Carbohydrate feeding after exercise Flashcards
(16 cards)
What is long term classified as for post-exercise recovery?
8 - 24 hours
What is short term classified as for post-exercise recovery?
0 - 8 hours
During the need for short term recovery e.g. having a training session within 8 hours of each other, what is the recommended timing for CHO consumption?
Immediately after exercise.
Provides the most significant uptake of muscle glycogen.
What is the advice for long term post ex. recovery?
Less about when you take it an more about the quantity you consumed for the exercise intensity you performed. (Over a 24 hr period, even up to 8 hours, no significant impact in the effect of timing).
During exercise, what ion becomes present causing the movement of GLUT 4 transporters to the sarcolemma?
Calcium (Ca2+)
During feeding, what is responsible typically for the movement of GLUT 4 to the membrane?
Insulin (storage molecule) - Activated when plasma glucose levels are high in the blood (e.g. after feeding)
What is the first phase when glucose enters the cell for storage?
ATP is hydrolysed during glucose’s reaction with hexokinase, Glucose = glucose-6-phosphate which allows it to stay present in the cytoplasm.
Muscle glycogen recovery occurs in two phases, what are they?
Fast phase (independent of insulin), rapid formation of glycogen over 2-4 hours
Slow phase (dependent of insulin), slow formation of glycogen over 24 hours
Explain the rapid phase of muscle glycogen storage.
During exercise, muscular contractions occur with the presence of certain molecules e.g. Ca2+, NO, adenosine, AMPK which increase glycolysis and GLUT 4 translocation but inhibit Glycogen synthase.
However, when contractions stop. The increased number of GLUT 4 transporters are still present on the membrane, therefore glucose enters the cells but instead of being oxidised by glycolysis they are moved to glycogen synthase.
Explain the slow phase of glycogen storage.
After feeding, insulin response occurs. Insulin binds to the insulin receptor on the cell membrane resulting in a long chain reaction resulting in the movement of GLUT 4 transporters to the membrane. Glucose then enters the cell and is converted to glycogen via glycogen synthase.
The amount of carbohydrate intake for optimal glycogen synthesis (in the slow phase, 4-6 hrs post) is …………
1.2 g/kg bw/h (grams/kg body mass/hr)
Little/no benefit for greater consumption than that.
What are the best sources for CHO resulting in glycogen synthesis and what is the worst and why?
Glucose and sucrose due to their high glycaemic index
Not Fructose; preference is the liver and doesn’t enter the blood stream as glucose.
Why does the addition of protein into dietary intake further increase the synthesis of glycogen?
The presence of protein as well as CHO further boost the insulin response to feeding resulting in a greater uptake of CHO and therefore increased glycogen synthase activity.
What is the limitation to the boosting effect of protein consumption?
If CHO consumption is less than 1 g/kg/hr, the presence of proteins does have a boosting effect to glycogen synthesis.
However, if CHO consumption is already at quantities reaching 1.4 g/kg/hr and greater, presence of protein has no significant effect.
For the speediest CHO fuelling after exercise it is recommended that ………..
Consume as early as possible post exercise (within first hr) then at 30 min intervals for 4 hrs after.
After can return to normal diet.
Quantity = 1.2 g/kg CHO/hr for first 4 hrs of mod-high glycaemic index.
(addition of protein is advised is 1.2 g/kg/hr can not be reached) (Protein is probably consumed for muscle protein synthesis regardless).
Explain the effects of consuming a fructose-glucose blend opposed to just glucose.
In terms of synthesis rate 4 hrs post in the muscle, there is negligible effect.
However, liver glycogen synthesis rates are almost doubled with the fructose-glucose combination compared to just glucose.
