Cardiorespiratory responses to exercise (Year 2)

Question 1

Respiratory Volume Parameters:

Answer 1

• Tidal Volume(TV)-Volume inspired or expired per breath
• Inspiratory Reserve Volume(IRV)-Maximum inspiration at end of TV
• Expiratory Reserve Volume (ERV)-Maximum expiration at end of TV

Question 2

Ventilation during Exercise:

Answer 2

• Resting minute ventilation:5 –6 l/min
• Maximal minute ventilation:>100l/min
• Linear increase at submaximal intensities

•Breathing capacity does not reach maximal regardless
of exercise intensity

•Not the factor limiting O2 delivery during exercise

Question 3

Cause of hypoxemia in Athletes

Answer 3

• IncreasedO2extraction→decreasedPO2invenous blood
• Increased cardiac output→decreased transit time
• CombinedeffectismoreO2needs to be taken up in less time
• If this isn’t achieved→hypoxemia

Question 4

Adaptions to endurance training?

Answer 4

• Little effect on lung structure or function at rest
• Decreased submaximal ventilation
• Increased pulmonary ventilation during maximal exercise:
• Increased respiratory rate
• Increased tidal volume
• Increased pulmonary diffusion:
• Increased ventilation
• Increased perfusion

Question 5

Respiratory Muscle Fatigue and exercise tolerance?

Answer 5

• Study explored the effects of increasing and decreasing inspiratory muscle work on quadriceps muscle fatigue
• Percent change in twitch force: the reduction in the average quadriceps force output
• Equal cycle ergometer work rates and durations

Question 6

Respiratory Muscle Training:

Answer 6

• Utilises restricted airflow breathing exercise to increase the mechanical load on the respiratory muscles
• Provides a stimulus to elicit a hypertrophic response
• Resistive training -muscles subjected to an external load
• Inspiratory flow resistive loading
• Inspiratory threshold loading
• Expiratory threshold
• Endurance training-high target levels of ventilation for up to 30 minutes

Question 7

Heart rate Variability?

Answer 7

• Analysis of variability in consecutive RR
intervals

• Insight into autonomic nervous system control
• Central to physiological coordination
• High variability is healthy
• Sensitive to numerous factors

Question 8

Factors affecting heart rate variability: Non-Influenceable Physiological parameters

Answer 8

Age, gender, circadian rhythm, genetics

Question 9

Factors affecting heart rate variability: Diseases

Answer 9

Sepsis, heart disease, lung diseases,
renal diseases, psychiatric diseases,
metabolic diseases

Question 10

Factors affecting heart rate variability: Influenceable Lifestyle Factors

Answer 10

Physical fitness, sporting activity, increased

body weight, smoking, alcohol abuse

Question 11

Factors affecting heart rate variability: External Factors

Answer 11

Noise, night shift work, harmful

substances, medications

Question 12

Heart rate variability and posture: standing up?

Answer 12

decrease venous return–>

decrease end-diastolic volume–>

decrease stroke volume–>

decrease cardiac output–>

decrease blood pressure–>

baroreceptors–sensory neurons–>

Medulla oblongata increases sympathetic input and decrease parasympathetic input–>

increase in cardiac rate and vasoconstriction of arterioles–>

increase in peripheral resistance and cardiac output–>

increase blood pressure (negative feedback response)

Question 13

Cardiovascular hemodynamics?

Answer 13

Cardiac output= stroke volume x heart rate

CO (Q) – volume of blood pumped by one ventricle in a given period
- Typically ~5L∙min-1

SV – volume of blood pumped by one ventricle in one contraction
- Typically ~70mL at rest

HR – rate of contraction of the heart
- Typically ~70-75 bpm but innate HR is 90-100 bpm

Question 14

Effect of pH, CO2 and O2 on the CV system?

Answer 14

• Effect of each related through detection by chemoreceptors and by relationship with respiratory system
• Two sets of chemoreceptors

• Peripheral – sensitive to pH, CO2
, O2

• Central – sensitive CO2

• Increases in CO2
concentration decrease pH because CO2
is mainly
transported as carbonic acid

• Parasympathetic withdrawal and sympathetic stimulation
• Increased HR contractility -> increased Q

• Greater blood flow through the lungs so CO2
is expired

• Negative feedback loop

Question 15

Stroke volume

Answer 15

Stroke Volume (SV) = EDV – ESV

• Frank Starling Mechanism
• EDV increases with venous return
• ESV decreases due to stretch
• Increase in SV with exercise intensity until:
• 40-60% VO2max (Wilmore and Costill, 1994)
• Or 120-140 bpm (McArdle et al, 1995)

Question 16

Heart rate?

Answer 16

• Submaximal work rates
• Linear increase proportional to oxygen consumption
• Conconi deflection

• Point at which HR tends to increase at a reduced
rate

Question 17

Blood Composition Changes During Exercise: Blood pH

Answer 17

• Lowered due to dissociation of lactate and transport of CO2
• Arterial blood: rest ~7.4 to exercise ~7.1 (Cheetham et al., 1986)

Question 18

Blood Composition Changes During Exercise: Oxygen Content

Answer 18

• Increased arteriovenous oxygen difference
• Decreased venous oxygen content
• Oxyhaemoglobin dissociation curve shifts right

Question 19

Blood Composition Changes During Exercise: Plasma Volume

Answer 19

• Exercise decreases blood plasma volume and increases haematocrit
• Initially due to an increase in blood pressure and osmatic pressure
• Later, increased by sweating

Question 20

Influence of Training on Hemodynamics

Answer 20

• Training is a potent stimulus to the cardiovascular system
• Endurance training is associated with:
• Increased SV at rest and peak
• Decreased resting, unchanged peak HR
• Increased Q at peak – rest?
• Influence of resistance training less clear but likely similar

• Influence of training in children controversial but likely similar on a
smaller magnitude

Question 21

Mechanistic Basis for Increased Peak VO2: Morphological

Answer 21

• Increased left ventricular dimension and mass
• Increased intraventricular wall thickness?
• Increased posterior wall thickness?

Peak VO2 = cardiac output (Q) * arterio-venous O2 difference (a-vO2 diff)= stroke volume (SV) * heart rate (HR)

Question 22

Mechanistic Basis for Increased Peak VO2: Functional

Answer 22

• Altered SV response pattern

• No influence of training status at rest or
maximal exercise

• Right shifted response pattern

Peak VO2 = cardiac output (Q) * arterio-venous O2 difference (a-vO2 diff)
Balance between O2 delivery and O2 utilisation; can be assessed using NIRS

Question 23

Athlete’s heart: Characterised by?

Answer 23

• Characterised by:
• Bradycardia
• Cardiac hypertrophy
• Cardiomegaly

Question 24

Athlete’s heart: Hypertrophic cardiomyopathy is characterised by:

Answer 24

• Thickening of heart’s walls
• Similar ECG pattern
• 1 in 500 – leading cause of sudden cardiac death in young athletes