Transport & Energy

Unit 2
 Topics & Subtopics
A.1.3 Transport (7 hours)
A.2.3 Energy systems (7 Hours)

SL Subtopics HL Subtopics
A.1.3.1—The cardiovascular system transports
nutrients, hormones, gases, heat and waste to perform A.2.3.3—The lactate inflection point is the
necessary bodily functions. maximum intensity at which the body can
metabolize lactate at the same rate as its
A.1.3.2—The respiratory system enables the exchange production.
of gases between the external environment
and the body, to facilitate cellular respiration. A.2.3.4—Excess post-exercise oxygen
consumption (EPOC) is required for the body to
A.2.3.1—The body relies on the phosphagen, glycolytic return to homeostasis and is dependent on the
and oxidative systems for energy oxygen deficit incurred during exercise. EPOC is
production to sustain life and physical activity.
typically divided into two subsections: fast and
A.2.3.2—Maximal oxygen consumption (VO2 max) is slow.
influenced by an individual’s age, sex differences, body
composition, lifestyle factors and level of fitness.
A.1.3 Transport
CV Values
Respiratory Values
 A.1.3.1—The cardiovascular system transports
nutrients, hormones, gases, heat and waste to
perform necessary bodily functions.

Heart rate, stroke volume, cardiac output, blood pressure

and blood redistribution vary, and depend on factors such
as age, sex differences, body size, level of fitness, type of
activity and intensity of activity.
A diagram of the cardiovascular system is found in the
SEHS data booklet.
A.1.3.1 Cardiovascular System

● Main function: Transport gases, nutrients,

waste products, and hormones.
● Consists of the heart, blood vessels, and
blood.
● Two types of circulation:
○ Pulmonary circulation: Deoxygenated blood to
lungs.
○ Systemic circulation: Oxygenated blood to the
body.
● The heart has four chambers (two atria, two
ventricles) and valves to prevent backflow.
A.1.3.1 Blood

● Total volume of blood in the body: ~5 liters.

● Major components:
○ Plasma (~55%): Fluid containing water, proteins,
and dissolved substances.
○ Platelets (<1%): Assist in blood clotting.
○ White blood cells (<1%): Immune function.
○ Red blood cells (~40-45%): Transport oxygen
and carbon dioxide.
● During exercise, carbon dioxide is
transported primarily as bicarbonate.
 More on blood…

Key Points:

1. Erythropoietin (EPO) Role: EPO hormone increases

haemoglobin concentration, enhancing red blood cell production
and oxygen transport.
2. Altitude Training: Endurance athletes train at high altitudes to
naturally boost haemoglobin due to lower oxygen levels,
improving performance upon returning to sea level.
3. Illegal Practices: Some athletes use illegal methods, like blood
doping, to artificially increase haemoglobin levels for better
performance.
4. Blood Doping Method: Blood doping involves extracting blood,
storing it, and reintroducing it before competitions to elevate
haemoglobin concentration.
5. Synthetic EPO Use: Athletes may also inject synthetic EPO to
increase haemoglobin without blood removal.
6. Detection Challenges: The World Anti-Doping Agency faces
difficulties in detecting synthetic EPO and blood doping, despite
the immediate performance benefits they provide to athletes.
A.1.3.1 Circulation

● Blood vessels include:

○ Arteries: Thick-walled,
transport oxygen-rich
blood away from the
heart.
○ Capillaries: Thin-walled,
site of gas and nutrient
exchange.
○ Veins: Transport
deoxygenated blood back
to the heart.
● Arterioles and Venules:
Regulate blood flow and
pressure.
A.1.3.1 The Cardiac Cycle

● Heart functions as a four-chamber pump.

