ExErcisEExErcisE
PhysiologyPhysiology
CHAPTER 84
ExErcisE
Is the period of enhanced energy
expenditure
This energy is provided by increased
fuel consumption which is refle...
incrEasEd o2 dElivEry to thE
tissuEs and incrEasEd rEmoval
of co2from thE tissuEs is
achiEvEd by
cardiovascular responses ...
tyPEs of ExErcisEtyPEs of ExErcisE
SStatictatic exerciseexercise = constant muscle
length and increased tension
Dynamic ex...
tyPEs of ExErcisEtyPEs of ExErcisE
Anaerobic exerciseAnaerobic exercise
weight-lifting) –
short duration,
great intensity
...
oxygEn consumPtion
during ExErcisE
The increase in ventilation during exercise
prevents large changes in the partial
press...
o2 consumPtion and
vEntilation during ExErcisE
OXYGEN CONSUMPTION (VO2) AT
REST = 250 ml and increases with
severity of exercise
MAXIMAL OXYGEN CONSUMPTION
(VO2 MAX)= le...
vo2 max
Average VO2 max in
adults=3L/min
trained athletes=5L/min
So VO2 max represents the max
attainable rate of aerobic ...
AlveolAr ventilAtion And
ArteriAl PCo2 during exerCise
The decrease PCO2 at the
onset of exercise
demonstrates that
increa...
o2 defiCit And o2 debt
Period of muscular exercise can be
divided into 3 phases
Adaptation phase
Steady phase
Recovery pha...
AdAPtion PhAse
First 2-4 min after beginning
exercise
O2 consumption reaches VO2 max
VO2 max is less than O2 demand….O2
de...
steAdy PhAse
Plateau phase of work done and O2
consumption
Anaerobic respiration continues
Built up of lactic acid which i...
reCovery PhAse
After cessation of exercise extra
amount of O2 is consumed called
oxygen debt
Oxygen debt is proportional t...
signifiCAnCe of oxygen
debt
To remove excess lactate
accumulated
To replenish the ATP
To replace myoglobin O2
MusCle fAtigueMusCle fAtigue
Lactic acid
↓ATP (accumulation of ADP and Pi,
and reduction of creatine phosphate)

 Ca↓ ++...
↓ the rate of ATP hydrolysis,
↓ efficiency of glycolytic enzymes,
↓Ca2+
binding to troponin,
↓ interaction between actin a...
How does tHeHow does tHe
respiratory systemrespiratory system
respond to exercise?respond to exercise?
major factors wHicH stimulatemajor factors wHicH stimulate
increased ventilation duringincreased ventilation during
exerci...
Before expected exerciseBefore expected exercise
Begins,Begins, ventilationventilation risesrises
emotional
hyperventilati...
During the exercise,During the exercise, stimulistimuli
from the muscles, joints andfrom the muscles, joints and
perhaps s...
increase oxygen uptake
By lungs
Increases from 250ml at rest to
4L/min
This is achieved by
*increased ventilation
* increa...
cHanges at tHe tissue
level
Increased blood flow to the
exercising muscles
Increased PO2 gradient between the
systemic cap...
How does tHeHow does tHe
cardiovascular systemcardiovascular system
respond to exercise?respond to exercise?
cardiovascular
responses to exercise
Increase in cardiac output (COP)
Increase in heart rate
Increase in blood pressure
In...
Increased CO can be achieved by raising either
stroke volume (SV) or heart rate (HR)
steady-state HR rises essentially lin...
Venous
return
Skin and
splanchnic blood
volume
Maintenance of
ventricular fillingMuscle
“pump”
Cardiac
output
Cardiac
cont...
BloodBlood ppressureressure (Bp)(Bp) also rises inalso rises in
exerCiseexerCise
systolic pressure
(SBP) goes up to
150-17...
CardiovasCularCardiovasCular
adaptations toadaptations to eexerCisexerCise
trainingtraining
Adaptations that increase musc...
inCrease in skeletal
musCle Blood flow
It is 2-4ml/100gm/min of muscle tissue
Increases 20 times i.e.50-80
ml/100gm/min
Ac...
redistriBution of Blood
flow
Hormonal responsesHormonal responses
during exerCiseduring exerCise
during exerCiseduring exerCise
Norepinephrine rises again ('fight or flight'). Increases
glycogen breakdown and elevates f...
