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PDHPE Teacher Notes
Comes to Life
Energy Systems and
Athlete Performance
Energy systems and physiological adaptations
By completing a number of common sports science testing procedures such as VO2max, Wingate and vertical jump assessment,
this set of activities will demonstrate to students the role of the energy systems and how they influence athletic performance. The
interactive activities will allow students the opportunity to apply/learn syllabus content whilst being industry tested and having
fun. Throughout the testing, students will be encouraged to review the contribution of individual energy systems and also consider
how training may be adapted to benefit the performance of a given athlete.
Students will each receive an activity sheet that includes explanatory notes, relevant graphics and images, and areas in which to
record their results, while extensive teacher notes will also be supplied. These include syllabus references, detailed discussion
points, “interesting facts”, further study suggestions and answers to each of the questions that will be posed to students during
the activities.
Curriculum Guide
Curriculum
Students learn about
Reference
Science Comes to Life
9.2
Energy systems:
- Alactacid System
- Lactic Acid System
- Aerobic System
Conduct repeated vertical jump testing to induce fatigue, raising an
opportunity to discuss the energy systems (source of fuel, efficiency
of ATP production, duration, cause of fatigue, by-products of energy
production and process and rate of recovery)
9.2
Assess the types of training and training
methods
Use evidence from exercise test and breath analysis to identify
the types of training and how they contribute to cellular
processes/adaptation
9.2
Examine the relationship between the principles
of training, physiological adaptations and
improved performance
Discuss how breath analysis, oxygen saturation, heart rate and
energy system pathways will change as a result of training, and
consider the impact this will have on performance
9.6
Anaerobic training (power and speed) vs
aerobic training (continuous and long-interval)
Students will discuss how anaerobic strength training could be
utilised to train specific performance requirements
Interesting fact
Measuring breath concentration allows Exercise Scientists
to identify which energy system is working in
the cells to produce ATP.
School of Science
and Technology
ACTIVITIES TO BE COMPLETED DURING YOUR UNE EXPERIENCE
1
Activity 1: : Vertical Jump Performance
Activity 1 provides students with the opportunity to monitor how the body responds to high-intensity anaerobic
exercise. Students will complete consecutive vertical jumps on electronic jump mats for a period of 2 minutes,
designed to target anaerobic energy pathways, and induce local leg fatigue. Students will use pulse oximeters to
monitor heart rate (HR), and breath analysis equipment to identify changes in O2 and CO2 following high intensity exercise
before leading into discussions about energy systems on a cellular level. Vertical jump analysis will also demonstrate the
impact of fatigue on performance, and how this relates to physiology.
Interesting Facts:
Vertical jump performance is often used by sports scientists to assess
athletic power profiles.
2
Activity 2: Maximal Oxygen Uptake Testing (VO2max)
The VO2max test is generally considered the best indicator of cardiorespiratory fitness, and is conducted by
analysing the air inhaled and exhaled during an incremental exercise test to fatigue. The underlying principle
behind the VO2max test is that almost every process in the human body is dependent on the availability of
oxygen (O2) for muscle cells, and the removal of carbon dioxide (CO2). During Activity 2, one or possibly two
of your students will be given the opportunity to complete a VO2max test, either cycling or running. Throughout the activity,
students will be able to monitor and record results, and assess which energy systems are contributing to ATP production.
Students will be asked to review the impact of training on thresholds, and consider which physiological adaptations may
contribute to improved performance.
Interesting Facts:
Training under low oxygen conditions causes a number of responses
in the human body, including but not limited to changes in red blood
cell mass, glucose transport, pH regulation and improved utilisation of
fatty acids
3
Activity 3: Wingate Testing
All students will be given the opportunity to complete a 30 second Wingate test, where the goal is to perform
with maximal power throughout the activity. Using either Watt bikes, timing gates or GPS units to monitor power
or speed output, students will be able to identify how transition between the energy systems will contribute to
performance decrement. This provides for some fun competition between students and/or teachers, whilst still addressing
important syllabus learning goals.
