Cardiorespiratory system

Question 1

Responses to acute exercise

Answer 1

increases blood flow to working muscles to achieve a higher VO2 max

Question 2

Heart rate

Answer 2

Resting heart rate
- Normal ranges
Untrained RHR- 60-80 beats/min
trained RHR: as low as 30-40 beats/min
affected by the neural line, temperature, altitude
- Anticipatory response: HR increases above RHR just before the start of exercise, decreases vagal tone
norepinephrine and epinephrine increase
Response during exercise
- Directly proportional to exercise intensity
Max HR: highest HR achieved in an all-out effort to volitional fatigue
- highly reproducible
- slight decline w/ age
Steady-state HR= point of the plateau, optimal HR for meeting circulatory demands at a given sub-max intensity
- if the intensity increases, so does steady state HR. Adjustment to new intensity takes 2-3 min
Steady-state HR basis for simple exercise tests estimating aerobic fitness and HR max.

Question 3

Stroke volume

Answer 3

• Increases with intensity to 40-60% VO2 max
• Beyond this, plateau to exhaustion
• Possible exception: elite endurance athletes
  Max exercise SV= double standing SV
  But max exercise SV is only slightly higher than supine SV
  Supine SV is much higher than standing SV
  Supine end-diastolic volume > standing EDV

Question 4

Factors that increase Stroke volume

Answer 4

• increase preload: EDV stretch
  
  • increase in EDV= increase in contraction strength
    Frank - starling mechanism= increase preload: stretch myocardium
• Increase contractility: inherent ventricle property
• Increase norephedrine or epinephrine= increase force of contraction
  Independent of EDV
• Decrease afterload: aortic resistance

Question 5

Stroke volume changes during exercise

Answer 5

• an increase of preload at lower intensities: increase of SV
• venous return: increase EDV: increase of preload
  Muscle and respiratory pumps, venous return
  Increase in HR: decrease of filling time: slight decrease in EDV; decrease in SV
• Increase contractility at higher intensities: increase SV
• Decrease afterload via vasodilation: increase SV

Question 6

Cardiac output

Answer 6

Q= HR x SV
- increase with intensity (plateau near VO2 max)
Normal values
resting Q= 5 L/min
untrained Q max= 20 L/min
Trained Q max= 40 L/min
Q max a function of body size, aerobic fitness

Question 7

Blood pressure

Answer 7

• During endurance exercise, an increase in mean arterial pressure, and systolic BP increase proportional to exercise intensity
• Diastolic BP slightly decrease or slightly increases at max exercise
  
  • MAP= Q x Total peripheral resistance
• Q increase, TPR decrease slightly
  Muscle vasodilation vs sympatholytic
• Related to myocardial O2 uptake and myocardial blood flow
  Resistance exercise
• resistance exercise: periodic large increases in MAP up to 480/350 mmHg
  More common when using valsaliva manoeuvre

Question 8

Blood

Answer 8

Constituent and plasma volume
- plasma (55-60% of blood volume)
- Can decrease by 10% with dehydration
- Can increase by 10% with training and heat acclimation
Capillary fluid movement into and out of tissue
- hydrostatic pressure
- Oncotic, osmotic pressures
Upright exercise: decrease plasma volume
- compromise of exercise performance
- increase of MAP: increase capillary hydrostatic pressure
- Metabolite build-up: increase tissue osmotic pressure
Sweating further decreases plasma volume