ADH is released in considerable quantities.
It's not just socially inconvenient to have to
urinate during exercise - it's ...
Chap 84
Chap 84
Chap 84
Chap 84
Chap 84
Chap 84
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Chap 84

  1. 1. ExErcisEExErcisE PhysiologyPhysiology CHAPTER 84
  2. 2. ExErcisE Is the period of enhanced energy expenditure This energy is provided by increased fuel consumption which is reflected as increased O2 consumption and increased CO2 production
  3. 3. incrEasEd o2 dElivEry to thE tissuEs and incrEasEd rEmoval of co2from thE tissuEs is achiEvEd by cardiovascular responses to exercise respiratory responses to exercise changes at tissue level during exercise
  4. 4. tyPEs of ExErcisEtyPEs of ExErcisE SStatictatic exerciseexercise = constant muscle length and increased tension Dynamic exerciseDynamic exercise = rhythmic cycles of contraction and relaxation; change in muscle length
  5. 5. tyPEs of ExErcisEtyPEs of ExErcisE Anaerobic exerciseAnaerobic exercise weight-lifting) – short duration, great intensity (fast-twitch muscle fibers); creatine phosphate + glycogen (glucose) from muscle o2 Aerobic exerciseAerobic exercise running, swimming)- prolonged but at lower intensity (slow-twitch mucle fibers) fuels stored in muscle, adipose tissue and liver (glucose – early, FFA – later) o2
  6. 6. oxygEn consumPtion during ExErcisE The increase in ventilation during exercise prevents large changes in the partial pressure of O2 or CO2. The increase in ventilation occurs before there is a change in blood chemicals. Neuronal signals are sent to the respiratory center during exercise, possibly at the same time signals are being sent to the skeletal muscles.
  7. 7. o2 consumPtion and vEntilation during ExErcisE
  8. 8. OXYGEN CONSUMPTION (VO2) AT REST = 250 ml and increases with severity of exercise MAXIMAL OXYGEN CONSUMPTION (VO2 MAX)= level of O2 consumption beyond which no further increase in O2 consumption occurs with further increase in severity of exercise
  9. 9. vo2 max Average VO2 max in adults=3L/min trained athletes=5L/min So VO2 max represents the max attainable rate of aerobic metabolism during performance of rhythmic muscular work that exhausts the subject in 5-10 minutes
  10. 10. AlveolAr ventilAtion And ArteriAl PCo2 during exerCise The decrease PCO2 at the onset of exercise demonstrates that increasing blood CO2 does not trigger the increase in ventilation during exercise. However, chemical changes do fine-tune the ventilation rate. Notice the decrease in ventilation associated with the decrease in PCO2 at the onset of exercise.
  11. 11. o2 defiCit And o2 debt Period of muscular exercise can be divided into 3 phases Adaptation phase Steady phase Recovery phase
  12. 12. AdAPtion PhAse First 2-4 min after beginning exercise O2 consumption reaches VO2 max VO2 max is less than O2 demand….O2 deficit develops Anaerobic respiration begins
  13. 13. steAdy PhAse Plateau phase of work done and O2 consumption Anaerobic respiration continues Built up of lactic acid which is buffered by bicarbonate buffer system H+ + HCO3-……..H2CO3….H2o + CO2 Extra CO2 evolved is removed by hyperventilation
  14. 14. reCovery PhAse After cessation of exercise extra amount of O2 is consumed called oxygen debt Oxygen debt is proportional to extent to which oxygen deficit occurred during exercise
  15. 15. signifiCAnCe of oxygen debt To remove excess lactate accumulated To replenish the ATP To replace myoglobin O2
  16. 16. MusCle fAtigueMusCle fAtigue Lactic acid ↓ATP (accumulation of ADP and Pi, and reduction of creatine phosphate)   Ca↓ ++ pumping and release to and from SR↓ ccontraction and relaxation Ionic imbalances muscle cell is less responsive to motor neuron stimulation
  17. 17. ↓ the rate of ATP hydrolysis, ↓ efficiency of glycolytic enzymes, ↓Ca2+ binding to troponin, ↓ interaction between actin and myosin (muscle fatigue) during rest is converted back to pyruvic acid and oxidized by skeletal muscle, or converted into glucose (in the liver)
  18. 18. How does tHeHow does tHe respiratory systemrespiratory system respond to exercise?respond to exercise?
