Carbohydrate Flashcards
1
Q
History of carbohydrate and exercise? (Levine et al. 1924)
A
Low blood glucose at the end of a marathon was associated with fatigue and an inability to concentrate
2
Q
History of carbohydrate and exercise? (Gordon et al. 1925)
A
Exhaustion, weakness, shock, and other symptoms of hypoglycemia following prolonged effort may be prevented by adequate and timely ingestion of CHO
3
Q
History of carbohydrate and exercise? (Christensen & Hansen 1939)
A
A high-CHO diet for 3-7days enabled subjects to exercise for 210min, whereas a high-fat diet reduced performance to 88min
4
Q
Name different sources of substrate?
A
CHO
Fat
Amino acids
5
Q
How to get energy for muscular effort?
A
Substates are feed into oxidative metabolism to produce ATP
6
Q
Define glycolysis?
A
Generation of ATP from glucose to produce pyruvate
7
Q
What substrate is the most efficient way to produce ATP from the Krebs cycle?
A
CHO
8
Q
Why is carbohydrate the most efficient way to produce ATP from the Krebs cycle?
A
Requires less oxygen to form the same amount of ATP
9
Q
Effect of exercise on muscle glycogen concentration and stores? (Areta & Hopkines 2018)
A
Increase in muscle glycogen stores
Exercise might be linked to muscle glycogen stores
Exercise might enable the process of taking in glucose from muscle glycogen storage to be more developed
10
Q
Name the three processes carbohydrates undergo in the body?
A
Ingestion
Absorption
Utilisation
11
Q
How is glucose absorbed?
A
Na-glucose linked transported 1 (SGLT1) - intestinal lumen to cell microvilli (rate-limited step)
GLUT2 - cell -> capillaries
12
Q
What rate is glucose absorbed?
A
60g/hr
13
Q
What rate is fructose absorbed?
A
30g/hr
14
Q
How is fructose absorbed?
A
GLUT5 -> intenstinal lumen to cell
GLUT2 -> cell to capillaries
15
Q
Glucose metabolism in the fasted state?
A
The liver produces glucose through glycogenolysis
Small uptake of glucose through GLUT2 in the liver
Glucose is transferred into circulation where it is delivered to other tissues
Glucose is transferred from the circulation into the muscle, adipose tissue, and the brain
16
Q
Define glycogenolysis?
A
The process of producing glucose from liver glycogen
17
Q
Which transporter transfers glucose and fructose from the cell into the capillaries?
A
GLUT2
18
Q
Which transporter transfers glucose from the intestinal lumen to the cell?
A
Na-glucose linked transported 1 (SGLT1)
19
Q
Which transporter transfers fructose from the intestinal lumen to the cell?
A
GLUT5
20
Q
Which transporter transfers glucose from the circulation into muscle and adipose tissue?
A
GLUT4
21
Q
Which transporter transfers glucose from the circulation into the brain?
A
GLUT2
22
Q
Name types of monosaccharides?
A
Glucose
Fructose
Galactose
23
Q
Name types of disaccharides?
A
Sucrose
Maltose
Lactose
24
Q
What makes up sucrose?
A
Glucose and fructose
25
What makes up maltose?
Glucose and glucose
26
What makes up lactose?
Galactose and lactose
27
Name types of oligosaccharides?
Maltodextrin
28
Name types of polysaccharides?
Amylopectin
| Amylose
29
Glucose metabolism in the fed state?
Contribution of CHO from the small intestine
Increases glucose concentration in circulation
Pancreas increases insulin concentration on circulation
Reduced glucose production in the liver
Increased uptake in the liver
Increased uptake in the muscle
Increased uptake in the adipose tissue
30
What is the process of glucose metabolism in the liver? (Gonzalez & Belts 2019)
Glucose is phosphorylated into glucose-6-phosphate by glucokinase (rate-limiting step)
Glucose can be metabolised into liver glycogen
- glucose-6-phosphate -> glucose-1-phosphate -> UPD-phosphate -> liver glycogen
Glucose can be metabolised into trioses
31
Fructose metabolism in the liver? (Gonzalez & Belts 2019)
Metabolised into trioses
| Fructose -> fructose-1-phosphate -> trioses
32
In what processes are trioses metabolised in the liver? (Gonzalez & Belts 2019)
```
Gluconeogenesis = glucose
Glycolysis = pyruvate (ATP)
```
33
The role of glucose kinase receptor protein (GKRP) in glucose metabolism?
In a normal state has a greater affinity to glucokinase
- inhibit phosphorylation of glucose to glucose-6-phosphate
- reduces glucose uptake in the liver
Fructose binds to GKRP and causes an increase in glucokinase
- increases glucose uptake and downstream glycogen
34
Glucose uptake in the muscle? (Rose & Richter 2005)
Glucose -> glucose-6-phosphate by hexokinase
| Glucose-6-phosphate used for glycolysis or glycogenolysis
35
Which will increase GLUT4 translocation more, exercise or insulin?
