Exam 3- Lecture 17 & 18 Flashcards
2 major factors that influence endurance performance
- maximal capacity to utilize oxygen (reflected by VO2max, sets upper limit)
- Exercise intensity at lactate threshold (approximates max work-rate that can be maintained for prolonged periods)
Enhancement of maximal exercise capacity
- enhancement of VO2max in healthy persons primarily due to increased cardiovascular capacity
- improved ability to deliver oxygen to the active muscle
Submaximal exercise capacity
- enhanced capacity for prolonged submaximal exercise strongly related to factors inhaling aerobic capacity of trained muscle
- A consequence of structural and metabolic adaptations in muscle
Degree of VO2max improvement is inversely linked to…
initial fitness level
VO2 max =
maximal CO x max a-v O2 difference
enhance VO2max with training is due to increases in
- max CO
- max a-v O2 difference
how does max CO increase?
- max HR does not change with exercise training
- rise in max CO is completely due to augmented max SV
HR response to training
- At rest: decreases due to greater vagal tone
- Max HR doesn’t change much –> allows for more ventricular filling time
- HR at any submax VO2 is less
SV response to training
- Rest: higher after training
- Max SV is higher
- SV at any given submax VO2 is higher
What factors contribute to augmented max SV?
- Increased ventricular chamber volumes results in increased EDV and eccentric hypertrophy (greater left ventricular muscle mass)
- Enhanced blood volume (preload factor)
- Time course - BV, PV, and RBC
Athlete’s Heart
Increased heart mass
Normal cardiac function
Reversible
Failing Heart
Increase heart mass
Reduced cardiac function
Irreversible cell death and fibrosis
Increased mortality
Endurance athlete’s heart
- thickening of LV walls
- LV dilation
Practical implications of changes in HR-VO2 relationship after training
- When a person endurance trains, HR after any given absolute workload will decrease after training
- Fall in HR at submax workload is a common marker for a training effect
When HR at absolute workload decreases due to training, how can you continue to achieve training HR?
adjust absolute workload upwards
What occurs to myocardial oxygen consumption after training?
- it is likely reduced at rest and at any submaximal exercise intensity
(indexed by RPP) - HR x SBP
- Beneficial for patients with exertion anginal symptoms
Is cardiac output affected by exercise training?
- No
SV increases but HR decreases
factors that contribute to increased max a-v O2 difference with training
- greater delivery of blood to the active muscle at max exercise
- enhanced diffusion capacity for oxygen at the active muscle (increased surface area available for exchange and capillary density)
- increased aerobic capacity of the active muscle
- increased vasodilation in active muscle and redistribution of blood flow
What is the primary reason why the ability of the heart to pump is believed to be the limiting factor in VO2 max?
- Sympathetic activity to muscle vasculature is still present at maximal exercise
- brain must limit vasodilation of the active muscles or blood pressure would fall because the heart couldn’t keep up with fall in vascular resistance
CV Adaptation to exercise training summary- At a given absolute submaximal workload:
- same CO
- Same a-v O2 difference
- lower HR
- increased SV
- Same VO2 (assuming the economy of movement hasn’t changed)