  19. 19. major factors wHicH stimulatemajor factors wHicH stimulate increased ventilation duringincreased ventilation during exercise include:exercise include: neural input from the motor areas of the cerebral cortex proprioceptors in the muscles and joints ↑ body temperature circulating NE and E pH changes due to lactic acid Rest Exercise intensity V02max Arterial blood pH
  20. 20. Before expected exerciseBefore expected exercise Begins,Begins, ventilationventilation risesrises emotional hyperventilation‘ at any rate, impulses descending from the cerebral cortex are responsible
  21. 21. During the exercise,During the exercise, stimulistimuli from the muscles, joints andfrom the muscles, joints and perhaps such sensoryperhaps such sensory receptors as pressurereceptors as pressure endings in the feet,endings in the feet, contribute to the elevationcontribute to the elevation ofof ventilationventilation so do chemicals, originating in the active muscles.
  22. 22. increase oxygen uptake By lungs Increases from 250ml at rest to 4L/min This is achieved by *increased ventilation * increased alveolar capillary PO2 * increased pulmonary diffusion capacity
  23. 23. cHanges at tHe tissue level Increased blood flow to the exercising muscles Increased PO2 gradient between the systemic capillaries and tissues Rightward shift of oxygen Hb dissociation curve (increased 2,3DPG and temperature)
  24. 24. How does tHeHow does tHe cardiovascular systemcardiovascular system respond to exercise?respond to exercise?
  25. 25. cardiovascular responses to exercise Increase in cardiac output (COP) Increase in heart rate Increase in blood pressure Increase in skeletal muscle blood flow Changes in blood volume
  26. 26. Increased CO can be achieved by raising either stroke volume (SV) or heart rate (HR) steady-state HR rises essentially linearly with work rate over the whole range from rest to VO2max : increased sympathetic and decreased parasympathetic discharge to the cardiac pacemaker + catecholamines reflex signals from the active muscles blood-borne metabolites from these muscles temperature rise CCardiaC output (Cop)ardiaC output (Cop) inCreaseinCrease
  27. 27. Venous return Skin and splanchnic blood volume Maintenance of ventricular fillingMuscle “pump” Cardiac output Cardiac contractility HR ExerciseExercise  Muscle pump + symp. vasocon.↑ ↑Muscle pump + symp. vasocon.↑ ↑  Venous↑ Venous↑ returnreturn ↑↑ stroke volumestroke volume  ↑↑ cardiac outputcardiac output
  28. 28. BloodBlood ppressureressure (Bp)(Bp) also rises inalso rises in exerCiseexerCise systolic pressure (SBP) goes up to 150-170 mm Hg diastolic scarcely alters in isometricisometric (heavy static) exercise, SBP may exceed 250 mmHg, and diastolic (DBP) can itself reach 180
  29. 29. CardiovasCularCardiovasCular adaptations toadaptations to eexerCisexerCise trainingtraining Adaptations that increase muscle oxidative capacity and delay lactate production  ↓↓ muscle chemoreflexmuscle chemoreflex influence on cardiovascular system As a result sympathetic activity is decreased, which lowers BP and HR (trained people)
  30. 30. inCrease in skeletal musCle Blood flow It is 2-4ml/100gm/min of muscle tissue Increases 20 times i.e.50-80 ml/100gm/min Achieved by * arteriolar dilatation * opening up of dormant capillaries
  31. 31. redistriBution of Blood flow
  32. 32. Hormonal responsesHormonal responses during exerCiseduring exerCise
  33. 33. during exerCiseduring exerCise Norepinephrine rises again ('fight or flight'). Increases glycogen breakdown and elevates free fatty acids; also cardiovascular effects as in anticipatory phase Glucagon rises (to keep up blood sugar). Increases glucose release from liver Cortisol rises (response to the stress). Increases use of fatty acids, reinforces glucose elevation Growth hormone begins to rise (damage repair). Stimulates tissue repair, enhances fat use instead of glucose
  34. 34. ADH is released in considerable quantities. It's not just socially inconvenient to have to urinate during exercise - it's a waste of fluid which will probably be needed as sweat. Testosterone/estrogen increase with exercise - probably, over many repetitions, promoting increased muscle bulk Aldosterone also rises, reducing Na+ loss in sweat (and in such urine as is still produced).
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