PMID- 8609825
OWN - NLM
STAT- MEDLINE
DCOM- 19960528
LR  - 20190725
IS  - 0026-0495 (Print)
IS  - 0026-0495 (Linking)
VI  - 45
IP  - 4
DP  - 1996 Apr
TI  - Fuel substrate kinetics of carbohydrate loading differs from that of carbohydrate 
      ingestion during prolonged exercise.
PG  - 415-23
AB  - This study compared fuel substrate kinetics in trained cyclists who ingested a 
      10% carbohydrate (CHO) drink without prior CHO-loading ([NLC] n=9) with those in 
      cyclists who ingested a water placebo after CHO-loading ([CLP] n=7) during 180 
      minutes of cycling at 70% maximum oxygen consumption (Vo2 max). Muscle glycogen 
      at the start of exercise was 194 +/- 4 and 124 +/- 8 mmol/kg wet weight (mean +/- 
      SEM) in CLP and NLC subjects, respectively . Total CHO oxidation was similar. 
      Total rate of appearance of glucose from endogenous (Raend) and exogenous 
      (Raexog) origin and plasma glucose oxidation increased significantly (P<.05), 
      with NLC subjects ending significantly higher than CLP subjects (104 +/- 17 v 79 
      +/- 9 and 115 +/- 16 v 74 +/- 11 micromol/min/kg fat-free mass [FFM], 
      respectively). However, Raend was lower (P<.05) in NLC than in CLP subjects (40 
      +/- 10 v 79 +/- 9 micromol/min/kg FFM), as was endogenous plasma glucose 
      oxidation (42 +/- 13 v 75 +/- 11 micromol/min kg FFM). Muscle glycogen 
      disappearance was identical in the first hour, but declined thereafter in NLC 
      subjects. Two NLC subjects with the lowest muscle glycogen content were unable to 
      complete the trial despite CHO ingestion. We conclude that with respect to the 
      groups studied (1) CHO loading before exercise reduces the relative contribution 
      of plasma glucose oxidation to total CHO oxidation, but may prolong time to 
      exhaustion as a function of higher muscle glycogen concentration; (2) CHO 
      ingestion has a liver glycogen-sparing effect, causes a reduction in 
      gluconeogenesis, or both, that should delay the onset of hypoglycemia; (3) the 
      progressive increase in plasma glucose oxidation that occurs during prolonged 
      exercise is related to muscle glycogen status and occurs irrespective of whether 
      CHO is ingested: (4) the effects of CHO ingestion and CHO-loading on fuel 
      substrate kinetics are different.
FAU - Bosch, A N
AU  - Bosch AN
AD  - Department of Physiology, University of Cape Town Medical School, South Africa.
FAU - Weltan, S M
AU  - Weltan SM
FAU - Dennis, S C
AU  - Dennis SC
FAU - Noakes, T D
AU  - Noakes TD
LA  - eng
PT  - Clinical Trial
PT  - Journal Article
PT  - Randomized Controlled Trial
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Metabolism
JT  - Metabolism: clinical and experimental
JID - 0375267
RN  - 0 (Blood Glucose)
RN  - 0 (Dietary Carbohydrates)
RN  - 0 (Insulin)
RN  - 0 (Lactates)
RN  - 9005-79-2 (Glycogen)
RN  - IY9XDZ35W2 (Glucose)
SB  - IM
MH  - Adult
MH  - Blood Glucose/analysis/metabolism
MH  - Dietary Carbohydrates/administration & dosage/*pharmacokinetics
MH  - Energy Metabolism/*physiology
MH  - Exercise/*physiology
MH  - Glucose/metabolism
MH  - Glycogen/metabolism
MH  - Humans
MH  - Insulin/blood
MH  - Lactates/blood
MH  - Male
MH  - Muscle, Skeletal/metabolism
MH  - Oxidation-Reduction
MH  - Oxygen Consumption/physiology
MH  - Time Factors
EDAT- 1996/04/01 00:00
MHDA- 1996/04/01 00:01
CRDT- 1996/04/01 00:00
PHST- 1996/04/01 00:00 [pubmed]
PHST- 1996/04/01 00:01 [medline]
PHST- 1996/04/01 00:00 [entrez]
AID - S0026-0495(96)90213-9 [pii]
AID - 10.1016/s0026-0495(96)90213-9 [doi]
PST - ppublish
SO  - Metabolism. 1996 Apr;45(4):415-23. doi: 10.1016/s0026-0495(96)90213-9.