Home Current News News Archive Shop/Advertise Ridecamp Classified Events Learn/AERC
Endurance.Net Home Ridecamp Archives
[Archives Index]   [Date Index]   [Thread Index]   [Author Index]   [Subject Index]

[RC] caffeine - Ridecamp Guest

Please Reply to: ti tivers@xxxxxxx or ridecamp@xxxxxxxxxxxxx

Authors SE Yeo, RLPG Jentjens, GA Wallis, AE Jeukendrup
Title   Caffeine increases, exogenous carbohydrate oxidation during exercise
Full source     Journal of Applied Physiology, 2005, Vol 99, Iss 3, pp 844-850

Both carbohydrate (CHO) and caffeine have been used as ergogenic aids during 
exercise. It has been suggested I hat 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 
center dot kg(-1)center dot 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 (Gluধ, 48 
g/h  5 mg center dot kg(-1)center dot h(-1)), or plain water (Wat). The glucose 
solution contained trace amounts of [U-C-13]glucose so that exogenous CHO 
oxidation could be calculated. CHO and fat oxidation were measured by indirect 
calorimetry, and C-13 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&#2471; (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&#2471; 
was ingested (1.21  0.37, 1.84  0.14, and 2.47  0.23 g/min for Wat, Glu, and 
Glu&#2471;, respectively; P, < 0.05). There was also a trend (P = 0.082) toward 
an increased endogenous CHO oxidation with Glu&#2471; (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 center dot kg(-1)center dot h(-1) of caffeine 
coingested with glucose increases exogenous CHO oxidation, possibly as a result 
of an enhanced intestinal absorption.

NOTE: Somebody (maybe everybody) knew this at a Dubai championship race a few 
years ago?hundreds of little brown vials lying around at water stops, labels 
intact, indicating a caffeine-containing liquid. I told my sheikh?s suckalongs 
that ?this is illegal?. They said, ?Don?t worry, everybody?s doing it.?

Ridecamp is a service of Endurance Net, http://www.endurance.net.
Information, Policy, Disclaimer: http://www.endurance.net/Ridecamp
Subscribe/Unsubscribe http://www.endurance.net/ridecamp/logon.asp

Ride Long and Ride Safe!!