Interesting Facts:
The human body, despite only storing approximately 250g of ATP at
any one time, will turn over the equivalent of its body weight in ATP
every day. A marathon runner weighing in around 60kg may use up to
a massive 300-400kg of ATP!
Homework
Suggestions
Complete a brief
report to identify why
athletes with higher
VO2max may be
able to perform to a
higher level.
ANSWERS TO QUESTIONS POSED DURING THE UNE VISIT
Adenosine triphosphate (ATP) is required to perform any form of muscular contraction. Muscle cells only store enough ATP to generate 2-4
seconds worth of high-intensity exercise, therefore ATP must be continuously resynthesised via one of three pathways. This is where the
energy systems become important. The ATP/PC and glycolytic systems produce ATP at a high rate however are not sustainable for long periods
of time, leading to fatigue. In contrast, the aerobic energy system produces ATP at a slower rate, but is a more sustainable process allowing
athletes to perform up to 10 hours in duration. Breath concentration can be used to identify which energy systems are dominant during a
given exercise intensity.
Activity 1: Vertical Jump Performance
a. What happened to jump performance as the number of jumps increased? Can you explain this?
Jump performance declines with the increasing number of jumps. Students will be able to identify this from either flight time or from the
Power (W). The decline in performance can be explained as the result of the energy systems failing to meet ATP resynthesis demands, thus
muscle performance declining. The ATP/PC system will be predominant for the first 10 seconds, until the fuel source (creatine phosphate)
is depleted causing a shift to the lactic acid system. The lactic acid system will continue to resynthesis ATP; however will also cause lactic
acidosis in the muscle cells and blood, causing a further decline in performance. It will be emphasised that as performance continues,
the relative contribution from the aerobic energy system will continue to increase, however due to the slower rate of ATP production a
continued decline in performance is expected.
b. Can you explain the change in the concentration of O2 in the breath following the repeated jumping?
Oxygen (O2) is critical for almost every process within the human body, most importantly for the production of ATP. Students will identify
a fall in the concentration of oxygen in breath following the completion of the 2-minute jump protocol, which can be used to indicate to
them that O2 has been used in the body to produce ATP (reflecting VO2). Exercise causes an increase in the rate of ATP usage; therefore we
expect to see an increase in the rate of O2 usage.
c. What happened to the CO2 concentration of breath following the repeated jump protocol and why?
Students will identify an increase in the concentration of carbon dioxide (CO2) in the breath following the 2-minute jump protocol. This
will be used to emphasise that CO2 is a waste product produced during ATP resynthesis and must be removed. The role of the Carbonic
Acid-Bicarbonate buffer system in the body will also be emphasised, which sees blood pH controlled (in the presence of lactic acidosis) by
an increase in the production of CO2.
d. Given the evidence, which energy systems would have been dominant throughout the 2 minute jump activity? Would the contribution of
each energy system have been consistent throughout the activity, or would this change throughout?
Initial 10 seconds: ATP/PC
10sec- 1 minute: Lactic acid system
1-2 minutes: Increased reliance on the aerobic energy systems (as well as lactic acid system)
Most important point here is that each energy system does not work in isolation, but rather works together to produce the ATP in demand.
e. Which fuel source would have been predominant throughout the exercise protocol?
Given that anaerobic energy sources would have produced the majority of energy, carbohydrates would have contributed the most. Even
during the last minute, the aerobic system would utilise carbohydrates (glucose and glycogen), as it was still high-intensity exercise
meaning that aerobic ATP resynthesis from fatty acids would be too slow.
f. Giving consideration to the energy systems at play, what sort of athlete may benefit from using a 2 minute jumping protocol as training?
