CHO intake before & during exercise Flashcards
What are the recommendations of CHO ingestion before exercise?
Before Exercise> 60mins
1-4 g.kg-1 BM consumed
1-4h before exercise
- Very varied recommendations for grams of CHO
- Varied time period before exercise, depends on the amount and type of exercise
What limits exogenous CHO oxidation?
- Gastric emptying does not limit exogenous CHO oxidation (Rehrer et al., 1992)
- CHO oxidation did not change even when gastric emptying did
- Muscle glucose uptake does not limit exogenous CHO oxidation (Hawley et al., 1994)
- Much increased CHO oxidation rates
- Intestinal CHO absorption appears to be the rate limiting step
How effective is pre-exercise feeding?
- 10 males, 2 x 30km runs
- Trial 1 – 4h before CHO meal, water during exercise
Trial 2 – 4h before placebo drink, CHO-E drink every 5km - Blood glucose in fed, there is an increase, but then levels out
- During run feeding blood glucose is exogenous
What are the aims of taking exogenous CHO?
- To provide an additional source of fuel
- To maximise oxidation rates
- To prevent gastrointestinal distress
- To maximise performance
How is glucose absorbed?
Sodium glucose link transporter 1 - transports glucose
- Gets saturated at 1g per min
- Fructose uses different transporter, allowing CHO to still go through the system
- Glucose to fructose in 1:0.8 ratio transportation
What is the effect of CHO mouth rinse?
- CHO or PLA rinse every 12.5%
- ~1 hr/~40km TT performance with or without CHO-E (7.6%)
- CHO Mouth rinse increased performance more than water due to the sensing in the brain
As it detects that CHO is coming - 30g of CHO in 500mL of a CHO drink
What are the aims for CHO intake after exercise?
Recovery
* Ensure muscle and liver glycogen stores are restored
* The timing of this depends on when resynthesis is required
* Short v long recovery
* Immediate post-exercise meal/snack/drink
* 1-2 hours post-exercise
* Within 8 hours
* 24 hours
* General diet
Describe the recovery of muscle glycogen: (timeframe)
Glycogen depletion during exercise
- Ingestion straight after exercise is much quicker
- In the first 10hrs there is the most muscle glycogen resynthesis
Why is the timing of CHO important?
Delaying feeding by 2hrs after exercise - not much of an increase, no affinity to uptake glucose into the muscle
Immediately after exercise - there is a lot more replenishment of muscle glycogen
What is the optimum intake of CHO for glycogen resynthesis?
1-1.2g/kg BM/h 2-4hrs
How can ingesting CHO with protein further improve muscle glycogen resynthesis?
After 5hrs of exercise - insulin is much higher in CHO + protein trials
Addition of protein, due to leucine in protein helps to increase insulin