Lecture 6 - Carbohydrates Flashcards
carbohydrate can be broken down to release energy to phosphorylate …
phosphorylate ADP and from ATP
products of anaerobic glycolysis
lactate and H+
aerobic metabolism allows for a continuous supply of ATP as long as …
O2 available
3 phases of aerobic metabolism
- preparation
- krebs cycle
- electron transport chain
carbohydrate digestion in the mouth
salivary a-amylase hydrolyses dietary starch
carbohydrate digestion in the stomach
the acidity of the stomach temporarily inhibits a-amylase and stops carbohydrate digestion
carbohydrate digestion in the small intestine (bicarbonate secretion)
bicarbonate secretion from the pancreas neutralises the stomach contents and pancreatic α-amylase continues to digest starch
carbohydrate digestion in the small intestine (disaccharide enzymes)
Several disaccharidase enzymes breakdown disaccharides in the brush border of the small intestine producing monosaccharides (glucose, fructose etc
glucose is absorbed in the small intestine via
via a sodium glucose transporter (SGLT-1)
fructose is absorbed in the small intestine by a different transporter to glucose, what is this
GLUT5
GLU and FRU are transported across the basolateral membrane via the transport of
GLUT-2
GLU & FRU are transported to the … where what is removed from the circulation
liver
where fructose is removed from the circulation
3 steps in glycogenesis
- CHO ingestion stimulates the release of insulin from the pancreas
- insulin stimulates GLUT4 translocation to muscle membrane
- glucose-6-phosphate stimulates the production of glycogen
carbohydrate stores within the body can be effected by…
fasting, exercise and diet
what is the CHO recommendation for extreme exercise programmes (>4-5hr)
8-12g/kg/d
why do many athletes not meet their needs of carbohydrates
- not hungry (pre and post event this can be common)
- limited knowledge
- high protein diet / energy imbalance
- overall energy intake
- availability of foods
- GI discomfort
when working with an athlete : understanding current behaviour is the first step in changing …
future behaviour
there is a big stigma around ..
carbohydrates
many adolescent athletes think what about carbohydrates
that they will make them fat or gain weight
what happens when there are insufficient CHO ingested
progressively decrease in muscle glycogen with a low carbohydrate diet
High pre-exercise muscle and liver glycogen concentrations are
believed to be essential for optimal performance.
An individualized nutritional strategy should be developed that aims to deliver carbohydrate to the working muscle at a rate that is
dependent on the absolute exercise intensity as well as the duration of the event.
pre competition (1-3 days before the event) what is a common nutrition strategy used
carbohydrate loading
carbohydrate loading leads to super concentrated …
muscle glycogen levels
why can females be put off carbohydrate loading
Glycogen storage is associated with weight gain as a result of water retention and this can put off some female athletes
the day before race day many athletes avoid what rich foods
fibre rich foods
pre race you want the meal to ideally be .. and why is this different to a meal you would normally recommend
high carb, low fibre, limited protein
considerations that must be account for the pre event meal
- time of the day
- how long the event is
- are there carbs available at the event
- home or away
- climate conditions
what are the aims of pre exercise fuelling
- prevent muscle and liver glycogen depletion
- prevent hypoglycaemia
- prevent gastrointestinal problems
- limit dehydration to ~<2% of body mass loss
- prevent hypoantraemia
“increasing endogenous and exogenous CHO availability improves ……”
exercise capacity and performance
how to train the gut with carbohydrate intakes
gradually increase intakes, start slow
why is oestrogen important
- important for muscle mass
- inhibits bone resorption
what is progesterone important for
- increases muscle protein synthesis rates
- stimulates osteoblasts
oestrogen may increase free fatty acids availability during exercise and may ….
promote lipid oxidation
progesterone may limit….
fat oxidation
what happens to fat and carbohydrate oxidation throughout the menstrual cycle
changes throughout the cycle
hormonal birth control causes elevated plasma what and what does this increase the reliance on during endurance exercise
elevated plasma oestrogen concentrations increase the reliance on fat as an energy source during endurance exercise
on loading days in carbohydrate loading you should aim for what % carbohydrate / meal
> 80% carbohydrate / meal
glycogen loading is recommended is your race is longer than ….
longer than 90 mins
glycogen loading can increase general cycling performance by how much
increase by 20%
glycogen loading can increase time trial performance by how much
increase by 2-3%
what is the CHO recommendation for very light training (g/kg/d)
3 - 5 g/kg/d
what is the CHO recommendation for moderate duration / low intensity training (~1hr/d) (g/kg/d)
5 - 7 g/kg/d
what is the CHO recommendation for moderate to heavy endurance training (1-3hr/d) (g/kg/d)
6-10 g/kg/d
how many ATP are produced via anaerobic metabolism of glucose
2 ATP
how many ATP are produced via anaerobic metabolism of glycogen
3 ATP
how man ATP are supplied via aerobic metabolism
30-32 ATP
where does aerobic metabolism occur
mitochondria
anaerobic glycolysis causes pH to
decrease
what is the average carbohydrate stores in the muscle and liver
~350g in muscle
~100g in liver
carbohydrate loading results in
weight gain
The total carbohydrate store for an 80kg male is approximately
450-500g
American College of Sports Medicine suggest how much carbohydrate is adequate to sustain muscle glycogen stores during training and competition
500-600g
Fatigue during prolonged exercise is often associated ….. (Jeukendrup, 2004)
…. with muscle glycogen depletion and reduced blood glucose concentrations
there was a systematic review on carbohydrate supplementation on exercise performance or capacity or varying durations, how many showed statistically significant performance benefits
82%