One of the most important principles of training is specificity. During the 2 minute jump protocol, we have established that the anaerobic
energy systems would be predominant in resynthesising ATP. This would cause a significant increase in lactic acidosis. Any athlete who
wants to improve their tolerance of H+ ions may benefit from this protocol, completing near maximal intensity exercise for periods greater
than 1-2 minutes. Some examples may include a 400m sprinter, 200m swimmer. In addition, this form of training would be suited to an
athlete completing repeated sprints (e.g. team sports such as hockey and rugby). In order to adapt the training to individual sports, the
repetitions, rest and work periods may be adapted. Reducing the rest periods and increasing the repetitions or work periods would increase
the contribution, and training adaptations of the aerobic energy systems.
Interesting fact
Sprinting performance is heavily influenced by the capacity of the athlete to strike the ground forcefully
relative to their body weight. Repeated vertical jump training and plyometrics is very valuable for a sprint
athlete.
Activity 2: Maximal Oxygen Uptake Testing (VO2max)
a. What is the role of oxygen in the body, and why does it increase with exercise workload?
Oxygen is critical to ATP production in the body. The aerobic energy system can far exceed the anaerobic energy system in terms of the
quantity of ATP produced. However there is one drawback, it is slower to produce ATP than the anaerobic system. During exercise, the
muscles require ATP at a faster rate to meet the needs for contractions. As a result of this increasing ATP demand, the body will use more
oxygen, which will be reflected in the oxygen uptake (VO2).
b. Why is CO2 removed from the body?
CO2 is produced during cellular respiration in the body (ATP production in the cells). If allowed to accumulate in the body, CO2 causes the
blood to become more acidic. This will impact on metabolic enzymes which are responsible for ATP production, as a result causing the
performance of an athlete to decline. Not only does the rate of CO2 increase with the rate of ATP production, but CO2 is removed from the
body as a method of controlling blood pH changes due to lactic acidosis. This change in CO2 concentration of breath will be demonstrated
during the test.
c. Without looking at lactate levels, what evidence from the test suggests that lactate concentration in the blood was increasing during the
test?
The bicarbonate buffer system will increase the production of CO2 in breath as a method of modulating pH changes in the blood. Lactic
acidosis (H+ accumulation in blood) causes a fall in pH. A fall in blood pH causes an increase in the body’s removal of CO2 in the breath.
Therefore, a rise in the CO2 concentration of the athlete’s breath suggests that the lactate levels in the blood were increasing during the test.
e. What does the VO2max represent?
The VO2max value represents the maximum amount of oxygen the body can use to produce ATP aerobically. It is important to recognise
that at VO2max, the anaerobic energy systems (predominantly lactic acid system) will also be working. From this level on, the body can no
longer increase its rate of ATP production aerobically. Any further increase in workload means that ATP is being produced anaerobically.
f. What is the major limitation of the aerobic energy system? Complete the following table and consider why there is a shift from aerobic
ATP resynthesis to anaerobic ATP resynthesis during the later stage of the VO2max test.
The major limitation of the aerobic energy system is that its rate of ATP production is slower when compared to the anaerobic energy
systems. When VO2¬max is reached, the body is unable to increase its rate of aerobic ATP production any further and must rely on anaerobic
energy production to meet any further increases in exercise intensity/workload. This intensity can be maintained in the short term but
cannot be maintained indefinitely due to the build up of waste products such as lactic acid.
Anaerobic Energy Systems
Aerobic Energy Systems
ADVANTAGE
Fast production of ATP
High-ATP production & is sustainable for long periods of time
DISADVANTAGE
Production of waste products & not sustainable
Slower process
g. When performing at VO2max, this only reflects the ATP being resynthesised by the aerobic system. Is the anaerobic system also working
concurrently?
Yes; the lactic acid system will be continuing to resynthesise ATP to assist the aerobic system. If given the opportunity to test blood lactate
levels, students will be able to identify that at VO2max, there is also high levels of blood lactate. This infers that both the aerobic and
anaerobic energy systems are continuing to work.
h. The aerobic energy system is the only one able to use fats as a fuel source. Why is it that endurance athlete try to maximise the capacity of
their aerobic system to resynthesis ATP?
