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PHYL2730 > Nutrition and Exercise Performance > Flashcards

Nutrition and Exercise Performance Flashcards

1
Q

Overview

A
  • Dietary carbohydrate and muscle glycogen
  • Dietary fats and use of fat during exercise
  • Protein needs for the athlete
  • Fluid intake during and following exercise
  • Recovery nutrition
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2
Q

Classes of nutrients

A
  • Carbohydrate (CHO)
  • Fat (lipid)
  • Protein
  • Vitamins
  • Minerals § Water
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3
Q

questions to help devise nutritional strategies for an athlete:

A
  • What is the duration (and thus the intensity of the exercise involved)?
  • What are the environmental conditions?
  • What is the training status of the athlete?
  • What has been the success of prior nutritional strategies?
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4
Q

facts

A
  • higher intensity more glycogen, lower intensity more fat
  • exercise in heat, greater use of muscle glycogen due to catecholamine -will heat wall quickly
  • muscle fibres increase, endurance athlete can burn more fat and delay hitting wall
  • composition of sport drink (during or after exercise) - individual
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5
Q

nutritional factors associated with exercise-induced fatigue include:

A
  • Glycogen depletion
  • Hypoglycemia
  • ‘Central’ fatigue
  • Dehydration
  • Hyponatraemia
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6
Q

Carbohydrate

A

monosaccharides
disaccharide
polysaccharide
- glucose mainly used for brain and CNS

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7
Q

Glycogen depletion

A

hitting the wall - run out of glycogen in muscles being used

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8
Q

Hypoglycemia

A

Low Blood glucose - primary effect - loss of motivation and concentration

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9
Q

‘central fatigue’

A

Fatigue that originates in brain

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10
Q

Dehydration

A

Lead to heat stroke, coma or even death (medical condition)

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11
Q

Hyponatraemia

A
  • low plasma sodium concentrations - associated with prolonged exercises and who drink too much fluid (diluting sodium in blood) - medical condition
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12
Q

Sources of Carbohydrates

A
  • grains
  • fruits
  • vegetables
  • milk
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13
Q

Carbohydrates

A
  • stored in body as glycogen

- highest storage in liver (to maintain blood glucose levels)

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14
Q

dietary carbohydrate intake

A
  • for athletes is essential, given the critical role that muscle glycogen plays in exercise
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15
Q

Muscle glycogen

A
  • a unique fuel, as it can be used both aerobically (with oxygen) and anaerobically (without oxygen)
  • In contrast fat (which is the other main fuel used by exercising muscles) can only be used with oxygen
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16
Q

Glycogen stores

A
  • dietary carbohydrate intake should constitute at least 50% of the total calories consumed every day
  • heavy training and endurance exercises, should be ideally around 55-60%
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17
Q

e.g.

A

For an athlete consuming 3000 calories a day, 55-60% from CHO would equate to 1650-1800 calories (400 and 450 grams a day)

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18
Q

Percentages not usually used

A

%’s need to be balanced against total energy intake when CHO needs of athletes are considered; athletes who consume large amounts of energy per day may meet their maximal rates of glycogen resynthesis with CHO representing only 40% of the total energy.

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19
Q

Muscle glycogen resynthesis

A
  • complete resynthesis can take up to 24 hours
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20
Q

Pre-exercise glycogen ‘loading’

A
  • aim of CHO or glycogen loading is to super-compensate or maximise muscle glycogen stores
  • will delay fatigue and allow the exercising athlete to maintain moderate to high intensity exercise for longer
  • original studies in the 1960’s showed clear and unequivacal benefits to a 7-day depleting repleting schedule to maximise pre-exercise muscle glycogen stores
  • more recent work has shown that well-trained athletes can achieve the same ‘super-compensation’ of glycogen without the depleting phase (and just by tapering).
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21
Q

if seven days out from competition you would deliberately deplete glycogen levels on first day

A

3 days following high fat and high protein depriving muscles ability to resynthesis glycogen - making muscles desperate for carbohydrates that when store carbohydrates the next day get a super compensation

22
Q

Taper

A
  • reduce amount of glycogen cells
23
Q

Pre-event intake of CHO

A
  • To maximise muscle glycogen stores.
  • To maximise liver glycogen stores.
  • To ensure the athlete is adequately hydrated.
  • To prevent hunger but to avoid gastrointestinal discomfort.
24
Q

Glycaemic Index

A
  • measure of the rate of digestion and absorption of carbohydrate foods and the resultant effect on blood glucose level
  • CHO meals that have a low glycaemic index result in a slower rise in blood glucose response.
  • However, research has not shown a significant difference in performance between high and low GI meals consumed before exercise.
25
Q

High Glycemic Index

A
  • it would be bad as glucose spike, insulin then released which suppresses release of fat into blood which isn’t beneficial to exercise
  • catecholamines blocks insulin therefore can take high glycemic index
  • what actually happens is
26
Q

Priorities during prolonged exercise

A
  1. Substrate replacement (prevention of hypoglycemia and sparing of muscle glycogen). This is likely to delay but not prevent fatigue
  2. Fluid replacement
    The choice of food and drinks to be consumed during exercise should be closely related to the distance and intensity of the race and also to environmental conditions.
    - max sweating twice rate of fluid replacement
    - post exercise - max sweating twice rate of fluid replacement
27
Q

mechanisms as to performance improved with CHO intake during exercise

A
  • not clear, muscle glycogen sparing may occur (if does probably only in type 1 fibres)
  • In addition, CHO taken during exercise better maintains blood glucose concentrations
28
Q

CHO: a ‘central’ influences

A

CHO ingestion during exercise can improve mental performance as well as exercise capacity.
Indeed, CHO intake during exercise appears to improve performance independent of glycogen depletion – suggesting a central (CNS) effect.

