Nutrition D.4 Flashcards
D.4.1. State the approximate glycogen content of specific skeletal muscle fibre types
Slow Twitch (Type 1) – Low glycogen content
Fast Twitch (Type IIa) – Medium-glycogen content
Fast Twitch (Type Iib) – High-glycogen content
Type IIa and Type IIb are high in glycogen content depending on training status
D.4.2. Describe, with reference to exercise intensity, typical athletic activities requiring high rates of muscle glycogen utilization
- As the intensity of exercise increases, the rates of ATP needed increases and muscle glycogen constitutes a greater portion of the energy source
D.4.3. Discuss the pattern of muscle glycogen use in skeletal muscle fiber types during exercise of various intensities
- Glycogen is used in aerobic and anaerobic activities to make ATP
- Continuous moderate exercise (such as cycling at low intensity) will use slow twitch muscle fibers, and therefore the rate of glycolysis will be low
- High intensity exercise (such as sprinting) will use fast twitch fibers, and therefore more glycogen
- As the intensity of the activity increases there is an increased contribution to the overall energy supply provided by glycogen. High intensity: 75% VO2max , 85% max HR
D.4.4. Define the term Glycemic Index (GI)
GI is the ranking system for carbohydrates based on the immediate effect of the food on blood glucose concentrations when compared with a reference food such as pure glucose
D.4.5. List foods with low and high glycemic indexes
High - glucose = 100
Medium - brown rice = 50
Low - green vegetables = <15
D.4.6. Explain the relevance of GI with regard to carbohydrate consumption by athletes pre- and post-competition
- Lower GI foods may be beneficial prior to exercise
- Use of high GI foods post-exercise may assist the body in restoring its glycogen stores more rapidly, aiding refueling prior to future training/competition bouts
The Glycemic Index in Sports Nutrition
In general, the following is recommended:
- Low GI foods before exercise (slow release of energy, more stable blood sugar levels response to exercise, reduced insulin, may increase use of fats…)
- High GI during exercise (rapidly digested and absorbed, fast release to supply energy)
- High GI immediately after exercise (increased rate of muscle glycogen synthesis)
- Any other meal should be predominately Moderate or Low GI
- Low GI diets may be beneficial for athletes trying to maintain low levels of body fat.
D.4.7. Discuss the interaction of carbohydrate loading and training programme modification prior to competition
Carb loading:
- A tactic used by athletes in high-intensity endurance exercise to maximize glycogen stores in body since normal glycogen stores are not enough to provide the required energy used during a high-intensity competition
- Depletion of glycogen stores causes inadequate fueling to the muscles, inducing fatigues and diminishing athletic performance
Who needs carb loading?
- Athletes who participate in high-intensity endurance sport or training session require carb loading
Rule of thumb:
- Any sports events in which aerobic system is used more than 25% requires carb loading
- It is recommended in endurance sport even lasting longer than 90 minutes
Why Carbohydrate Loading?
- Increases glycogen stores up to 300%
- Provide a sustained source of energy during training or competition
Steps to follow for carb loading (important)
- Reduce intensity and duration of training by ~50% (tapering)
- Increase daily intake of carbs to 8-10g/kg (70-80% of total kcal should come from complex carbs)
- Carbs consumed GI should be below 55
- Sweet potatoes, brown rice, spaghetti, and quinoa are preferred choices
D.4.8. State the reasons for adding sodium and carbohydrate to water for the endurance athlete
- CHO are the main components of functional sports drinks - improve physical performance by delaying the depletion of muscle glycogen
- During an exercise, a CHO intake of 30-60 g/h is suggested
- Glc-Fru (glucose - fructose) mixture is very beneficial for athletes as its able to absorb a greater amount of exogenous CHO in systemic circulation, which can be used immediately as energy fuel
D.4.9. Discuss the use of nutritional ergogenic aids in sports
What is an ergogenic aid?
- A performance enhancer, or ergogenic aid, is anything that gives you a mental or physical edge while exercising or competing.
- This can range from caffeine and sports drinks to illegal substances.
Use of ergogenic aids in sports
- Sports drinks, bars and gels are products formulated around macronutrients and micronutrients.
- They are intended as a convenient means of ingesting fluid and/or macronutrients in an exercise setting when “normal” food may be impractical
Compounds and supplements as ergogenic aids
Caffeine:
- Increase exercise performance at a range of exercise intensities
- Anxiety, insomnia, mild diuretic, weakly addictive
Creatine:
- Benefit exercise that relies on the PCr energy system such as strength, power and sprinting sports
- Increase in body mass
Bicarbonate:
- Increase performance during high-intensity exercise lasting 1-7 minutes
- Can cause gastrointestinal upset
D.4.10. State the daily recommended intake of protein for adult male and female non-athlete
- 0.8g/kg of body weight
- Exercising or training 5 or more days/week requires 1.2 - 1.7 g/kg/day
D.4.11. LIST SOURCES OF PROTEIN FOR VEGETARIAN ATHLETES
D.4.11. LIST SOURCES OF PROTEIN FOR NON-VEGETARIAN ATHLETES
D.4.12. Discuss the significance of strength and endurance training on the recommended protein intake for male and female athletes
- Protein needs for an athlete are greater than for the average sedentary individual.
- This is a result of the effects of exercise on metabolism.
- Endurance athletes metabolize protein differently during long-lasting activity. They would need 1.2 to 1.4 g/kg of body weight per day.
- For strength-training athletes, muscles tear during a workout and protein is required to repair and rebuild these muscles. They would need 1.2 to 1.7 g/kg of body weight per day.
Recommended protein intake:
- Strength training athletes > Endurance athletes > sedentary individual
D.4.13. Outline the possible harmful effects of excessive protein intake
- High cholesterol and higher risk of cardiovascular disease
- Increased cancer risk
- Kidney disease and kidney stones
- Weight gain
- Constipation or diarrhea
