Sports Nutrition Flashcards
Key Goals in Sports Nutrition
- Energy and Stamina
- Build and Maintain Strength
- Adaptation
- Immunity
- Recovery
- Focus and concentration
Anaerobic: Phosphate Energy System
- Phosphate Energy System:
– Uses phosphocreatine as fuel
– For bursts of speed up to 6 seconds duration (i.e. 20m sprint).
– Produces no waste products.
– Recovery =
50% by 30 seconds
100% by 2 minutes
Phosphocreatine
- Creatine is either produced in the liver from glycine, arginine, methionine or from exogenous sources eg supplements. It is then transported to muscle cells where it combines with phosphate producing phosphocreatine (PC).
- PC is stored in the muscle cells so it can be quickly used for maximum energy bursts by breaking the phosphate + creatine bond and using phosphate to regenerate ADP producing ATP.
Aerobic Energy Production
- When oxygen supply and usage can match the energy demand, energy is produced via glycolysis, citric acid cycle and electron transport chain (ETC).
- When the demand for oxygen-based energy systems is exceeded, the body switches to fermentation based energy systems (anaerobic).
- Aerobic energy uses primarily carbohydrates and lipids but can also protein as fuel in extreme conditions.
- Produces ATP + CO2 + H2O (plus heat and FOR’s)
- Aerobic energy systems are generally dominant up to 80% maximum heart rate (MHR).
- Used in long distance, high volume events with moderate intensity.
Anaerobic: Lactate Energy System/Cori Cycle
- In the absense of oxygen, glucose conversion halts at pyruvate and excess is converted into lactate. This must then be reconverted into glucose via the liver.
- Compromised lactic acid conversion can lead to reduced energy recycling and poor cognitive performance during exercise
- Lactate Energy System:
– Uses stored muscle glycogen and serum glucose only.
– At 95% intensity lasts 30 seconds.
– At 60% intensity lasts 30 minutes.
– Produces lactic acid as a by product
– Recovery =
20min – 2hrs to fully remove lactic acid build up.
VO2 Max
- Aerobic metabolism relies on optimally functioning cardiovascular and respiratory systems to deliver oxygen to active skeletal muscle. This is commonly measured as VO2max (maximum oxygen uptake).
- VO2max is measured by ml/kg bodyweight/minute.
Resting VO2max is approximately 3-5ml/kg/min. Elite endurance athletes have been recorded with levels of up to 92ml/kg/min. - The higher the uptake of oxygen the longer aerobic energy production is sustained.
Traditional Calculation for Calorie Uptake
Estimate Basal Metabolic Rate (BMR):
* Female: BMR = kg body weight x 22 kCal
* Male: BMR = kg body weight x 24 kCal
Estimate Physical Activity Level (PAL):
* Mostly inactive/sedentary = 1.2
* Moderately active (2-3 x wk) = 1.4
* Active (exercise hard more than 3 x wk) = 1.5
* Very active (exercise hard daily) = 1.7
Multiply BMR x PAL = Daily calorie intake
* i.e. 70kg x 22 = 1540 x 1.4 = 2156 kCal daily
Cell Specific Fuels
RBCs: glucose
Brain: glucose/ketone bodies
Adipose Tisse: Fatty acids and glucose
Liver: Fatty acids
Muscle cells: Fatty acids, glucose, amino acids
Cardiac muscle: Fatty acids/ketone bodies
Guidelines for Daily Carbs
Starts at 3.5 hours per week with 4-5g/kg/day
Goes up 1g/kg/day as exercise doubles until 8-10g/kg/day
Carbohydrate dosing
Before exercise: 2.5g/kg, 2-4 hours before exercise
During exercise: 30-60g per hours, 60mins and over
After exercise: 1g/kg up to 2hrs then every 2hrs
Carbohydrate Loading
LCD or moderate CD followed by HCD
– Glycogen depletion stimulates glycogen synthase activity which increases glycogen storage when glucose become available again.
– Higher glycogen stores means longer optimal performance.
Protein and Exercise
Inappropriate protein consumption can:
* Reduce performance
* Hinder training and recovery
* Lower immunity
* Catabolise muscle
Protein requirements are affected by:
* Individual requirements
* Intensity of exercise
* Duration of exercise
* Phases of the training
Protein requirements
Low/moderate sports activity: 0.8g-1g / kg of body weight
Endurance training athletes: 1.2 - 1.6 grams
Weight training and power athletes: 1.8 - 2.4 grams
Protein Timing
Ideal ratio carbohydrate to protein 4:1
* Promotes the release of insulin thus stimulating muscle glycogen replacement.
* Stimulates the transport of amino acids into muscle cells thus promoting muscle protein synthesis (MPS) and blunting cortisol levels.
- Protein intake within 45’-60’ post exercise was positively associated with increase MPS. On average consuming CHO with protein enhanced recovery.
Body Fat in Athletes
Athletic population group averages are:
Female = 12-18%
Male = 6-13%
Essential body fat has been estimated at (American Council for Exercise):
2-5% in Male
10-13% in Female
