Exercise physiology 7

S
Cardiovascular System
and Exercise

Cardiovascular System
S Functions during physical activity includes:
S Oxygen delivery
S Blood aeration
S Thermoregulation
S Nutrient delivery
S Hormone Transportation

Components of the Cardiovascular
System
S Heart
S Arteries
S Capillaries
S Veins

Cardiovascular Dynamics During
Exercise
S Parameters
S Heart Rate
S Stroke Volume
S Cardiac Output
S Blood Pressure
S Blood Flow
S Blood

Heart Rate
S Defined as the number of beat per unit of time, usually
expressed in beats per minute.
S Ones heart rate can be determined through:
S Palpation
S Auscultation
S Heart Rate Monitor
S ECG Recorder

Heart Rate
S Resting Heart Rate Values
S Averages 60 – 80 beats/min
S Averages 28 – 40 beats / min - highly conditioned, endurance trained
athletes
S Secondary to increase in vagal tone
S Affected by environmental factors, it increases with extremes in
temperature and altitude
S Best taken when totally relaxed, such as early mornings.
S Heart Rate During Exercise
S HR increases directly in proportion to the increase in exercise intensity

Heart Rate
S Moving towards maximal intensity, the HR starts
to plateau even with further increase in exercise
intensity.
S This indicates that HR is reaching a maximum
value.
S Maximum heart rate (HRmax) is the highest HR
value achieved in an all out effort to the point of
exhaustion.

Heart Rate
S HR max can be estimated based on age because of
a slight but steady decrease of about one beat per
year beginning at age 10 – 15 years
S Equations:
S HRmax = 220 – age
S HRmax = 208 – (0.7 X age)

Heart Rate
S If intensity is held at a submaximal intensity, HR
increases fairly rapidly until it reaches a plateau.
S This plateau is the steady state HR.
S This is an optimal HR for meeting the circulatory
demands at that specific rate of work.
S Valid predictor of cardiorespiratory fitness
S A lower steady state HR reflects a greater
cardiorespiratory fitness.

Stroke Volume
S Defined as the volume of blood pumped from
one ventricle of the heart with each beat.
S Determinants of SV:
S Preload
S Ventricular Distensibility
S Ventricular Contractibility
S Afterload

Stroke Volume
S SV increases above resting values during exercise.
S Untrained: 60 – 70 ml/ beat @ rest to 110 – 130
ml/beat during maximal exercise.
S Highly trained endurance athletes: 80 – 100ml/beat
@ rest to 160 – 200 ml/ beat during maximal
exercise.
S Percentage increase can be determined by body
position.

Stroke Volume
S Contributing Factors for increase:
S Frank Starling mechanism
S States that the stroke volume of the heart increases in response to
an increase in the volume of blood filling the heart. The increased
volume of blood stretches the ventricular wall, causing cardiac
muscle to contract more forcefully.
S Increased contractility
S Increased neural stimulation
S Increased release of circulatory catecholamines
S Decreased afterload

Cardiac Output
S Defined as the volume of blood pumped by
the heart per minute (L/min).
S CO is the product of HR and SV
S CO = HR x SV
S Resting CO is approx. 5 L/min
S Maximal CO varies between 20 (sedentary
person) and 40 (elite endurance athlete)
L/min

Cardiac Output
S One of the major purpose for the increase in CO is to
meet the muscles’ demand for oxygen.
S Ensuring that adequate supply of oxygen and nutrients
reach the exercising muscles, and waste products of
muscle metabolism are removed quickly.

Blood Pressure
S Pressure exerted by circulating blood against the wall of
the blood vessels.

Blood Pressure
S During dynamic exercise mean arterial blood pressure
(MAP – average pressure exerted by the blood as it
travels through the arteries) increases substantially.
S Rhythmic whole body endurance exercise increases
systolic blood pressure in direct proportion to the
increase exercise intensity.
S Diastolic pressure does not change significantly, and
may even decrease.

