Cardiovascular System Response and Adaptation to Exercise Flashcards
1
Q
Introduction
A
- response describes short term changes which accompany exercise (acute phenomenon)
- adaptations come thru regular training (chronic)
- knowledge of this area crucial to: understand role of exercise physiology in healthcare, fitness, and human performance; interpret diagnostic and functional testing; prescribe exercise in health and disease
2
Q
Summary of Acute Cardiovascular Response to Aerobic Exercise
A
- HR
- SV
- CO
- arteriovenous oxygen difference
- blood flow
- BP
- maximal oxygen consumption
3
Q
Heart Rate
A
- increase in linear fashion during submax dynamic exercise with work rate and oxygen uptake
- max attainable HR typically decreases with age: 220 - age is typically max HR but variance is considerable (SD +/- 10 bpm)
- magnitude of HR response related to age, body position, fitness, type of activity, presence of disease, medications, blood volume, environmental factors such as temp, humidity, or altitude
4
Q
Stroke Volume
A
- equal to difference between EDV and ESV
- EDV dependent upon: HR, filling pressure, ventricular compliance
- ESV dependent on contractility and afterload (amt of blood ejected per ventricular contraction or beat)
- curvilinear increase with exercise
- for most individuals SV reaches near max at 50% aerobic capacity and increase only slightly thereafter
- world class endurance athletes often display increased SV beyond 50% of aerobic capacity
5
Q
Cardiac Output
A
- product of SV x HR
- increases linearly with increased work rate
- resting value of about 5 L/min which increases 4-8 times with exercise
- increase in CO during exercise due to increased HR and SV at intensities up to 50% of VO2max and increases thereafter almost entirely secondary to increased HR
- maximum values for CO depend on many factors: age, posture, body size, presence of disease, level of conditioning
6
Q
Arteriovenous Oxygen Difference
A
- reflects difference in oxygenation in blood
- at rest: arterial blood ~20 ml O2/100ml/dl; venous blood ~15 ml O2/100ml/dl
- thus difference is 5 ml
- approximates an O2 use coefficient of 25%
- during exercise to exhaustion: venous oxygen level decreases to 5 ml O2/100ml/dl or lower
- thus widens a vO2 difference
- corresponds to a use coefficient of ~75%
7
Q
Blood Flow
A
- SM receives a 15-20% of CO at rest
- remainder goes to viscera, heart, brain, etc
- SM receives as much as 85-90% of CO during max exercise: selectively delivered to working MU; shunted away from skin, visceral, hepatic and renal vascular beds
- myocardial BF increases 4-5 times
- supply to CNS remains at resting levels
8
Q
Blood Pressure
A
- directly related to CO and peripheral vascular resistance
- thus provides noninvasive means to measure hearts pumping capacity
- response to exercise measured manually with cuff and stethoscope
9
Q
Blood Pressure Response to Aerobic Exercise
A
- systolic BP: linear increase with exercies intensity; 8-12 mmHg per MET (1 MET=3.5 mlO2/kg/min); max levels typically reach 190-220 mmHg; aerobic max > 260 mmHg contraindicated
- diastolic BP: remains unchanged or decreases slightly; thus pulse pressure (SBP-DBP) generally increases proportionally to intensity; if DBP increases during exercise ventricular filling not very effective and should slowly stop exercise
10
Q
Abnormal BP Response
A
- SBP that fails to increase or decrease with change in intensity may indicate plateau or decrease in CO (not good)
- terminate exercise testing if participant demonstrates exertional hypotension: SBP toward end of test below baseline standing level and/or SBP decreases 20 mmHg or more during exercise after initial rise
- this response shown to correlate with myocardial ischemia, left ventricular dysfunction or increased risk of cardiac events
- one study men with max SBP < 140 mmHg: 15 fold increase in annual rate of sudden death compared with those whose pressures > 200 mmHg
11
Q
Maximal Oxygen Consumpton
A
- VO2max most widely recognized measure of CP fitness/function
- defined as highest rate of oxygen transport and use achieved at max physical exertion
- may be expressed as VO2 = HR x SV x (a-VDO2) where a-VDO2 is arteriovenous oxygen difference
- apparent VO2 magnitude affected by both central factors and peripheral factors
- VO2max may be expressed in 2 ways: absolute or relative
- absolute value reflects total body energy output and caloric expenditure
- relative allows more fair comparison: individuals have different body masses, large absolute O2 consumption secondary to large muscle mass
- contrast the increase in O2 transport and use: 10 fold increase for sedentary guy, 23 fold increase for WC endurance athlete
- increased aerobic capacity derives primarily from increased max CO: greater relative increase in HR and SV rather than increased peripheral O2 extraction
- thus VO2max virtually defines heart’s pumping capacity
12
Q
Cardiovascular Responses to Dynamic Aerobic Exercsie
A
- steady state: condition which energy expenditure is balanced with energy required
- the factors responsible for energy supply reach a level of elevated equilibrium
13
Q
Short-Term, Light to Moderate Submaximal Aerobic Exercise
A
- following variables increase rapidly at onset of exercise and reach steady state within 2 minutes: CO, SV, SBP, rate pressure product (RPP)
- peripheral resistance decreases rapidly then plateaus
- DBP remains relatively unchanged
14
Q
Long-Term, Moderate to Heavy, Submaximal Aerobic Exercise
A
- cardiovascular drift: changes in observed CV variables that occur during prolonged, heavy submax exercise without a change in workload
- linked to increased body temperature during prolonged exercise
- following variables increase rapidly: CO, SV, HR, SBP, rate pressure product
- SBP and TPR may drift downward with prolonged, heavy exercise
15
Q
CV Response to Aerobic Exercise
A
- decrease in TPR: allows greater blood flow to working muscles; prevents excessive rise in SBP
- BV decreases during heavy aerobic exercise: biggest loss is during 1st 10 minutes of activity; 10% loss not uncommon
