Challenging decks Flashcards
What is the typical blood glucose, liver glycogen and muscle glycogen values (grams) of a 70kg man?
Blood glucose: 3-5g / 4-6g
Liver glycogen: 80-100g / 80-110g
Muscle glycogen: 300-400g / 300-600g
What is the typical adipose tissue and muscle triglyceride values for a 70kg man?
Adipose tissue: 3.5-14kg
Muscle triglyceride: 200-500g
What are the 3 physiological and biomechanical functions of nutrients in the body?
1) Provision of energy
2) Regulation of metabolism
3) Promotion of growth and development
3 types of carb-rich foods
1) Sugars: fruit juices, fruits, sports drinks, sweets, honey, sweetended cereals
2) Starches: cereal, potatoes, rice, bread
3) Fibre: whole-grain cereals and bread, oats, fruits and vegetables
Roles of fats
- Energy source
- Protection of vital organs
- Cell membrane constituents
- Precursors of bile, hormones, and steroids
- Essential fatty acids and fat-soluble vitamin intake (vitamins most abundant in fat foods such as vitamin A, D, E, K)
Protein (amino acids) roles
- Provide structure to all cells in the human body
- Central roles in the metabolism of many organs and tissues
- Precursors for the synthesis of body proteins
- Regulators of the synthesis of neurotransmitters, hormones, DNA and RNA
- Enzymes that increase the rate of metabolic reactions
Functions of water
- Nutrient transport
- Protection
- Temperature regulation
- Biochemical reactions + medium for reactions
What are the two ways that exercise increases CHO oxidation as intensity increases?
1) Increased liver glycogen breakdown (liver glucose output equal to muscle glucose uptake)
2) Increased muscle glycogen breakdown
How does carbohydrate loading and carb intake during exercise affect fatigue?
Carb loading increases muscle glycogen and carb intake during exercise maintains blood glucose –> more able to match demands of ATP.
What can explain fatigue during prolonged strenuous exercise?
Fatigue strongly correlated with CHO depletion.
- Muscle glycogen depletion
- Hypoglycaemia (low blood glucose) reflecting liver glycogen depletion
This means we cannot produce ATP at an adequate rate to meet ATP demand.
What are the adaptations of high fat diet (fat adaptation)? Is this diet beneficial?
- Increased fat oxidation
- Decreased carbohydrate oxidation
- Spared muscle glycogen
Evidence suggests that fat adaptation impairs high-intensity exercise performance.
Describe the adaptations of a ketogenic diet (Keto-adaptation). What is the logic/benefit of this type of diet?
- Takes at least 2-3 weeks.
- We get elevated blood levels of ketones (known as ketosis) and tissue adaptations to enhance their use as fuel.
- This increase use of fat as muscle fuels.
Fatigue is due to reduced CHO availability and inability to use alternative lipid sources. Keto-adaptation ensures stable fuel source for exercising muscle (and brain) in the face of low CHO availability.
What does the “Periodised approach” to carb intake refer to?
refers to daily carb intake being flexible to the demands of training and competition.
Why would a low-fat, low fibre nutritional strategy be recommended for a pre-exercise meal?
to reduce the risk of gastro-intestinal (GI) problems
Why should athletes try to avoid restricting fat intake below 20% of total energy intake for sustained periods of time?
It may reduce fat soluble vitamin and essential fatty acid uptake.
Give examples of slow and fast carbohydrates.
Fast carbs
- Glucose
- Maltose
- Sucrose
- Maltodextrins
- Starches rich in amylopectin
Slow carbs
- Fructose
- Galactose
- Isomaltulose
- Starches rich in amylose
What is the effect of carbohydrate feeding during exercise on performance?
- Improve endurance capacity and performance
- Effects of carb feeding during exercise increase with exercise duration
- May also benefit other aspects of sport performance such as motor skills during prolonged sports events (pen)
What are the metabolic effects (benefits) of carb feeding during exercise?
- Maintains plasma glucose concentration and helps to sustain high rates of carbohydrate oxidation
- Spares liver glycogen stores which can be used during later stages of exercise
- May spare muscle glycogen in certain situations
Why is using multiple transporters carbohydrates beneficial for prolonged exercise?
It increases rates of exogenous carbohydrate oxidation by 20-50% above single transported carbohydrates.
It does this by reducing competition for SGLT1 transport (glucose) in the intestines due to stimulating other protein transporters (GLUT5 for fructose).
What are multiple transportable carbohydrates?