Blood Pressure
S Blood pressure responses to resistance exercise is
exaggerative.
S High intensity resistance training, blood pressure can
reach 480/350 mmHg.
S Because of the sustained muscular force which
compresses the peripheral arterioles, considerably
increasing resistance to blood flow.

Blood Pressure
S Blood pressure increases more in rhythmic arm compared with
rhythmic leg exercise.
S The smaller arm muscle mass and vasculature offers greater
resistance to blood flow than the larger and more vascularized
lower – body region.
S The difference between the systolic blood pressure during upper
and lower body exercise has important implications for the heart.
S Myocardial oxygen uptake and myocardial blood flow are directly
related to the product of HR and systolic blood pressure [rate
pressure product/ double product (DP = HR X SBP)]

Blood Pressure
S In Recovery
S After a bout of sustained light to moderate intensity
exercise, systolic blood pressure temporarily decreases
below pre exercise levels for up to 12 hours in normal and
hypertensive individuals.

Blood Flow
Exercise Effects
S Acute changes in CO and BP during exercise allows for
an increase in total blood flow to the body.
S This facilitates getting blood flow to the exercising
muscle.
S Additionally, sympathetic control of the cardiovascular
system can redistribute blood to areas of greatest
metabolic need.

Blood Flow
Blood Flow Regulation
S Pressure differentials and resistances determine fluid
movement through the vessel.
S Resistance varies directly with the length of the vessel
and inversely with its diameter.
S Flow = Pressure ÷ Resistance

Blood Flow
S Three factors determine resistance to blood flow:
S Viscosity or Blood thickness
S Length of conducting tube
S Radius of blood vessel
S Poiseuille’s Law expresses the general relationship
between pressure differential (gradient), resistance, and
flow in a cylindrical vessel:
S Flow = Pressure gradient × Vessel radius4 ÷ Vessel length ×
Fluid viscosity

Blood Flow
S Blood viscosity and transport vessel length remains relatively
constant in the body.
S Blood vessel radius represents the most important factor affecting
blood flow.
S Resistance to blood flow changes with vessel radius raised to the
fourth power (reducing a vessel’s radius by one half decreases
flow by a factor of 16, conversely doubling the radius increases
volume 16 fold).
S This means that a relatively small degree of vasoconstriction or
vasodilation can dramatically alter regional blood flow.

Blood
S Blood is the fluid of life, growth and health.
S As metabolism increases during exercise, the function of
the blood becomes more critical for optimal performance.
S At rest the blood’s oxygen content varies from 20 ml of
oxygen per 100 ml of arterial blood to 14 ml of oxygen
per 100 ml of venous blood.

Blood
S The difference between these two values is referred to as
the a-v O2 difference.
S With increasing exercise intensity, the a-v O2 difference
increases progressively and can increase approximately
threefold from rest to maximal exercise intensities.

Blood
S With the onset of exercise there is almost an immediate
loss of plasma from the blood to the interstitial space.
S Approx. 10 – 15% reduction in plasma volume can occur
in prolonged exercise and with brief bouts of exhaustive
exercise.

Blood
S If exercise intensity or environmental conditions cause
sweating, additional plasma volume is lost.
S For prolonged duration activities in which dehydration occurs and
heat loss is a problem, a reduction in plasma volume will impair
performance.
S When plasma volume is reduced, hemoconcentration occurs.
S Increases red blood cell concentration substantially (20% – 25%)
S Hematocrit increases from about 40% - 50%.
S Total volume and number of red blood cells do not change
substantially.
S Increases the blood’s oxygen carrying capacity during exercise.

S
Respiratory System
and Exercise

Pulmonary Structure and
Function

Lung Volumes and Capacities
S Static Lung Volumes
S Evaluates the dimensional component for air movement
within the pulmonary tract and impose no time limitation on
the individual.
S Dynamic Lung Volumes
S Evaluates the power component of pulmonary performances
during different phases of the ventilatory excursion.