Aerobic ATP resynthesis only produces CO2 and water as waste products, both which can be removed from the body easily by breathing.
In contrast the anaerobic energy system produces H+ ions from lactic acidosis. The goal of an endurance athlete is to minimise the
contribution of anaerobic ATP resynthesis, therefore avoiding the accumulation of H+ ions. If an athlete can meet the ATP demands of a
higher workload using only aerobic energy systems, then this will be beneficial to performance. In order for an athlete to optimise fatty
acid utilisation, they must perform at levels below the anaerobic threshold. The goal of training in these athletes should be to increase the
workload at which the anaerobic threshold occurs.
Fatty acids produce significantly more ATP per molecule (130 ATP), thus it is advantageous for endurance athletes to use fatty acids
compared to carbohydrates when producing ATP aerobically (approx 36 ATP). The use of fatty acids for ATP resynthesis will also allow
for glycogen storing, for later in the race when a sprint finish may require a high-intensity effort which cannot be met via aerobic ATP
production.
i. What is the anaerobic threshold? What would you expect to see in terms of blood lactate levels at exercise intensities greater than the
anaerobic threshold?
The anaerobic threshold is the point at which the body can no longer meet ATP demands using the aerobic energy systems, due to its slower
speed of ATP production. As a result, the body will increase its reliance on anaerobic ATP production, causing a significant increase in blood
lactate levels, and a corresponding increase in the removal of CO2 from the body (buffering mechanism).
j. How might the information gained from this form of testing be used to make training decisions for an athlete?
An athlete may use information relating to the anaerobic threshold and VO2max to assess their current state of training, identify changes
in performance/fitness with training, or set training levels based on which adaptations they desire. Training at levels below the anaerobic
threshold will induce improvements in the aerobic energy system, whilst training at levels above the anaerobic threshold will induce
improvements in lactate tolerance and anaerobic energy pathways.
Activity 3: Wingate Testing
a. What happened to the power output as the test progressed?
Students will identify that flight time and power both decline throughout the testing. This will be used to identify the cause of fatigue of
the energy systems, and how it impacts upon performance.
b. Which energy systems do you think would have been contributing to ATP resynthesis throughout the test?
ATP-PC system for the first 8-10 seconds; followed by an increased contribution from the lactic acid system. The aerobic energy system
would contribute very little initially, but increase slightly throughout the test. Scientists have previously underestimated the contribution of
the aerobic energy system in short to moderate duration exercise.
c. How might this test be used or adapted to train for team sports, consisting of repeated sprints?
Team sports require an athlete to complete repeated sprints over longer periods of time (up to 90 minutes), interspersed with lower intensity
bouts. Depending on the specifics of the sport, an athlete may complete multiple Wingate tests interspersed with lower intensity bouts.
Work to rest ratios may be adapted according to the specific demands of the sport: i.e. maximal intensity sprint for 10 seconds followed by
low intensity for 2 minutes: repeating this over a 30 minute period. Increasing the work periods and reducing rest periods will contribute to
an increased contribution and adaptations of the aerobic energy system.
d. An athlete completes 4 Wingate Tests on 3 occasions each week for 12 weeks (4 min rest between each):
i) How would the aerobic contribution change during the fourth test?
Aerobic contribution would continue to rise with each successive test, as a result of fuel sources (especially glucose and glycogen being
depleted), and lactic acidosis
ii) What physiological adaptations would you expect to see following this training phase?
Reduced resting heart rate, increased stroke rate, increased maximal cardiac output, improved oxygen uptake (myoglobin, capillaries,
mitochondria and enzyme activity), increased lung capacity, increase haemoglobin, muscle hypertrophy, lactate tolerance.
e. How might an athlete train to improve their Wingate test performance if they didn’t have a bike?
