Ok so in order to help myself and others this year, I have decided to develop a notes thread whereby information can be posted to allow for students to not forget minor details in SAC's or the exam at the end of the year. I have decided to only do from chapters 4-6 as these chapters are known to be the most complicated chapters within the book, as the rest, namely the NPAG's are all rote-learned. So If you have any extra information you would like added into this post I'd be happy to add it, so we all have a great advantage at the end of the year
This thread will include the following chapters out of the Nelson Physical Education Unit 3 & 4 textbook;
- Chapter Four: Foods, Fuels and Energy Systems
- Chapter Five: Oxygen Uptake, Oxygen Deficit and Oxygen Debt
- Chapter Six: Muscular Fatigue Mechanisms
Chapter Four
Food FuelsFirstly, there are three different food fuels that are used for being able to carry out everyday movements.
- Carbohydrates
- Fats
- Protein
Carbohydrates are the preferred food fuel source during high-intensity exercise and is the predominant food fuel used by the Lactic Acid System and Aerobic System. Carbohydrates are split into three different categories; Low GI, Medium GI, and High GI. Low GI foods are slowly digested and absorbed into the blood stream and thus are best consumed around one and a half to two hours prior to endurance physical activity. Some Low GI foods can include; lentils, yoghurt, apples etc. High GI foods are digested and absorbed immediately by the body and are best consumed either in small amounts during exercise or immediately after exercise. So I suppose your wondering why would you consume High GI foods over Low GI foods, since Low GI foods provide energy for longer? Well firstly they are broken down quicker and because of this would be more appropriate to consume in order to replenish food fuel stores (glycogen) during or after exercise. In addition having Low GI foods to close to exercise or during exercise could result in a decreased performance from the athlete as they would have a bloated feeling in the stomach, thus effecting their performance.
Fats are a concentrated food fuel source which can generate large amounts of ATP (adenosine tri-phosphate, used for energy) with the presence of oxygen. Fats are the preferred fuel source at rest and during low-intensity exercise. Fats are also useful for endurance runners as they allow the endurance runner to improve their use of fats as a fuel source rather than glycogen so they have a competitive advantage when finishing the race. This is referred to as glycogen sparring. Some fat predominant foods can include; full cream dairy products, meat products, avocados etc.
Protein is generally used for growth and recovery of muscles after exercise, but in some extreme cases can be used negligibly during pro-longed exercise (100km marathon). This will ony occur when all glycogen and fat stores are depleted, and is not preferred in racing conditions. Some foods containing protein include; eggs, seafood, lean meat products etc.
There are also some disadvantages of exceeding the recommended dietary intake (15%) of protein;
- It can lead to the displacement of carbohydrate-rich foods
- Some protein rich foods contain excess amounts of unwanted fats
- Can lead to an increase in nitrogen excretion, which increases urinary loss and thus results in dehydration
Where are these foods stored/What are they used as during exercise/What is the RDI of each food?Carbohydrates are stored as glycogen within the muscle (roughly 400g) and the liver (roughly 100g). During exercise the glycogen is broken down to glucose which is used as the fuel source. The recommednded dietary intake of carboydrates is between 55-60% of the total foods consumed daily
Fats are stored as triglycerdies within the adipose tissue and muscle sites around the body. During exercise they are broken down to free fatty acids (FFA's). The RDI of fats is around 25-30% of the daily diet.
Protein is stored as protein and enzymes within the muscles. During exercise they are broken down to amino acids once glucose and free fatty acids have been depleted. For the dietary needs an average person should take in anywhere between 10-15% protein per day.
Vitamins and MineralsVitamins are essential in the diet of an individual and assist in the production of enzymes and metabolism of carbohydrates and fats within the body. Most often vitamins need be to absorbed through foods e.g. B complex and Vitamin C need to be absorbed through food because the body doesn't make sufficent amounts of this vitamin
Minerals are inorganic componds which are used to assist regulating the bodys functions e.g. Iron, Calcium etc.
