PE

• Energy systems


  All three energy systems are always working, except one will be more dominant & making a greater contribution at any given time. This is dependent upon the intensity, duration, oxygen and fuels available.
• Fuels


  • Carbohydrates
  • Fats
  • Protein
• ATP


  Adenosine triphosphate, energy for muscle contraction and movement of muscle fibres
• ATP resynthesis


  1. ATP is recharged via the three energy systems

  2. ATP is recharged at a slow rate while sleeping, but while jogging this happens at a much quicker rate, by breaking down different food fuels
• Carbohydrates (CHO)


  • The body's preferred source of fuel particularly during exercise
  • CHO are the sugars and starches found in fruit, cereal, bread, pasta and vegetables
  • Major food fuel for the production of ATP
  • Blood glucose and muscle and liver glycogen are the two forms of CHO
  • CHO converted into glucose (sugar) for immediate energy
  • Glycogen to be stored in the muscle
• Fats (triglycerides)


  • The body's preferred source of fuel at rest
  • MAIN ROLES
  • Protecting body organs +
  • Maintaining body temperature,
  • Hormone production
  • Energy stores for the body
  • A greater amount of oxygen is required by the body to utilise fats as a fuel than to use carbohydrates to produce ATP
• Protein


  • Last Resort fuel source
  • Foods such as fish, meat, poultry eggs and cereal
  • Their main role: growth and repair of tissue
• Everything we eat is broken down and either used immediately, excreted or stored as chemical energy, which must be converted to mechanical energy so muscular contractions and movement can occur
• Adenosine Triphosphate (ATP)


  • The major source of energy that allows muscles to contract and cells to perform KEY functions
  • It consists of an adenosine molecule with 3 phosphates joined together in a row
  • ATP into adenosine diphosphate (ADP) and an inorganic phosphate CP
  • Chemically ATP is an adenosine nucleotide bound between the 2nd and 3rd phosphate groups. This releases a LARGE amount of energy, forming ADP & P (inorganic phosphate)
• Glycogen breakdown


  1. Glycogen is broken down via a process called glycolysis

  2. Each glucose molecule is split into two pyruvic acid molecules, and energy is released to form ATP, allowing more muscle contractions to occur

  3. Under aerobic conditions with sufficient oxygen, the pyruvic acid enters the mitochondria and undergoes aerobic glycolysis to produce more ATP

  4. When there is insufficient oxygen supplied (anaerobic conditions), the pyruvic acid transforms into lactic acid and then into lactate and hydrogen ions via anaerobic glycolysis
• At rest


  The body shows a clear preference for fats as a food fuel over carbohydrates
• At varying exercise intensities

  • Food fuel sources will differ
  • Carbohydrate is the only source of energy used during maximal-intensity exercise
  • Fats are used increasingly during prolonged submaximal or endurance activities
  • Once glycogen stores start to deplete during an endurance event (at approximately the two-hour mark), there will be a transition to fats as the major fuel source
• Glycaemic Index


  • A ranking between zero and 100 describing how quickly the carbohydrate in a food is digested and absorbed into the blood
  • Foods are typically classified as being low, medium or high GI
  • Low GI = 55 or less, Medium GI = 55–69, High GI = 70 or higher
• Proteins and fats contain no carbohydrate and so have minimal effect on glucose production. They are considered to be 'low GI'
• Carbohydrate-fat 'fuel mixture' during prolonged endurance events


  • The body relies more on fats as exercise intensity decreases and duration increases
  • In marathons or triathlons, the body uses a mix of carbohydrates and fats
  • Initially, glycogen is the main fuel source, but the body shifts to using free fatty acids
  • Conserving glycogen is crucial to avoid 'hitting the wall'
  • Depletion of glycogen leads to increased reliance on free fatty acids, requiring more oxygen
  • The heart works harder to supply more oxygen to the muscles
  • Metabolism of fatty acids also requires glucose
• The 'crossover concept'


