10- Energy Systems Flashcards
Adenosine triphosphate (ATP) (the only usable form of energy in the body) of
-is the energy we use for muscle contractions. We have to constantly rebuild ATP by converting ADP and Pi back into ATP using phosphocreatine, carbs, fats and protein in one of three energy systems
Energy transfer during short duration/ high intensity exercise (ATP-PC system/anaerobic glycolytic system)
The ATP-PC system
•the ATP-PC system provides energy for high intensity activities lasting less than 10 seconds. The system is anaerobic and occurs in the sarcoplasm. Creative kinase is the enzyme that breaks down the PC that is stored in the muscles into creative and phosphate. Energy is released for ATP synthesis and aerobic energy is needed for recovery
Anaerobic glycolytic system
•provides energy for high intensity activity for longer than the ATP-PC system. How long this system lasts depends on the fitness of the individual and the intensity of the exercise. Working flat out to exhaustion means that the system will last a shorter time. This is because the demand for energy is extremely high. However at a slightly lower intensity the system can last longer - up to 2-3 minutes -because the demand for energy is slightly lower.
KEY POINTS FOR THIS SYSTEM ARE AS FOLLOWS:
•it is anaerobic and occurs in the sarcoplasm.
•PFK is the enzyme that is responsible for glycolysis (is the breakdown of glucose into pyruvic acid)
• glycogen is converted to glucose-6-phosphate and broken down to pyruvic acid
•pyruvic acid is then broken down into lactic acid
•2 ATP are produced
Lactate accumulation/OBLA
- as lactate accumulated in the muscles so do the hydrogen ions, and it is actually the presence of hydrogen ions that increases acidity.
- this slows downs enzyme activity, which affects the breakdown of glycogen, causing muscle fatigue
- OBLA and lactate threshold can be used interchangeably. Lactate threshold is the point at which lactic acid rapidly accumulated in the blood, whereas OBLA is the point at which lactate levels go above 4 millimols per litre. Measuring OBLA gives an indication of endurance capacity l. Some individuals can work at higher levels of intensity than others before OBLA.
- lactate threshold is expressed as a percentage of VO2 max. As fitness increases, the lactate increases, the lactate threshold becomes delayed. Average performers have a lower lactate threshold than elite performers and work at much lower percentage of their VO2 max. Elite power athletes have a much better anaerobic endurance than non elite performers. This is because their body has adapted to cope with higher levels of lactate. In addition. L, through a process called buffering, they are able to increase the rate of lactate removal and consequently have lower lactate levels. (Buffering- the process that aids the removal of lactate and maintains acidity levels in the blood and muscle)
Factors affecting the rate of lactate accumulation
- intensity of exercise: the higher the intensity, the faster lactate accumulation occurs
- slow twitch fibres produce less lactate than fast twitch fibres
- VO2 max of a performer/buffering capacity- the higher the level; the more reduced the rate of lactate accumulation
- a respiratory exchange ratio close to 1.0 means that glycogen becomes the preferred fuel and there is quicker lactate accumulation.
- higher level of fitness of the performer/regular training- delays OBLA because adaptions occur in trained muscles, for example increased numbers of mitochondria risk and myoglobin, a greater capillary density.
Energy transfer during long duration/ lower intensity exercise (aerobic system)
The aero pic system provides energy for low intensity activities lasting longer than 1-2 minutes and has three stages
- ) stage one- glycolysis occurs(the breakdown of glucose into pyruvic acid where 2 ATP are produced)
- ) stage two- the Krebs cycle. The pyruvic acid produced in the glycolysis splits into 2 acetyl groups, which are carried into the Krebs cycle by coenzyme A. Acetyl coenzyme A diffuses into the matrix of the mitochondria and combines with oxaloacetic acid, forming citric acid. This is oxidised and CO2 is removed. Hydrogen ions are formed and oases into the electron transport chain, and 2 ATP are resynthesised. Fats can also enter the Krebs cycle after a process called beta oxidation has taken place, where fatty acids are broken down to acetyl coenzyme A.
