Food as Fuel for Fitness

Question 1

CNS Fatigue

reduced what?

Answer 1

CNS) fatigue is associated with reduced neural drive – either an inability to maintain it or unwilling too – protective mechanism?

Question 2

Peripheral fatigue

Answer 2

• is more closely associated with physiological changes at the local level e.g., unable to match energy demand in the muscles

Question 3

Why do carbs help limit fatigue

Serotonin

Answer 3

If glycogen stores are depleted, free fatty acids increase in the blood, to be used as fuel

Tryptophan is a precursor for serotonin, and therefore more serotonin goes to the brain

• Serotonin promotes lethargy and fatigue; thus, could reduce exercise performance

Question 4

Should you Carb Load

Answer 4

If exercise is very high intensity (≥100% VO2max and short duration (5-10 min) there does not seem to be an additional benefit to maximising glycogen stores (Hawley et al., 1997).

Question 5

Carb loading intake for 60 - 90 minutes of exercise

how loing before exercise should it be don

Answer 5

Consuming 7 – 10 g/kg/ BM 24 – 36 hours prior to competition should be adequate to optimise glycogen stores
- as long as there are no CHO restrictions in the days preceding this
- 770 grams for a 77kg person

Question 6

Things to consider for Carb loading

wait, rest, zones

Answer 6

Important to be mindful of those who might restrict intake for weight management reasons (Burke, 2017)

Also important to avoid muscledamaging exercise in the days leading up to exercise

Zone 1 or zone 2 relatively for heart rate

Question 7

Carb Load recommendations for exercises and timeline

Answer 7

• Events are highly reliant on glycogen as a fuel source, so CHO loading encouraged Several different protocols have been suggested and modified over-time
  
  • 60s
    
    • 3 days of depletion followed by 3 days of loading
  • 80s
    
    • 3 days of loading – no depletion phase
  • 20s

Question 8

Loading recommendations for exercises over 90 minutes

Answer 8

• 36 – 48 h prior should be sufficient to optimise stores (10-12 g/BM/day)
• CHO loading improved performance in these events

Question 9

Pre-Exercise meal: Key factors that might impact performance

Answer 9

• CNS fatigue
• GI discomfort
  
  • Gastro-intestinal
    
    • Stiches
    • Stomach Pain
• Carbohydrate availability/depletion of glycogen
• Hypoglycemia
  
  • Low blood sugar
• Poor recovery
  
  • Lack of sleep
  • Lack of Carbohydrates
• Dehydryation
  
  • when 2% of our body mass has been lost through sweating

Question 10

Pre-exercise Fueling: Aim

Answer 10

The aim of pre-exercise specific fuelling is to implement nutritional strategies that will optimise performance; specifically, delay the onset of factors that cause fatigue/negatively affect performance

Question 11

Nutrient timing:1 hour before exercise snacks

Answer 11

1 hour pre exercise
- Carbohydrate-rich snacks that are low in fibre, fat, and protein
- Bannana
- Jam Sandwich
- Haribos
- Yoghurts
- Cornflakes
- Granola
- No wholemeal pasta or meals
- Remember – some athletes experience hypoglycaemia
- Some may get low blood sugar due to hyper consumption
- Avoid by providing low GI CHO, consuming CHO in event and importantly, experiment in training!

Question 12

Nutrient timing: Pre-exercise meal and food

Answer 12

• Should be consumed 1 – 4 h before competition
• Should be just to restore/top up glycogen stores – the heavy lifting should have been done in the previous few days!
• Prevent hunger and GI distress
  
  • Low in Fibre or Fats due to the time that it takes for the body to digest it
    
    • Carbohydrate-rich (1-4 g/kg/BM)
• Restore liver glycogen content after sleeping

Question 13

What does this look like for a 56 kg marathon runner?

Answer 13

• 10 g per kg/BM/day = 10 x 56 = 560 grams of carbohydrate
  
  • Only for the Elite Elite level

Question 14

Fues as fuel during exercise

Answer 14

Muscle glycogen and plasma glucose are the most important for exercise

Exercise is associated with different training adaptations
- Endurance training
- Strength Training
- Sprint training
- Capilarry density
- Glycogen density
- Muscle size
- Plasma Volume

Question 15

Carb needs for an athlete

Answer 15

The principal role of carbohydrates is to provide energy for muscular contraction (Gleeson & Jeukendrup, 2011)
- We consume carbohydrates in the diet and store them in muscle and liver in the form of glycogen

Question 16

Liver stroage of glycogen

Answer 16

• Liver stores aropund 320-440 calories of glycogen

    - All of this gets broken down into glucose and enters your muscles
        - It is well established that there is a heavy reliance of muscle glycogen during high intensity exercise
            - If insufficient carbohydrates consumed, then suboptimal muscle glycogen for competition is possible
    - Stomach can break it down as well

• 12 – 16 g/kg W.W. in muscles (300 – 400 g of CHO or 1200 – 1600 Kcal