W2 - CHO Supplementation Flashcards
Recap CHO digestion
CHO in mouth is broken down by salivary amylase
Travels down oesophagus where it continues to mix w/ S.amylase but not a lot of breakdown due to speed through oesophagus.
High levels of acid in stomach stop amylase action - no CHO breakdown.
Pancreatic amylase in small intestine continues to break down CHO –> Disaccharides –> Monosaccharides
Monosaccharides are transported into blood + into liver.
Monossacharide absorption
Glucose + galactose
Co-transported w/ na+ through sodium-glucose transporter from the intestinal lumen into intestinal wall.
GLUT2 from intestinal wall into blood
Monossacharide absorption
Fructose
Through GLUT5 from intestinal lumen into intestinal wall.
GLUT2 from intestinal wall to blood.
With what type of exercise does MUSCLE glycogen deplete quicker?
More intense exercise
Predominant fuel used at 25%VO2 max
Plasma FAs
Predominant fuel used at 65%VO2 max
TAGs
Predominant fuel used at 85%VO2 max
Muscle glycogen
Super-compensation protocol (1960s)
Starts 7 days before race/event day
7th day before: Hard bout of training.
3 days after: low CHO intake + no training.
3 days after: high CHO intake + no training
Issues with the super-compensation protocol
Could get:
- Hypoglycaemia in low CHO stage
- Practicality
- GI distress
- Poor recovery
- Poor mental state
Moderate super compensation protocol
Starts 7 days before race/event day
Gradually increase CHO + gradually decrease training
1 or 2 days might be enough
No exercise
10g/kgBM/d CHO intake
Is CHO loading worth it?
Depends on duration/nature of activity
Yes for…
Repeated sprints
Intermittent sport lasting >1hr maybe
Exercise >90 mins
No for…
Short + explosive
When is CHO loading before event especially important?
If not intaking CHO during event
Why is CHO loading prior to an event in the morning especially important?
To replace liver glycogen used overnight
CHO loading hours before event
AMOUNT
1-4g/kgBM (range involving how long until race, individual needs + ind gut).
What CHO would you want to avoid when CHO loading hours before event
Low GI + fat
Effects of CHO loading hours before event
Transient fall in plasma glucose at exercise onset (won’t effect perf)
Incr CHO oxidation + accelerated glycogen breakdown
Blunting of FA mobilisation + Fat oxidation
Solutions to reactive hypoglycaemia
Low GI food
Consume closer to exercise
Nothing for 90mins prior to start of exercise
Goals + considerations for CHO intake
Prevent depletion of blood glucose + muscle + liver glycogen
Maintain hydration
Duration of event, quantity of CHO, type + form of CHO
What is the oxidation of ingested CHO limited to?
~1g/min (60g/h)
Does the form of CHO ingestion affect performance?
NO
Does infusion of CHO relate to an improved performance?
No
What can CHO intake improve?
Endurance capacity >2hr
High intensity exercise lasting ~75 mins
What will CHO ingested during exercise do?
“Spare” liver glycogen + completely block hepatic glucose output
What do exogenous CHO oxidation rates of a single CHO peak at?
~1.0-1.1 g/min
Ingestion of multiple transportable CHO can increase exogenous CHO oxidation rates by how much?
20-50%
What are the daily dietary recommendations of CHO intake if you are doing moderate training?
5-7g/kgBM