- ) stage three- the electron transport chain occurs in the cristae of the mitochondria, water is former and 34 ATP are resynthesised so there are 36 ATP produced overall
Energy continuum for physical activity
Energy continuum is a term that describes the type of respiration used by a physical activity. Whether it is aerobic or anaerobic respiration depends on the intensity and duration of the exercise
ENERGY SYSTEM USED ACCORDING TO INTENSITY AND DURATION OF EXERCISE
-duration of performance: less than 10 secs
intensity: very high
energy supplied by: ATP-PC
-duration of performance: 8-90 seconds
Intensity: high-very high
energy supplied by: ATP-PC and anaerobic glycolytic system
-duration of performance: 90 seconds-3mins
Intensity: high
Energy supplied by: anaerobic glycolytic and aerobic
-duration of performance: 3+ minutes
Intensity: low-medium
Energy supplied by: aerobic
Differences in ATP generation between slow and fast twitch fibres
Slow twitch fibres (type 1)
-produce ATP aerobically
Fast twitch fibres (type IIx)
-produce ATP anaerobically
Slow twitch fibres (type 1)
-produce up to 36 ATP per glucose molecule
Fast twitch fibres (type IIx)
-produce only 2 ATP per glucose molecule
Slow twitch fibres (type 1)
-production is slow, but these fibres are more endurance based and so less likely to fatigue
Fast twitch fibres (type IIx)
-production of ATP is fast this way, but cannot last for long because these fibres have the least resistance to muscle fatigue.
Oxygen consumption during exercise (maximal and submaximal oxygen deficit)
Oxygen consumption is the amount of oxygen we use to produce ATP, whereas submaximal oxygen deficit is when there is not enough oxygen available at the start of exercise to provide all the energy (ATP) aerobically. Maximal oxygen deficit is usually referred to as maximal accumulated oxygen deficit, or MAOD. It gives an indication of anaerobic capacity.
Oxygen consumption during recovery (excess post exercise oxygen consumption-EPOC)
EPOC- the amount of oxygen consumed during the recovery above that which is normally consumed at rest. It is the breathlessness we experience when exercise is finished- the extra oxygen that is taken in is used to put things back to normal. That which can be returned to normal quickly is called the fast replenishment stage (alactacid compinent). This involves the restoration of ATP and PC, together with the restoration of myoglobin with oxygen. Restoration of PC takes up to 3 minutes for 100%/30 seconds for 50% and uses 2-3 litres of oxygen. Myoglobin replenishment takes up to two minutes and uses 0.5 litres of oxygen.
The slow replenishment stage (lactacid component) involves the removal of lactic acid and can take an hour or more. It is achieved by oxidising lactic acid into carbon dioxide and water, and so is used as an energy source. Lactic acid can also be converted into glycogen, glucose and protein, and removed through sweat and urine. During this stage, heart rate, respiratory rate and body temp remain elevated
Factors affecting VO2 max/aerobic power (VO2 max is the maximum volume or oxygen that can be taken up and used by the muscles per minute. A good VO2 max allows a performer to work at a higher intensity for longer by utilising oxygen more effectively)
The following structural/physiological characteristics will enable a performer to have a higher VO2 max:
- increased maximum cardiac output
- increased stroke volume/ejection fraction/cardiac hypertrophy (cardiac hypertrophy is the abnormal enlargement, or thickening, of the heart muscle)
- greater heart rate range
- increased levels of haemoglobin and red blood cell count
- increased stores of glycogen and triglycerides
- increased myoglobin content
- increased capillarisation around the muscles
- increased number and size of the mitochondria
- increased surface area of alveoli
- increased lactate tolerance
- reduced body fat
- slow-twitch hypertrophy
The following general factors can also affect the VO2 max
- lifestyle: smoking, sedentary lifestyle, poor diet and fitness can all reduce V02 max
- training: V02 max can be improved by up to 10 to 20% following a period of aerobic training
- genetics: V02 max is largely genetically determined, which limits the impact of training
- gender: Men generally have an approximately 20% higher V02 max than women
- age: as we get older, the O2 max declines because our body systems become less efficient
- Body consumption: A higher percentage of body fat decreases V02 max
Measurements of energy expenditure (indirect calorimetry, lactate sampling, the VO2 max test, respiratory exchange ratio)
- indirect calorimetry measures how much carbon dioxide is produced and how much oxygen is consumed both at rest and during aerobic exercise. It is a reliable test because it gives a precise calculation of the VO2 and VO2 max. Works with footballers