Exercise
36
Recommended carbohydrate intake for light training load (low-intensity or skill-based activities)?
3-5g/kg/day
37
Recommended carbohydrate intake for moderate training load (moderate exercise, 1hr/day)?
5-7 g/kg/day
38
Recommended carbohydrate intake for high training load (endurance program, 1-3hr/day)?
7-10 g/kg/day
39
Recommended carbohydrate intake for very high training load (extreme commitment, 4-5hr/day)?
10-12 g/kg/day
40
Do carbohydrate diets improve performance? (Reviewed by Burke et al. 2004)
The majority of articles shows that high CHO consumption results in improved exercise performance
41
When to consider CHO loading?
The activity places a heavy demand on glycogen stores
The activity >90min of continuous activity
Habitual diet produces less than 7-9g/kg BM/day
There are no medical reasons contradicting a high CHO intake for 3-5days
42
How many grams of water are there per grams of glycogen?
3g
43
When not to consider CHO loading?
The exercise is not an endurance activity (<60-80min)
The activity would be adversely affected by weight gain associated with loading
Habitual diet is already >8-9g/kg BM/day
The athlete has unstable diabetes, meaning a high CHO diet would put them at risk
44
The metabolic/molecular effects of exercising in the fasted state? (Barlett et al. 2015)
Relying on fatty acid
Increase in PPARd
Increase in P38MAPK -> increase PGC-1a -> increased translocation
45
The metabolic/molecular effects of exercising in the fed state (Barlett et al. 2015)
Increase in glucose
Increase in GLUT4 translocation
Blunting of AMPK and P38MAPK -> reduces activation of PGC-1a
46
6 methods to train low (glycogen)
```
Low CHO diet
Training after an overnight fast
No CHO during recovery
Sleep low
Long training without CHO intake
Training twice a day
```
47
What supplementation methods can be used to overcome a reduction in exercise intensity?
Caffeine
Mouth rinse
Hydration
Creatine
48
What is the goal of pre-exercise feeding?
To replenish liver glycogen and encourage some muscle glycogen synthesis so there is enough blood glucose available late in exercise
49
What is the effect of pre-exercise feeding on substrate oxidation during exercise?
Increase CHO oxidation during exercise at the expense of fat metabolism
50
What carbohydrate intake is recommended before exercise? (Burke et al. 2011)
>60min 1-4g/kg consumed 1-4hr before exercise
51
If Naharudin et al. 2020 was conducted for a longer duration, what do you think the results could be?
CHO had a better performance than placebo and water
52
The effect of carbohydrate ingestion before exercise on performance? (Reviewed by Jenkendrup & Killer 2011)
Consuming CHO immediately before exercise has no detrimental effect on performance
Hypoglycemia appears to be very individual
53
How many grams of carbohydrates are in a 500mL of a 6% drink?
= 500ml x 0.06
| = 30g
54
An athlete consumes a 15% drink during a 3hr race. What volume should they consume, assuming they are exercising at a high intensity?
Require 90g/h = 270g
= 270g / 0.15
= 1800ml
55
Effect of increasing carbohydrate intake on exogenous carbohydrate oxidation during exercise and what is the idea amount? (Jeukendrup & Jentijens 2000)
When the ingestion rate is 60g/hr it shows an exogenous CHO oxidation of around 0.4-1g/min
When the ingestion rate is further increases there is no further increase in CHO oxidation (rate-limiting)
56
What limits exogenous carbohydrate oxidation?
Intestinal CHO oxidation appears to be the rate-limiting step
57
Effects of different carbohydrate mixtures on exogenous carbohydrate oxidation? (Jeukendrup 2010)
Maximising ingestion rate doesn't have an additional benefit on exogenous CHO oxidation
Combining glucose and fructose increases exogenous CHO oxidation compared to glucose alone
58
4 ways to assess exogenous carbohydrate oxidation during exercise?
Ingestion of a 13C-labelled CHI
Digestion, absorption, oxidation
Body CHO stores
CO2
59
What's the equation to determine carbohydrate oxidation?
4.55 x VCO2 - 3.21 x VO2
60
What's the equation to determine fat oxidation?
1.67 x VCO2 - 1.67x VO2
61
What is hydrogel technology?