29
Q

Fat

A
  • an essential component of cell membranes and nerve fibers
  • a primary energy source
  • protects organs
  • stores the fat-soluble vitamins
  • necessary for steroid hormone production
  • provides insulation
  • isn’t critical
30
Q

mechanisms as to performance improved with CHO intake during exercise

A
  • not clear, muscle glycogen sparing may occur (if does probably only in type 1 fibres)
  • In addition, CHO taken during exercise better maintains blood glucose concentrations
31
Q

CHO: a ‘central’ influences

A

CHO ingestion during exercise can improve mental performance as well as exercise capacity.
Indeed, CHO intake during exercise appears to improve performance independent of glycogen depletion – suggesting a central (CNS) effect.

32
Q

Fat

A
  • an essential component of cell membranes and nerve fibers
  • a primary energy source
  • protects organs
  • stores the fat-soluble vitamins
  • necessary for steroid hormone production
  • provides insulation
33
Q

Protein

A
  • 20 amino acids required by the body, 8 have to be gained from the diet.
  • There is an insulin response to EAA intake and insulin + AA’s are together important for increasing protein synthesis.
  • Amino acids and protein contribute to structure, transport, enzyme function, hormone production, immune function, acid-base balance, fluid balance and energy availability.
34
Q

Fat intake and exercise performance

A
  • in four days muscles would adapt to store more fat - muscles increase capacity to burn fat (oxidative phosphorylation) and decrease capacity to burn glycogen
  • reduce rate at which muscle glycogen is used and can delay athlete hitting the wall
35
Q

Challenges on low CHO diet

A
  • potential to undertake high exercise intensity
  • for endurance athlete in training exercising for a couple of days a week on low CHO diet may be valuable
  • must precede competition
36
Q

Protein

A
  • 20 amino acids required by the body, 8 have to be gained from the diet.
  • Amino acids and protein contribute to structure, transport, enzyme function, hormone production, immune function, acid-base balance, fluid balance and energy availability.
37
Q

BV

A

Biological value

38
Q

Protein amount for athletes

A

well trained endurance:
- between 1.2 and 1.6g · kg−1 · d−1
majority of athletes consume in excess of 1.8g · kg−1 · d−1

39
Q

example

A

For example, take an athlete who consumes 6400 kcal/day. If 14% of this energy intake is protein, that corresponds to 2.5g · kg−1 · d−1 (for a large athlete) or 3.2g · kg−1 · d−1 for a smaller athlete.
Even when consuming 3500 kcal/day, a balanced diet will provide 1.6-1.9g · kg−1 · d−1 .

40
Q

Whey protein

A
  • Whey protein elicits a greater initial rate of protein synthesis than casein.
  • Whey is a soluble protein that is quickly absorbed; casein clots in the stomach – leading to slower absorption.
  • Also, whey has a higher leucine content and this may be related to the faster protein synthesis.
41
Q

Leucine

A
  • essential amino acid
  • important in triggering muscle growth
  • doesnt matter when take it
  • has more whey than casein
  • contained in nuts
  • stimulate protein synthesis; as little as 6g will initiate synthesis; >20g does not appear to elicit any further effect.
42
Q

daily intake of protein

A
  • 20g 5-6 times a day
  • timing is more important than daily intake for athletes seeking hypertrophy of muscles
  • no adverse consequences
  • supplementation does not confer any advantage or benefit
  • older athletes might need more protein
43
Q

Fluid intake

A
  • in last 30mins will not benefit performance
  • for endurance events fluid intake (especially when weather leads to sweating) will benefit
  • can drop max 4kg due to prolonged endurance exercise (6% deficit in body water)
44
Q

gastric emptying

A
  • maximising is important
  • high volumes of fluid favor
  • keeping CHO concentration of sport drink below 6% will reduce risks of lowering GE
45
Q

Beverages

A

gatorade is best?? half the sweetness of soft drink

46
Q

Hyponatremia

A
  • condition in which blood sodium concentrations are lower than 135-145mmol/L
  • dilutes sodium in body
  • from over-consumption of fluid during exercise
47
Q

symptoms

A
  • weakness
  • disorientation
  • seizures
  • coma
48
Q

nutrition for recovery after training and competition

A
  • Between 6 and 24 hours often separate high intensity training sessions
  • Nutritional issues relating to recovery include restoration of muscle and liver glycogen, rehydration and repair/growth of tissue
49
Q

Glycogen Resynthesis

A
  • Post-exercise muscle glycogen resynthesis is most rapid within 2-4 hours following exercise
  • This is because glucose enters the muscle cell independent of insulin
  • This means that once exercise has been completed, CHO intake must immediately begin
  • muscles highly permeable to glucose
  • there is a max amount of glycogen that muscles can store
50
Q

Fluid replacement

A
  • Athletes typically only replace 30-60% of fluids lost as a result of exercise
  • 150% of the volume of lost fluid needs to be consumed – to replace the losses.
  • Sodium concentrations need to be high in order to prevent post-exercise excessive urine loss. If sodium concentrations in the drink are low, more fluid will need to be consumed.
  • Sports drinks contain 10-25 mmol/L of sodium – which is not high but keeps the drink palatable.
  • Sodium-containing foods consumed post-exercise may lift the sodium concentration and assist in fluid retention.

PHYL2730 (6 decks)

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