conversion of food to energy week 12. what you need to know… what happens when cho break down? how...
TRANSCRIPT
What you need to know…
What happens when CHO break down? How are CHO used? What is the glycemic index? High GI & Low GI
examples How can GI be used to benefit performance? How are fats used? How is protein used? What is the importance of fluid?
Introduction When food is digested, _____________ is
released The amount of energy released from food is
measured in kilojoules The three main food fuels are:
• Fat• 38 kilojoules per gram
• Carbohydrate• 17 kilojoules per gram
• Protein• 17 kilojoules per gram
Carbohydrates (CHO)
Most readily available source of energy to fuel working muscles
Digestion breaks CHO down to simpler forms to use for energy
• _____________ (stored in the blood)
• _____________ (stored in the muscles and liver)
• Any excess CHO is stored as fat
• Triglycerides (muscles)
• Adipose tissue (around the body)
Carbohydrates (CHO) The body uses glycogen as one of its major
fuels during exercise CHO are versatile. Predominant supplier of
energy for:• High intensity, short duration activities (lactic acid
system)• Eg:
• Repeated work periods (restoring ATP-PC system)• Eg:
• Sub-maximal, longer duration activities (aerobic system)• Eg:
CHO Needs of the AthleteSituation Recommended CHO
Everyday activity <90mins
Low intensity
5-7 grams per kg of body mass
Training programs >90-120mins 7-10 grams per kg of body mass
Pre-event meal Meal eaten 1-4hrs pre-competition
1-4 grams per kg of body mass
CHO intake during training sessions & competition events >1hr
60 grams per hr
Rapid recover after training session or multi-day competition
1 gram per kg of body mass in first 30mins, repeated every 1-2hrs until normal meals resumed
Glycemic Index A ranking of _____________ according to how quickly
they are digested and therefore release energy, as well as the way they affect blood glucose levels
Foods that break down _____________ have the highest glycemic index
• Blood glucose response is fast and high
• Appropriate for recovery of muscle glycogen stores after strenuous exercise
Foods that break down _____________ have low glycemic indexes
• Slower rise in blood glucose
• Appropriate for pre-event meals for sustained energy during the event
Glycemic Index of Common CHO
Low glycemic index
< 50
Moderate glycemic index
50-70
High glycemic index
>70
Glycemic Index and Exercise
The ideal meal immediately before exercise should provide CHO that sustain blood glucose levels while minimising increases in insulin release
By keeping insulin levels relatively unchanged, blood glucose should be preserved, fats should be mobilised and broken down and both liver and muscle glycogen stores spared for later use
Glycemic Index and Exercise Consuming high glycemic index foods
immediately before exercise results in rapid increases in blood glucose and insulin (hypoglycaemia)• Impairs functioning of central nervous system• Reduces free fatty acid mobilisation• Accelerates glycogen depletion
Consuming low glycemic index foods 45-60mins prior to exercise allows a slower rate of glucose absorption and supplies slow release glucose for use during exercise• These foods also avoid the insulin surge associated
with food that have a high GI
Fat
Stored as triglycerides (adipose tissue and skeletal muscle)
Triglycerides broken down into free fatty acids (FFA)• FFA broken down aerobically to provide
energy for movement
• Uses _____________ oxygen than CHO, therefore not the preferred fuel during exercise
Importance of Fat
Provides FFA that provide energy Produces more energy per gram than all other
nutrients (39kj per gram) Makes up to 50% of body’s everyday energy Carries fat-soluble vitamins A,D,E&K Contributes to taste, texture, aroma of food Provides protection for certain organs Helps produce cell membranes, skin hormones
and cholesterol
Fat During Exercise Recommended amount is 20-30% of a sporting diet Any more can cause health problems Not preferred to CHO because it is harder to break
down (uses more oxygen) When _____________ depleted during prolonged,
continual exercise fat becomes vital Athletes can teach their body to use fats first
(through aerobic training) in long events to keep glycogen stores in reserve for the high intensity end part of an event• Known as CHO/glycogen sparing
• Avoid ‘hitting the wall’
Protein Broken down into _____________ _____________ Makes up to 15% of diet Protein has several important functions:
• Formation and _____________ of body tissues, especially muscle tissue and cells
• _____________ and recovery of damaged such as muscle tissue
• Production of red blood cells, hormones, antibodies and enzymes
• Provision of emergency fuel source during exercise when CHO and fat stores are depleted
Protein During Exercise
Average diet supplies sufficient protein and essential amino acids to meet an athlete’s requirements
Some endurance athletes and power athletes believe more protein is required• Disadvantages:
• Less CHO in diet
• Excess fat intake associated with animal protein
• Increase chance of dehydration and constipation
Vitamins
Assist chemical reactions within the body Two types
• Fat soluble: stored in the body
• Water soluble: not stored in the body A balanced diet ensures adequate vitamin
intake No need for additional intake as these tend to
leave the body via urine Athletes should increase their intake via
increased food intake
Minerals
Important role in muscle contraction, nerve transmission, fluid balance, assisting enzymes in energy production and an important component of bone, muscle, skin and blood
Readily available in a well-balanced diet Two most important minerals
• Iron
• Calcium
Fibre
Eg: Important functions:
• Helps ensure a slow release of energy
• Helps to feel full
• Regulates bowel movements
Two types• Soluble:
• Insoluble:
Fluid
70% of our body is water Each day the body needs to replace 2 litres of
fluid• Not even accounting for sweating
Important functions• Transport energy, waster, hormones, antibodies
• Dilute waste products
• Lubricate surfaces and membranes
• Help regulate body temperature
• Involved in all chemical reactions in the body
Fluid Dehydration is a major cause of
_____________ Athletes must ensure fluid intake
compensates for sweat lost during exercise Dehydration leads to a drop in performance
and can be life threatening 300-400mL prior to exercise 400-1000mL per hr during exercise Sports drinks that contain CHO and
electrolytes are better during prolonged exercise