Glycemic Index (GI)The glycemic index is a ranking of carbohydrates from 0-100 depending on their immediate influence on blood glucose or insulin levels within the muscle. Therefore the higher the ranking the quicker the glucose is digested and absorbed into the muscle ready for use. (Types of GI were spoke about earlier in the carbohydrates section)
Food Fuels at Rest and During ExerciseAt rest the predominant food fuel is fats which is supported through the aerobic energy system. This is because there are no energy demands from the body and it is easier for the body to utilise fats so that if immediate exercise is required, the body can switch over to glucose as the predominant food fuel.
During exercise, the type of food fuel is dependant on the level of intensity and duration of the exercise. In most cases the predominant food fuel is carbohydrates, (keeping in mind that phosphocreatine is not classified as a food fuel, but instead is fuel source, since it is made by the body) and this type of fuel is utilised by the lactic acid and aerobic energy systems during high intensity exercise, (generally 85% + of max heart rate). Now because the predominant food fuel isn't always going to be carbohydrates, there will also be contribution from the Phosphocreatine fuel source and fats and protein sources of fuel.
The carbohydrate/fat fuel ‘mixture’ during prolonged endurance eventsAs stated earlier on, there is a 'mixture' of carbohydrates and fats during endurance events or activities. Generally the preferred fuel source is glucose, but some athletes or non-athletes won't have planned in advance for the intensity or potential duration of the event and may deplete all of their glucose stores. This phenomenon is referred to as 'hitting the wall', which in laymans terms means depleting all sources of glucose so that fats are used as the predominant fuel source. Sounds simple! Ok so there are a disadvantage with this occuring which is that the performance of the athlete will diminish as more oxygen is required to break down the fats to use as energy, therefore meaning the respiratory and circulatory system will have to worked twice as hard to ensure sufficient oxygen is being delivered to meet these demands. Generally from an onlookers perspective, they will notice that the athlete will be slowing down.
Fats as a Fuel SourceAs stated in the previous sub-heading, when the athlete 'hits-the-wall', this is when hypoglycaemia sets in (lower levels of blood glucose within the body). Generally athletes tend to avoid this by training their body to utilise fats in order to resynthesise ATP through aerobic training which results in an increase in mitochondria within the muscle or through glycogen sparring.
The ATP-PC System - Comprehensive(You probably won't have to know all of this but most is recommended)
The ATP-PC system is the primary reason a human is able to jump, throw a ball, kick a goal in soccer etc. This is because of the high-energy phosphate compound known as ATP (adenosine tri-posphate). ATP is made up of adenosine and three phosphates (Pi) known as inorganic phosphates. In order for the body to be able to jump for example, the ATP would have to split (known as ATP-Split...well no shit) its further most phosphate bond thus turning into adenosine di-phosphate (ADP) and inorganic phosphate. This process creates energy! Now, in order for the body to do this movement continuously it needs the assistance of the fuel source PC/phosphocreatine/creatine phosphate which re-synthesises the ADP and the Pi molecule back to ATP so that the process can start over again and provide energy for movement. Generally we have about 50g of ATP already stored within our muscles which enables us to provide energy for roughly around 1-2 seconds. Through PC the body is able to continue high intensity exercise (95%+ max heart rate) for up to 10-15 seconds which is when PC will have been fully depleted.
