Exercise physiology Flashcards

1
Q

What is the Fick equation?

A
Equation used to calculate the VO2/VO2max 
VO2 = Q x (CaO2 - CvO2)
Where:
- Q = cardiac output 
- CaO2 = arterial O2
- CvO2 = venous O2
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2
Q

What is the VO2 of a healthy 70kg male?

A

250 ml/min

3.6 ml of O2 consumed/min for each kg

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3
Q

What is VO2 max?

A

highest O2 uptake during dynamic exercise

reached when O2 consumption remains at a steady state despite increase in workload

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4
Q

What is anaerobic/lactate threshold?

A

the point where lactate begins to accumulate in the blood

*lactic acid is produced faster than it is metabolised leading to metabolic acidosis

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5
Q

What adjustments occur in the cardiovascular system during exercise?

A
  1. rise of cardiac output –> SV + HR

2. redistribution of blood to active muscles

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6
Q

Where is there an increase in HR and vasoconstriction during exercise?

A
  • 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)
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7
Q

Why does the heart remodel as a long-term consequence of exercise?

A
  • heart adapts to sustained increase in BP

- physiological change (increased cardiomyocytes + muscles mass)

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8
Q

Compare heart remodelling in an athlete’s heart and a failing heart.

A

Athlete’s heart:

  • increased muscle mass
  • normal cardiac function
  • reversible

Failing heart:

  • increased muscle mass
  • reduced cardiac function
  • irreversible (cell death leading to fibrosis)
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9
Q

Why does bradycardia occur in athletes?

A
  • volume-induced cardiac hypertrophy
  • increased resting EDV and SV
  • causes reduction in HR
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10
Q

Compare distribution of blood to the muscles at rest and at maximal exercise.

A

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

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11
Q

Explain systemic mechanisms regulating distribution of blood.

A
  • 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)
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12
Q

Explain local mechanisms regulating distribution of blood.

A
  • 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)
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13
Q

How does MAP change during exercise?

A
  • 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
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14
Q

What adjustments to the resp system occur during exercise?

A
  • 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
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15
Q

How does oxygen delivery to cells change during exercise?

A
  • during exercise there is increased CO2, increased H+ and increase in temperature
  • this reduced HbO2 binding affinity and therefore facilitates O2 delivery to cells
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16
Q

What stimulates chemoreceptors during exercise?

A

Build up of CO2 –> major drive for ventilation

Plasma [K+] also increases during exercise = extra stimulus to peripheral chemoreceptors