CHO intake before & during exercise Flashcards

1
Q

What are the recommendations of CHO ingestion before exercise?

A

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

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2
Q

What limits exogenous CHO oxidation?

A
  • 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
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2
Q

How effective is pre-exercise feeding?

A
  • 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
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2
Q

What are the aims of taking exogenous CHO?

A
  • To provide an additional source of fuel
  • To maximise oxidation rates
  • To prevent gastrointestinal distress
  • To maximise performance
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3
Q

How is glucose absorbed?

A

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

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4
Q

What is the effect of CHO mouth rinse?

A
  • 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
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5
Q

What are the aims for CHO intake after exercise?

A

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

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6
Q

Describe the recovery of muscle glycogen: (timeframe)

A

Glycogen depletion during exercise
- Ingestion straight after exercise is much quicker
- In the first 10hrs there is the most muscle glycogen resynthesis

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7
Q

Why is the timing of CHO important?

A

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

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8
Q

What is the optimum intake of CHO for glycogen resynthesis?

A

1-1.2g/kg BM/h 2-4hrs

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9
Q

How can ingesting CHO with protein further improve muscle glycogen resynthesis?

A

After 5hrs of exercise - insulin is much higher in CHO + protein trials
Addition of protein, due to leucine in protein helps to increase insulin

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