Exercise physiology Flashcards
What is the Fick equation?
Equation used to calculate the VO2/VO2max VO2 = Q x (CaO2 - CvO2) Where: - Q = cardiac output - CaO2 = arterial O2 - CvO2 = venous O2
What is the VO2 of a healthy 70kg male?
250 ml/min
3.6 ml of O2 consumed/min for each kg
What is VO2 max?
highest O2 uptake during dynamic exercise
reached when O2 consumption remains at a steady state despite increase in workload
What is anaerobic/lactate threshold?
the point where lactate begins to accumulate in the blood
*lactic acid is produced faster than it is metabolised leading to metabolic acidosis
What adjustments occur in the cardiovascular system during exercise?
- rise of cardiac output –> SV + HR
2. redistribution of blood to active muscles
Where is there an increase in HR and vasoconstriction during exercise?
- HR is kept low by the action of the parasympathetic nervous system
- partial vasoconstriction arises from activity of the sympathetic nervous system
- in exercise there is a reduction in activity of the PNS and increase in activity of the SNS leading to increased HR and increased vasoconstriction
The effect of this is increased venous return, increased EDV/preload and increased stroke volume (Starling’s Law)
Why does the heart remodel as a long-term consequence of exercise?
- heart adapts to sustained increase in BP
- physiological change (increased cardiomyocytes + muscles mass)
Compare heart remodelling in an athlete’s heart and a failing heart.
Athlete’s heart:
- increased muscle mass
- normal cardiac function
- reversible
Failing heart:
- increased muscle mass
- reduced cardiac function
- irreversible (cell death leading to fibrosis)
Why does bradycardia occur in athletes?
- volume-induced cardiac hypertrophy
- increased resting EDV and SV
- causes reduction in HR
Compare distribution of blood to the muscles at rest and at maximal exercise.
Rest: 20-25% of resting CO distributed to muscles (~1 L/min)
Maximal exercise: 80-90% increase in CO to muscles (~22L/min)
- brain: 750 –> 750; heart: 250 –> 1000
Explain systemic mechanisms regulating distribution of blood.
- increased sympathetic outflow to heart + systemic resistance levels
- adrenergic receptors:
1. alpha: vasoconstriction in gut and veins
2. beta1: increased rate and force of myocardial contraction
3. beta2: relax muscles, increase ventilation and O2 uptake and vasodilation of blood vessels (esp. to skeletal muscles)
Explain local mechanisms regulating distribution of blood.
- involves blood vessels or surrounding tissues
- endothelial/myogenic mechanisms: NO relax smooth muscle cells resulting in vasodilation
- -> tissue factors: adenosine + inorganic phosphates, CO2, H+ and K+(released from contracting muscles)
How does MAP change during exercise?
- Total peripheral resistance reduces (~ 1/3 of resting resistance) –> reduces diastolic pressure
- Mean arterial pressure = (CO x TPR) + CVP
- reduced TPR is offset by increased CO
- MAP increases only slightly
What adjustments to the resp system occur during exercise?
- Pulmonary ventilation increases form 8l/min to 100l/min
- increase in ventilation due to increased respiratory rate and tidal volume (increased minute ventilation)
- in moderate exercise increased ventilation is proportional to work done
- in heavy exercise increased ventilation is not proportional to work done
How does oxygen delivery to cells change during exercise?
- during exercise there is increased CO2, increased H+ and increase in temperature
- this reduced HbO2 binding affinity and therefore facilitates O2 delivery to cells