  • A theoretical model that explains the balance of carbohydrate and fat usage during sustained exercise
  • The crossover point is the intensity at which energy from carbohydrates predominates over energy from fats, with further increases in intensity resulting in greater carbohydrate use and decreased fat oxidation
  • Endurance training results in adaptations that increase fat oxidation during mild- to moderate-intensity exercise – this is known as glycogen sparing
• Fats as fuel source

  • Glycogen Depletion and Hypoglycemia: When liver glycogen is depleted, athletes rely heavily on fat for energy, but hypoglycemia can set in. This can be remedied by ingesting soluble sucrose.
  • Aerobic Training and Fat Utilization: Endurance athletes increase their ability to use fatty acids for ATP resynthesis through aerobic training, which involves developing more mitochondria and glycogen sparing.
  • Oxygen Cost and Muscle Oxygen Availability: Switching from carbohydrates to fats as the main fuel source increases the oxygen cost. This reduces the oxygen available to working muscles and increases the risk of working anaerobically, potentially explaining the need to slow down during high-intensity activities when fats are used.
  • Energy Density and Oxygen Requirement: Fats are a more energy-dense source than carbohydrates but require more oxygen per ATP of energy produced, as shown in Table 6.3.
• Strategies to shift the crossover point to the right and preserve carbohydrates until later in the event

  1. Increase Fat Adaptation

  2. Maintain a Steady Pace

  3. Nutrition and Hydration

  4. Training at Race Intensity

  5. Optimise Recovery
• ATP-PC energy system


  • Provides the bulk of ATP resynthesis during powerful explosive efforts
  • ATP-CP system is fuelled by stored ATP as well as creatine phosphate (CP)
  • When CP is broken down, the energy and phosphate group is released and then used to resynthesise ATP
• Anaerobic Glycolysis System


  • LA system is predominant during high-intensity, repeated efforts when CP had been depleted and given insufficient time to recover and there is insufficient oxygen at the muscle
  • Muscle stores of glycogen are anaerobically (without oxygen) broken down to release energy for ATP to be synthesised from ADP and Pi
  • This breaking down of glycogen is called glycolysis
  • Energy is obtained from the breakdown of glycogen; However since oxygen is not present, glycogen is not completely broken down and pyruvic acid is formed
  • The hydrogen ions increase muscle acidity, decrease muscle pH and prevent the coupling of cross-bridges
• Aerobic Energy System


  • Uses oxygen and is by far the most powerful of the 3 systems
  • We use this system for sports or activities that required endurance
  • It is also known as aerobic glycolysis because it is the breakdown of glucose in the presence of oxygen
  • The difference between anaerobic and aerobic is the complete breakdown of glycogen with no fatiguing toxic by-products
  • The waste products are carbon dioxide, which we breathe out and water
• Biomechanics


  The study of how and why the body moves
• Unknown: '"Biomechanics is the science concerned with the internal and external forces acting on a human body and the effects of these forces..."'
• Types of motions


  • Projectile Motion
  • Torque
  • Angular Velocity & Momentum
  • Levers
  • Classes of Levers
  • Use of Levers
  • Factors that affect levers
• A body’s resistance to change its state of motion is called inertia
• Inertia


  A body’s resistance to change its state of motion, directly related to its mass
• The heavier a golf club, the greater the inertia, and thus the greater force required to move or slow it down
• Mass


  The amount of matter that makes up an object (KG)
• Mass directly measures the amount of inertia of a body
• The head of a driver has greater mass than the head of a putter


  Consequently, it has greater inertia than a putter
• Force


  A push or pull placed upon an object to either get it moving, speed it up, slow it down, stop it or change direction
• Types of forces


  • Internally
  • Externally
• Internally


  Produced by contraction of muscles
• Externally


  Gravity, friction, water, air
• Force is measured in Newtons (Nt)
• A force is required to initiate, slow down, or stop movement of an object
• Newton's 1st Law: '"A body will remain at rest or in uniform motion in a straight line until an external unbalanced force acts on that body to change its state of motion."'
• Inertia


  A body's resistance to change its state of motion
• Correct Answer: C - A body's resistance to change its state of motion
• Correct Answer: C - Greater mass means greater inertia