Refer to sugars that are transported across the intestine and into the blood by stimulating more than one protein transporter (e.g. glucose {via SGLT1} and fructose {via GLUT5}).
Difference between short-term and long-term post-exercise recovery.
Short-term recovery is from 0-8 hours after exercise has stopped to the next session/bout. Involves strategies to ensure rapid glycogen repletion.
Long-term recovery is from 8-24hours after exercise. Adoption of general daily CHO intake should ensure repletion on a day-to-day basis.
How does carb intake immediately post-exercise compare with carb intake 2hours post-exercise?
When we consume carbs immediately post-exercise we have very high rates of glycogen synthesis. If we consume carbs 2hours post-exercise, glycogen synthesis rates aren’t so high.
Essential for short recovery window (0-4hrs from one exercise to another)
Why do we get high rates of glycogen synthesis 1-2hrs after exercise?
some GLUT4 remains on the cell membrane which increases uptake of glucose into the cell and as exercise has finished we no longer get calcium release, AMPK, free adenosine… therefore glycogen synthesis is favoured over glycolysis.
What are the 2 phases of glycogen re-synthesis?
Insulin independent (rapid phase)
- 1-2hours post-exercise
- Glut4 remains on cell membrane so glucose used for glycogen resynthesis
Insulin dependent (slow phase)
- 3-4hours post-exercise
- Feeding results in pancreas releasing insulin into bloodstream which enhanced glut4 translocation and glycogen synthesis.
Describe the regulation of muscle glycogen synthesis during exercise and post-exercise.
During exercise, glycogen synthesis is inhibited by Ca2+, vasodilator agents NO, free adenosine and AMPK. These factors enhance glycolysis.
When exercise finished, these chemical signals are no longer produced therefore glycogen synthase is no longer inhibited. Furthermore, glut4 remains on the cell membrane so entering glucose is used for glycogen synthesis. Additionally, when we consume food, insulin is released, and this positively regulates glycogen synthase.
How does the addition of protein to post-exercise carbohydrate intake increase muscle glycogen resynthesis?
the extra protein stimulates insulin secretion when carbohydrate intake is sub-optimal –> greater uptake of glucose that can be used for muscle glycogen resynthesis
How may fructose-glucose ingestion post-exercise be beneficial?
When fructose is co-ingested alongside glucose-based carbs it accelerates the replenishment of glycogen stores (mainly liver glycogen stores).
Fructose co-ingested with glucose in recovery from exercise can also enhance subsequent time-to-fatigue.
What is the % of water in…
a) the adult body
b) lean body tissue
c) fat mass
a) 50-60%
b) 75%
c) 5-10%
Where is most of the total body water stored?
Intracellular fluid (62.5% of total body water) and extracellular fluid (37.5% of total body water - interstitial fluid and blood plasma)
Define dehydration (hypohydration) and how this can be indicated.
Dehydration is defined as a body water deficit greater than normal daily fluctuation. This can be indicated by a body mass loss >2%.
What is the best static physiological index of hydration status?
the measurement of plasma osmolality (a measure of the total dissolved particle concentration)
- Typically 275-395 mOsm/kg
- Increase in this suggests dehydration.
Examples of dynamic assessments of hydration status before and after an exercise bout.
- Body mass change (in energy balance)
- Plasma osmolality (>5mmol/kg)
- Urine specific gravity (urine density relative to water (1.00), euhydrated at 1.003-1.035U)
How is the sweating response initiated during exercise in hot temperatures?
For every L of oxygen consumed 4kcal of heat is produced and most of this heat is passed to the body core.
Thermoreceptors senses increased in body and skin temperature (from 36-38 to 38-40 degrees C) and sends this to the hypothalamus.
This responds by increasing blood flow to the skin (vasodilation) and initiates sweating response. This cools body temperature and prevents hyperthermia.
What is evaporative cooling? For every 1L of sweat evaporated, how many kcal of heat is removed from the body?
Evaporative cooling is where we remove heat from the body via sweat evaporation.
573kcal of heat from the body
How does sweat influence plasma osmolality?
it increases plasma osmolality - This is because sweat is hypotonic compared to plasma. When you sweat you lose more water but concentrations of sodium, glucose… remain high which increases plasma osmolality.
How may hypohydration impair performance when we have a BM loss of >2%?
1-2%: Minimal impact
2-3%
- Degrade aerobic performance
- Deterioration of sport-specific skills
- Minimal cognitive function impact (without heat stress) and reduced cognitive function (with heat stress)
> 3%: Impaired cognitive function
3-4%: Minimal impact on muscle strength and power.
