Carbohydrate feeding during exercise Flashcards
(25 cards)
Carbohydrates in the body? Blood, liver and muscle?
Liver = 80-110g
Muscle = 300-600g
Blood = 4-6g
What is maltose made of?
2 glucose molecules
What is sucrose made of?
1 fructose and 1 glucose
What is lactose made of?
1 galactose and 1 glucose
What carbohydrates are fast release? (quickly digested, absorbed and made available for energy provision)
Glucose
Maltose
Sucrose
Maltodextrin
Amylopectin (starch)
What carbohydrates are slow release? (slowly digested, absorbed and made available for energy provision)
Fructose (alone)
Galactose
Isomaltulose
Amylose (starch)
Classical guidelines for carbohydrate feeding during exercise, with examples.
1 g/min or 60g/hr during exercise
E.g. litre of sports drink or 2 gels (30g each) or 80g jelly babies (78g per 100 grams)
At what quantity is there a ceiling effect for improved performance while consuming carbs during exercise? (classic guidelines)
1 gram/min or 60 gram/hr
Updated guidelines suggest what for durations lasting 30-75 mins?
Small amounts of supplementation
Mouth wash could be sufficient
single or multiple transport carbs
Updated guideline suggests what for durations lasting 1-2 hours?
30g/hr
Single or multiple transport carbs
Updated guideline suggests what for durations lasting 2-3 hours?
60 g/hr
Single or multiple transport carbs
Updated guideline suggests what for durations lasting >2.5 hours? What else may you have to consider?
90 g/hr
Only multiple transportable carbohydrates
This level of consumption may require gut training.
Same sugar consumption may also cause GI distress; use a variety (prevent stomach cramping)
The effects of carb feeding during exercise increases with the duration of the event? T or F?
True
What else could feeding benefit during sport performance?
Motor skills during prolonged sport
Feeding Carbs during low intensity exercise effect? (Fast vs Fed) (on plasma glucose)
Fasted - Plasma glucose stays maintained in circulation
Fed - Spike in plasma glucose (similar response to when a sports drink is had at rest)
What does not increase when carbohydrate feeding?
Muscle glycogen stores
Whereas, increases in plasma glucose and carbohydrate oxidation are seen.
In some scenarios e.g. running, why are glycogen stores around a muscle greater when supplementing CHO compared to Water?
Increasing plasma glucose levels could possibly create a glycogen sparing effect in the muscles when running - not seen in cycling.
When fasted where are plasma glucose levels supplied from?
Glucose from the liver
When supplementing high glucose during exercise, what happens to liver glucose contribution?
Almost negligible contribution from the liver
What are the metabolic effects of carbohydrate feeding during exercise?
Maintains plasma glucose concentrations (helps sustain high rates of carbohydrate oxidation)
Spares liver glycogen (sustains plasma glucose and carb oxidation)
Possible sparing of muscle glycogen (not often observed)
Possible non-metabolic effects
During exercise, body undergoes thermal, metabolic and physical stress. The brain takes this information and will change motor unit recruitment and therefore power output (lower)
However, the presence of an oral CHO mouth rinse causes reward sensors in the brain to activate further neural drive which increases motor unit recruitment.
This occurs independent of sweetness and is not related to the apparencies of glucose in the bloodstream.
Explain the limiting factor of CHO oxidation from ingested CHO during exercise in the intestines.
After ingesting CHO, it moves from the stomach into the intestines. Glucose molecules are then moved from the intestinal lumen to the blood stream via membrane transporters (active process) SGLT 1 (sodium dependent glucose transporter 1).
However, there is a limited amount of these transporters. This can causes a CHO blockage in the intestine, which can result in GI distress and cause urges to defecate.
How can this limiting factor in the intestinal tract be mitigated or minimise GI distress when attempting CHO consumption during exercise?
By consuming a different source of CHO.
For example, fructose, as it utilises a different membrane transporter (GLUT 5). This reduces the CHO blockage in the intestine.
Definition of a multiple transportable carbohydrate
Refers to sugars that are transported across the intestines by stimulating more than one protein transporter. E.g. SGLT 1 for glucose and GLUT 5 for fructose.