● Two sides work in parallel:
○ Left side: Pumps oxygenated blood to the
body.
○ Right side: Pumps deoxygenated blood to the
lungs.
● Blood flow is regulated by valves
(tricuspid, mitral, aortic, pulmonary).
● Contraction (systole) and relaxation
(diastole) phases alternate.
A.1.3.1 Blood Pressure

● Blood pressure fluctuates between:

○ Systolic pressure (ventricles contract).
○ Diastolic pressure (ventricles relax).
● Normal range:
○ Systolic: 90-120 mmHg.
○ Diastolic: 60-80 mmHg.
● High blood pressure: ≥140/90 mmHg.
○ Healthy pressure ensures efficient blood flow to tissues.
How does Isometric contractions influence blood
pressure?
Isometric contraction, which involves muscle activation without changing the muscle length, can
influence blood pressure in several ways:

Increased Vascular Resistance: During isometric exercises, the contracting muscles compress the blood
vessels, leading to increased vascular resistance. This can temporarily elevate blood pressure.

Sympathetic Nervous System Activation: Isometric contractions stimulate the sympathetic nervous system,
which releases hormones like norepinephrine. This increases heart rate and constricts blood vessels, further
raising blood pressure.

Muscle Pump Effect: While isometric contractions do not change muscle length, they can still create pressure
that helps circulate blood. This can improve venous return, but the initial contraction may lead to acute spikes in
blood pressure.

Duration and Intensity: The extent of blood pressure increase can depend on the intensity and duration of the
isometric exercise. Higher intensity and longer durations typically lead to greater increases in blood pressure.

Post-Exercise Effects: After the cessation of isometric exercise, blood pressure may gradually return to baseline
levels, and regular isometric training can lead to long-term adaptations, potentially improving vascular health.
Partner Discussion
A.1.3.1 Blood Flow Distribution
● At rest: Blood is distributed to
organs such as muscles, liver, and
kidneys.
● During exercise:
○ Blood flow to muscles increases
significantly (up to 25 times).
○ Organs like liver and kidneys receive
less blood.
○ Muscles: 84% of total blood flow
during exercise.
○ Heart: Maintains blood supply to itself
and the brain.
Acute Cardiovascular Responses to Exercise

Key Points:

1. Importance of Cardiovascular System: The cardiovascular system

plays a crucial role in maintaining homeostasis and function during
exercise, especially as respiratory responses are sufficient for gas
exchange.
2. Heart’s Central Role: The heart's responses during dynamic exercise
are critical and are precisely regulated based on the exercise demands.
3. Cardiac Output Definition: Cardiac output is the volume of blood
ejected from the left side of the heart per minute, essential for supplying
the body (excluding the lungs).
4. Factors Determining Cardiac Output: Cardiac output is calculated by
the equation:
cardiac output = heart rate X stroke volume / 1000 , where heart rate is
in beats per minute and stroke volume is in millilitres per beat.
5. Heart Rate and Stroke Volume Increase: During exercise, both heart
rate and stroke volume increase to meet the higher demand for cardiac
output until maximum levels are reached, indicating exhaustion.
6. Prolonged Exercise Adaptations: In prolonged submaximal exercise,
cardiac output remains constant, but heart rate may gradually increase
while stroke volume stabilizes above resting levels.
A.1.3.2—The respiratory system enables the exchange
of gases between the external environment
and the body, to facilitate cellular respiration.

Minute ventilation, tidal volume and

change in respiration rate can vary, and
depend on factors such as age, sex
differences, body size, level of fitness,
type of activity and intensity of activity.
A diagram of the respiratory system is
found in the SEHS data booklet.
noun

a thick muscle on each side

of the neck, the action of
which assists in bending the
head and neck forward and
sideways.
A.1.3.2 Respiratory System

● Main function: Transport and exchange

oxygen for cellular respiration.
● Involves inhalation (active) and exhalation
(passive).
● Breathing mechanism:
○ Inhalation: Diaphragm contracts, lungs expand, air
enters.
○ Exhalation: Diaphragm relaxes, lungs recoil, air
exits.
● Air moves from high-pressure areas to
low-pressure areas.
● Anatomy of the respiratory system:
○ Nose/mouth, Pharynx, Larynx, Trachea, Bronchi,
Bronchioles, Alveoli.
Definitions:

● Minute Ventilation: Total volume of air inhaled and exhaled per minute.
● Tidal Volume: Amount of air inhaled or exhaled in a single breath.

