Energy Systems of The Body

SYLLABUS CONTENT

Analyse the ATP-PCr, Glycolytic (Lactic Acid) and Aerobic energy systems of the body including fuel source and efficiency of ATP production, duration, intensity and rate of recovery, causes of fatigue and interplay of the energy systems

ATP: Adenosine Triphosphate

As a class read through pages 241-242 of the Cambridge textbook and watch the video. Then, complete the marshmallow practical activity below.

ATP - Marshmallow Activity

Energy Systems

ATP has the ability to be re-synthesized, rather than being expelled from the body as waste. This is critical as it allows the body to continue to function, even if ATP stores are limited.

The body can synthesize energy using three methods:

Anaerobic methods (without oxygen) including the ATP/PC and lactic acid system
Aerobic system (with oxygen).

Alactacid (ATP/PC) System

The ATP-PCr system, also known as the phosphocreatine or alactacid system, is the predominant energy system for short, high-intensity efforts lasting up to 10 seconds.

Initially, it uses stored ATP within muscle cells to provide immediate energy, with ATP stores lasting for approximately 1-2 seconds during maximal effort.

As ATP stores are depleted, the system transitions to utilising stored phosphocreatine (PCr), where the high-energy bond between creatine and phosphate is broken to release energy, helping regenerate ATP from ADP.

After PCr stores are depleted, a rest period of 2-3 minutes is needed to fully replenish them.

Athletes in sports like sprinting and weightlifting focus on training this system with anaerobic interval exercises, emphasising recovery to restore PCr levels before the next effort.

Activity

Refer to the table that outlines all three energy systems and fill in the key details as we go through each one. For the ATP/PC, read through pages 243-244 to assist you.

Energy System Table

Activity

As a class we will read through the snapshot below, exploring creatine supplementation. Then answer the following:

What type of exercise is the ATP/PC system used for? Provide examples as support.
Explain why creatine supplementation may boost athletic performance.

Glycolytic (Lactic Acid) System

The glycolytic system is an anaerobic method, that uses glucose to produce ATP, through a process called anaerobic glycolysis. As a class we will read through the text and discuss.

Glycolysis

The Lactic acid and aerobic energy system both use glycolysis to create ATP. However, the process is slightly different when conducted anaerobically (anaerobic glycolysis) and aerobically (aerobic glycolysis).

As a class we will go through the process of anaerobic glycolysis on the board. This is the energy synthesise method of the lactic acid energy system

Myth!!

Traditionally it was thought that lactic acid was the culprit for muscle aches and lethargy! This has recently been proven wrong.

Pyruvate, Hydrogen Ions and Acidity: When glucose is broken down to create ATP it releases Pyruvate and hydrogen ions. Under anaerobic conditions (without oxygen), the accumulation of hydrogen ions makes the cell more acidic, which is associated with the burning sensation and can contribute to fatigue or lethargy during high-intensity exercise.
Formation of Lactate: To counteract the acidity, pyruvate binds to the hydrogen ions, forming lactate. This helps to reduce the acidity in the cell. The lactate then leaves the muscle cell and can be transported to the liver.
Lactate in the Liver: In the liver, lactate can be converted back into glucose through a process called the Cori cycle or, in some cases, back into pyruvate to be used in the aerobic system.
Anaerobic Threshold: When high-intensity exercise exceeds a certain duration, the body reaches its anaerobic threshold. This is the point at which lactate is produced faster than it can be cleared from the bloodstream. As a result, lactate accumulates, leading to fatigue.

Activity

Read through the following article and as a class we will discuss:

What is lactate?
What is the anaerobic threshold?
How can lactate benefit us?

https://dailyburn.com/life/fitness/truth-about-lactic-acid-lactate/

Activity

Refer to the table that outlines all three energy systems and fill in the key details as we go through each one. For the Glycolytic system, read through pages 245-247of the Cambridge textbook to assist you.

Energy System Table

Practical Activity

As a class we will participate in a practical activity to highlight the anaerobic systems. Complete the activity sheet as you conduct the exercise.

Practical Activity

Aerobic Energy System

The third system used to resynthesize ATP is called the aerobic energy system. This energy system is by far the largest producing energy pathway in the body, as it is used to fuel activity ranging from sedentary activity right through to longer endurance exercise at moderate intensity. As the name suggests, this energy pathway is dependent on a constant and adequate supply of oxygen, and therefore interplay with an efficient cardiovascular and respiratory system is needed. Out of the three energy pathways, it is also the most complex, requiring a range of intricate chemical processes to produce energy.

Aerobic System: ATP Production

Earlier we explored anaerobic glycolysis. The aerobic system also uses glycolysis as it primary fuel method , however with the presence of oxygen in a slightly different process.

Besides carbohydrates (glucose) the aerobic system also uses fats and to a lesser degree protein as fuel for ATP production.

The aerobic system uses these fuels, the Krebs cycle and the electron transport chain to synthesize ATP.

As a class we will we will go through the process on the board

Activity

Refer to the table that outlines all three energy systems and fill in the key details as we go through each one. For the Aerobic System, read through pages 248-251 of the Cambridge textbook to assist you.

Energy System Table

Activity

Watch the following short video and answer the following questions in your book:

Choose two sports that primarily utilise the aerobic energy system and justify.
Explain why gels may benefit energy production during long distance events.

Interplay of Energy Systems

The body’s use of each energy system represents a complex interplay of fuel supply, as the resynthesis of ATP seamlessly draws energy from all three energy systems to varying degrees. They do not operate independently of one another, with one switching off and the other switching on. At certain intensities and times within a sport or training session, the body may rely more heavily on one energy system over an other; however, the other energy systems can be used almost instantly if required.

Examples of energy system transitions:

A boxer at rest completing five burpee tuck jumps instantly uses the ATP-PCr system as the dominant source of energy, before skipping for two minutes where they return to aerobic levels.
An AFL forward running a 60-second, 400-meter fast lap will primarily rely on anaerobic glycolysis after using up ATP-PCr for the first 10 seconds.
A triathlete jogging at a moderate pace for 5 km, maintaining around 70% of their Maximum Heart Rate (MHR), predominantly relies on the aerobic system for energy. However, during the start and transition phases, the body initially uses ATP-PCr and anaerobic glycolysis to meet the immediate energy demands. As the pace increases towards the final 500 meters, surpassing 85% of MHR, anaerobic glycolysis becomes the predominant energy system again to support the higher intensity.

Activity

As a class we will complete the practical activity exploring energy systems.

Exploring Energy Systems Worksheet

Activity

As a class we will participate in a Kahoot exploring the energy systems:

https://create.kahoot.it/details/4e335dd9-dd98-498c-a303-92d0a236b532