Answers to ‘Revise as you go’
1. Describe the mechanics of breathing at rest and during exercise.
Mechanics of breathing at rest
Inspiration
 Diaphragm contracts (active)
 External intercostal muscles contract
 Ribs move up and out
 Volume of the thoracic cavity increases
 Pressure of air within the lungs decreases
 Air rushes into lungs
Expiration
 Diaphragm relaxes (passive)
 External intercostal muscles relax
 Ribs move down and in
 Volume of the thoracic cavity decreases
 Pressure of air within the lungs increases
 Air rushes out of lungs
Mechanics of breathing during exercise
Inspiration
Additional muscles are involved:
 Sternocleidomastoids, scalenes and pectoralis minor contract
 External intercostals and diaphragm contract with more force
 Thoracic cavity is lifted further up and out, increasing the volume inspired and decreasing pressure further
 More air is inspired
Expiration
Additional muscles contract:
 Abdominal/oblique muscles push diaphragm up with more force
 Internal intercostals pull ribs downwards and in
 Greater decrease in thoracic cavity volume, increasing pressure within the thoracic cavity
 Increased the volume of air expired and increased respiration rate
2. Define the terms minute ventilation, tidal volume and respiratory frequency, and give average values for
minute ventilation during rest and during maximal exercise.
Minute Ventilation (VE) – Volume of air inspired/expired in one minute
Rest = 6-7.5 L/min
Max = 120/180+ L/min
Tidal Volume (TV) – Volume of air inhaled/exhaled per breath
Rest = 500ml Max = 3-4 L
Respiratory frequency (f) – Number of breaths in one minute
Rest = 12-15 Max = 40-60
3. Explain how gas is exchanged between the alveoli and the alveoli capillaries during exercise.
External (Alveoli) Respiration
Deoxygenated venous blood in alveoli capillaries has a higher Partial Pressure of carbon dioxide and lower PP of
oxygen than inspired alveolar air which has a high PP of oxygen and low PP of carbon dioxide.
This increases the diffusion gradient for both oxygen and carbon dioxide between the alveoli-capillary membrane,
resulting in both a quicker and greater amount of gaseous exchange of O 2 and CO2.
The high PP of oxygen in the alveoli and low PP of oxygen in the capillaries ensures haemoglobin is almost fully
saturated with oxygen.
4. Explain how gas is exchanged between the capillaries and muscle cells during exercise.
How gas is exchanged:
 high partial pressure of O2 (PO2) in blood, lower exercise PO2 in muscle, so O2 diffuses into muscle
 increased diffusion gradient and therefore speed of diffusion
 higher partial pressure of carbon dioxide (PCO2) in tissues, low PCO2 in blood, so CO2 diffuses into blood
 increase in temperature encourages greater release of O2 from haemoglobin
 increase in acidity/lower pH of blood allows greater release of O2 from haemoglobin, called the Bohr effect
 increase in CO2 diffused into blood results in greater release of O2 from haemoglobin
 myoglobin has a higher affinity for O2 than haemoglobin
 myoglobin is used to transport more O2 to mitochondria.
5. Describe and explain the factors that affect the activity of the RCC.
Chemoreceptors from within the medulla and carotid arteries send information to the inspiratory centre on:
 increase in PP carbon dioxide – thought to be the primary factor
 decrease in PP oxygen
 decrease in pH (increasing acidity).
Proprioreceptors located in the muscles and joints send information to the inspiratory centre on motor movement
of the active/working muscles.
Thermoreceptors send information to the inspiratory centre on increase in blood temperature.
Baroreceptors or stretch receptors located in the lungs send information to the expiratory centre on the extent
of lung inflation during inspiration.
6. Explain how the RCC controls respiration during exercise.
Chemoreceptors, baroreceptors and proprioreceptors stimulate the Respiratory Control Centre.
The RCC controls/regulates breathing via the inspiratory/expiratory centres.
During exercise pulmonary ventilation increases, which increases both the depth and rate of breathing.
The inspiratory centre:
 increases the stimulation of the diaphragm and external intercostals
 stimulates additional inspiratory muscles for inspiration, the sterno-cleidmastoids, scalenes and pectoralis
minor, which increase the force of contraction and therefore the depth of inspiration.
The expiratory centre:
 stimulates the expiratory muscles, internal intercostals, rectus abdominus and obliques, causing a forced
expiration which reduces the duration of inspiration.
7. Explain the effects of exercise-induced asthma on the respiratory system and suggest how performers
may treat/prevent these symptoms occurring.
