Carbohydrates and fat (wk 2) Flashcards
Describe carbohydrates and where they are found in the body:
-> Energy, central nervous system, fuel for physical activity, fibre: health benefits
-Glycogen in the liver (80-110g) and skeletal muscle glycogen (300-600g)
What is liver (hepatic) glucose output and blood glucose?
-> Exercise increases liver glucose output in an intensity dependent manner. Close matching between muscle glucose uptake and liver glucose output.
Describe carbohydrate utilisation during exercise:
-> Exercise increases carbohydrate oxidation in an intensity dependent manner. This involves: increased liver glucose output (to equal muscle glucose uptake) and increased muscle glycogen breakdown.
What was found in the study by Hermansen et al about muscle glycogen and fatigue?
-> 10 endurance trained men of a VO2 mac of 60-72 mL/kg/min, cycling to exhaustion. Found ‘ at high relative workloads, glycogen stores in exercising muscle is a decisive factor for maximal work time’.
Describe fatigue prolonged during strenuous exercise:
- Fatigue strongly correlated with carbohydrate depletion – muscle glycogen depletion and hypoglycaemia reflecting liver glycogen depletion
- Evidence that diet (carbohydrate feeding) can affect these processes – carbohydrate loading to increase muscle glycogen and carbohydrate during exercise to maintain blood glucose.
What are the daily carbohydrate recommendations for sport?
Daily carbohydrate intake recommendations for athletes are based on body weight (not % of energy intake)
What are the daily carbohydrate intake goals for athletes?
+ draw the graph
-> Focus on intensity demand of training sessions and sport focused sessions to determine the intensity used. High can be around 1-3 hours of exercise for example. Very high can be 4-6 hours+.
What happens with insufficient carbohydrate intake?
-> Fall in muscle glycogen stores by 50% in around 2 hours. Can recover the stores through a high CHO diet than a low CHO diet.
Why should you fuel for the work required?
-> Carbohydrate intake can be flexible, depending on training and competition needs – Periodised approach, fuel for the work required, must consider the planned training load
What are acute fueling strategies?
+ draw the graph
-> Promoting high carbohydrate availability to promote optimal performance in key training sessions or competition
Describe and draw the day/s leading up to the event:
-> Practicality, sustainability, necessity, side effects
Describe and draw the day of the event:
-> The main goal here is around ensuring liver glycogen stores are high ready for performance. Function is to restore liver glycogen levels.
Describe carbohydrate recommendations for athletes:
-Opportunity before exercise around 4 hours to grow the carbohydrate stores in the body as the body is able to digest it sufficiently for exercise.
Describe what fat is:
-> Fat availability for energy production not limited even in leanest of athletes. Fat is a fuel source during low-to-moderate intensity aerobic exercise.
What are the fat recommendations for sport:
- Fats have many important functions in the body and should not be excluded from the diet
- Daily fat intake: 20-35% of total energy intake
- Proportion of saturated fat limited to less than 10% of energy intake
- For weight loss/ body composition changes, chronic fat intakes <20% of energy intake discouraged
What are functions of fat?
-> Fuel source. Protection of vital organs. Cell membrane constituents. Precursors of bile, hormones and steroids. Essential fatty acids and fat-soluble vitamin intake. Palatability.
What are acute high fat, low carbohydrate and exercise capacity?
-> High carbohydrate diet (83%) for 3-7 days enables subjects to complete 240 mins of exercise, but a high fat diet (94%) reduced capacity to just 88 mins.
What is found in fat adaptation and carbohydrate restoration studies?
-> High carb, low fat Vs High fat, low carb diets in cyclists. Fat adaptation: increased fat oxidation, decreased carbohydrate oxidation and spared muscle glycogen. There was also no effect on cycle time trial performance in either conditions. Fat adaptation impairs high-intensity exercise performance.
What is ketogenic and keto-adaptation?
-> <50g carbohydrate/ day, fit intakes > 70-80% energy - ~15% or 1/5 g/kg/d protein and ensure adequate sodium/ potassium. At least 2-3 weeks adaptation, keto-adaptation. Elevated blood levels of ketones and tissue adaptations to enhance their use as fuel. Goal is to increase use of fat as muscle fuel.
Why re-think fat as a fuel for endurance exercise?
-> Fatigue due to reduced CHO availability and inability to use alternative lipid sources. Lowering CHO intake and increasing fat intake will induce ketosis (>0.5mmol/L) over several weeks. Keto-adaptation ensures stable fuel source for exercising muscle (and brain) in the face of low CHO availability. Shifts to fat and ketones as primary fuels could benefit endurance performance.
