energy systems

• ATP


  The only source of energy for movement
• ATP-ATPase


  Breaks down ATP into ADP (+ P + energy)
• Phosphocreatine


  Broken down when ATP levels fall
• Phosphocreatine breakdown


  Releases energy to resynthesize ATP
• ATP-PC system


  • Fuel is phosphocreatine, site is sarcoplasm, yield is 1:1, enzyme is creatine kinase, no by-products
• ATP-PC system advantages


  • High intensity (explosive), no harmful by-products, no delay in O2 delivery
• ATP-PC system disadvantages


  • Short duration (10s), inefficient energy yield
• Anaerobic glycolysis


  Fuel is glycogen stored in muscle/liver, enzymes are GP, PFK, LD, energy yield is 1:2
• Glycolysis


  Glycogen is broken down into glucose, glucose is broken down into pyruvic acid, pyruvic acid is broken down into lactic acid (due to insufficient O2)
• Anaerobic glycolysis advantages


  • High intensity energy, no O2 delay
• Anaerobic glycolysis disadvantages


  • Short duration, inefficient energy field, fatiguing by-product
• OBLA


  Onset of blood lactate accumulation (above 4 mmol), trained athletes can delay OBLA, lactate threshold measured as a % of VO2 max
• Aerobic glycolysis


  Pyruvic acid is formed into acetyl-coenzyme A in the presence of oxygen and then broken into citric acid, Krebs cycle: citric acid undergoes oxidative carboxylation and carbon dioxide are given off, hydrogen ions form water and provide energy to resynthesize ATP
• Aerobic glycolysis advantages


  • Long-duration, high energy yield (1:38), no fatiguing by-products
• Aerobic glycolysis disadvantages


  • Moderate intensity, delay for O2 delivery
• Beta oxidation


  Fatty acids are broken down into acetyl-coenzyme A which enters the Krebs cycle
• VO2 max


  The maximum volume of oxygen that can be taken in and consumed by the body in 1 minute (ml/kg/min)
• VO2 max measurement


  Calculated with a multi-stage fitness test or direct gas analysis (more accurate)
• Factors affecting VO2 max

  • Physiology: increased slow twitch muscle fibres, surface area of alveoli, haemoglobin/myoglobin, capillary density. Genetics: 90% genetically determined. Training: can be improved with aerobic training. Lifestyle: smoking, diet and sedentary lifestyle reduces VO2 max. Other factors: decreases with age, higher in men than women, higher body fat percentage decreases VO2 max
• Energy continuum


  The relative contribution of all three energy systems to the re-synthesis of ATP: <10 seconds - ATP-PC, 10 to 90 seconds - ATP-PC and anaerobic glycolytic, 90 seconds to 3 minutes - anaerobic glycolytic and aerobic, 3+ minutes - aerobic
• Oxygen consumption


  The amount of oxygen we use
• Submaximal oxygen deficit


  When there isn't enough O2 at the start of exercise to provide all ATP aerobically
• EPOC (excess post-exercise oxygen consumption)

  The amount of oxygen consumed during recovery above what would have been consumed at rest. Fast (alactacid): resaturation of myoglobin with oxygen, re-synthesis of PC stores, re-synthesis of ATP. Slow (lactacid): removal of lactic acid, converted into O2, CO2 (excreted in sweat and urine)
• Cori cycle


  Lactic acid is transported in the blood to the liver where it is converted into glucose and glycogen
• Indirect calorimetry


  Measures the oxygen consumed and carbon dioxide produced (calories), helps to determine if mainly fats or carbohydrates are used. Calculates energy expenditure, estimates which substrates are being used
• Respiratory exchange ratio


  0.7 = fats, close to 1 = carbohydrates, greater than 1 = anaerobic respiration
• Blood lactate (OBLA)

  Measures training zones (intensity), very accurate
• VO2 max testing


  Direct gas analysis (treadmill / cycle ergometer), measures oxygen consumed at different intensities
• Altitude (2000m)


  • Lower partial pressure of O2, haemoglobin isn't fully saturated, lower oxygen carrying capabilities, natural increase in EPO which increases red blood cell production and haemoglobin levels, increase oxygen carrying capability and delivery, delays OBLA, quicker recovery, works at higher aerobic intensities
• Altitude disadvantages

  • Acclimatisation period (drop in performance / altitude sickness), benefits are temporary, expensive / exclusive
• HIIT (high-intensity interval training)

  Alternate periods of short intense work with recovery periods, variables: duration of work, number of work and recovery intervals (reps + sets), duration of recovery, intensity (speed of work), generally: 20-60 minutes, 4-10 reps, 2:1 work:recovery
• HIIT advantages

  • Mimics demands of sport, aerobic and anaerobic, faster adaptations, higher calorie consumption
• HIIT disadvantages


  • Injury from high intensity, no skill
• Plyometrics

  Increasing muscle power through repeated rapid stretching and contracting of muscles (explosive movements), eccentric muscles lengthen under tension, concentric muscles shorten under tension
• Plyometrics advantages

  • Increased contractability of fibres, elasticity, strength, stretch reflex (muscle spindles)
• SAQ (speed, agility, quickness)

  Develops coordination and explosive power
• SAQ advantages

  • Develops precision, timing, foot placement
• SAQ examples


  • Ladders, hurdles, parachutes, dodging cones / agility poles
• SAQ benefits


  • Develops neuromuscular patterns, coordination of antagonistic muscle groups, improved rhythm, improves technique, reduces injury