Effects of exercise on respiration and cardiovascular system.pptx

Effects of exercise on respiratory
and cardiovascular system
Presented by HARSHA J
ASSISTANT PROFESSOR
COLLEGE OF OCCUPATIONAL THERAPY
@medical_sciences_king_1

Effects of exercise on respiration and
cardiovascular system
• EFFECT ON PULMONARY VENTILATION
• Pulmonary ventilation is the amount of air
that enters and leaves the lungs in 1 minute. It
is the product of tidal volume and respiratory
rate. It is about 6 litre/minute, with a normal
tidal volume of 500 mL and respiratory rate of
12/minute.

• During exercise, hyperventilation, which
includes increase in rate and force of
respiration occurs. In moderate exercise,
respiratory rate increases to about 30/minute
and tidal volume increases to about 2,000 mL.
Thus, the pulmonary ventilation increases to
about 60 L/ minute during moderate exercise.
In severe muscular exercise, it rises still
further up to 100 L/minute.

• Factors increasing pulmonary ventilation
during exercise
1. Higher centers
2. Chemoreceptors
3. Body temperature
4. proprioceptors
5. Acidosis.

1. Higher Centers
Rate and depth of respiration increase during the
onset of exercise. Sometimes, before starting the
exercise, thought or anticipation of exercise itself
increases the rate and force of respiration. It is a
psychic phenomenon due to the activation of
higher centers like Sylvian cortex and motor cortex
of brain. Higher centers, in turn accelerate the
respiratory processes by stimulating respiratory
centers.

2. Chemoreceptors
Chemoreceptors which are stimulated by
exercise induced hypoxia and hypercapnea, send
impulses to the respiratory centers. Respiratory
centers, in turn increase the rate and force of
respiration.

3. Proprioceptors
Proprioceptors, which are activated during
exercise, send impulses to cerebral cortex
through the somatic afferent nerves. Cerebral
cortex, in turn causes hyperventilation by
sending impulses to the medullary respiratory
centers.

4. Body Temperature
Body temperature which increases by muscular
activity, increases the ventilation by stimulating
the respiratory centers.
5. Acidosis
Acidosis developed during exercise also
stimulates the respiratory centers, resulting in
hyperventilation.

• EFFECT ON DIFFUSING CAPACITY FOR
OXYGEN
• Diffusing capacity for oxygen is about 21
mL/minute at resting condition. It rises to 45
to 50 mL/minute during moderate exercise
because of increased blood flow through
pulmonary capillaries.

• EFFECT ON CONSUMPTION OF OXYGEN
Oxygen consumed by the tissues, particularly
the skeletal muscles is greatly enhanced
during exercise. Because of vasodilatation in
muscles during exercise, more amount of
blood flows through the muscles and more
amount of oxygen diffuses into the muscles
from blood. The amount of oxygen utilized by
the muscles is directly proportional to the
amount of oxygen available.

• EFFECT ON OXYGEN DEBT
• Oxygen debt is the extra amount of oxygen
required by the muscles during recovery from
severe muscular exercise. After a period of
severe muscular exercise, amount of oxygen
consumed is greatly increased.

• Oxygen required is more than the quantity
available to the muscle. This much of oxygen is
required not only for the activity of the muscle
but also for reversal of some metabolic processes
such as:
1. Reformation of glucose from lactic acid,
accumulated during exercise
2. Resynthesis of ATP and creatine phosphate
3. Restoration of amount of oxygen dissociated
from haemoglobin and myoglobin.

• Thus, for the above reversal phenomena, an
extra amount of oxygen must be made
available in the body after severe muscular
exercise. Oxygen debt is about six times more
than the amount of oxygen consumed under
resting conditions.

• EFFECT ON VO2 MAX
• VO2 max is the amount of oxygen consumed
under maximal aerobic metabolism. It is the
product of maximal cardiac output and maximal
amount of oxygen consumed by the muscle. In a
normal active and healthy male, the VO2 max is
35 to 40 mL/kg body weight/minute. In females,
it is 30 to 35 mL/kg body weight/minute. During
exercise, VO2 max increases by 50%.

• EFFECT ON RESPIRATORY QUOTIENT
• Respiratory quotient is the molar ratio of
carbon dioxide production to oxygen
consumption. Respiratory quotient in resting
condition is 1.0 and during exercise it
increases to 1.5 to 2. However, at the end of
exercise, the respiratory quotient reduces to
0.5.

EFFECTS OF EXERCISE ON
CARDIOVASCULAR SYSTEM
1. ON BLOOD
Mild hypoxia developed during exercise
stimulates the juxtaglomerular apparatus to
secrete erythropoietin. It stimulates the bone
marrow and causes release of red blood cells.
Increased carbon dioxide content in blood
decreases the pH of blood.