Factors Influencing Variability:

● Age:
○ Respiratory capacity can decrease with age.
● Sex Differences:
○ Men typically have larger lung volumes than women.
● Body Size:
○ Larger body size often correlates with greater tidal volume.
● Level of Fitness:
○ Trained individuals may have a more efficient respiratory response.
● Type of Activity:
○ Different activities (rest vs. exercise) demand varying ventilation levels.
● Intensity of Activity:
○ Higher intensity increases minute ventilation to meet oxygen demands.
A.1.3.2 Lung Volumes & Capacities

● Vital Capacity: Maximum air exhaled after

maximum inhalation.
● Residual Volume: Air remaining in lungs after
full exhalation.
● Tidal Volume: Air inhaled/exhaled during
normal breathing.
● Total Lung Capacity: Sum of all lung volumes.
● Inspiratory/Expiratory Reserve Volumes:
Extra air inhaled/exhaled beyond tidal
volume.
A.1.3.2 Gas Exchange

● Occurs in the alveoli via diffusion.

● Oxygen diffuses into the blood;
carbon dioxide diffuses out.
● Gas exchange driven by pressure
gradients:
○ High partial pressure of oxygen in the
alveoli.
○ Low partial pressure of oxygen in the
blood.
● During exercise, increased oxygen
demand and CO₂ production
accelerate gas exchange.
A.1.3.2 Ventilation During Exercise

● Minute Ventilation (V̇E): Volume of air

exhaled per minute.
● Formula:
○ V̇E = TV × B
○ (Tidal volume × Breathing frequency)
● V̇E increases with exercise intensity.
● Ventilation is regulated by arterial blood gas
levels, pH, temperature, and hormones.
● Increased ventilation ensures oxygen supply
matches tissue demand and removes CO₂.
A.1.3.2 Control of Ventilation

● Ventilation responds to the intensity of

exercise and metabolic demands.
● Controlled by:
● Chemoreceptors: Detect changes in CO₂
and O₂ levels.
● Stretch receptors: Monitor lung inflation.
● Nervous system: Adjusts breathing rate
and depth.
● Hyperventilation: Excessive breathing
reduces CO₂ levels, causing dizziness.
● Rebreathing technique: Helps normalize
CO₂ levels during hyperventilation.
Nervous and chemical control of ventilation during
exercise

Neural control of ventilation includes:

● Chemoreceptors - detects changes in the chemical

composition of the blood and reports this to input to
respiratory centers in the brain control the force and
frequency of respiratory muscle contraction.

● Lung stretch receptors - A protective reflex that

inhibits the lungs from over inflating. They monitor the
movement of the lungs and send messages through
connecting nerves back to the brain to control
breathing.

● Muscle proprioceptors - receive messages from the

muscles, bones and tendons about changes in length,
tension, shape which sends sensory input to the
respiratory centres in the brain.
A.1.3.2 Functional Capacity

● Maximal Oxygen Uptake (V̇O₂max):

○ Measures the maximum rate of oxygen uptake and
usage during exercise.
○ Increases with higher exercise intensity until V̇O₂max is
reached.
○ Indicator of aerobic fitness and endurance capacity.
○ Patients with low V̇O₂max struggle with exercise; elite
athletes have high V̇O₂max and superior endurance.
● Fick Equation:
○ V̇O₂max = Cardiac Output × Arteriovenous Oxygen
Difference.
○ Endurance training improves cardiac output, blood
distribution, and muscle microcirculation.
● Children vs. Adults:
○ Children have higher heart rates but lower stroke volume
compared to adults during submaximal exercise.
○ Larger arteriovenous oxygen difference in children
compensates for lower cardiac output to meet oxygen
demands.
 Linking Question:
How do specific qualities in long term training influence the
structures and functions of the cardiovascular system?(A3.1)

Task:
Consider:
● Itensity, duration and frequency of
training
● Effects on cardiac output
● Delivery of oxygen and nutrients to
exercising skeletal muscle and
tissue
● What happens to blood pressure
during exercise
● Improved blood flow
A.2.3 Energy systems
 A.2.3.1—The body relies on the phosphagen,
glycolytic and oxidative systems for energy
production to sustain life and physical activity.
The energy systems have different fuel sources for ATP production, recovery capabilities, benefits and limitations during
physical activity.