Static Lung Volumes
Lung Volume/
Capacity
Definition Average Values
(mL)
Male
Female
Tidal Volume (TV) Volume inspired or expired per breath. 600 500
Inspiratory Reserve
Volume (IRV)
Maximum inspiration at end of tidal inspiration. 3000 1900
Expiratory Reserve
Volume (ERV)
Maximum expiration at end of tidal expiration. 1200 800
Inspiratory Capacity
(IC)
Maximum volume inspired after tidal
expiration.
3600 2400
Functional Residual
Capacity (FRC)
Volume in lungs after tidal expiration 2400 1800
Forced Vital
Capacity (FVC)
Maximum volume expired after maximum
inspiration
4800 3200
Residual Lung
Volume (RLV)
Volume in lungs after maximum expiration. 1200 1000
Total Lung Capacity
(TLC)
Volume in lungs after maximum inspiration 6000 4200

Dynamic Lung Volumes
S Normal values for vital capacity can exist in severe lung
disease if no time limit is present to expel air.
S Hence, why a dynamic lung function measure such as
percentage of the FVC expelled in 1 second (FEV1.0) serves
as a more useful diagnostic purpose than static measures.
S Forced Expiratory Volume to Forced Vital Capacity Ratio
(FEV1.0 / FVC)
S Reflects the expiratory power and overall resistance to air
movement in the lungs.
S Normally this averages 85% of the vital capacity.

Dynamic Lung Volume
S Maximum Voluntary Ventilation
S This dynamic assessment of ventilatory capacity requires
rapid, deep breathing for 15 seconds.
S This 15 second volume is then extrapolated to the volume
breathed for 1 minute.
S Healthy young men: 140 – 280 L/min
S Healthy young women: 80 – 120 L/min

Pulmonary Ventilation
S Pulmonary Ventilation – Describes how ambient air moves into and
exchanges with air in the lungs.
S Minute ventilation – Volume of air breathed per minute.
S Minute ventilation = Breathing rate × Tidal Volume
S Alveolar ventilation – Refers to the portion of the minute ventilation that
mixes with the air in the alveolar chamber.
S Anatomic dead space – Portion of the air that does not enter the alveoli and
engage in gaseous exchange with the blood. 150 – 200 mL or ~30 % of the
resting TV.
S Physiologic dead space – Portion of the alveolar volume with poor tissue
regional perfusion or inadequate ventilation. This can increase to 50% of
the resting TV.

Relationship amongst Tidal Volume, Breathing Rate, and Minute and Alveolar
Minute Ventilation
Breathing
Condition
Tidal Volume
(mL)
×
Breathing
Rate
(breaths/min)
=
Minute
Ventilation
(mL/min)
-
Dead Space
Ventilation
(mL/min)
=
Alveolar
Ventilation
(mL/min)
Shallow 150 40 6000 150 × 40 0
Normal 500 12 6000 150 × 12 4200
Deep 1000 6 6000 150 × 6 5100

Partial Pressure of Gases
S Partial Pressure – Individual pressures from each gas in a
mixture.
S The air breathed is a mixture of gases; and each exerts a
pressure in proportion to its concentration in the gas mixture.
S Dalton’s Law – the total pressure of a mixture of gases equals
the sum of the partial pressures of the individual gases in that
mixture.
S Partial pressure = Percentage concentration × Total pressure of
gas mixture (standard atmospheric pressure)

Movement of Gas
S According to Henry’s Law
S Gases dissolves in liquids in proportion to their partial
pressures, depending also on their solubilities in specific
fluids and on the temperature.
S The amount of gas dissolved in a fluid depends on two
factors
S Pressure differential between the gas above the fluid and
dissolved in it
S Solubility of the gas in the fluid.