2. ON BLOOD VOLUME
More heat is produced during
exercise and the thermoregulatory system is
activated. This in turn, causes secretion of large
amount of sweat leading to: i. Fluid loss ii.
Reduced blood volume iii. Hemoconcentration
iv. Sometimes, severe exercise leads to even
dehydration.

3. ON HEART RATE
Heart rate increases during exercise. Even the
thought of exercise or preparation for exercise
increases the heart rate. It is because of impulses
from cerebral cortex to medullary centers, which
reduces vagal tone. In moderate exercise, the heart
rate increases to 180 beats/minute. In severe
muscular exercise, it reaches 240 to 260
beats/minute. Increased heart rate during exercise
is mainly because of vagal withdrawal. Increase in
sympathetic tone also plays some role.

• Increased heart rate during exercise is due to four
factors:
i. Impulses from proprioceptors, which are present in
the exercising muscles; these impulses act through
higher centers and increase the heart rate
ii. Increased carbon dioxide tension, which acts through
medullary centers
iii. Rise in body temperature, which acts on cardiac
centers via hypothalamus, increased temperature also
stimulates SA node directly
iv. Circulating catecholamines, which are secreted in
large quantities during exercise.

4. ON CARDIAC OUTPUT
Cardiac output increases up to 20 L/minute in moderate
exercise and up to 35 L/minute during severe exercise.
Increase in cardiac output is directly proportional to the
increase in the amount of oxygen consumed during
exercise. During exercise, the cardiac output increases
because of increase in heart rate and stroke volume.
Heart rate increases because of vagal withdrawal. Stroke
volume increases due to increased force of contraction.
Because of vagal withdrawal, sympathetic activity
increases leading to increase in rate and force of
contraction.

5. ON VENOUS RETURN
Venous return increases remarkably during
exercise because of muscle pump, respiratory
pump and splanchnic vasoconstriction

6. ON BLOOD FLOW TO SKELETAL MUSCLES
There is a great increase in the amount of blood
flowing to skeletal muscles during exercise. In
resting condition, the blood supply to the skeletal
muscles is 3 to 4 mL/100 g of the muscle/minute. It
increases up to 60 to 80 mL in moderate exercise
and up to 90 to 120 mL in severe exercise. During
the muscular activity, stoppage of blood flow occurs
when the muscles contract. It is because of
compression of blood vessels during contraction.

• And in between the contractions, the blood flow
increases. Sometimes the blood supply to
muscles starts increasing even during the
preparation for exercise. It is due to the
sympathetic activity. Sympathetic nerves cause
vasodilatation in muscles. The sympathetic nerve
fibers causing vasodilatation in skeletal muscle
are called sympathetic cholinergic fibers since
these fibers secrete acetylcholine instead of
noradrenaline.

Several other factors also are responsible for the
increase in blood flow to muscles during exercise.
All such factors increase the amount of blood
flow to muscles by means of dilatation of blood
vessels of the muscles.
Such factors are:
1. Hypercapnea 2. Hypoxia 3. Potassium ions 4.
Metabolites like lactic acid 5. Rise in temperature 6.
Adrenaline secreted from adrenal medulla 7.
Increased sympathetic cholinergic activity.

7. ON BLOOD PRESSURE
During moderate isotonic exercise, the systolic
pressure is increased. It is due to increase in
heart rate and stroke volume. Diastolic pressure
is not altered because peripheral resistance is
not affected during moderate isotonic exercise.

• In severe exercise involving contraction, the
systolic pressure enormously increases but the
diastolic pressure decreases. Decrease in
diastolic pressure is because of the decrease
in peripheral resistance. Decrease in
peripheral resistance is due to vasodilatation
caused by metabolites. During exercise
involving isometric contraction, the peripheral
resistance increases. So, the diastolic pressure
also increases along with systolic pressure

• During exercise involving isometric
contraction, the peripheral resistance
increases. So, the diastolic pressure also
increases along with systolic pressure.

• Blood Pressure after Exercise Large quantities
of metabolic end products are produced
during exercise. These substances accumulate
in the tissues, particularly the skeletal muscle.
Metabolic end products cause vasodilatation.
So, the blood pressure falls slightly below the
resting level after the exercise. However, the
pressure returns to resting level quickly as
soon as the metabolic end products are
removed from muscles.

REFERENCES
• SEMBULINGAM 6 TH EDITION

Effects of exercise on respiration and cardiovascular system.pptx

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