New sports drink (maltodextrin and fructose) include the addition of pectin and sodium alginate to encapsulate the CHO
The formation of a hydrogel when in the acidic conditions of the stomach
Potential to increase gastric emptying leading to an increased CHO delivery to the muscle and subsequently improved performance
62
The effect of hydrogel technology and gastric emptying at rest? (Sutehall et al. 2020)
Increased gastric emptying at rest
63
What further research is needed for hydrogel technology (Barber et al. 2020)
Further work is needed at higher intensities (>70% VO2max) when gastric emptying is reduced
Further work needed at greater ingestion rate
64
The effect of hydrogel technology on moderate-intensity exercise? (Reviewed by King et al. 2020)
There was no additional effect on moderate-intensity cycling and running performance with hydrogel technology
65
The effect of the amount of carbohydrate intake on glycogen resynthesis? (Jentiens & Jeukendrup 2003)
Levelling off of the rate of muscle glycogen synthesis after ingestion rate of 1-1.2g/kg BW/hr of CHO
A diet low in CHO may benefit from the addition of protein
66
What amount of carbohydrate intake results in a levelling off of glycogen resynthesis? (Burke et al. 2004)
In the general diet, there is a levelling off of muscle glycogen storage (muscle glycogen synthesis) at around 10-12g/kg/ BM of CHO
67
What effects GLUT4 translocation? (Huang & Czech 2007)
Nutrient pathway - increase in insulin to upregulate GLUT4 translocation to the plasma membrane which increases glucose uptake
Energy demand - increase in AMPK and calcium turnover, which increases GLUT4 translocation
68
The effect of co-ingestion of carbohydrate on performance and liver glycogen? (Gray et al. 2019)
There was an 18% increase in endurance capacity with the co-ingestion of glucose and fructose
Increases in performance were primarily due to increases in liver glycogen storage
69
The effect of carbohydrate and protein ingestion on the short-term recovery of muscle glycogen? (Betts & Williams 2010)
When CHO intake is optimal the addition of protein has no additive effect on muscle glycogen synthesis
When CHO intake in sub-optimal the addition of protein has an additive effect on muscle glycogen synthesis
70
Define the carbohydrate recommendation during a cycling event
DAY 1 = light/medium day over a 4hr flat
DAY 2 = 5hr mountain stage with 3 climbs taking 1hr, 30min and 30min and two descents
```
DAY 1
- 5-6g/kg BM/day overall
- 60g/h during cycling
- high CHO evening meal to prepare for day 2
DAY 2
- 10-12g/kg BM/day overall
- 90g/h during cycling
- pre-exercise meal = 1-4g/kg
- recovery = 1-1.2g/kg/h for 2-4hrs
- evening meal = 2-3g/kg
```
71
Assuming the cyclist is riding for 5hr how much fluid is required over the duration of the ride?
Mass = 70kg
Sweat rate = 1.5l/h
Total sweat = 1.5 x 5 = 7.5L
2% BM loss = 70 x 0.02 = 1.4g (1.4L)
Required fluid intake = 7.5 - 1.4 = 6.1L
72
What carbohydrate intake is recommended during a high-intensity, long-duration workout?
90g/h
73
What carbohydrate intake is recommended in the first 2-4hr after exercise?
1-1.2g/kg BW/hr
74
What is the role of glucokinase?
To convert glucose to glucose-6-phosphate in the liver
75
What is the role of hexokinase?
To convert glucose to glucose-6-phosphate in the muscle
76
What is the effect of increasing p38MAPK?
Increase PGC-1a -> increased GLUT4 translocation
77
What is the rate-limiting step in glucose metabolism in the liver?
Glucose -> glucose-6-phosphate via glucokinase
78
What can increase the translocation of GLUT4 to the muscular membrane?
Exercise
| Insulin
79
What is the relationship between muscle glycogen concentration and VO2max? (Areta & Hopkines 2018)
Muscle glycogen concentration increases as VO2max increases
80
What doesn't limit exogenous carbohydrate oxidation?
Gastric emptying does not limit exogenous CHO oxidation
| Muscle glucose uptake does not limit exogenous CHO oxidation
81
What carbohydrate intake is recommended during a low/medium-intensity, long-duration workout?
60g/h
82
What ingestion rate of carbohydrates causes a levelling off of muscle glycogen synthesis? (Jentiens & Jeukendrup 2003
1-1.2g/kg BM/hr
83
A successful male 5 and 10km runner (1.65m 58kg) plans to change their training focus with a view completing the first marathon in 6 months time, describe how training volume and intensity might change?
Increase volume
| Decrease intensity
84
A successful male 5 and 10km runner (1.65m 58kg) plans to change their training focus with a view completing the first marathon in 6 months time, what would be the general recommendation for dietary CHO intake?
7-10g/kg BM/day
85
A successful male 5 and 10km runner (1.65m 58kg) plans to change their training focus with a view completing the first marathon in 6 months time, describe the recommended CHO intake in the days before the morning of and during the race?
Days before - CHO loading
Morning of race - 1-4kg/BM 1-4hrs before
During race - 60g/hr of CHO with multiple transporters
86
How do maximal rate of fructose oxidation during exercise compare with that of glucose?
- 25%
- 50%
- 100%
- 150%
50%
87
PGC-1a is a transcriptional factor primarily implicated in?
Promoting mitochondrial biogenesis