The energy continuum aids in describing the relative contribution of each energy system depending on the nature of the
activity.

While at rest, and during extended periods of submaximal intensity, the oxidative system is the dominant supplier of ATP to
support the body’s activities.

During both short- and high-intensity periods, and sudden increases of intensity, anaerobic ATP production (phosphagen and
anaerobic glycolysis) supports the body’s functions.

Knowledge of biochemical details of the Krebs cycle and the electron transport chain are not assessed.
A.2.3.1 Introduction & Metabolism

● Metabolism: Chemical processes

for energy production.
○ Anabolism: Builds larger molecules.
○ Catabolism: Breaks down molecules for
energy.
● Mitochondria:
● Present in all cells (except red
blood cells)
● Involved in aerobic energy
production (Krebs cycle, electron
transport chain)
A.2.3.1 Energy Currency: ATP

● ATP (Adenosine Triphosphate):

Main energy source for cellular
processes.
● ATP Breakdown: Releases energy
for muscle contraction.
● Energy Systems:
○ Phosphagen: Immediate, short-term
energy.
○ Glycolytic: Anaerobic energy from
glucose.
○ Oxidative: Aerobic energy from
carbohydrates and fats.
A.2.3.1 Carbohydrate Metabolism

● Glycogenolysis: Conversion
of glycogen to glucose - when
the body needs more than it’s
ingested.
● Glycogenesis: Glucose to
glycogen - when we have
surplus glucose from our diet.
● Glycolysis: Glucose breaks
down into pyruvate for energy.
Can be aerobic or anaerobic.
● Gluconeogenesis: Formation
of glucose from
non-carbohydrate sources
(lactate).
A.2.3.1 Aerobic Energy Systems

● Oxidative System: Utilizes

oxygen for sustained
energy production.
● Glucose & Fat Oxidation:
Provides ATP for
long-duration, low-intensity
activities (e.g., marathon
running).
A.2.3.1 Aerobic (oxidative) Energy System
● Glucose oxidation is the final product of glycolysis, and
pyruvate has a different fate depending on the metabolic
conditions in cells.
● During less demanding metabolic conditions, pyruvate is
converted to acetyl coenzyme A (CoA) in the
mitochondria.
● The acetyl CoA then enters the Krebs cycle in the
mitochondria, where chemical reactions involving oxygen
convert it to water and carbon dioxide.
● During glycolysis and the Krebs cycle, hydrogen ions are
released, and specific coenzymes bind the hydrogen ions
and carry them to the electron transport chain.
● In the electron transport chain, the energy from the
hydrogen ions is used to produce ATP, which is the energy
currency of the cell.
● This process of converting glucose to ATP through the
aerobic (oxidative) energy system is described as the
"Aerobic glucose oxidation" pathway.
A.2.3.1 Fat Metabolism
β-oxidation: The energy-yielding process in the metabolism of
fat, where fatty acids are broken down to acetyl-CoA molecules.

Mitochondria: The cellular organelles where β-oxidation of fatty

acids occurs, with the support of the shuttle enzyme carnitine.

Fatty acid chain shortening: The process where β-oxidation

involves a repeat cycle of four reactions, reducing the fatty acid
chain by two carbons on each cycle.

Excess fat storage: Eating more fat than the body requires can
lead to excess fat being stored as adipose tissue and skeletal
muscle.

Lipolysis: The process of breaking down stored triglycerides into

glycerol and fatty acids, which are then available for
energy-generating β-oxidation.
A.2.3.1 The Phosphagen System (ATP-PC)
● The phosphagen system uses creatine phosphate (PCr) to generate ATP, providing rapid, high-energy for muscle
contraction.
● PCr, combined with the existing ATP in muscle, dominates energy provision during the first 10-20 seconds of exercise.
● This chemical reaction in the phosphagen system can occur very quickly, making it important for high-intensity activities.
● The PCr stores, along with existing ATP, can only contribute meaningful energy for the first 20 seconds of all-out exercise.
● After the initial 20 seconds, the phosphagen system's ability to provide ATP becomes limited, and other energy systems
must become available.
A.2.3.1 The glycolytic system (lactic)