Asthma is characterised by a reversible narrowing of airways (bronchoconstriction) with common symptoms of
hyper-irritability of airways, coughing, wheezing, breathlessness or mucus production. Asthma occurs in response
to a trigger or allergen and is often brought on shortly after exercise or some hours after and is termed ‘exercise
induced asthma’ (EIA).
Treatments
Normally treated by inhaled medication – bronchodilators – which are ‘reliever’ (blue) medications which relax
muscles around airways; taken before exercise or in response to symptoms.
Corticosteroids are ‘preventer’ (non-blue) medications which suppress the chronic inflammation and improve the
pre-exercise lung function and reduce the sensitivity of the airway structures.
Non–medical treatments
A warm up, at least 10-30 min at 50/60% max HR provides a ‘refractory period’ for up to 2 hours, after which
exercise is possible without triggering EIA.
Dietary modification, by reducing salt and increasing fish oils and (antioxidant) vitamins C + E, has also shown to
help reduce the inflammatory response to EIA.
Caffeine is also a bronchodilator, but you must be aware that the IOC limit is 12 mg/ml.
Inspiratory Muscle Training
Increased respiratory effort is a major principal symptom of breathlessness; hence, there is a strong relationship
between the strength of the respiratory muscles and the sense of respiratory effort.
General prevention
Refrain from endurance training when suffering respiratory infections, avoid exercise in cold (winter)/dry air
conditions; minimise effects by wearing a mask to cover the nose/mouth to enable exhaled air to help raise
temperature of the air inhaled.
8. How does smoking affect the efficiency of the respiratory system?
Smoking Effects
Impairs lung function and diffusion rates.
Increased damage and likelihood of respiratory diseases, infections, and symptoms summarised below:
Asthma
Irritates/damages respiratory structures; cilia, alveoli, bronchioles
Narrows/ constricts respiratory airways
Emphysema (decrease elasticity of respiratory structures)
COPD (Chronic Obstructive Pulmonary Disease)
Cancers of respiratory structures
Shortness of breath
Performance effects
Decreases the efficiency of the respiratory system to take in (VO 2 max) and supply O2 to our working muscles.
Impairs performance, even among highly trained athletes, mostly affects endurance based exercise, especially high
intensity maximal activity like the triathlon.
9. Describe the effects of altitude on the respiratory system and how altitude would affect the performance of a
marathon runner.
Effects:
 haemoglobin saturation depends on partial pressure of oxygen in alveolar air/the lungs
 at altitude the (partial) pressure/concentration of oxygen is reduced, therefore there is a reduction in the
diffusion gradient
 haemoglobin is not fully saturated which results in a lower oxygen carrying capacity.
Influence:
 less oxygen delivered to working muscles
 so earlier onset of fatigue

resulting in decrease in performance (of aerobic activities).
10. Evaluate critically the impact of aerobic training on the respiratory system and how this affects
performance/a lifelong involvement in an active lifestyle.
Respiratory adaptations to physical activity
The net effect of aerobic training on the respiratory system is an increase in its efficiency to supply O 2 to the
working muscles during higher intensities of physical activity.
Respiratory structures
Increased alveoli increasing surface area for diffusion.
Increased elasticity of respiratory structures (lung, alveoli, pleura).
Increased longevity of respiratory structure efficiency.
Breathing Mechanics
Increased efficiency/economy of respiratory muscles reduces the O2 costs of the respiratory muscles reducing
respiratory fatigue.
Increase in strength, power and endurance of respiratory muscles.
Respiratory Volumes
TV can increase during maximal exercise.
Respiratory frequency decreases at rest/sub-maximal activity but can increase during maximal work.
Maximal VE can significantly increase from around 120L/min in an untrained athlete to 150L/min following training.
180/200+ in elite due to increase in TV and f at maximal exercise.
Diffusion
Diffusion unchanged at rest and sub-maximal exercise.
Increase in pulmonary diffusion during maximal activity.
Increased VO2 diff (arterial-venous oxygen difference) at maximal activity (less O2 in venous blood representing
increased delivery and extraction of O2 to active muscles).
The net effect of all the above efficiency improvements is that VO2 max and the lactate threshold increase, both
of which improve performance. The main performance benefits are:
Aerobic performance during higher/maximal work rates is both increased and prolonged.
More effect with aerobic endurance activity that is dependent more upon O 2, although it will delay the anaerobic
threshold and therefore delay fatigue during anaerobic activity.
Reduces the effort of sub-max work therefore increasing duration of performance.
A more efficient and healthy respiratory system encourages and promotes a lifelong involvement in an
active/healthy lifestyle.