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NUTR 380 > Module 2: CHO Recommendations for Athletes > Flashcards

Module 2: CHO Recommendations for Athletes Flashcards

1
Q

Consuming CHO wil?

A
  • Maintain high rates of carbohydrate oxidation
  • Reduce ratings of perceived exertion
  • Increase endurance capacity
  • Delay the onset of fatigue
  • Prevent hypoglycemia
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2
Q

What is the goal for blood glucose levels during sport?

A

To keep BG levels as stable and as close to the normal range as
possible during exercise (~4-6mmol/L)
* Less variation = constant availability of CHO to fuel activity = stable performance
* Some variation will occur BUT adequate nutrition during training and before, during and after activity can help to limit the magnitude of BG fluctuations
* To prevent hypoglycemia
* To spare glycogen

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3
Q

How are glycogen stores utilized?

A

The body will do everything it can to keep blood glucose at the 4 grams so
1. muscle glycogen
2. liver glycogen
3. blood glucose

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4
Q

What influences the size of glycogen stores?

A

diet

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5
Q

Abnormally low levels of glucose in blood <3.3 mmol/L

A

hypoglycemia

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6
Q

Triggers the release of counter-regulatory hormones to prevent further declines in BG levels and promote gluconeogenesis

A

hypoglycemia

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7
Q

What hormones does hypoglycemia trigger?

A

Counter-regulatory hormones
* Epinephrine/norepinephrine
* Glucagon
* Cortisol

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8
Q

Adrenergic manifestations with hypoglycemia

A
  • Shakiness, anxiety, nervousness
  • Palpitations, tachycardia
  • Pallor, coldness, clamminess
  • Dilated pupils (mydriasis), blurred vision
  • Feeling of numbness “pins and needles” (paresthesia)
  • Fatigue, weakness, incoordination
  • Impaired judgement
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9
Q

Glucagon/Cortisol manifestations with hypoglycemia

A
  • Hunger
  • Nausea, vomiting, abdominal discomfort
  • Headache
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10
Q

Stimulus and action of glucagon

A
  • Stimulus: Decrease in blood glucose; Exercise stress
  • Action: Promotes gluconeogenesis in liver; helps increase blood glucose levels.
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11
Q

Stimulus and action of cortisol

A
  • Stimulus: Exercise stress; decrease in blood glucose
  • Action: Promotes breakdown of protein and resultant gluconeogenesis; helps increase blood glucose levels
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12
Q

Stimulus and action of epinephrine

A
  • Stimulus: Exercise stress; decrease in blood glucose
  • Action: Promotes glycogen breakdown and glucose release from the liver: helps increase blood glucose levels
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13
Q

How to prevent hypoglycemia in athletes

A
  • Adequate CHO intake on a daily basis - promote euglycemia
  • CHO rich, pre-training or pre-event meal or snack before activity - good BG at onset of activity
  • CHO feeding during prolonged activity - “top up”
  • CHO rich re-feeding after activity - repletion of glycogen stores
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14
Q

Reactive hypoglycemia

A

A condition in which low BG levels are induced by a combination of:
1. The timing of an athlete’s intake of CHO-rich foods/beverages
2. The time of the start of activity.

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15
Q

How does reactive hypoglycemia happen?

A

Excessive glucose intake by an athlete whose BG levels are marginally acceptable in the hour before activity can trigger an excessive release of insulin before exercise promotes skeletal muscle glucose uptake.
* Exercise (muscle contractions) also stimulate glucose uptake.
* results in hypoglycemia

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16
Q

preventing reactive hypoglycemia before activity

A

CHO rich, pre-training or pre-event meal or snack before activity
* Ensures the athlete’s BG levels are within the normal range at the onset of activity

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17
Q

preventing reactive hypoglycemia during activity

A

CHO feeding during prolonged activity
* “Tops up,” blood glucose levels quickly and spares glycogen

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18
Q

preventing reactive hypoglycemia after activity

A

CHO rich re-feeding after activity
* Promotes repletion of glycogen stores used to fuel activity

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19
Q

Difference between regular CHO intake and immediate sport performance

A
  • To support immediate sport performance, (pre/during/post exercise) the focus should be on quickly oxidized CHO
  • Throughout the rest of the day, athletes should focus on nutrient- rich sources of CHO, regardless of oxidation rate, including fruits, vegetables, whole grains and legumes
20
Q

recommended fiber intake from food

A

25-30 g/d

21
Q

Why are CHO recommendations higher for athletes?

A

Meant to support CHO availability for the muscle and central nervous system based on the demands of the sport.

22
Q

How are recommendations for CHO given to athletes?

A

based on bodyweight
* And sport, intensity and duration

23
Q

Daily CHO intake for strength training

A

4-7 g/kg/day
* CHO may increase the total amount of work an athlete is able to complete during longer duration, high volume training sessions
* Athletes should consume an amount of CHO that they can tolerate and makes them feel energized during their workout

24
Q

Daily CHO intake for endurance athletes

A

6-10 g/kg/day - moderate training
8-12 g/g/day - heavy training
* Fatigue in an endurance athlete is often due to depleted muscle glycogen and low levels of blood glucose

25
Q

Ergogenic dietary strategy designed to maximize glycogen stores in endurance athletes by manipulating CHO intake

A

CHO Loading (Glycogen Super-Compensation)

26
Q

What is the theoretical basis for CHO loading?

