Transcript CHO Use Before, During & After Exercise

CHO Use Before, During & After
Exercise
Recall: Important Aspects of
Glycogen Use
• 1.) Glycogen + Phosphate  begins
reactions in glycolysis
cascade of
– in working muscle, free P levels are higher than in non working
muscle due to breakdown of ATP and CP
2.) Blood Glucose  enters cell via diffusion, then is
phosphorylated by hexokinase to G-6-P (takes ATP)
blood glucose use  2ATP/mole glucose
muscle glycogen use  3 ATP/mole glucose
Important Aspects of Glycogen
Use
(cont.)
2.) continued– , best to use muscle glycogen during exercise
because you get more ATP
How does the body know to do this?
Glucose concentration gradient
GLUT 4 transporters
3.) The more glycogen present in muscle, more is used.
Why is this?
More glycogen  more branching  more ends
exposed to phosphorylase
Important Aspects of Glycogen
Use (cont.)
4.) When exercising in hot conditions, more
epi/norepi is released
–  more glycogen use (due to glycolysis)
– run out of fuel faster  appear less trained
5.) Trained individuals have about 50% more stored muscle
glycogen than untrained
GLUT 4 in muscle   glucose uptake from blood
 glycogen synthase in muscle w/ training
CHO use before, during and after
exercise
1. Before exercise
– 3 days
• eat more, store more
• humans (trained) can  glycogen storage by 50% (takes about
three days)
• During three days prior to event, eat 70% CHO, only do activity
under 50% VO2 max
3 hours
focus shifts to liver glycogen
effect of glycemic index
CHO use before, during and after
exercise
(cont.)
• During exercise
for events > 90 minutes, want to consume CHO at rate of
1g/min
will slow use of glycogen
After exercise
must consume >100g CHO w/in 2 hrs post exercise to
completely recover
Large amount of GLUT 4s activated post exercise
very easy to bring glucose into muscle to restore
glycogen
Hydration during exercise
•  dehydration causes  heart rate
– lower cardiac output causes  core temp.
Sweat rate
normal  1 L/hr
athletes  2 L/hr
Most athletes only consume 500 ml/hr
Gastric emptying
max rate 2 L/hr
controlled by:
volume in stomach, and osmolarity in stomach
Hydration during exercise (cont.)
• Intestinal absorption
– max rate 2 L/hr
*Unfortunately, people don’t drink 2 L/hr!
Three important ingredients in fluid replacement drinks:
H2O
CHO
Na  main extracellular ion which enhances H2O
retention in small intestine