Cardiorespiratory responses to exercise (Year 2) Flashcards
Respiratory Volume Parameters:
- 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
Ventilation during Exercise:
- 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
Cause of hypoxemia in Athletes
- IncreasedO2extraction→decreasedPO2invenous blood
- Increased cardiac output→decreased transit time
- CombinedeffectismoreO2needs to be taken up in less time
- If this isn’t achieved→hypoxemia
Adaptions to endurance training?
- 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
Respiratory Muscle Fatigue and exercise tolerance?
- 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
Respiratory Muscle Training:
- 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
Heart rate Variability?
• 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
Factors affecting heart rate variability: Non-Influenceable Physiological parameters
Age, gender, circadian rhythm, genetics
Factors affecting heart rate variability: Diseases
Sepsis, heart disease, lung diseases,
renal diseases, psychiatric diseases,
metabolic diseases
Factors affecting heart rate variability: Influenceable Lifestyle Factors
Physical fitness, sporting activity, increased
body weight, smoking, alcohol abuse
Factors affecting heart rate variability: External Factors
Noise, night shift work, harmful
substances, medications
Heart rate variability and posture: standing up?
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)
Cardiovascular hemodynamics?
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
Effect of pH, CO2 and O2 on the CV system?
- 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
Stroke volume
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)