A

Low CHO diets deplete glycogen stores and high CHO diets are known to increase muscle glycogen stores in trained individuals. Therefore, acutely increasing CHO intake in the days before an event will increase or super-compensate glycogen stores and enhance endurance.

27
Q

WHat does CHO loading provide?

A

More glycogen = more substrate for aerobic metabolism = reduced risk for “Hitting the Wall.”

28
Q

Previous CHO loading protocols

A
  1. Eliminating all high CHO foods for 5-7 days before a race or competition to “empty” glycogen stores PLUS
  2. Hard training to further deplete glycogen stores PLUS
  3. Eating a large amount of CHO rich foods the night before the event to enhance glycogenesis.
29
Q

Modern CHO loading protocol

A

Athletes should follow a CHO rich training diet most of the time to ensure sufficient pre-competition glycogen stores. One week before race or competition:
1. Increase CHO intake gradually; peaking one day before the race or competition
2. Decrease fat intake at the same time to allow for more CHO rich foods
3. At the same time, decrease or taper training across the week leading up to the race or competition

30
Q

What is the target for CHO loading?

A

36-48 h of 10-12 g/kg body weight/24 h

31
Q

What types of CHO are typically chosen for CHO loading?

A

Athletes may choose carbohydrate-rich sources that are low in fiber/residue and easily consumed

32
Q

What are some side effects of CHO loading?

A
  • weight gain/fluid retention
  • digestive discomfort
  • blood sugar changes
33
Q

Weight gain/Fluid retention with CHO loading

A
  • The body stores 3-4 g of water with every 1 g of glycogen it stores.
  • Much of this weight is extra water, but if it can create a heavy, sluggish feeling that can hamper performance.
34
Q

Digestive discomfort with CHO loading

A

CHO rich foods are often high in fibre and dramatic increases in fibre intake can lead to gassy cramps, bloating and diarrhea in some athletes.

35
Q

Blood sugar changes with CHO loading

A

Carbohydrate loading can cause dynamic, unpredictable changes to blood sugar levels, especially in athletes with diabetes, reactive hypoglycemia or other endocrine conditions.

36
Q

Why isn’t CHO loading a sport nutrition strategy for sprinters?

A

Dont utilize glycogen stores during competition usually

37
Q

CHO recommendations during activity

A

Athletes who are active for > 1 hour should consume 30-60 g/h
Of easily digestible, quickly oxidized carbohydrate.
* This is a time that fast CHO sources in the right amounts, are appropriate choices

38
Q

CHO sources during sport

A
  • Fluid Replacement Beverages Containing CHO
  • Sport Gels
  • Sport Bars
  • Sport Beans or Gummies
  • Dried Fruits
39
Q

What is CHO mouth rinse?

A

routinely rinsing the mouth (not drinking) with a carbohydrate-containing solution for 5-10s during sport is associated with improved high intensity endurance exercise performance.
* Brain imaging studies have identified areas of the brain activated when carbohydrate is in the mouth, and it is likely that mouth rinsing carbohydrate results in afferent signals capable of modifying motor output and perceptions of effort.

40
Q

Practicality of CHO mouth rinse

A

Athletes using the mouth rinse technique have to spit out the rinse – it is not swallowed.
* This is messy, and potentially a vector for the spread of disease.
* Many coaches and trainers oppose mouth rinsing as a result.
* These practical issues need to be considered before attempting to implement this strategy.

41
Q

Fructose ingestion

A

associated with GI distress, higher perceived exertion ratings, higher serum cortisol levels, and decreases in BG levels compared to ingestions of glucose or sucrose.
* misconception amoung athletes that it is a superior energy source

42
Q

advantages/disadvantages of liquid vs. solid CHO during activity

A
43
Q

Common complaint of liquid CHO sources

A

GI distress
For the fastest absorption of sports drinks its total concentration of electrolytes and CHO (osmolality) should be lower than the plasma osmolality (275–290 mOsmol/Kg).
* The osmolality of a beverage can influence the rate of gastric emptying and hypertonic solutions slow gastric emptying and can promote GI distress.

44
Q

CHO after training for short recovery time

A

An athlete should consume 1-1.2 g of CHO/kg/hour (0.45-0.55 g/lb/hour) every hour for the first 4-6 hours post-exercise
* Then resume regular dietary habits in order to quickly replenish glycogen stores

45
Q

CHO after training for greater amounts of recovery

A
  • Meeting daily CHO needs should be adequate to restore muscle glycogen
  • Muscle glycogen stores can generally be normalized within 24 hours but more time may be needed if an athlete follows a low-carbohydrate diet
46
Q

Overall CHO recommendations to support athletic performance before, during and after

A

NUTR 380 (23 decks)

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