Transport: big picture

· Transport = movement of nutrients, hormones, gases, heat and waste around the body to support health, exercise and performance.
· Two linked systems are central: cardiovascular system = transports blood-borne substances; respiratory system = enables gas exchange with the external environment.
· During exercise, transport demands increase because working muscles need more oxygen and nutrients, while producing more carbon dioxide, heat and metabolic waste.
· Exam focus: explain how heart rate, stroke volume, cardiac output, blood pressure, blood redistribution, minute ventilation, tidal volume and respiration rate change with exercise demands.

Cardiovascular system: what it transports

· The cardiovascular system transports nutrients, hormones, gases, heat and waste products.
· Nutrients move from digestive/storage sites to active tissues for energy and repair.
· Hormones travel in blood to target tissues to regulate physiological responses.
· Gases: oxygen is delivered to tissues; carbon dioxide is transported away from tissues.
· Heat is redistributed through blood flow to help regulate body temperature.
· Waste products are carried away from active tissues for removal or processing.

Key cardiovascular variables

· Heart rate (HR) = number of heart beats per minute.
· Stroke volume (SV) = volume of blood ejected from the heart per beat.
· Cardiac output (Q/CO) = total volume of blood pumped by the heart per minute: $Q = HR \times SV$.
· Blood pressure (BP) = force exerted by blood against blood vessel walls.
· Blood redistribution = shifting of blood flow towards tissues with greater immediate demand, especially working muscles during exercise.
· In exam answers, link these variables to the body’s need to maintain oxygen delivery, carbon dioxide removal, nutrient supply, heat transfer and waste removal.

These diagrams help students interpret why blood pressure changes across arteries, arterioles, capillaries, venules and veins. They are useful for linking cardiac output, vessel resistance and blood flow to exercise transport demands. Source

Factors affecting cardiovascular responses

· Age can affect cardiovascular capacity and response to exercise.
· Sex differences can influence cardiovascular variables and exercise responses.
· Body size affects blood volume, oxygen demand and total transport requirements.
· Level of fitness affects how efficiently the cardiovascular system supports exercise.
· Type of activity affects which tissues require more blood flow.
· Intensity of activity strongly influences increases in HR, SV, cardiac output, blood pressure and blood redistribution.
· Strong exam phrase: cardiovascular responses vary depending on individual characteristics and exercise demands.

Blood redistribution during exercise

· During exercise, blood flow is redirected towards active skeletal muscles to meet increased demand for oxygen and fuel.
· Blood flow also supports heat transport, helping move heat from active muscles towards the skin.
· Redistribution depends on type of activity and intensity: higher intensity generally requires greater delivery to working muscles.
· It helps maintain performance by supporting cellular respiration, waste removal and temperature regulation.
· In exam explanations, avoid saying blood simply “goes everywhere more”; emphasise selective redistribution according to demand.

Respiratory system: role in transport

· The respiratory system enables exchange of gases between the external environment and the body.
· Its key role in A.1.3 is to support cellular respiration by bringing in oxygen and removing carbon dioxide.
· Gas exchange occurs because oxygen and carbon dioxide move between air spaces in the lungs and the blood.
· The respiratory system works with the cardiovascular system: lungs load blood with oxygen, and blood transports that oxygen to tissues.
· Performance depends on matching ventilation to the body’s demand for oxygen uptake and carbon dioxide removal.

This diagram shows the structures where air reaches the alveoli and can exchange gases with blood in nearby capillaries. It is ideal for linking respiratory structure to the function of supporting cellular respiration during exercise. Source

Mechanics of breathing and gas exchange

· Breathing mechanics enable air to move into and out of the lungs so gas exchange can occur.
· During inspiration, air enters the lungs, increasing the supply of oxygen available for diffusion into blood.
· During expiration, air leaves the lungs, removing carbon dioxide from the body.
· Effective breathing supports performance by maintaining oxygen supply for aerobic energy production.
· Poor gas exchange or insufficient ventilation can limit the body’s ability to sustain exercise intensity.

This image highlights the microscopic structure of the alveolus and its close contact with capillaries. It supports exam explanations of how the respiratory system enables efficient oxygen uptake and carbon dioxide removal. Source

Key respiratory variables

· Minute ventilation (VE) = total volume of air breathed in or out per minute.
· Tidal volume (TV) = volume of air breathed in or out per breath.
· Respiration rate (RR) = number of breaths per minute.
· Key relationship: $VE = TV \times RR$.
· During exercise, minute ventilation can increase through a rise in tidal volume, respiration rate, or both.
· Exam focus: explain how changes in ventilation help meet increased demand for oxygen intake and carbon dioxide removal.

Factors affecting respiratory responses

· Age can influence respiratory capacity and breathing responses.
· Sex differences can affect respiratory variables and exercise responses.
· Body size influences lung volumes and total ventilatory demand.
· Level of fitness affects how effectively ventilation supports exercise.
· Type of activity determines the pattern and size of ventilatory response.
· Intensity of activity strongly affects increases in minute ventilation, tidal volume and respiration rate.

Cardiovascular-respiratory link in performance

· The respiratory system brings oxygen into the body and removes carbon dioxide.
· The cardiovascular system transports oxygenated blood to tissues and returns blood carrying carbon dioxide to the lungs.
· Together, these systems support cellular respiration, especially during sustained or intense exercise.
· As exercise intensity rises, the body usually needs increased cardiac output and increased minute ventilation.
· High-quality answers should connect both systems rather than describing them separately.

Common exam command links

· Describe: state what changes, e.g. heart rate increases with exercise intensity.
· Explain: link the change to function, e.g. increased cardiac output improves oxygen delivery to working muscles.
· Apply: use factors such as age, sex differences, body size, fitness, activity type and intensity to a specific performer or activity.
· Interpret: use data on HR, SV, Q, BP, VE, TV or RR to infer transport demands.
· Compare: contrast responses at rest, low intensity and high intensity, or between trained and less-trained individuals.

High-scoring exam reminders

· Always link transport changes to function: oxygen delivery, carbon dioxide removal, nutrient supply, heat transfer or waste removal.
· Use precise terms: cardiac output, not just “blood pumped”; minute ventilation, not just “breathing more”.
· When discussing exercise, mention both demand and response.
· Remember that both cardiovascular and respiratory variables vary between individuals and activities.
· There is no additional higher level content for A.1.3 Transport, so the same core content applies to SL and HL students for this subtopic.