● The glycolytic system is activated when aerobic

metabolism is limited, such as due to low oxygen or
mitochondrial supply.
● In the glycolytic system, pyruvate is converted to lactate,
generating a small amount of ATP (2 molecules).
● This glycolytic process occurs very quickly, making it
well-suited to meet the high energy demands of intense,
short-duration exercise.
● The glycolytic system can only be sustained for a short
time, as it relies on the phosphagen system which begins
to fade.
● Like the phosphagen system, the high-speed energy
provided by the glycolytic system can only be maintained
for a limited period.
A.2.3.1 Energy Continuum

● Intensity and Duration: The

contribution of each system
varies based on exercise
intensity and duration; the
ATP-CP system is predominant
in explosive efforts, while the
oxidative system is crucial for
sustained endurance activities.
● Transition: As exercise
progresses, the body transitions
between these systems, with the
ATP-CP system giving way to
anaerobic glycolysis and
eventually the aerobic system as
energy demands change.
1. Evaluating the dominating energy systems during the sports shown in Figure 16:

a. Rugby: The image shows a physical, intense contact sport, suggesting the dominance of the anaerobic
energy systems (ATP-CP and glycolytic) to fuel the explosive movements and high-intensity bursts.

b. Tour de France cycling: This endurance-based cycling event would primarily rely on the aerobic energy
system to sustain the prolonged efforts.

c. High jump: The explosive, short-duration nature of the high jump event indicates a greater contribution
from the ATP-CP (phosphagen) system.

2. Labeling the diagram in Figure 17 according to the type of sport:

Green - Phosphagen (ATP-CP) system

Orange - Glycolytic (anaerobic) system

Blue - Oxidative (aerobic) system

Rugby: The diagram shows a greater contribution from the anaerobic energy systems (phosphagen and
glycolytic) compared to the aerobic system, reflecting the high-intensity, intermittent demands of rugby.

High jump: The diagram indicates a predominant contribution from the phosphagen (ATP-CP) system, in
line with the explosive, short-duration nature of the high jump event.

Tour de France cycling: The diagram depicts a greater reliance on the aerobic energy system, which is
consistent with the endurance requirements of long-distance cycling.
 A.2.3.2—Maximal oxygen consumption (VO2 max) is
influenced by an individual’s age, sex differences, body
composition, lifestyle factors and level of fitness.
 Maximal Oxygen Consumption (VO2 max) and
Endurance
• VO2 max (maximal oxygen consumption) is the maximum rate
at which an individual can take in and use oxygen. It is a key factor
in evaluating an individual's cardiovascular-respiratory function.

• Individual differences and genetic factors can influence VO2

max. These are important determinants of endurance
performance.

• VO2 max is one of the key factors determining endurance

performance. It reflects the capacity of the
cardiovascular-respiratory system to deliver oxygen.
 Absolute vs Relative VO2 max

Absolute VO2 max is reported in liters per

minute (l·min⁻¹), while relative VO2 max is
normalized according to body mass in milliliters
per minute per kilogram (ml·min⁻¹·kg⁻¹).
• For weight-bearing activities, the relative VO2
max value is more appropriate to use, as it
attempts to account for individual differences in
size and mass.
• There is significant variability in absolute VO2
max values between individuals, due to factors
such as age, gender, heart size, and blood
volume.
 VO2 Max and Sex Differences

• Absolute VO2 max values are typically lower in biological females

compared to males, primarily due to smaller body size.

• Even when expressed in relative terms (normalized to body mass), females

typically have lower VO2 max values than males.

• Biological females have a smaller heart, reduced cardiac output, and lower
capacity to pump blood compared to males.

• Hemoglobin concentration, which facilitates oxygen transport, is slightly

higher in biological males.

• Lung capacity is lower in biological females, leading to lower lung volume

and gas exchange capacity.

• Body composition differences, with biological females having a higher

percentage of non-oxygen-using body fat, contribute to the VO2 max gap.

