Sports Science

• Protein


  The key food
• What food is converted to once in the body

  • Carbohydrates - transported to the muscles and stored as glycogen so that it is ready to use once we start exercising
  • Proteins - rebuilds muscle that is damaged during training and racing
  • Fats - helps cover and protect vital organs such as the brain and reproductive system
• Excess consumption of food

  • Beyond what we need for day to day living, including exercise, is stored as adipose tissue (fat)
  • In males, this is usually around the gut
  • In females, this is usually around the bottom, thighs and breasts
• Female vs Male Comparison
• Commercial sports drinks fall under 3 main headings

  • Hypotonic - These are less concentrated than the body's fluids (little or no carbohydrates or electrolytes) and will be absorbed at the fastest rate. They will help with rapid rehydration during long exercise sessions or immediately afterwards
  • Isotonic –These have similar concentration to the body's fluids (have some carbohydrates and electrolytes) and are also absorbed quickly. They are ideal for rehydration and topping up glycogen stores during or following exercise
  • Hypertonic - These are more concentrated than body fluids and are absorbed slowly, therefore these are not ideal for re-hydration because of their high carbohydrate content. They are suitable for replenishing fuel stores to aid recovery and these drinks should be taken with isotonic or water/hypotonic drinks
• Athletes should drink chocolate milk because it contains carbs, proteins and electrolytes that are crucial to recovery
• The Gatorade and Sports water have 0g of fat while the milk has 15g of fat. This is due to the Gatorade and the Sports water being produced mainly for consumption while exercising and is mainly focused on refueling the body with glucose and water. The chocolate milk had high amounts of nutrients while the Gatorade had lower amounts and the Sports water had the lowest amount of nutrients
• Adenosine Tri-Phosphate (ATP)


  All actions in the body require energy and it can only come from ATP
• ATP


  1. ATP 🡪 ADP + P + ENERGY

  2. ATP is resynthesised (rebuilt) from food sources: Carbohydrates, fats and protein

  3. Also from a fuel called PC

  4. ATP can be rebuilt Anaerobically (without O2) or Aerobically (with O2)
• ATP-PC system


  • Uses Creatine Phosphate (CP or PC) without the presence of O2
  • PC is stored in the muscle
  • It breaks down easily to rebuild ATP very fast, but runs out very quickly. 1 PC molecule rebuilds 0.7 of an ATP
  • PC is the main fuel used to rebuild ATP for up to 10 seconds of high intensity (95+% MHR)
• Anaerobic glycolysis system


  • Uses glycogen (comes from carbohydrates) without O2
  • Once PC stores start rapidly depleting, glucose/glycogen that is stored in the muscle becomes the main fuel for rebuilding ATP
  • Anaerobic glycolysis system is also increased when exercising above 85% MHR
  • Glycogen breaks down fast, but because there is no O2, it produces lactic acid
  • Lactic acid is made up of lactate and H+ (Hydrogen ions)
  • 1 glucose molecule produces enough energy to rebuild 2 ATP
• Anaerobic glycolysis (cont)


  1. Lactate can be used to rebuild more ATP or converted back to glycogen

  2. When H+ accumulates, it causes fatigue by inhibiting muscle contraction

  3. H+ reaches muscle inhibitive levels around 40 seconds at maximal intensity. The lower the intensity of exercise, the longer it takes to inhibit muscle contraction

  4. If the intensity is below 85% MHR, then H+ may not reach fatigue levels, due to adequate O2
• Fat Metabolism


  • Fats are also very useful stores of energy (intramuscular triglycerides). Blood fats(FFA)
  • They are the main fuel source in low intensity aerobic activities along with glycogen (below 70% MHR)
  • Fats are the slowest to rebuild ATP and require more O2 than glucose/glycogen
  • When glycogen is depleted, we rely heavily on the breakdown of fats
  • In a marathon this depletion is called "hitting the wall". Mental and physical stress occurs because the brain needs glucose
• Protein metabolism


  • Protein repairs muscle but is an energy source for the body as a last resort
  • This means that it is used when there are no carbohydrates or fats to be used
  • This happens to Anorexic or starving people, their body breaks down to survive
  • This causes enormous stress on the liver and kidneys which makes toxins build up
  • This can lead to brain damage and/or death
• Energy Systems vs. Food Fuels @ Various Exercise Intensities & Durations


