Cardiovascular System and Exercise
CV System’s Important Functions During Physical Activity
n
Deliver O2 to active tissues, e.g. muscle
n
Aerates (put O2 into) blood returned to
lungs
n
Transport heat from body’s core to skin
n
Deliver fuel nutrients to active tissues
n
Transport hormones to target organs
Components
of CV System
n
Heart
–
4 chambers/2 pumps
§ Right atrium and ventricle (provide blood to lungs in order to pick up O2
– “pulmonary circulation” pump)
§ Left atrium and ventricle (provide blood to body – “systemic circulation”
pump)
n
Vascular system
§ Arteries – takes O2 to body tissues
§ Capillaries – transfer gases, nutrients, and waste products across
tissues
§ Veins – return unoxgenated blood to heart via one-way action of its
valves
The
Venous System
n
Contains ~ 65% of total blood volume
–
This serves as a reserve for
maintaining appropriate amount of blood in vascular system
n
Potential problem
–
Varicose veins – distension of
superficial veins due to poor circulation
§ In severe cases, these veins become inflamed and degenerate (phlebitis)
§ May be prevented by regular rhythmic -physical activity
n
Active cool-down
–
Important, not only for lactate
removal but also prevention of blood pooling
Blood
Pressure
n
Amount of pressure exerted on the
vascular system
n
Measured by:
–
Systole – pressure exerted on blood vessels upon contraction of the heart
–
Diastole – pressure exerted on blood vessels when heart is relaxed
n
Typical numbers
–
120/80 is an average “good” blood
pressure
–
Hypertension
§ Systolic BP of 140-159 or Diastolic of 90-99 (Stage 1)
§ 160-179 100-109 (Stage 2)
§ >
180 >
110 (Stage 3)
Blood Pressure Response to Exercise
Comparison of Aerobic vs Resistance Training BP’s
Comparison of Upper vs Lower Body Exercise with BP
Body Inversion and
Blood Pressure
n
Devices that allow an individual to
hang upside-down have been used for:
§ Relaxation
§ Facilitate strength-training response
§ Relieve low back pain
* None of these have
been proven by research
n
These devices put extreme pressure
within the eye; should be avoided also in individuals with hypertension
Recovery
Blood Pressure
n
Will decrease upon cessation of exercise
– Systolic
pressure may actually decrease below resting values up to 12 hours
post-exercise
§ Occurs
primarily after light-to-moderate intensity exercise
§ Due to
pooling of blood in lower extremities
§ May be
beneficial for hypertensive therapy
Heart
Function
Heart’s
Blood Supply
n
Coronary circulation
Myocardial
O2 Utilization
n
Heart extracts 70-80% of its O2 need from
coronary vessels at rest
§ Other
tissues can only extract about 25% from available capillaries
n
Mechanical factors that affect heart’s uptake of O2
– Tension
development within myocardium
– Contractility
of heart
– Heart rate
Myocardial
Work
n
How do we measure the heart’s effort?
Rate Pressure
Product (RPP) = SBP x HR
or Double
Product
§
RPP helps predict possibility of
heart problems
§
Typical RPP values:
§ 6000 at rest (HR = 50 bpm; SBP =
120 mmHg)
§ 40,000 during intense exercise (HR
= 200 bpm; SBP = 200 mmHg)
Heart’s
Energy Supply
n
Relies almost exclusively on aerobic metabolism
– Myocardial
fibers have greatest mitochondrial content of any body tissues
– Rely on
energy from glucose, fatty acids, and lactate
§ May get as
much as 50% of its total energy from circulating lactate
§ During
prolonged submaximal exercise, may derive up to 70% of its energy from fat
metabolism
Heart
Regulation
n
Intrinsic control
–
Specialized cells (sino-atrial node)
send out and carry electric signal through the heart on a rhythmic basis
§ i.e. resting HR (60-100 bpm)
n
Extrinsic control
–
Nervous System
§ Sympathetic – speeds up heart and increases contractility
§ Parasympathetic – slows down heart rate
–
Hormonal System
§ Regulates heart function in response to exercise
Electrical
System of Heart
Normal
vs Abnormal HR
n
60-100 bpm – normal range for resting HR
n
< 60 bpm – bradycardia
n
> 100 bpm - tachycardia
How do we follow the Heart’s Electrical Activity?
