Food fuels

What is in the food we eat? When food is digested, energy is released. The amount of energy released from each food is measured in kilojoules (KJ) The body breaks down the food into 3 sources of fuels and each provides different amounts of energy FATS – 38kj per gram CHOs – 17kj per gram PROTEIN – 17kj per gram Energy required depends on: age, sex, body size and activity level

Food Fuels for Energy Carbohydrates (CHO) Preferred source of fuel during exercise (Glycogen) Fat Concentrated fuel used during rest and prolonged sub-maximal exercise. Protein Used for growth and repair (Negligible use during exercise)

Using Table 5.1 of your text book, complete the following table into your workbooks Food Fuel RDI for a balanced diet Food Fuel after conversion/ digestion Storage CHO’s FATS PROTEIN

carbohydrates Foods rich in CHO play a vital role in exercise performance because they are the most readily available source of energy to fuel working muscles. Digestion breaks CHO into glucose for energy which is absorbed by the bloodstream, if the body does not require energy immediately the glucose is stored in glycogen in the liver and muscles. Any excess CHO are stored as fats

Carbohydrates cont... Can predominantly supply energy for high intensity short duration activities such as 200m sprints but also supply energy for sub-maximal longer duration activities such as a 5km jog. THEREFORE the body uses glycogen as its major fuel during exercise and CHO as a fuel can last up to 90 minutes of continuous activity. The athlete needs to continually top up CHO stores to ensure there is enough in the muscles before the start of training and competition.

Carbohydrate Contributions Storage (Based on 80kg person) Muscle glycogen – 400g Liver glycogen – 100g Intake of Carbohydrates depends on the intensity and duration of exercise bouts. Normal contribution to diet is 55-60% CHO Carbohydrate loading (7-12g CHO / kgBM) is used to prevent depletion of glycogen in endurance activities. Carbohydrate rich diet; Increases glycogen stores Glycogen is used in rebuilding ATP CHO preferred fuel over fats during exercise due to requiring less oxygen to release energy. Athletes need to be aware of their dietary intakes of CHO. Excess CHO is converted to adipose tissue (Fat). VCE Physical Education - Unit 3

Glycemic Index The Glycemic Index (high or low) is a ranking for CHO that the rate at which glucose is released into the bloodstream. HIGH GI: Glucose is released quickly into the bloodstream. If at rest, insulin will be released to regulate glucose levels. LOW GI: Glucose is released slowly into the bloodstream without the corresponding increased insulin release.

What is Insulin? Insulin is a substance released to regulate blood glucose levels An increase in blood glucose levels – caused by consuming high GI foods – result in the increase in insulin secretion which results in increased glycogen metabolism (use) Ingesting protein in recovery amplifies insulin response increasing glycogen uptake

Contribution of CHO’s for energy Comes from muscle glycogen first, followed by liver glycogen Varies according to the nature of the activity CHO Loading – The practice of increasing CHO stores within the muscles and body by increasing CHO intake and tapering training in the time leading up to major competition (up to 10 days). As much as 80% of the athletes diet is CHO. High intensity efforts via the anaerobic glycolysis system and aids endurance performance via the aerobic energy system Provides energy from PC restoration During high intensity/short duration activities, CHO’s are the primary energy source once PC has been depleted. During moderate intensity/longer duration (aerobic energy system) CHO’s and then fats are the sources of energy. CHO’s are preferred over fats. WHY?

Events less than 1 hr in length require normal CHO reserves Events lasting around 90 mins require well filled glycogen stores Events 2 hrs or more require ‘super filled’ glycogen stores (CHO loading) QUESTIONS Make a list of 5 events that would require an increase in CHO’s prior to the event. What types of foods should an athlete consume before, during and after a marathon? Complete the following table. Before Event During Event Post Event Food Fuel Glycemic Index

DID YOU KNOW??? One glucose molecule yields 36 – 38 ATP’s in the presence of O2 but only 2 to 3 ATP’s without O2.

