Carbohydrate Utilization During Exercise

1. Carbohydrate Utilization During Exercise

2. Are CHO important during exercise? • 1.) Fatigue often associated with CHO depletion. 2.)  CHO,  OAA  Fat metabolism can only support exercise at 50% VO2 max. 3.) Hypoglycemia associated with liver CHO depletion.

3. Muscle glycogen breakdown during exercise • Two biggest factors are intensity and duration of exercise Recruitment order of slow twitch vs. Fast twitch fibers • Glycogen use from only exercising muscle • 1 leg experiments • deltoid vs. vastus lateralis

4. Regulation of Muscle Glycogenolysis - + ADP ATP • PFK-1 AMP H+ Pi citrate -Energy state of muscle cell with impact from substrate supply Phosphorylase -local factors -substrate availability -hormonal regulation

5. Regulation of Muscle Glycogenolysis (cont.) Phosphorylase (cont.) -local factors: -substrate availability -hormonal regulation Local factors: cytosolic Ca++ - activates phosphorylase kinase ADP, AMP, Pi - allosteric activators of phosphorylase -Need for Pi as a substrate for phosphorylase

6. Regulation of Muscle Glycogenolysis (cont.) Substrate availability: -Glycogen - allosteric activator of phosphorylase -Plasma FFA FFA glycogen use FFA glycogen use -FFA citrate - PFK-1 acetyl-Co-A activates PDH Kinase  P-PDH its activity -Caffeine glycogen use Corn Oil/Heparin glycogen use -Plasma Glucose - Hypoglycemia glycogen use

7. Hormonal Regulation Hormonal Regulation Epi/N-Epi via  receptors C-AMP  - blockade glycogen use Removal of adrenal medulla glycogen use

8. Glycogen Degradation With Exercise

9. Regulation of Glycogen Synthesis/Degradation

10. Muscle Fiber Recruitment

11. Muscle Fiber Recruitment (cont.)

12. Muscle Glycogen Depletion

13. Muscle Glycogen Depletion