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LESSON 6 Factors Affecting the Energy System used

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1 LESSON 6 Factors Affecting the Energy System used
ENERGY SYSTEMS LESSON 6 Factors Affecting the Energy System used

2 LEARNING OBJECTIVES Can I explain the factors affecting the energy system used?


4 STARTER ANSWER The bus is headed to the right, otherwise we would see the entrance door!

Explain how the following affects the energy system used by athletes: Exercise Intensity and Duration Energy System Threshold O2 Transport/Supply Food/Fuel available Enzyme Activation Levels Fitness Level

A combination of exercise intensity and duration can determine the predominant energy system(s) being used. When exercise intensity is anaerobic (high intensity, short duration), then the ATP/PC and LA Systems will be predominant. If the exercise intensity is aerobic (medium/low intensity, long duration), then the Aerobic System will be predominant.

When the aerobic system cannot supply energy quick enough, it has to use the LA system to continue to provide energy for re-synthesis of ATP. During high intensities lactate production will start to accumulate above resting levels. This is termed Lactate Threshold. When blood lactate levels reach 4mmol/L (normal resting levels are 1-2mmol/L), the exercise intensity is referred to as ‘the Onset of Blood Lactate Accumulation’ (OBLA). OBLA continues to increase if exercise intensity is maintained or increased and will cause muscle fatigue.

After training the intensity level for lactate threshold is increased and this will delay the point at which OBLA is reached and therefore increases the potential duration/threshold of the LA energy System.

The Threshold for any system is ‘the point at which that energy system is unable to provide energy.’ Or ‘the point at which one energy system is taken over by another as the predominant energy system to provide energy for ATP re-synthesis.’

Performance Duration Energy System(s) Involved (predominant in bold) Practical Example Less than 10 seconds ATP/PC Triple Jump/100m sprint 10-90 seconds LA m sprint 100m swin 90 secs – 3 mins Aerobic Boxing (3 min rounds) 800/1500m 3+ mins Low impact aerobics class Marathon

The energy system threshold alters in response to a combination of both intensity and duration of exercise and will not always go through each energy system in turn. For example, a cyclist cycling at a low intensity will be using the Aerobic System, although when going up hill they may exceed the intensity threshold of the aerobic system and the lactic acid system will take over as the predominant energy system. In team games, players will switch between the three energy systems.

12 O2 TRANSPORT/SUPPLY If there is O2 present then the aerobic system can provide energy to re-synthesise ATP. If O2 supplies falls below that demanded by the exercise then the aerobic system threshold is met and the lactic acid system will start to break down glucose anaerobically.

13 FOOD/FUEL AVAILABLE If the body has sufficient stores of PC, it is able to use the ATP/PC system for very high intensity, short duration activity/movements. PC stores are limited, but are available at the start and after recovery during exercise. If exercise starts too high then PC stores will quickly deplete and exercise at that intensity cannot be sustained. PC stores can be conserved by pacing and re-synthesising PC stores during recovery periods using spare energy from the aerobic system.

14 FOOD/FUEL AVAILABLE Glycogen is the major fuel for the first 20 minutes of exercise. This is due to O2 supplies being limited as it takes 2-3 minutes for the cardiovascular system to supply sufficient O2. As well as glycogen being readily available in the muscles, requires less O2 and is easier to break down than FFA’s

15 FOOD/FUEL AVAILABLE After about minutes there is a greater breakdown of fats alongside glycogen as the energy fuel. FFA’s are a more efficient fuel than glycogen, but require 15% more O2. If a performer has larger muscle/liver glycogen store, then they can perform work aerobically at a higher intensity.

16 FOOD/FUEL AVAILABLE Glycogen stores become nearly depleted after about two hours, then FFA’s have to be used for aerobic energy production, and unless exercise intensity is reduced it can bring on the sudden onset of fatigue (‘hitting the wall’). Once OBLA is reached the body has insufficient O2 available to burn FFA’s and will then have to break down glycogen ‘anaerobically’ to re-synthesise ATP

Factors Affecting Enzyme Activation for the Energy Systems Activating Factor Releases Controlling Enzyme(s) Activating Energy System Increase in ADP; decrease in ATP Creatine Kinase PC Decrease in PC PFK LA System Increase in adrenalin; decrease in insulin Aerobic System

18 FITNESS LEVEL The more aerobically fit the performer, the more efficient their cardiovascular and respiratory systems are. Aerobic athletes have also shown that they can start to use FFA’s earlier during sub-maximal exercise, which conserves glycogen stores. The overall effect is that the aerobic threshold in terms of intensity and duration can be increased as the lactate threshold/OBLA would be delayed.

19 FITNESS LEVEL A typical untrained athlete would reach OBLA at about 50-56% of their VO2 max, whereas an aerobic-trained athlete would not reach OBLA until about 85-90% of their VO2 max. An anaerobic-trained athlete will increase their ATP/PC, glycogen stores, anaerobic enzymes and tolerance to lactic acid. All of this would increase the threshold of both ATP/PC and Lactic Acid Systems.

20 Summarise the factors that affect the energy system used
PLENARY Summarise the factors that affect the energy system used

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