Relating to training specificity, an athlete may use resistance training to improve Wingate performance. Whole body exercises focusing on
the lower limbs would be preferable, with the intent to complete repetitions over 30 seconds with a high rate of muscle contraction to
emphasis adaptations in power development.
Glossary
Adenosine triphosphate (ATP) - energy source for all muscular contractions in the human body. Without ATP, we cannot live, let
alone exercise!
Cell - the human body is made up of millions of cells. ATP production starts in the cells. Once ATP is produced in the cell,
muscles can use it to fuel contractions for exercise.
Carbohydrates - the only fuel for ATP production during high-intensity (anaerobic) exercise. Examples of carbohydrates used for
ATP production include glucose and glycogen:
Glucose/Glycogen † 2 Lactic Acid + Carbon Dioxide + 2 ATP
Anaerobic ATP production - must occur during high intensity exercise when aerobic ATP production cannot keep up with the
ATP demands of the muscles. The ATP/PC and glycolytic pathways are both anaerobic, occurring without oxygen
Rate of ATP production - increases with increasing exercise intensity
Lactic acid - product of anaerobic ATP production, causing performance to decline
Aerobic ATP production - occurs more slowly than anaerobic, but can be sustained for long periods
Carbon Dioxide (CO2) - produced during the breakdown of carbohydrates to ATP
Higher carbon dioxide concentration of expired air means that ATP is being produced anaerobically
Waste product - produced during ATP production, and has a negative effect on athlete performance. Examples include carbon
dioxide and lactic acid.
Homework Sample Answer:
Question:
Complete a brief report to identify why athletes with higher VO2max may be able to perform to a higher level.
Maximal oxygen uptake (VO2max) is considered as one of the more accurate reflections of athlete performance. Whilst there are a
number of other critical factors which may contribute to an athlete’s success, the VO2max test is considered as an important test
to reflect cardiorespiratory fitness. Cardiorespiratory fitness, as the name suggests, takes into account the capacity of the respiratory
system to take in oxygen from the atmosphere, the circulatory system to transport this oxygen to muscle cells where it is utilised for
ATP production, and the subsequent removal of by products such as CO2.
VO2max is used to reflect the upper limit of the cardiorespiratory system to utilise oxygen for the aerobic production of ATP. As
exercise workload increases, oxygen consumption eventually plateaus despite further increases in workload, labelled the VO2max.
Maximal oxygen uptake values can range from 20mL/kg/min in sedentary individuals to in excess of 80mL/kg/min in supreme
endurance athletes. It is important to understand however that the oxygen uptake of a person can only be used to reflect the amount
of ATP produced aerobically. Concurrently, ATP may also be produced anaerobically which is not reflected in the value for maximal
oxygen uptake.
As the intensity of exercise increases, the rate at which ATP is required by muscles also increases. An athlete with a higher VO2max can
produce a higher amount of ATP aerobically without being required to produce ATP anaerobically. This is an advantage given that the
chemical reaction characterising anaerobic ATP production is incomplete, causing an accumulation of lactate and hydrogen ions in the
blood. This lactate accumulation contributes to a decline in performance by inhibiting important enzymes involved in the production
of ATP, due to a decline in muscle and blood pH. Therefore, the longer the body can refrain from using the anaerobic energy pathways,
the more effective ATP production will be for ongoing endurance performance.
It is reasonable to say that if an athlete has a higher VO2max, they can perform at a higher exercise intensity/workload without
becoming dependent upon anaerobic energy pathways. Endurance training allows adaptations to occur in the body which allow more
oxygen to be delivered to muscles for ATP resynthesis, with 15-20% improvement in VO2max demonstrated with a 20-week training
program. These improvements contribute to better performance due to increased reliance on aerobic ATP pathways at a higher
intensity, thereby reducing the detrimental effects of lactate accumulation on performance.
School of Science
and Technology
Produced by Marketing and Public Affairs UNE, April 2016.
Information correct at time of printing. CRICOS Provider No. 00003G.