1. Circulatory Changes During Exercise
28-Jan-18
circulation & exercise

2. Circulatory Changes During Exercise
During exercise there is
Increase demand for energy
To meet the increased metabolic demands
Demands is met by adjustment of
Cardio respiratory system
28-Jan-18
circulation & exercise

3. circulation & exercise
Muscle Blood Flow
At rest muscle blood flow
3 to 4 ml/ min/ 100 gm of muscle
During exercise
50 to 80 ml /min /100 gm of muscle
Intermittent flow
Decreases during contraction phase
Increase between contractions
Rhythmic exercise 40
Blood flow 20 10 16 18
Minutes
28-Jan-18
circulation & exercise

4. Circulatory Changes During Exercise
Major effects occur during exercise
Facilitate adequate supply of blood required by working muscle include
28-Jan-18
circulation & exercise

5. Circulatory Changes During Exercise
Local mechanisms
Also during exercise there is increase
Sympathetic discharge
Arterial pressure
Cardiac output
28-Jan-18
circulation & exercise

6. circulation & exercise
Local Mechanisms
Maintain high blood flow in exercising muscles
 Tissue PO2
 Tissue PCO2
 Local temperature
 Metabolites
28-Jan-18
circulation & exercise

7. circulation & exercise
Local Mechanisms
Dilatation of
Arterioles
Pre-capillary symphicters
Cause
10 to 100 fold increase in number of open capillaries
28-Jan-18
circulation & exercise

8. circulation & exercise
Local Mechanisms
Oxygen consumption of skeletal muscles
 100 fold during exercise
This is met by
 CO
Diffusion capacity of lung
Opening of capillaries
28-Jan-18
circulation & exercise

9. O2-Hb Dissociation Curve
During exercise
The curve shift to right
 PH
 Temp
 2:3 DPG
100 80
pH 7.4
pH 7.2
Hb saturation (%) 60 50 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
28-Jan-18
circulation & exercise

10. circulation & exercise
Local mechanism maintains a high blood flow in exercising muscles
Distribution of blood flow at rest and during heavy exercise
Dilation of the arterioles and precapillary sphincters cause a fold increase in the number of open capillaries. The capillary pressure increases exceeding the oncotic pressure throughout the length of the capillaries. Lymph flow is also increased limiting the accumulation of tissue fluid
Oxygen consumption of skeletal muscle increase 100-fold during exercise
From Hansen Taher Sherief Physiology book CD
28-Jan-18
circulation & exercise

11. Sympathetic Discharge
Command signals to the muscle
Relayed to VMC
 Sympathetic discharges
 parasympathetic activity to the heart
This causes increase in HR
Contractility of myocardium
28-Jan-18
circulation & exercise

12. Sympathetic Discharge
Cause constriction of most of arterioles except
In active muscles
Vasodilatation
Effect of local metabolites
Blood is shunted to working muscles
Coronary and cerebral vessels
Spared of the vasoconstriction
28-Jan-18
circulation & exercise

13. Sympathetic Discharge
Constriction of capacitance vessels leads to
 Mean systemic filling pressure
 Venous return
 Cardiac output
28-Jan-18
circulation & exercise

14. circulation & exercise
Command signals to muscles relayed to VMC
Symp discharge
 parasymp
HR, Contractility
Venoconstriction  venous capacity and  venous return
From Hansen Taher Sherief Physiology book CD
28-Jan-18
circulation & exercise

15. circulation & exercise
Arterial Pressure
Arterial pressure increases during exercise due to
Vasoconstriction of arteries & arterioles
Increased pumping activity of myocardium
Increase mean systemic filling pressure
28-Jan-18
circulation & exercise

16. circulation & exercise
Arterial Pressure
All the above will tend to increase BP
(BP = CO x TPR)
The extent of the rise in BP
Depend on the type of exercise performed
28-Jan-18
circulation & exercise

17. circulation & exercise
Arterial Pressure
When person perform exercise under tense conditions
Few areas of vasodilatation
Vasoconstriction occurs in most tissue
TPR increases much more
MAP rises significantly ( = 170 mm Hg)
28-Jan-18
circulation & exercise

18. circulation & exercise
Arterial Pressure
When a person performs whole body exercise
Running, swimming
Rise in MAP
Not profound
Large muscle mass active
Vasodilatation
Lower TPR
28-Jan-18
circulation & exercise

19. circulation & exercise
Cardiac Output
Systemic blood flow
Increases with increase in intensity of exercise
CO increases rapidly initially then gradually
Until blood flow meets metabolic demand for the exercise
28-Jan-18
circulation & exercise

20. circulation & exercise
Cardiac Output
In sedentary people
CO can increase four fold (from 5 to 20 L/ min)
Mainly by increase in both
HR & SV
HR can increase up to 190 bpm
SV can increase up to 103 to 113
28-Jan-18
circulation & exercise

21. circulation & exercise
Cardiac Output
Other factors
Venous return greatly increased by
 Activity in working muscles
Muscle pump
Thoracic pump
Mobilization of blood from viscera
Venoconstriction
Mobilization of blood from reservours
28-Jan-18
circulation & exercise

22. Distribution of CO Tissue At rest (ml/min) Strenuous exercise (ml/min)
Brain
750 (13%)
750 (4%)
Heart
250 (4%)
Muscle
1,200 (20%)
12,500 (73%)
Skin
500 (9%)
1,900 (11%)
Kidney
1,100 (20%)
600 (3%)
Abdominal viscera
1,400 (24%)
Others
600 (10%)
400 (2%)
TOTAL
5,800
17,500
28-Jan-18
circulation & exercise

23. circulation & exercise
Distribution of CO
28-Jan-18
circulation & exercise

24. circulation & exercise
Local mechanism maintains a high blood flow in exercising muscles
Distribution of blood flow at rest and during heavy exercise
Dilation of the arterioles and precapillary sphincters cause a fold increase in the number of open capillaries. The capillary pressure increases exceeding the oncotic pressure throughout the length of the capillaries. Lymph flow is also increased limiting the accumulation of tissue fluid
Oxygen consumption of skeletal muscle increase 100-fold during exercise
28-Jan-18
circulation & exercise

25. circulation & exercise
Endurance Athlete
Resting CO = 5 L/min
HR in highly trained athlete is much lower
Increased vagal tone
Decreased resting sympathetic activity
HR = 40 to 50 bpm
28-Jan-18
circulation & exercise

26. circulation & exercise
Endurance Athlete
Resting CO of 5 L/min is achieved
Increase in SV
(CO = SV x HR
Untrained
(5000 = 71 x 70)
Trained
(5000 = 100 x 50)
28-Jan-18
circulation & exercise

27. SV & HR in Trained and Untrained
28-Jan-18
circulation & exercise

28. circulation & exercise
Endurance Athlete
During maximal excise
CO of endurance athlete
Can increase up to 35 – 40 L/min
Untrained
(22,000 = 113 x 195)
Trained
(35,000 = 179 x 195)
28-Jan-18
circulation & exercise