Some important facts about the ATP-PC system;
- Peak power is between 3-6 seconds (generally 5 seconds)
- The Lactic Acid system becomes the dominant energy system after peak power (5 seconds)
- The ATP-PC system is used for activities above 95% heart rate
- Recovery for the Pc stores can take 30 seconds to replenish 70% of stores and 3 minutes to replenish 100% of stores
- Replenishment is best achieved through passive recovery (at rest)
The Lactic Acid System - ComprehensiveSimilar to the ATP-PC system the lactic acid system utilises ATP in order to provide energy for movement. Although unlike the ATP-PC system the Lactic acid system resynthesises ATP from food fuel sources, this being glycogen (from carbohydrates). Once the ATP-PC system has depleted around 40 to 50% of its fuel sources (5 seconds roughly) the Lactic acid system becomes to predominent energy system providing energy for movement. After the ATP-Split the body utilises glycogen as its fuel source in order to resynthesise ATP. This is done anaerobically and is where the glycogen is broken down to glucose where it is then used to resynthesise ATP. Luckily normal glycogen stores can last up to 60 minutes so glycogen can last a fairly long time during exercise even though the LA system is the predominant energy system between 5 and 30 seconds whereby the aerobic system takes over. Some interesting information worthwhile noting regarding the LA system (I know a bit wordy there):
- Peak power is between 5-15 seconds
- Generally the LA system can last up to 2-3 minutes before fatiguing
- Is used for exercise intensities above 85% heart rate
- Recovery time can take anywhere from 20 minutes to 2 hours
- The best recovery strategy is an active recovery
- The metabolic by-products of this system include Lactic Acid, Pi and H+ (which contributes to lactic acid accumulation)
LIP (Lactate Inflection Point)The LIP is an important and often neglected aspect of the energy systems chapter. Firstly it occurs when lactic acid accumulation exceeds lactic acid removal. The point at which lactic acid occurs is around the 85% heart rate or 70% Vo2 max of an athlete. In terms of blood lactate accumulation the Lactate threshold occurs around 1 mmol/L. Once lactate inflection point has been exceeded the energy pathway used to provide energy includes the anaerobic energy system, with the LA system being the most predominent out of the two. When working above LIP the significance is that the athlete is performing above the steady state, lactic acid accumulation increases thus resulting in the athlete fatiguing much quicker, and the exercise intensity may diminish quicker due to the accumulation of lactic acid. Some advantages of training above the LIP include that it can train the respiratory system to take in larger quantities of air per breath (increased tidal volume), train the circulatory system to utilise and transport larger quantities of oxygenated blood to the working muscles, trains the working muscles to transport the oxygenated blood into energy (or for any other uses such as heat removal etc.) and allows the individual to perform at a higher intensity for a longer amount of time.
The Aerobic Energy System - ComprehensiveOk so unlike the ATP-PC system and the LA system who both rely on providing energy without the presense of oxygen (anaerobically) the aerobic system is probably the most powerful system as it can last for hours by providing energy with the presense of oxygen. There are three stages to provide energy with the aerobic energy system, firstly there is aerobic glycolysis, which is where glucose is used as the primary food fuel in order to resynthesise ATP and provide energy. Through this process the metabolic by-products of H+ and Inorganic phosphates are developed as well as the acid, Pyruvic acid (PYRUVIC ACID IS NOT A METABOLIC BY-PRODUCT!). The second stage is where greater amounts of ATP are produced through the pyruvic acid developed in stage one. During the Kreb's cycle the pyruvic acid is converted to ATP with the presence and development of the metabolic by-product of Carbon Dioxide, This stage produces 2 ATP molecules. The third stage involves the electron transport system, which involves the by-product of H+ (hydrogen Ions) to be fused with heat and water in order to generate 36 ATP molecules. Keeping in mind this three stage process is when carbohydrates are being converted to energy. Some important facts to note regarding this system include;
- Its peak power is between 1-2 minutes
- At 75 seconds of exercise both the aerobic and anaerobic energy systems are contributing to exercise equally
- It becomes the predominant energy system after 30 seconds roughly
- It is used for extended high-intensity events such as the 800m and 1500m
- It contributes to energy demands generally between 65-85% max heart rate
- Metabolic by-products can include Water, Heat and Carbon Dioxide
- Recovery can take anywhere between 2-5 days
- Best recovery strategy is an active recovery
Some additional information worth notingRecovery StrategiesThere are two different recovery strategies that are used in order to help....well recover the body. They are Active recovery and Passive Recovery. The Passive recovery is fairly straight forward and I personally shouldnt have to explain how to rest after exercise, so i'll just explain the benefits of doing so. This can allow the body to replenish energy systems and allow PC stores to replenish.
The Active recovery, I believe, is the most important as it allows the body to recover the energy systems, almost complete PC stores are replenished and it aids in the removal of metabolic by-products such as Hydrogen Ions, lactic acid and inorganic phosphates. Ways of conducting an active recovery can include;
- Contrast Bathing (bath in cold water then in warm water and repeat)
- Massage as this allows oxygen to be pumped to the muscles to get rid of by-products
- Jog/light run
AND THATS THE END OF CHAPTER FOUR!
I'll post chapter five up later on
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