Week 3 - Carbohydrate feeding after exercise Flashcards
Difference between short-term and long-term post-exercise recovery.
Short-term recovery is from 0-8 hours after exercise has stopped to the next session/bout. Involves strategies to ensure rapid glycogen repletion.
Long-term recovery is from 8-24hours after exercise. Adoption of general daily CHO intake should ensure repletion on a day-to-day basis.
How does carb intake immediately post-exercise compare with carb intake 2hours post-exercise?
When we consume carbs immediately post-exercise we have very high rates of glycogen synthesis. If we consume carbs 2hours post-exercise, glycogen synthesis rates aren’t so high.
Essential for short recovery window (0-4hrs from one exercise to another)
Why do we get high rates of glycogen synthesis 1-2hrs after exercise?
some GLUT4 remains on the cell membrane which increases uptake of glucose into the cell and as exercise has finished we no longer get calcium release, AMPK, free adenosine… therefore glycogen synthesis is favoured over glycolysis.
What are the two key enzymes in glycogen synthesis in the skeletal muscle?
Glycogen synthase and branching enzyme
What are the 2 phases of glycogen re-synthesis?
Insulin independent (rapid phase)
- 1-2hours post-exercise
- Glut4 remains on cell membrane so glucose used for glycogen resynthesis
Insulin dependent (slow phase)
- 3-4hours post-exercise
- Feeding results in pancreas releasing insulin into bloodstream which enhanced glut4 translocation and glycogen synthesis.
Describe the regulation of muscle glycogen synthesis during exercise and post-exercise.
During exercise, glycogen synthesis is inhibited by Ca2+, vasodilator agents NO, free adenosine and AMPK. These factors enhance glycolysis.
When exercise finished, these chemical signals are no longer produced therefore glycogen synthase is no longer inhibited. Furthermore, glut4 remains on the cell membrane so entering glucose is used for glycogen synthesis. Additionally, when we consume food, insulin is released, and this positively regulates glycogen synthase.
What is the guidelines for carbohydrate intake after exercise in terms of:
- Timing of intake
- Amount of carbs
- Types of carbs.
Early and frequent carbohydrate feeding (within the first hour and at 30min intervals for 4h thereafter, before resuming normal diet).
1.2 g/kg/h for first 4-6 hours, of carbs with a moderate-to-high glycaemic index which provides a readily available source of substrate for glycogen synthesis.
Role of protein co-ingestion in post-exercise recovery
Protein can be co-ingested if CHO intake is sub-optimal (below 1.2 g/kh/h) as it increases muscle glycogen synthetic rate when compared to just sub-optimal CHO intake.
How does the addition of protein to post-exercise carbohydrate intake increase muscle glycogen resynthesis?
the extra protein stimulates insulin secretion when carbohydrate intake is sub-optimal –> greater uptake of glucose that can be used for muscle glycogen resynthesis
How may fructose-glucose ingestion post-exercise be beneficial?
When fructose is co-ingested alongside glucose-based carbs it accelerates the replenishment of glycogen stores (mainly liver glycogen stores).
Fructose co-ingested with glucose in recovery from exercise can also enhance subsequent time-to-fatigue.
What is the recommended carbohydrate ingestion rate to maximize muscle glycogen resynthesis after exercise?
1.2 g/kg/h
