDAT- 2005/04/16 09:00
MHDA- 2005/10/28 09:00
CRDT- 2005/04/16 09:00
PHST- 2005/04/16 09:00 [pubmed]
PHST- 2005/10/28 09:00 [medline]
PHST- 2005/04/16 09:00 [entrez]
AID - 00170.2005 [pii]
AID - 10.1152/japplphysiol.00170.2005 [doi]
PST - ppublish
SO  - J Appl Physiol (1985). 2005 Sep;99(3):844-50. doi: 
      10.1152/japplphysiol.00170.2005. Epub 2005 Apr 14.