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CVS changes during Exercise
• The Cardiovascular system changes to match supply and demand.Components of the CV system during exercise
heart rate strove volume cardiac output blood flowblood pressure
Heart rate
• Measure at the radial or carotid site.• Reflects the amount of work that it is
performing to meet the demands of the body with increasing work.
• Resting HR: 60 to 80 bts/min. – Anticipatory response-prior to starting
exercise just knowing that you are going to have to start exercise.
– 220-age= predicted Max HR.
Heart Rate
100
120
140
160
180
200
40 90 140 190 240 290 340
Treadmill Speed (m/min)
HR
(b
pm
)
trained
sedentary
Change in HR during ExerciseChange in HR during Exercise
As exercise begins, Para-SNS withdraws influence.
SNS stimulates heart. Adrenal gland secretes catecholamines. Increase in body temperature ,as in intense
exercise.
Stroke VolumeStroke Volume
May increase with increasing rates of work up to intensities of 40% to 60% of maximum exercise.
May continue to increase up through maximal exercise intensity, generally in highly trained athletes
Depends on position of body during exercise•upright-SV is less, supine is greater (easier to heart)upright-SV is less, supine is greater (easier to heart)
STROKE STROKE VOLUMEVOLUME
Cardiac Output• Resting is 5.0 L/min-
• 20 to 40 L/min during exercise.
• The need for an increase is to meet the muscle’s demands during exercise.
• An increase in HR and SV increases Q, (separate or together)
• After 40 to 60% of max, SV plateaus, Q increases due to increase in HR .
CARDIAC OUTPUTCARDIAC OUTPUT
Cardiac Output
0
5
10
15
20
25
30
40 90 140 190 240 290 340 390
Treadmill Speed (m/min)
Ca
rdia
c O
utp
ut
(L/m
in)
trained
detrained
Redistribution of Blood Flow
• Blood flow to tissues is controlled in relation to tissue needs– Tissue needs may 20-30 fold, but cannot Q
that much: 5 L/min 100 -150 L/min ! ? So flow is redistributed between tissues
• Muscle blood flow to working skeletal muscle• Splanchnic blood flow to less active organs
– Liver, kidneys, GI tract, & also to non-working muscle
Redistribution of Blood Flow During Exercise
Redistribution of Blood Flow
Local SystemicVasodilation Vasoconstriction
PO2 PCO2 [H+] adenosine [K+] Nitric oxide
Metabolites Epinephrine
Adrenal medulla
SympatheticNervousSystem
overrides
Blood pressure during Blood pressure during endurance activitiesendurance activities
• SBP increases in proportion to exercise intensity.
• DBP changes very little during endurance exercise.
• There is modest increase in mean arterial pressure .
Effects of Incremental Exercise on BPEffects of Incremental Exercise on BP
0
25
50
75
100
125
150
175
200
225
250
0 50 100 150 200 250 300Workload (W)
Blo
od
Pre
ss
ure
(m
m H
g)
Systolic BP
Diastolic BP
Cardiovascular Adjustments to Exercise
Cardiac Output Components in Trained & Untrained Subjects
Untrained
Rest 70 72 5.0
Max Exercise 195 113 22.0
Endurance Trained
Rest 50 100 5.0
Max Exercise 195 179 35.0
Heart rate Stroke volume Cardiac outputSubject/Activity (beats/min) (ml/beat) (L/min)