• Sex differences in body size and muscle mass also lead to lower strength,
power, and anaerobic performance in biological females.
 VO2 Max and Age
● Children typically have lower VO2 max values than adults due to their
smaller size.
● During childhood and adolescence, absolute VO2 max increases
according to patterns of growth and maturation.
● For biological males, the highest VO2 max values are typically seen in late
teens and early 20s.
● For weight-bearing activities, it is more appropriate to use relative VO2
max (ml/min/kg), as this accounts for changes in body size.
● In sedentary adults, VO2 max generally decreases by about 10% per
decade.
● Trained endurance athletes will begin with a higher VO2 max, and if they
maintain training, their VO2 max may decline at a slower rate over time.

The key takeaway is that VO2 max changes significantly with age, with
childhood values being lower, a peak in late teens/early 20s, and then a gradual
decline in sedentary adults, but a slower decline in trained endurance athletes.
 How does training increase VO2 Max

• Training increases VO2 max through adaptations in the cardiovascular and muscular systems.

• The primary training response is an increase in stroke volume at submaximal and maximal
exercise intensities.

• In contrast, the heart rate response becomes lower at submaximal intensities, as the maximum
heart rate is unchanged with training.

• The increased stroke volume is mainly due to an increase in the volume of the left ventricle,
allowing more blood to fill the ventricle.

• There are also changes in the blood, such as the development of more capillaries, which allows
more oxygen to be supplied to the exercising muscles.

• These central and peripheral adaptations permit an individual to exercise harder as their VO2
max has increased.

In summary, the key mechanism by which training increases VO2 max is through improvements in
the cardiovascular system's ability to deliver more oxygen to the working muscles during exercise.
 VO2 Max and type of Exercise

● The type of exercise performed can influence recorded VO2 max

values.
● The pattern of oxygen uptake differs depending on whether the
exercise involves weight-bearing activities or not.
● For weight-bearing activities like running, the upper-body and postural
muscles are heavily engaged, which would be expected to result in
higher VO2 max values.
● In contrast, for non-weight-bearing activities like cycling, the
upper-body muscles are not as heavily utilized, leading to relatively
lower VO2 max values.
● Cross-country skiing places greater oxygen demands on the
upper-body muscles compared to lower-body and postural muscles
involved in other types of exercise.
● The type of exercise is an important final factor that can impact the
recorded VO2 max measurements.

In summary, the specific type of exercise performed, and the muscle groups
engaged, can significantly influence the observed VO2 max values for an
individual.
 Running Economy (RE)

The steady-state oxygen consumption (VO2) at a given running

velocity is known as the running economy (RE).

RE reflects the energy demand of running - runners with good RE use less
oxygen than runners with poor RE at the same steady-state speed.

RE is believed to be a useful predictor of endurance running

performance, as it indicates the metabolic, cardiovascular, biomechanical,
and neuromuscular efficiency of an individual during running.

Improving an athlete's RE can have important implications for coaches and

athletes, as it indicates more efficient energy utilization during running.

In summary, running economy is an important metric that reflects the energy

demands of running and can provide insights into an individual's running
performance and efficiency, independent of their maximal oxygen uptake
(VO2 max).
Running Economy Explained

1. Running economy refers to the

efficiency of running, which is
crucial for improving
performance and speed.
2. Maintaining good posture and
form, along with incorporating
strength and power training, are
essential for enhancing running
economy.
3. It's important to gradually
increase training intensity and
duration to effectively improve
running economy over time.
 Linking Question:
How does a lack of ATP affect muscular contraction?
(B1.3)
Task:
Research the following concepts:
● Structure and function of ATP.
● The process of muscular contraction (including the
sliding filament theory).
● The sources and regeneration of ATP during muscle
activity.
● Effects of ATP depletion on muscle performance and
fatigue.
Design a simple experiment or simulation to observe the
effects of ATP depletion on muscular contraction.
A.2.3.3—The lactate inflection point is the maximum
intensity at which the body can metabolize
lactate at the same rate as its production.
A.2.3.1 Energy Systems Summary
1. ATP-PC System (Phosphagen System)
● Duration: 0-10 seconds
● Primary Energy Source: Adenosine triphosphate (ATP) and phosphocreatine
(PC)
● Key Characteristics:
● Immediate energy for high-intensity activities (e.g., sprinting, weightlifting)
● Rapid replenishment of ATP through anaerobic processes
● Limited capacity, quickly depleted
2. Anaerobic Glycolysis (Glycolytic System)
● Duration: 10 seconds to 2 minutes
● Primary Energy Source: Glucose (from glycogen or blood sugar)
● Key Characteristics:
● Produces ATP without oxygen, leading to lactic acid accumulation
● Supports moderate to high-intensity efforts (e.g., 400m sprint, HIIT)
● Faster than aerobic metabolism but less efficient
3. Aerobic Respiration (Oxidative System)
● Duration: Over 2 minutes
● Primary Energy Source: Carbohydrates and fats
● Key Characteristics:
● Requires oxygen for ATP production
● Sustains lower-intensity, endurance activities (e.g., long-distance running,
cycling)
● High capacity for energy production but slower to activate
A.2.3.3 Energy for Muscle Contraction