- Lactate sampling measures lactate levels in the blood and is an accurate and objective measure. It can measure exercise intensity, give an idea of level of fitness and enable the performer to select relevant training zones. It also provides a comparison to see whether improvement has occurred. If test results show an increase this would indicate that the performer has improved peak speed/power, increase time to exhaustion, improved recovery heart rate and a higher lactate threshold. Works best with runners or swimmers and rowers as it is a reliable guide to safe and effective training. It helps to avoid under or over training
- respiratory exchange ratio is the ratio of carbon dioxide released compared with oxygen used by the body. It calculates energy expenditure and provides information about which energy source (fat or carbohydrates) is being oxidised, and hence whether the performer is working aerobically or anaerobically. an respiratory exchange ratio (RER) value close to one indicates that the performer is using carbohydrates; an RER value of approximately 0.7 means the performer is using fats; an RER value greater than one implies anaerobic respiration. It works of all sports as it works to measure and show the muscle oxidative capacity to get energy which is useful for all sports
- VO2 max tests, such as the multistage fitness test and the Cooper 12 minute run, only give an indication or prediction of VO2 max. Direct gas analysis – measures concentration of oxygen that is inspired and the concentration of carbon dioxide that is expired the tests include increasing intensity is on a treadmill, cycle Urgo meter or rowing machine. Works best with endurance sports such as rowers, cyclists and runners as it is based on the fact that the more oxygen and athlete consumes during high intensity exercise, the more the body will generate ATP energy in cells.
The impact of specialist training methods on energy systems (altitude training, high intensity interval training, plyometrics, speed agility quickness)
- altitude training (altitude starts to have an affect at around 1500 m above sea level but most athletes choose to train at 2500 m plus). Here the partial pressure of oxygen is lower, so haemoglobin is not fully saturated, which lowers the oxygen carrying capacity of the blood. Advantages include increase in red blood cells, increase concentration of haemoglobin, increase blood viscosity anchor pillarisation, enhanced oxygen transport and increase lactate tolerance and improve aerobic energy system. And disadvantages is that is expensive, altitude sickness, detraining because training intensity has to reduce when they perform a first train is at altitude due to the decreased availability of oxygen, benefits quickly lost on return to sealevel, physiological such as homesickness. A marathon runner would benefit from this training method as overall there is an increase in their performance due to increase myoglobin, increased haemoglobin and therefore an increase oxygen carrying capacity
- HIIT involves short intervals of anaerobic maximum intensity exercise followed by recovery interval of aerobic exercise. It is used for both anaerobic and aerobic training and involves short duration of maximum intensity exercise. Footballers would benefit from this training method as during their games, the intensity ranges as they aren’t always working at periods of high intensity, it is more short, sharp bursts of energy’s. HIIT improves fat burning potential, glucose metabolism and both aerobic and anaerobic endurance
- and plyometric training improves power/speed. It involves high intensity explosive activities for example jumping and works on the principle that muscles can generate more force if they have previously been stretched. An eccentric contraction occurs first followed by concentrate contraction. It has three phases:
1. Eccentric phase – on landing, the muscle performs an eccentric contraction which stretches the muscle
2. Amortisation phase – The time between the eccentric and concentric muscle contractions. This time needs to be short so that the energy stored from the eccentric contraction is not lost
3. Concentric contraction phase – this uses the stored energy to increase the force of the contraction. Plyometrics would benefit a basketballer as it involves high-intensity explosive activities which reflects the play of the game
-speed agility and quickness training aims to improve the multi directional movement through developing the neuromuscular system, for example foot ladders. Activities are perform with maximum force at high speed so energy is provided anaerobically. It would benefit a goalkeeper. This is because they have to have speed combined with agility, which is the ability to move and position the body quickly and effectively well under control. A goalkeeper may have to make a save close to the ground and then move quickly to save a rebound, it improves multi directional movement through developing the neuromuscular system
