L289 Exercise Physiology - Oxygen, Heat and Fluids Flashcards
O2 uptake is ______ dependent
Intensity-dependent
Describe O2 uptake + ex intensity relationship
Linear increase until reach plateau - VO2max
Equation for VO2 max
- VO2 = Q x (CaO2 – CvO2) = CO x AVO2 difference
Describe O2 uptake at the beginning of exercise
• O2 deficit: lag between O2 uptake needed for workload and actual O2 uptake
- In this time, anaerobic energy sources help supplement energy needs
CO + intensity relationship
↑ intensity, ↑CO
With increasing intensity, describe the BF to muscle, kidneys, heart, skin, brain and gut.
- ↑BF to muscle, heart, ↑/= BF to brain
- ↓BF to kidneys, gut
- ↑ then ↓ to skin
Why does BF to kidneys and gut decrease?
- Compensatory VC to redistribute BF where needed
Why does BF to skin increase then decrease?
- Initially ↑BF with ↑ intensity to lose heat
- Until the point where muscle requires BF going to skin - skin then VC ∴ potential for overheating
Hierarchy of BF importance during ex
brain > muscle > skin
What does the hierarchy of BF importance mean for BF to the muscle?
muscle can have ↓BF (VC) if brain perfusion is at risk
small muscle group vs dynamic body ex effect on BP
Small muscle group exercise → ↑↑ BP cw. dynamic all body exercise - because of the ↑ VC
↑BF during exercise is called…
ex hyperaemia
4 plausible mechanisms for exercise hyperaemia
- Metabolic vasodilators from contracting skeletal muscle, endothelium and/or RBCs
- Muscle pump
- “Conducted vasodilation”
- Functional sympatholysis
Muscle pump during ex: important for maintaining what?
VR cw BF
Explain conducted vasodilation
- Local relaxation of smooth muscle through smooth muscle gap junctions
- Relaxation is conducted proximally
Explain functional sympatholysis
- SNS-mediated VC is desensitised in response to metabolic vasodilators
- ↑SNS activity at rest → significant ↑ VC at muscle, but ↑SNS activity during exercise → less significant ↑ VC at muscle
What occurs to HR and systole during incremental ex?
↑HR, ↑SV that plateaus
Explain the increased and levelled off SV during incremental ex
• ↑HR during exercise → shortened diastole
- Because systole relatively fixed
∴ ↑ SV eventually level off, due to impact on diastolic filling
During ex, SBP and DBP mimic what?
SBP mimics CO and DBP mimics peripheral resistance
Therefore, what happens to SBP and DBP during ex?
- ↑CO → ↑SBP
- DBP maintained/falls slightly if TPR falls
What happens to MAP during ex, and why?
exercise → ↑MAP: because of ↑SBP + ↓DBP (i.e. systole becomes larger component of equation)
Why can MAP and HR increase simultaneously during ex?
Because baroreceptors reset to a higher level in exercise
CV responses to prolonged exercise
• CV drift: = ↑HR and ↓SV over time
Which comes first is chicken or egg debate!
Reasons for CV drift during prolonged exercise (4)
- Hyperthermia
- Dehydration
- ↑ plasma [adrenaline]
- Peripheral displacement of BV due to cutaneous vasodilation