  • Intensity
  • Total event duration
  • Dominant Energy system
  • Main Food / Chemical Fuel
  • Rest
  • Not Applicable
  • Aerobic
  • FFAs
  • Submaximal
  • 30 seconds
  • Aerobic
  • Glucose
  • Submaximal
  • 30 minutes
  • Aerobic
  • Glycogen
  • Submaximal
  • 4+ hours
  • Aerobic
  • FFAs
  • Maximal
  • 1-3 seconds
  • ATP-PC
  • Stored ATP & PC
  • Maximal
  • 5 seconds
  • ATP-PC
  • PC
  • Maximal
  • 30 seconds
  • Anaerobic glycolysis
  • Glycogen
  • Maximal
  • 1-2 minutes
  • 50% ATP-PC & Anaerobic glycolysis
  • 50% Aerobic
  • Glycogen
• When an activity commences, all 3 energy systems start contributing to energy production
• At any point, only one of them will rebuild the most ATP (dominant). The intensity and duration of the activity will dictate which energy system is dominant
• The energy systems don't activate in sequential order but work together to supply ATP to varying amounts
• Steady state


  Oxygen supply equals oxygen demand. Heart rate should plateau
• Oxygen deficit


  Oxygen demand exceeds oxygen supply. Heart rate climbs
• Oxygen debt/EPOC


  The period after exercise stops when heart rate remains above resting levels. Heart rate slowly drops. Fast part replenishes PC stores, slow part oxides H+
• VO2 maximum


  The maximum oxygen that can be taken up, transported and used by working muscles
• Lactate Inflection Point (LIP)


  • Defined as the highest point at which lactate and H+ production = removal. This is the highest steady state where O2 demand still = O2 supplied to the muscles
  • It occurs at 85% maximum heart rate
  • Above this point is where lactate and H+ production is greater than what can be removed and they begin to accumulate in the blood. This is due to insufficient O2 supplied to the muscle and therefore the Anaerobic glycolysis system has to increase the amount of ATP it rebuilds
• Fatigue


  • Fuel depletion
  • Accumulation of metabolic by-products
  • Thermoregulation
• Types of Fatigue


  • Peripheral/Local (in muscles)
  • Central/General (CNS)
  • Chronic (long term eg Glandular fever and Chronic fatigue syndrome) are due to overtraining
• Examples of fuel depletion (Peripheral- fatigue in muscles)

  1. ATP – muscle stores deplete after approx. 3 seconds after which we resynthesise them

  2. PC – almost all stores deplete after 10 seconds of maximal intensity activity

  3. Increased contribution from Anaerobic glycolysis system

  4. Slower to resynthesise ATP= reduced exercise intensity

  5. Muscle Glycogen – depletes significantly after 90+ mins at submaximal intensity

  6. greater reliance on fats

  7. Fats become dominant
• Therefore the Anaerobic glycolysis system has to increase the amount of ATP it rebuilds
• Fatigue


  The inability to sustain a required exercise intensity
• Fatigue is noticeable when exercise performance begins to deteriorate
• Mechanisms (types) of Fatigue

  • Fuel depletion
  • Accumulation of metabolic by-products
  • Thermoregulation
• Areas where fatigue can occur

  • Peripheral/Local (in muscles)
  • Central/General (CNS)
  • Chronic (long term eg Glandular fever and Chronic fatigue syndrome)
• Chronic fatigue


  Due to overtraining
• Fuel depletion (Peripheral- fatigue in muscles)

  • ATP – muscle stores deplete after approx. 3 seconds
  • PC – almost all stores deplete after 10 seconds of maximal intensity activity
  • Muscle Glycogen – depletes significantly after 90+ mins at submaximal intensity
  • Fats become dominant fuel (hitting the wall) around 2-3 hours of continuous exercise
• Slower to resynthesise ATP

  Reduced exercise intensity
• Accumulation of metabolic by-products

  • Hydrogen Ions – reduce the pH level within muscles (muscle acidosis)
  • Inorganic Phosphate – from splitting ATP and PC
  • ADP – created after ATP splits
  • Calcium ions (Ca2+) – ADP and Pi interferes with the release of Ca2+ causing a reduction of muscle contraction force
• Lactate inflection point (LIP)


  The maximum intensity athletes can still be working Aerobically without accumulating lactate and H+
• LIP occurs at


  85% maxHR for most people. Higher aerobic capacities are associated with higher values of LIP (85–95% maxHR)
• H+ contribution to fatigue

  • Reduces force of muscle contraction
  • Reduces rate of ATP resynthesis
• Central Nervous System (CNS) fatigue

  The brain can send fewer and weaker signals to the working muscles. This results in less forceful and less frequent muscle contractions
• Thermoregulation (Central) fatigue


  • The body overheats when core body temperature rises beyond 37.5oC
  • Body reacts by redirecting blood flow away from working muscles (vasoconstriction) and more to the skin's surface (vasodilation)
  • Less O2 and fuels reach the muscle and therefore have a greater reliance on the anaerobic glycolysis system