FATS Fats are stored in the body in the form of triglycerides in fat cells (adipose tissue) and in the skeletal muscle. FFA the broken-down form of triglycerides provide energy for sub-maximal exercise aerobically. Nutritionists recommended that fat make up 25- 30% of a sporting diet. The transport of FFA to muscle fibres is slow and breakdown requires O2, putting added stress on the O2 transport system It is more difficult to use the energy from fat during exercise however fats become increasingly important when the stores of CHO are depleted during prolonged, continual physical activity. Trained athletes use fat as an energy source to a greater extent than untrained athletes

Fat Contributions At rest Storage of fats 50% of energy supplied by fats Oxygen demand is easily met to burn fats Benefits of fat Large energy store Transport medium for fat soluble vitamins Negative aspects of fat Obesity, heart disease etc. Storage of fats Adipose tissue Triglycerides (Broken down into free fatty acids) Aerobic metabolism of fat is; Slow Requires more oxygen Adds stress to the oxygen transport system ATP yield is much higher from fat (460 molecules) in comparison to glucose (36). VCE Physical Education - Unit 3

Fats as an energy source Fats are mainly used to produce ATP when the body is at rest – 2/3’s fuel source Also used as a fuel source during low intensity exercise, but as the intensity of exercise increases, the percentage of fat being used decreases Fat breaks down into triglycerides which are stored in the skeletal muscle or adipose tissue. Fat transported in the blood in the form of FFA Muscle triglycerides are predominantly used for exercise of long duration where FFA are used earlier (aerobically) to spare glycogen stores.

Protein Has several important functions in the body Formation and growth of body, tissues, especially muscle tissue and cells Repair and recovery of damaged tissues Production of RBC, hormones & enzymes (speed up chemical reactions). Provision of emergency fuel source during exercise when CHO and fat stores are depleted Protein is broken down through digestion into amino acids Essential amino acids – cannot be made by the body, so must be consumed Non-essentials – can be made from other amino acids in the body

Protein Contributions Protein and exercise Not used as a fuel, therefore low priority. Only used in extreme circumstances Normal diet contains enough protein (10 -15%). Excess protein can lead to; Less intake of CHO Increase in fat intake from animal products Increase in fluid waste VCE Physical Education - Unit 3

PROTEIN as an energy source Contribute 5-10% of the total energy requirement of endurance events Requires large amounts of oxygen to break down to produce energy A hard training athlete will need to increase protein intake to assist in muscle growth and repair CHO rich foods are also good sources of protein e.g. Breakfast cereals, bread and pasta

Using food fuels during exercise Low intensity (moderate walking) exercises use approx even amounts of fats and CHO As exercise intensity increases CHO becomes the primary fuel used by the muscles. The body even with low levels of body fat will not run out of fat stores but has limited stores of glycogen Fat can produce more ATP but the process of converting fat is not efficient (requires more oxygen) Protein only used when glycogen and fat stores are depleted such as ultra-marathons.

QUESTION TIME!!! Into what does the body break down CHO’s? In what form and where is CHO stored within the body? Into what does the body break down Fats? In what form and where is fat stored within the body? Define ‘Glycogen Sparing’. Discuss how ‘Glycogen Sparing’ benefits endurance athletes. Explain how lowering blood glucose levels influences athletes. How could the athletes increase their blood glucose levels during exercise? Outline the type of diet an endurance athlete should consume 3 days prior to competition. Look at Figure 5.4 and 5.5. In your own words, explain what the diagrams are depicting.

ATP = ENERGY Major source of energy Chemical fuel source Energy is released when one of the phosphates splits off. Only a small amount exists in the muscles: sufficient for a few maximal contractions ATP must be continually resynthesised so that energy can be provided for longer periods of time To rebuild ATP, energy from the breakdown of PC is used ATP is resynthesised almost as quickly as it is broken down.