● ATP Sources: Phosphagen (immediate), glycolytic (short-term),

oxidative (long-term).
● Exercise Intensity: Higher intensities rely more on anaerobic systems;
lower intensities use aerobic systems.
 A.2.3.3 Lactate Fermentation
What is Lactate Fermentation?
● Energy from Food: When we exercise, our bodies need energy. We get this
energy from breaking down sugar (glucose).
How It Works
1. First Step - Glycolysis:
● In this step, glucose is split into something called pyruvate, and this gives
us 2 energy units (ATP).
2. When There’s No Oxygen:
● If we exercise really hard (like sprinting), our muscles might not get
enough oxygen.
● When this happens, the pyruvate turns into lactate (or lactic acid).
Why Do We Do This?
● Keep Making Energy: The main reason for making lactate is to help keep
glycolysis going. It helps recycle a helper molecule called NAD+. This is
important because we need NAD+ to keep making energy.
What It Means
● Total Energy Made: We only get 2 energy units (ATP) from the whole process.
● Lactate’s Job: It helps our muscles keep working hard, even when there isn’t
enough oxygen.
A.2.3.3 Lactate Inflection Point (LIP)

● LIP: The point where lactate accumulates

faster than it can be cleared, leading to
fatigue.
● Expressed as (% V̇O₂max)
● Occurs at a higher percentage of V̇O₂max in
trained individuals (70-80%) than untrained
individuals (50-60%).

It used to be thought that lactate is just a waste

product

Scientific consensus is moving away from this.

 Linking Question:
Is there a relationship between mental toughness and
the lactate inflection point? (C.1.2)

Task: Research further into lactate inflection point and

critical power.

Write an opinion piece for the above question.

Add it to the padlet.

 A.2.3.4—Excess post-exercise oxygen consumption (EPOC) is
required for the body to return to homeostasis and is dependent on
the oxygen deficit incurred during exercise. EPOC is typically
divided into two subsections: fast and slow.
A.2.3.4 EPOC
(Excess Post-exercise Oxygen Consumption)
A.2.3.4 EPOC
(Excess Post-exercise Oxygen Consumption)

● Fast Component: Replenishes ATP and PCr

stores.
● Slow Component: Clears lactate, restores
oxygen levels, and regulates body
temperature.
A.2.3.4
A.2.3.4 PC Restoration Rate
A.2.3.4
A.2.3.4
A.2.3.4
 Linking Question:
How might exercising in hot, humid conditions for extended periods
of time influence the predominant energy system used and the
lactate inflection point? (A.1.2)

Task:
● Answer this question in the form of a cartoon strip.
● Include at least three panels
● Work together to plan out the contents of each
panel
● Each person should then draw their own panel
● Start by researching energy systems in hot
conditions and reminding yourself of the lactate
inflection point.
● Be sure to incorporate your learning of EPOC
 Skill: Processing Uncertainties
Understanding the significance of uncertainties in raw and processed data.
Record uncertainties in measurements as a range (±) to an appropriate level
of precision.

What measurement
uncertainties should we
consider when recording and
processing data from our
mini run?
Task:
● Discuss the above
statements and prepare
a short response.
● Post it on the padlet