Extra

Question 1

Why is Brain blood flow (BBF) Vital? What are functional consequences and the continuum they fall on?

Answer 1

• Survival: Supplies oxygen and substrates to the brain.
• High Demand: Brain is 2-3% of body mass but uses 20% of cardiac output.
• If under/over perfused it can result in Strokes
• Functional Consequences:
  
  • Performance and cognitive function.
  • Impairments linked with diseases (e.g., dementia, stroke, TBI).
  • Prognostic value for cardiovascular mortality
• Continuum of Impairment:
  
  • Acute: Fainting, stroke.
  • Chronic: Hypertension, dementia, concussion/TBI

Question 2

Physical Activity, Ageing, and Brain Health?

Answer 2

• Ageing and Inactivity: Linked to a decline in BBF.
• Habitual Exercise:
  • Offsets age-related decline in BBF (~10-year delay).
  • Positive correlation between aerobic fitness and BBF.

Question 3

Measurement of Brain Blood Flow?

Answer 3

1. MRI (Magnetic Resonance Imaging):
   
   • Structure and functional imaging.
   • High spatial resolution but limited use during exercise.
2. Doppler Ultrasound:
   
   • Measures blood velocity as an index of flow.
   • Advantages: Beat-to-beat changes, robustness, and ease of use.
   • Commonly used with the Middle Cerebral Artery (MCA).
3. NIRS (Near-Infrared Spectroscopy):
   
   • Measures oxygen supply and demand at the capillary level.
   • Assesses brain activation (neurovascular coupling).
   • Portable and robust for exercise studies.
4. Arterial Spin Labelling (ASL):Brain perfusion imaging technique
   
   • Measures cerebral perfusion at rest.
   • Region-specific cerebral blood flow (CBF) analysis.
5. Phase Contrast Angiography: Brain perfusion imaging technique
   
   • Analyzes flux and velocity across cardiac cycles.
   • High spatial resolution but challenging to use during exercise.
     - Should be chosen based on what question is being asked.

Multimodal Approach:
- Combining different imaging methods enhances assessment of brain health.
- Accounts for both structural and functional aspects.

Question 4

Key Regulators of Brain Blood Flow?

Answer 4

1. Blood Pressure - Perfusion pressure
2. Neurogenic - Cerebral SNA
3. Metabolism - links to nerve cell activity
4. Chemical - Arterial PCO2
5. Cardiac Output

Question 5

Large changes in blood pressure can occur during and following exercise…
- What are the consequences for brain blood flow and brain function?

Answer 5

Fainting

Question 6

Brain blood flow responsiveness to CO2?

Answer 6

BBF highly sensitive to changes in arterial partial pressure of carbon dioxide (PaCO2).

During exercise it increases till about 65% vo2 max then declines due to increase hyperventilation and reduction in H+ ions so less Co2 produced in processes

Question 7

BBF Response to Exercises, intensities and modalities?

Answer 7

• Intensity:
  
  • Incremental increase in BBF with mild to moderate exercise (20-80% Wmax).
  • Maximal exercise (90-100% Wmax) may lead to a plateau or decrease due to hyperventilation-induced hypocapnia.
• Modality:
  
  • Different patterns observed between rowing, running, and cycling.
  • Rowing and Running:
    
    • BBF patterns mirror blood pressure profiles.
  • Cycling:
    
    • Shows modality- and fitness-specific profiles at high intensities (>65% VO2max).
• Aquatic Treadmill Exercise:
  
  • BBF changes similar to land running but influenced by hydrostatic pressure.
  • Mechanism: Increased venous return leading to higher cerebral perfusion

Question 8

High-Intensity vs. Moderate Exercise for BBF?

Answer 8

• High-Intensity Interval Training (HIIT):
  
  • BBF decreases during 30s sprints but rebounds immediately after.
  • Associated with enhanced neurotrophic factor circulation.
• Moderate Intensity Continuous Training (MICT):
  
  • Maintains relatively stable BBF throughout.
• Different BBF profiles could indicate varied adaptations from HIIT vs. MICT.

Question 9

Practical Implications for Brain Health?

Answer 9

1. Regular Physical Activity:
   
   • Counteracts age-related BBF decline.
   • Maintains cognitive function and reduces risk of neurodegenerative diseases.
2. Exercise Modality and Intensity:
   
   • Influence the magnitude and pattern of BBF responses.
   • Tailoring exercise prescriptions can optimize brain health benefits.
3. Potential for Targeted Interventions:
   
   • Utilizing exercise to improve neurovascular coupling and cognitive function.
   • Customizing interventions based on fitness levels and health conditions