Gas Exchange
S Oxygen Exchange
S PO2 = 159 mmHg of ambient air
S PO2 = 105 mmHg when inhaled and enters the alveoli. Due to
the increased water vapor pressure and increased partial
pressure of carbon dioxide in the alveoli.
S PO2 = approx. 40 mmHg in the pulmonary capillaries
S Fick’s Law
S States that the rate of diffusion through a tissue such as the
respiratory membrane is proportional to the surface area and the
difference in the partial pressure of gas between the two sides of
the tissue. The rate of diffusion is also inversely proportional to the
thickness of the tissue in which the gas must diffuse.

Gas Exchange
S Carbon Dioxide Exchange
S Moves along a pressure gradient
S PCO2 = 40 mmHg in the alveoli
S PCO2 = 46 mmHg in the venous blood

Partial Pressure of Respiratory
Gases at Sea Level
Partial Pressure (mmHg)
Gas % in dry
air
Dry air Alveolar
air
Arterial
Blood
Venous
Blood
Diffusion
Gradient
Water 0.00 0.0 47 47 47 0
Oxygen 20.93 159.1 105 100 40 60
Carbon
Dioxide
0.03 0.2 40 40 46 6
Nitrogen 79.04 600.7 568 573 573 0
Total 100.00 760 760 760 706 0

S
Transport of Oxygen
and Carbon Dioxide in
the Blood

Oxygen Transport
By two means:
S Combined with hemoglobin
S Dissolved in blood plasma
S 3 ml dissolved in every L of plasma
S If total blood plasma is 3 – 5 L only 9 – 15 ml can be carried
in the dissolved state.

Hemoglobin Saturation
S Each molecule of hemoglobin can carry 4 molecules of
oxygen. The combine molecule is termed oxyhemoglobin.
S Binding depends on:
S Partial pressure of oxygen in the blood
S Bonding strength, affinity between haemoglobin and
oxygen.

Blood Oxygen Carrying
Capacity
S The oxygen carrying capacity of blood is the maximal
amount of oxygen the blood can transport.
S Dependent on:
S The blood hemoglobin content
S 100 ml of blood – 14 to 18 g of Hb (men), 12 – 16 g of Hb
(women).
S Each gram of Hb can combine with about 1.34 ml of
oxygen, hence the oxygen carrying capacity of blood is
approx. 16 – 24 ml per 100 ml of blood

S At rest: Blood is in contact with the alveolar air for
approximately 0.75 secs.
S With exercise: the contact time is greatly reduced…

Carbon Dioxide Transport
S Carbon dioxide is carried in the blood in three forms:
S As a bicarbonate
S Dissolved in plasma
S Bound to hemoglobin (carbaminohemoglobin)

Bicarbonate Ion
S Majority carried in this form, accounting for the transport of 60% to 70% of
the carbon dioxide in the blood.
S Carbon dioxide and water combines to give carbonic acid; catalyzed by
the enzyme carbonic anhydrase.
S Carbonic acid is unstable and quickly dissociates, freeing the hydrogen
ion and forming a bicarbonate ion.
S The free hydrogen can bind to hemoglobin triggering off the Bohr effect.
S Bicarbonate diffuses into the plasma.
S When blood enters the lungs where the partial pressure of oxygen is
lower, the reverse holds true.

Dissolved Carbon Dioxide
S Only approximately 7% to 10% of the carbon dioxide
released from the tissues dissolves in plasma.
S The dissolved form comes out of solution when its partial
pressure is low as in the lungs.
S Here it diffuses from the pulmonary capillaries into the
alveoli to be exhaled.

Carbaminohemoglobin
S Binding of the gas to hemoglobin will give
carbaminohemoglobin.
S So named because it binds to the amino acids in the
globin part of the Hb molecule.
S No competition with oxygen when binding, however
binding varies with the oxygenation of the Hb and the
partial pressure of carbon dioxide.

