Physiology of Exercise

1. Circulatory responses to
exercises

2. Circulatory responses to exercises
 Challenges to homeostasis by exercise
 Increased muscular demand for oxygen
 During heavy exercise the demand may be 15-25
times greater than at rest
 “Cardiopulmonary system“ works to maintain
oxygen and carbon dioxide homeostasis in body
tissues.

3. Circulatory responses to exercises
 In cardiopulmonary system :
 Respiratory system adds oxygen and removes
carbon dioxide from the blood
 Circulatory system is responsible for the delivery of
oxygenated blood and nutrients to tissues in
according to their needs.

4. Circulatory responses to exercises
 To meet the inc. oxygen demands of muscle during
exercise, two major adjustments of blood flow
must be made
(I) an increased cardiac output (i.e,increased
amount of blood pumped per minute by the heart)
(2) a redistribution of blood flow from inactive
organs to the active skeletal muscles.

6. Organization of Circulatory system
 Heart creates the “pressure head” to move blood
through system.
 Blood travels away from the heart in arteries by
veins.
 Arteries convert into branches from arterioles and
arterioles develop much smaller vessels called
capillaries.
 All O₂,CO₂ and nutrients between tissues and
circulatory system occurs across capillaries.

7.  Blood passes from capillaries beds to small venous
called ‘venioles’.
 As the venioles move back towards the heart, they
increase in size and become veins.
 Mixture of venous blood from both upper and
lower body accumulates in the Right side of heart
called
“Mixed Venous Blood”

8.  Heart is divided into four chambers:
 Right atrium and right ventricle forms the Right
Pump.
 Left atrium and left ventricle forms the Left Pump.
 Right side of the heart and left side of the heart
separates by a muscular wall called “Inter
ventricular septum”. Septum prevents the mixing
of oxygenated and deoxygenated blood.

10. Pulmonary and systemic circuit
 Right side of the heart pumps blood which contain
elevated CO₂ contents
 Blood delivered from right heart into lungs, this is
“pulmonary circuit”
 At the lungs O₂ is loaded in the blood and CO₂is
released.
 This oxygenated blood travels through the left side
of heart and is pumped out throughout the body.

14. Cardiac cycle
 Cardiac cycle is the repeating pattern of contraction
and relaxation of heart.
 Heart has two steps of pumping:
 Contraction phase of ventricles called “Systole”
 Relaxation phase of ventricles called “Diastole”

15.  Atria also contract and relax called “Atrial Systole
and Diastole”
 Atrial (systole) contraction occurs when ventricles
are relaxed (diastole)
 Atrial (diastole) during ventricular (systole)
 Right and left atria contract together and empty
atrial blood into ventricles

17.  If an average heart rate of 75 beats/minute, the total
cardiac cycle lasts 0.8 second
 0.5 second spend in diastole and the remaining 0.3
second dedicated to systole.
 If heart rate increases at 75 bpm to 180 bpm (heavy
exercise) cardiac cycle= 0.33 second
 Rising heart rate results in a greater times reduction
in the diastole while systole is less effected
 Pacemaker of heart is SA node

18.  Average BP during a cardiac cycle is called “Mean
Blood Pressure”
 Blood pressure can be increased by one or all of the
following:
 increase in blood volume
 increase in heart rate
 increase in blood viscosity
 Increase in stroke volume.

19. Cardiac output
 Cardiac output is the product of heart rate (HR) and
stroke volume (SV)
 Q=HR×SV beat/minute (bpm)
 During exercise, the quantity of blood pumped by the
heart change according to the requirement of skeletal
elevated O2 demand
Stroke volume
 Amount of blood pumped per heart beat
EDV(End diastolic volume)
 amount of blood in the ventricles just before systole.

20. Adaptations during Xs:
 Left ventricle size increases as a result of endurance
training with little change in ventricular wall
thickness.
 While isometric exercise can increase in wall
thickness with little or no change in ventricular
volume.
 Plasma volume increases with endurance training
200-300 ml increases 4% in VO₂ Max.

22. EJECTION FRACTION
 EF serves as a general measure of a person's cardiac
function.
 Ejection fraction is commonly measured by ECG,
 In which the volumes of the heart's chambers are
measured during the cardiac cycle

23.  Causes and etiologies of systolic heart failure
include:
 coronary artery disease,
 congenital heart disease,
 valvular heart disease,
 conduction disease,
 infectious disease

24.  In a healthy 70-kilogram (150 lb) man,
SV is approximately 70 mL
left ventricular EDV is 120 mL,
giving an ejection fraction of 70⁄120,
or 0.58 (58%).
 Healthy older adults with ventricles become less
compliant are proven to have an EF from 55–85% with
the help of good genetics and a healthy lifestyle.

26. Haemodynamic
 Blood flow through circulatory system results from
pressure difference between the two ends of system.
 Physical regulation of blood flow to tissue consist of
inter relationship between pressure, flow and
resistance.
 These factors and the physical principles of blood
flow called “hemodynamic”
 Blood is composed to two principle components
(plasma and cells).

27.  Blood Flow= ∆ Pressure
Resistance
 Most important factors determining resistance to the
blood flow is the radius of blood vessels. Greater
vascular resistance to blood flow is offered in
arterioles
 Resistance = length × viscosity
Radius⁴

28. Changes inO2 delivery to muscles during Xs
 As compare to resting value O₂ needs in skeletal
muscle during exercise is by several times to meet
this rise in O₂ demand blood flow to muscles must
be increase.
 Increased O₂ delivery to exercising muscle is
provided by two mechanisms:
I. Increased cardiac output.
II. Redistribution of blood flow.

29.  Increased Cardiac Output:
 Cardiac output increased during exercise is directly
proportional to metabolic rate to perform required
task.
 Increased cardiac output during exercise is achieved
by an increased in both stroke volume and heart rate.
 Stroke volume does not increased beyond a work
load of approximate 40% VO₂ max
Max HR=220 age

30.  Redistribution of Blood Flow
 It is necessary to increase blood flow to the muscle at
the same time reducing blood flow to the less active
organs such as kidneys, GIT and liver
 Approximate 15-20% of the total cardiac output is
directed towards skeletal muscles and during
exercise 80-85% total cardiac output goes to the
contracting skeletal muscle.