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Nutrition and Metabolism > Carbohydrate Supplementation Pre-exercise > Flashcards

Carbohydrate Supplementation Pre-exercise Flashcards

- Identify the most appropriate nutritional strategy in the lead-up of prolonged bout of physical activity - discuss the distinct mechanisms through which your specific recommendations might facilitate performance

1
Q

What are the 2 main roles of CHO nutrition before exercise?

A
  1. Maximise CHO availability (CHO loading)

2. Ensure adequate hydration

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2
Q

What is the habitual diet for athletes?

A

10-15% protein
15-25% fat
60-70% carbohydrates

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3
Q

How does the CHO regimen work?

A
  1. Low CHO + hard training for 3 days = pushes muscle to store glycogen
  2. High CHO + low training = super compensation of glycogen storage
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4
Q

What is exercise capacity?

A

Time to exhaustion

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5
Q

What is the utility of measuring exercise capacity?

A

Understand fatigue

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6
Q

What is exercise performance?

A

How far athlete can go in a defined period of time

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7
Q

What is the Bergstrom et al. (1967) study ?

A

oExercise to exhaustion on cycle ergometer @75% VO2max
oOver 3 days prior to exercise participants ingested either: high fat/protein diet or mixed diet or high CHO diet
oMeasured how long they could go for
>High CHO diet is much more advantageous, longer time to fatigue

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8
Q

What is the Karlsson et al. (1971) study?

A

oTime to complete a 30km run
oOver 7 days prior to exercise participants ingested either mixed diet or high CHO diet
>High CHO is better, shorter time to complete run

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9
Q

What is the Pizza et al. (1995) study?

A

oExercise to exhaustion on treadmill @100% VO2max
oOver 3 days prior to exercise participants ingested either mixed diet or high CHO diet
oMeasured how long they can hold VO2max intensity
>Surprisingly high CHO is better, longer time to fatigue

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10
Q

What are the 2 effects of CHO ingestion 3-4 hours before competition?

A
  1. Increases liver/muscle glycogen concentrations

2. Provides a feeling of comfort and satiety

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11
Q

What is the Chryssanthopoulos et al. (1994) treadmill study?

A

oTime to complete a 30km treadmill run
oParticipants ingested either: CHO 4h Pre and H2O during or H2O pre and CHO during
oDuring exercise, CHO is liquid ingestion (6% CHO solution)
>No difference: as long as there is CHO ingestion before or during it is the same

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12
Q

What is the Wright et al. (1991) study?

A

oExercise to exhaustion on cycle ergometer @70% VO2max
oParticipants ingested either: no CHO, CHO 3h pre-ex, CHO during ex, CHO 3h pre + during ex
>In all times of feedings, CHO intake was helpful relative to no CHO

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13
Q

When is it ideal for athletes to ingest CHO?

A

Pre + during competition

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14
Q

What are the 3 effects of CHO ingestion within one hour before competition?

A
  1. Final pre-exercise boost for liver/muscle glycogen concentrations
  2. Provides an exogenous source of CHO as it empties from the stomach
  3. Can cause metabolic disturbances
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15
Q

Why don’t studies measure below 70% VO2max?

A

It represents athlete levels and is above fat oxidation rates

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16
Q

Why don’t studies measure over 75% VO2max?

A

Can lead to variations due to acidosis differences (lactate)

17
Q

What are the 5 metabolic responses to glucose ingestion?

A
  1. Increased plasma glucose
  2. Increased plasma insulin
    3a. Increased CHO metabolism
    3b. Lower plasma glucose
    4a. Increased glycogen utilisation
18
Q

What is the Costill et al. (1977) study?

Glucose ingestion and glycogen metabolism

A

o30 min of treadmill running
o45 prior to exercise participants ingested either: 300ml H2O + 75g glucose or 300ml H2O alone (placebo)
oGlucose group: fasted state, glucose levels rise with feeing, then adrenaline response due to exercise reduce plasma glucose
>Rebound hypoglycaemia in glucose group (below fasted glucose levels)
>CHO group using muscle glycogen faster (seems like a waste in terms of performance)

19
Q

What is the Foster et al. (1979) study?

Glucose ingestion and exercise capacity

A

oFollow-on study from Costill et al. (1977) findings translate on exercise capacity?
oExercise to exhaustion on cycle ergometer @80 VO2max
o30 min prior to exercise participants ingested either 300ml H2O + 75g glucose or 300ml H2O alone (placebo)
>Glucose group does worse
>Only paper to find - effect of CHO

20
Q

What is the Chryssanthopoulos et al. (1994) cycle study?

A

oExercise to exhaustion on cycle ergometer @70 VO2max
o30 min prior to exercise participants ingested either 300ml H2O + 75g glucose or 300ml H2O alone (placebo)
>Found no difference, if anything betters CHO

21
Q

What are the 2 solutions of metabolic disturbance?

A
  1. Ingesting different types of CHO can alter the metabolic response to that feeding
  2. Ingesting low GI carbs before exercise may minimise any transient metabolic disturbance
22
Q

What is the Glycaemic Index?

A

The incremental area under the blood glucose response curve of a 50g CHO portion of a test food expressed as a percent of the response to the same amount of CHO from a standard food (usually glucose) taken by the same subject

23
Q

What is the Glycaemic Index equation?

A

(IAUC of test food)/(IAUC of reference food)x100

in mmol.l-1.150min

24
Q

What is the Thomas et al. (1991) study?

A

oExercise to exhaustion on cycle ergometer @65-70% VO2max
o1h prior to exercise participants ingested either: H2O (placebo), Lentils (LGI), Potato (HGI), glucose (HGI)
>Sig positive effect of LGI compared to other 3

25
Q

What is the Wee et al. (1999) study?

A

oExercise to exhaustion on a treadmill @70% VO2max
o3h prior to exercise participants ingested either: 2g CHO/kg (HGI) or 2g CHO/kg (LGI)
>No effect

26
Q

What is the Wu and Williams (2006) study?

A

oExercise to exhaustion on a treadmill @70% VO2max
o3h prior to exercise participants ingested either: 2g CHO/kg (HGI) or 2g CHO/kg (LGI)
>Sig positive effect of LGI compared to HGI

27
Q

What is the Wong et al. (2009) study?

A

oTime to complete a 21km run
o2h prior to exercise participants ingested either: 1.5g CHO/kg (HGI) or 1.5g CHO/kg (LGI) or sugar-free control
>No effect

28
Q

What is the effect of CHO feeding on fatigue?

A

carbohydrate feedings delay fatigue

29
Q

How does CHO feeding increase work output?

A

CHO feeding improves work output by maintaining carbohydrate availability

30
Q

What is the effect of high CHO availability on CHO oxidation rates?

A

High CHO availability allows maintenance of the rate of carbohydrate oxidation at a level sufficient to maintain a high rate of energy expenditure

31
Q

How does pre-exercise feeding help maintain blood glucose?

A

The rate of gastric emptying of concentrated CHO drinks is slow so pre-exercise CHO feeding can be absorbed during exercise and prevent decline of blood glucose

32
Q

How does blood glucose curve respond to CHO feeding?

A

Significantly greater IAUC

33
Q

What is the effect of high blood glucose on CHO metabolism?

A

High blood glucose is an index of high CHO availability and high CHO utilisation

Nutrition and Metabolism (4 decks)

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