2 - Exercise (In Progress)

Question 1

Objectives: Define VO₂-Max and describe it as an indicator of a person’s ability to perform strenuous exercise over an extended period

Answer 1

• VO₂ Max: Can be used to represent person’s ability to perform vigorous exercise
  
  • VO₂ = Oxygen Uptake (Δ between O2 inhaled/O2 exhaled)
  • VO₂ Max = Highest rate of O₂ consumtpion that can be achieved during maximal (exhaustive) exercise
• Measure: Determined using a graded exercise test; plateau = VO2 Max

Question 2

Objectives: Explain how VO₂-Max is affected by age, genetics, and trianing

Answer 2

• Genetics: 25-50% variance observed
• Fitness Level: Extensive training can increase VO2-Max by 15 - 20%
• Age: Peaks at ~ 18 yrs
• Gender: (non-athletes) Males greater (~20%); less when comparing elite athletes
• Body Mass: Skeletal Muscle consumes more O₂ than fat

Question 3

Objectives: Compare the relative importance of the following in limiting VO2 Max:

Respiratory Fx

Cardiovascular Fx

Capacity of Skeletal Muscle to Utilize Delivered O2

Answer 3

• Most important = Cardiovascular Function

Question 4

Objectives: Decrribe the effects of steadily increasing levels of exercise on:

VO₂ (Oxygen Uptake)

Minute Ventilation

Tidal Volume

Breathing Rate

PaCO2

Arterial pH

PaO2

Answer 4

• VO₂ (Oxygen Uptake): Increases linearly until plateau is reached at maximal effort
• Minute Ventilation (V_E): Ventilation increases linearly for 2/3 time, then disproportionately increase at ventilatory threshold
• Tidal Volume: Increase ~ 60% of vital capacity @ max
• Respiratory Rate: Increase ~ 40-50 BPM @ max
• PaCO2: Remains relatively constant, UNTIL ventilatory threshold; which causes increase in lactate, and increase hyperventilation, lowering PaCO2 (this will eventually fail, see below)
• Arterial pH: Remains relatively constant, UNTIL ventilatory threshold; when pH decreases due to inability of compensation to fully clear metabolic acidosis
• PaO2: Relatively constant

Question 5

Objectives: Describe the role of central command in regulating cardiopulmonary responses to exercise

Answer 5

• Initial change happens too quick to be related to metabolic changes
• Central Command Mechanism works through hypothalamus and medulla to sympathetically activate:
  
  • Heart (also parasympathetic inhibition)
    
    • Increase: HR, Inotropy, Lusitropy
  • Adrenals
    
    • Catecholamine Release
  • Blood Vessels
    
    • Arterial / Venous Constriction
• Enhances motor cortex in parallel

Question 6

Objectives: Describe the effects of exercise intensity on:

Cardiac Output (CO)

Heart Rate (HR)

Stroke Volume (SV)

Blood Pressure

Systemic Vascular Resistance (SVR)

O₂ Extraction

Answer 6

• CO - Increase (SVxHR) both increase
• HR - Increase (max decreases with age)
  
  • 1st decrease in Vagal tone
  • 2nd increase in Sympathetics
• SV - Increase (~max 50%), plateeau then may decline at very high levels of activity
• BP:
  
  • Systolic:
  • Diastolic:
• SVR - Decrease due to vasodilation
• O2 Extraction -

Question 7

Objectives: Describe the mechanisms that mediate cardiovascular adaptations during exercise

Answer 7

• Cardiovascular
  
  • Early - Activation of Motor / CV Centers
  • Delayed - Mechanical / Chemical Signals
• Autonomic Nervous System Activation
  
  • Increase Sympathetic
  • Decrease Parasympathtic
• Mechanical Mechanisms
  
  • Muscle Pump Activity - Increase CO
  • Respiratory Activity - Enhanced blood-Q to heart
• Metabolic Mechanisms
  
  • Release of vasodilators after onset of contraction
    
    • Increases blood flow to muscle
• Hormones
  
  • Sympathetic Stimulation

Question 8

Objectives: Descrie changes in organ blood flow at different intensities of exercise

Question 9

Objectives: Describe effects of endurance training on cardiovascular function

Question 10

How does V/Q matching change with exercise?

Answer 10

Pulmonary blood flow increases, more pulmonary vessels are recruited

V/Q Matching is improved during exercise

Question 11

What are the major influences the hypothalamus exerts on the body at the onset of exercise (or even anticipation)?

What modulates these signals?

Answer 11

• Hypothalamus Impact:
  
  • Decrease Parasympathetics
  • Increase Sympathetics
• Modulation:
  
  • Afferent Signals from mechanoreceptors / chemoreceptors in joints / muscles
  • Central Command feed-forward mechanisms