Gas Exchange in Muscle
S Arterial venous oxygen
difference.
S Oxygen transport in muscle.
S Myoglobin

Factors Influencing Oxygen
Delivery and Uptake
S Oxygen Content in blood
S Blood Flow
S Local Conditions

Pulmonary Ventilation During
Dynamic Exercise
S Onset of exercise is accompanied by an immediate
increase in ventilation, followed by a more gradual
increase, then a slow rate steady decrease to resting
values.
S Respiratory recovery takes several minutes suggesting
that:
S The rate of breathing does not perfectly match the metabolic
demands of the tissue.
S Post exercise is regulated primarily by acid base
balance, partial pressure of dissolved carbon dioxide, and
blood temperature.

Ventilatory Response to
Exercise

Breathing Irregularities During
Exercise
S Dyspnea
S Common among individuals in poor physical condition.
S Increased levels of carbon dioxide and hydrogen ions
concentration triggers the inspiratory center to increase the
rate and depth of breathing.
S Although sensed as an inability to breathe the underlying
cause is the inability to adjust breathing to blood carbon
dioxide and hydrogen ion concentration.

S Hyperventilation
S Increase in ventilation in excess of that needed for exercise
metabolism.
S Decreases normal partial pressure of carbon dioxide from
40 mmHg to about 15 mmHg.
S Decrease in arterial carbon dioxide concentration, increases
blood pH.
S Resulting in a reduced ventilatory drive

S Valsalva Maneuver
S Closure of glottis  increase intra abdominal pressure 
increase intrathoracic pressure.
S As a result air is trapped and pressurized in the lungs.
S Restricted venous return, reducing volume of blood
returning to the heart, decreasing cardiac output, and
altering arterial blood pressure.

Ventilation and Energy
Metabolism
S Ventilatory equivalent for oxygen (VE/ VO2)
S The ratio between the volume of air expired or ventilated and
the amount of oxygen consumed by the tissues in a given
amount of time.
S Measured in liters of air breathed per liter of oxygen consumed
per minute.
S At rest: 23 to 28 L of air per liter of oxygen
S Mild exercise: Varies little
S Moderate – Near maximal levels: can be > 30 L of air per liter
of oxygen consumed.
S Generally speaking it remains relatively constant over a wide
range of exercise intensities, indicating the control of breathing
is properly matched to the body’s demand for oxygen.

S Ventilatory Threshold
S Point at which ventilation increases disproportionately to
oxygen consumption.
S Reflects the respiratory response to increased carbon
dioxide levels.
S Ventilation increases dramatically beyond this point.

Respiratory Regulation of Acid
- Base Balance
S The metabolism of carbohydrate, fats, or protein produces
inorganic acids that dissociate, increasing the hydrogen ion
concentration in the body fluid  lowering the pH.
S To minimize this effect the blood and muscles contains base
substances that combines with and hence buffer or neutralize
the ion.
S At rest the body fluids have more bases than acids, resulting in
a slightly alkaline tissue (7.1 in muscle to 7.4 in arterial blood).

S Acidosis – occurs with increased levels of H ions.
S Alkalosis – occurs with decreased level of H ions.
S The pH of intra and extra cellular fluid is kept within a
relatively narrow range by:
S Chemical Buffers
S Pulmonary Ventilation
S Kidney Function

Chemical Buffers
S Major chemical buffers:
S Bicarbonate
S Inorganic phosphates
S Protein

S Bicarbonate combines with H ion to give carbonic acid, which
dissociates to give carbon dioxide and water in the lungs.
S In the muscle fibers and kidney tubules H ion is primarily
buffered by phosphates.
S Blood and chemical buffers are required only to transport
metabolic acids from their sites of production to the lungs or
kidneys for removal.
S Once the H ion is transported and removed the buffer molecule
can be re used.

Pulmonary Ventilation
S Increased levels of free H ions
in the blood stimulates the
respiratory center to increase
ventilation.
S Both the chemical buffers and
respiratory system provides
short term means of
neutralizing the acute effects of
exercise acidosis.

Exercise physiology 7

More Related Content

What's hot (20)

Viewers also liked (20)

Similar to Exercise physiology 7 (20)

More from Sheldon Nelson (19)

Recently uploaded (20)

Exercise physiology 7

Editor's Notes