PMID- 9363378
OWN - NLM
STAT- MEDLINE
DCOM- 19971218
LR  - 20190826
IS  - 0305-1870 (Print)
IS  - 0305-1870 (Linking)
VI  - 24
IP  - 11
DP  - 1997 Nov
TI  - The glucose crossover concept is not an important new concept in exercise 
      metabolism.
PG  - 896-900
AB  - 1. The basic premise of the 'crossover' concept (i.e. that the balance of 
      carbohydrate (CHO) and fat utilization during exercise depends on the interaction 
      between exercise intensity and the individual's endurance training status) has 
      been accepted since at least the 1930s. 2. The crossover concept differs from 
      earlier perspectives mostly in its greater emphasis on the absolute exercise 
      intensity as an important determinant of substrate selection during exercise. 
      Because of this emphasis, it is argued that while trained subjects may utilize 
      less CHO than their untrained counterparts during low- or moderate-intensity 
      exercise, this is not true during high-intensity exercise, because during such 
      exercise even trained persons must 'crossover' to CHO dependency. In fact, the 
      crossover concept predicts that utilization of at least one CHO source (i.e. 
      plasma-borne glucose) should be greater in trained subjects during intense 
      exercise. This increase in glucose utilization is hypothesized to be supported by 
      an enhanced rate of gluconeogenesis. 3. In direct contradiction of the crossover 
      concept, the literature consistently shows that, compared with untrained 
      individuals, trained subjects rely less on CHO for fuel, even during 
      high-intensity exercise. In particular, it has been shown that the rate of 
      glucose utilization is lower in trained subjects under these conditions. Recent 
      data from Dr Brooks' own laboratory support this conclusion and also show that 
      this reduction in glucose use is associated with a decrease in the rate of 
      gluconeogenesis. These recent observations confirm prior studies of 
      moderate-intensity exercise. 4. Based on the above, it is clear that the 
      crossover concept cannot be considered an important new concept in exercise 
      metabolism. Instead, the crossover concept actually serves to hinder 
      understanding in this area.
FAU - Coggan, A R
AU  - Coggan AR
AD  - Metabolism Unit, Shriners Burns Institute, Galveston, Texas 77550, USA. 
      acoggan@utmb.edu
LA  - eng
PT  - Journal Article
PL  - Australia
TA  - Clin Exp Pharmacol Physiol
JT  - Clinical and experimental pharmacology & physiology
JID - 0425076
RN  - 0 (Fatty Acids, Nonesterified)
RN  - 0 (Triglycerides)
RN  - 9005-79-2 (Glycogen)
RN  - IY9XDZ35W2 (Glucose)
SB  - IM
MH  - Energy Metabolism
MH  - *Exercise
MH  - Fatty Acids, Nonesterified/metabolism
MH  - Glucose/*metabolism
MH  - Glycogen/metabolism
MH  - Humans
MH  - Kinetics
MH  - Muscles/metabolism
MH  - Triglycerides/metabolism
EDAT- 1997/11/18 00:00
MHDA- 1997/11/18 00:01
CRDT- 1997/11/18 00:00
PHST- 1997/11/18 00:00 [pubmed]
PHST- 1997/11/18 00:01 [medline]
PHST- 1997/11/18 00:00 [entrez]
AID - 10.1111/j.1440-1681.1997.tb02713.x [doi]
PST - ppublish
SO  - Clin Exp Pharmacol Physiol. 1997 Nov;24(11):896-900. doi: 
      10.1111/j.1440-1681.1997.tb02713.x.