The
ECG Tracing
Peripheral Inputs to alter HR and BP with Exercise
n
Mechanoreceptors
–
sensors in skeletal muscles that signal the
cardiovascular control center in the medulla to activate changes in blood flow
and heart rate
n
Chemoreceptors
–
sensors in blood vessels joints, and muscles
detect changes in chemical status of body and subsequently signal
cardiovascular control center to elicit appropriate responses
n
Baroreceptors
–
sensors in aortic arch and carotid sinus
respond to changes in pressure. As
pressure increases, vessels stretch causing HR to slow and peripheral blood
vessels to dilate. These receptors are
believed to prevent abnormally high BP
with exercise
–
carotid artery palpation can possibly decrease
HR response
Arrhythmias
n
Irregularities in heart rhythm
– Can occur in
the Atria
– Can occur in
the Junctional Tissue (between atria and ventricles)
– Can occur in
the Ventricles
Atria
ECG Irregularities
Atrial
ECG Irregularities
Atrial
ECG Irregularities
Junctional
ECG Irregularities
Ventricular
ECG Irregularities
Ventricular
ECG Irregularities
Ventricular
ECG Irregularities
Ventricular
ECG Irregularities
n
Ventricular Tachycardia – 3 or more
PVC’s in a row
n
Ventricular Fibrillation – 3 or more
PVC’s with no regularity
– This is a
emergency situation; may lead to stopping of heart
Blood
Distribution
n
Exercise Effect
– Blood
vessels near active muscles will dilate while vessels close to inactive tissues
will tend to constrict
How
is blood flow regulated?
n
Based upon the following equation:
Flow = Pressure ÷ Resistance
n
3 factors
determine resistance to blood flow:
– Viscosity
(or blood thickness)
– Length of
conducting tube
– Radius of
blood vessel (primary factor affecting
flow)
Muscle
regulation of blood flow
n
At rest, one out of 30-40 capillaries remains open in
muscle
n
Remainder of capillaries are available for blood flow
during exercise. These dormant
capillaries serve 3 functions:
– Increase
blood flow when needed
– Increase
blood volume when needed
– Increase
effective surface area for gas (O2 and CO2) and nutrient
exchange in muscle
Cardiovascular Dynamics
During Exercise
n
Cardiac Output – indicator of how well the
cardiovascular system is working
Cardiac Output = HR x Stroke Volume
also
Cardiac Output = VO2 (ml/min) X 100
aVO2
diff
a-VO2
Difference
n
The difference in the amount of
oxygen in the artery vs the vein after blood flows through the muscle.
n
Example: 20 ml O2 – 15 ml O2 = 5
ml O2
Resting
Cardiac Output
n
Approximately 5 liters/min
– Both in
untrained and trained individuals
§ Example
“Untrained”
– C.O. = HR x
SV
= 70 bpm x 71 ml per beat
= 5 liters/min
§ Example
“Trained”
– C.O. = HR x
SV
= 50 bpm x 100 ml per beat
= 5
liters/min
What accounts for Athletic Heart?
n
Increased vagal tone (↑ parasympathetic activity) slows
heart rate and allows for more filling time
n
Enlarged ventricular volume due to bigger heart and improved ability to
stretch
n
More powerful contraction due to bigger heart
Exercise
Cardiac Output
n
Blood flow from heart increases in
direct proportion to exercise intensity
Cardiac Output Response to Exercise
Heart
Rate Response to Exercise
Stroke Volume Response to Exercise
Why doesn’t stroke volume increase linearly?
n
Limitation of available space to fill with blood in
the left ventricle
n
Ability to contract
Cardiac
Output Distribution
n
At rest:
§ 27% of blood goes to liver
§ 22% of blood goes to kidney
§ 20% of blood goes to muscles
§ 4% of blood goes to heart
§ 14% of blood goes to brain
§ 6% of blood goes to skin
§ 7% of blood goes to remainder of
body tissues
n
During Intense Exercise
§ 2% of blood goes to liver
§ 1% of blood goes to kidney
§ 84% of blood goes to muscles
§ 4% of blood goes to heart
§ 4% of blood goes to brain
§ 2% of blood goes to skin
§ 3% of blood goes to remainder of
body tissues