Cardiovascular adjustments during exercise

1. Cardiovascular adaptation
to exercise
BY SHAMA
PHYSIOLOGY DEPARTMENT

2. Objectives
 Heart Rate
 Stroke Volume
 Cardiac output
 Blood pressure
 Blood flow
 Blood volume

3. Heart rate during exercise
 Increase in linearity with increase in physical effort
 Decreases with advancing age due to generalized reduction of biological functions
 Psychic stimuli and proprioceptor input are the major stimuli for the quick rise in
HR that occur at the onset of physical activity.
 Increased activity of limbic system and motor cortex due to psychic stimuli that
acts on directly on medulla.
 Decrease in vagal tone.

4.  Peripheral reflexes from
 Muscle spindles
 Muscle tendon receptors
 Organ ofCorti
 Increase in body temperature
 Decrease in pO2, decrease in pH, increased in pCO2

5. Stroke volume during exercise
 Increase to twice the normal volume during exercise.
 Increase in VR , maintained by muscle pump, negative intrathoracic pressure
 Modification of tone in capacitance vessels.
 Thus helps in redistribution of blood to active tissues from inactive tissues.
 Increased myocardial contractility by epinephrine and nor epinephrine from
Sympathetic nervous system and adrenal medulla.
 As stroke volume depends heart size it increase in athletes due to low resting
heart rate that increase end diastolic volume producing enlargement of heart

6. Cardiac output during exercise
 It increases to 5-6 times during maximum exercise due to increase in heart rate
and stroke volume.
 Max. CO can be achieved in youngscompared to old ones due to higher max.
Heart rate.

7. Blood pressure during exercise
 In systemic circulation
# SBP increase in linearity with severity of exercise due to increase in cardiac output.
#DBP –no change in mild & moderate exercise because total resistance falls considerably
due to drastic vasodilation in working muscles.
Slightly increase in severe exercise due to vasoconstriction in nonworking muscles and skin.
#MAP increase from 90 to 140mmHg during heavy exercise.
🚩in pulmonary circulation
# during mild and moderate exercise, MAP only increases to15mmHg due to intrathoracic
location of blood vessels which provides low resistance to blood flow in pulmonary circuit.

8. Blood flow during exercise
 3-4ml/100gm/min.
 During heavy exercise, increase by 25-30times due to increase in capillary density I.e,
opening of more capillary.
 Muscle blood flow increases before the starting of exercise and continues to increase
until plateau is reached.
 In mild, it takes 1-2mint. But in severe it is long.
 AV oxygen difference. 5ml/dl at rest
 During maximum exercise it increase by 3times with 80% coefficient of O2 utilization
because of O2 Hb dissociation curve shifts to right due to increase in temperature &
pCO2 and decrease in pO2 &pH.
 Increases muscle metabolism be approx. 100 times during severe exercise.

9. Coronary blood flow
 At rest: 250ml/min or 60-70ml/100gm/min with 70-80% coefficient of O2
utilization.
 During severe exercise, it increase by 5times with 100% coefficient of O2
utilization due to increased coronary blood flow, coronary vasodilation by
catecholamines, hypoxia, fall in blood pH and ATP and ADP.
. Pulmonary blood flow
 At rest : 350-800ml/min, increases in linearity with increase in cardiac output to
1400ml/min.during severe exercise

10. Skin blood flow
 Resting : 500ml/min, depends on cooling power of surrounding air and metabolic rate of body.
 Slightly decrease in the beginning exercise due to reflex vasoconstriction.
 Later increases upto 7times due to stimulation of hypothalamus secondary to increase in body temp.
This produces vasodilatation and helps heat loss and transport of metabolites.
 During severe exercise, decreases due to vasoconstriction of skin blood vessels
Adipose tissue blood flow
 Increases 4times during exercise. Helps to deliver fatty acids mobilized from triglycerides stores to
working muscles.
Brain blood flow
# there is no change during any grade of exercise

11. Blood volume
 Decreases by 15% causing hemoconcentration of blood due to:
 Increased hydrostatic pressure in capillaries causing loss of plasma water.
 Accumulation of osmotically active metabolites in tissue spaces, causing drainage
of plasma water from capillaries.
 Oxygen carrying capacity of blood increases because of increased concentration
of RBCs.
 Increase in acid buffering capacity due to increased plasma protein.
 Disadvantages are increases blood viscosity therefore blood flow decreases. WBCs
count increases, due to washing out of WBCs from storage places.

12. Visceral blood flow
 There is no change in visceral blood flow during mild and moderate exercise.
 During severe exercise, there is slightly decrease in kidney blood flow, portal
venous blood and splanchnic blood flow by 50-80%

13. Note
 In static effort (isometric exercise) the maximum tension that can be produced by
the given muscle group and the length of time ,can be depend on local functional
capacity of muscles. Whereas, in isotonic exercise, endurance and maximal power
output depend on efficiency of energy delivering mechanism.
 Static exercise produces more disturbances in the cardio- vascularbsyatem than
dynamic exercise. Static exercise cause compression of vesselsi. The contracting
muscles and a decrease in blood flow through them.

14. Athletic pseudonephritis
 Prolonged, heavy exercise increases proteins, cells and other abnormal substances
in urine due to:
 Decrease in renal blood flow (RBF) produces glomerular capillary hypoxia and
increases permeability to large molecules.
 Increase in plasma proteins during exercise.
 Decreased rate of RBF, thus larger time is required to filter these molecules.

15. Thank you😊