Energy continuum

Examples from hockey

• sprint to receive ball.........ATP/PC system

• long run to offer support......Lactic acid system

• jogging onto pitch.............Aerobic system

**The relative contribution of each system depends on the duration and intensity of exercise**

THRESHOLD

• POINT AT WHICH SYSTEM CAN NO LONGER SUPPLY ENERGY

OBLA

• ONSET OF BLOOD LACTATE ACCUMULATION
• POINT WHERE THERE'S A RAPID INCREASE IN AMOUNT OF LACTIC ACID IN BLOOD
• AT THIS POINT BLOOD PH DECREASES 
• MUSCLE FATIGUE OCCURS

Factors affecting energy systems

• fitness level
• exercise intensity and duration
• energy system threshold
• O2 transport and supply
• food / fuel available
• enzyme activation levels

Intensity and duration of exercise

• combination of intensity and duration decides energy system
• anaerobic exercise intensity = ATP/PC and LA systems
• aerobic exercise intensity = aerobic system
• during high intensity exercise lactate accumulates
• when lactate accumulates above resting levels it is called the lactate threshold
• OBLA is when blood lactate levels exceed 4mmol/L
• this causes muscle fatigue

Energy system thresholds

• threshold is point at which one energy system is taken over by another
• shows potential duration a system can perform for
• threshold alters in response to intensity and duration
• threshold doesn't always follow the same route
• in team games, players continually switch between energy systems

Oxygen availability

• availability dependent upon efficiency of respiratory and cardiovascular systems
• affects which food fuels can be broken down to resynthesise ATP

Fuel availability

• PC stores are limited
• PC can be conserved by pacing and resynthesising during periods of recovery
• Glycogen readily available in muscles, requires little oxygen so breaks FFAs down quickly
• The greater the liver / muscle glycogen stores, then the longer the performer can work aerobically at a higher intensity
• High intensity short duration activity = breaks down glycogen as energy fuel
• Low intensity long duration activity = breaks down FFAs and glycogen as energy fuel

Enzyme activation level

• enzymes are catalysts
• without enzymes there'd be no reactions and no energy for ATP resynthesis

Increase in ADP, decrease in ATP > creatine kinase released > PC system

Decrease in PC > PFK released > LA system

Increase in adrenalin, decrease in insulin > PFK released > Aerobic system

Fitness level

• the more aerobically fit the performer is, the more efficient their respiratory and cardiovascular systems are
• an aerobically trained athlete reaches OBLA later
• an anaerobically trained athlete has increased thresholds of ATP/PC and LA systems