Cardiovascular System Responses to Exercise - CV During Exercise

If Emotionally Charged

increases SNS activity → elevated HR and BP

Emotional Influence Can

increase pre-exercise HR and BP

Emotional Influence Does Not

increase peak HR or BP during exercise

Transition From Rest to Exercise to Recovery

• HR, SV and CO are all low at rest

• at beginning over exercise HR increases rapidly, SV and CO increase less rpaidly

• HR, SV and CO gradually decrease toward resting levels

Steady-Rate Exercise

• vasodilation in active muscles decrease TPR and increase BF

• alternating contractions propels blood through the system

SBP During Steady-Rate Exercise

• increase BF rapidly increases SBP during the first few minutes of exercise

• SBP gradually decreases because arterioles in the active muscles further dilate (decrease resistance)

DBP During Steady-Rate Exercise

remains unchanged

Cardiovascular Drift

• prolonged exercise and heat

• insufficient venous return → decrease in EDV

• increase in HR to deal with decrease in SV

How Much Can CO Drift During Intense Exercise

as much as 20 bpm

Cardiovascular Drift Recent Explanation

B-receptor action

• keep HR suppressed, no drift!

Incremental Exercise - HR and CO

• increase lineraly with work rate

• plateau at 100% VO2max

Incremental Exercise - BP

MAP increases linerly

• SBP increase

• DBP remains fairly constant

Double Product or Rate-Pressure Product Equation

HR x SBP

Double Product or Rate-Pressure Product

• indicates the work of the heart

• increases linerly with exercise intensity

The Heart’s Blood Supply - At Rest

extracts 70-80% of O2 from blood

Increased Blood Flow Is The

sole mechanism for increase O2 supply during exercise

Blood Flow Increases During Exercise Due To

• increased myocardial metabolism causes vasodilation

• increases BF out of aorta increases pressure and a proportionally greater BF to heart

Arm vs Leg Exercise

at same VO2 arm work results in higher:

• HR (higher sympathetic stimulation)

• BP (vasoconstriction of large inactive muscle mass)

Effects of Body Position

supine or prone exercise

• decrease hydrostatic load

• decrease HR

• increase SV

Effects of Hydrostatic Load - HR

• lying down: lowest HR

• sitting: HR increases

• standing: highest HR

Effects of Hydrostatic Load - SV

• lying down: highest SV

• sitting: SV decreases

• standing: lowest SV

Effects of Hydrostatic Load - CO

• lying down: slightly higher

• sitting: slightly lower

• standing: remains around 4 L/min

Intermittent Exercise - Extent of Recovery Depends On

• fitness level

• environmental conditions

• duration (exercise bout/interval and recovery)

• intensity (exercise bout/interval and recovery)

Resistance Exercise Mechanically Compresses

vascular compression increase TPR and decrease muscle perfusion

To Restore Muscle Blood Flow

substantial increases occur in SNS, Q, MAP

Acute CV Strain With Heavy RT Could

prove harmful to individuals with heart and vascular disease

Central Command Theory

• motor signal from within the brain

• changes at onset of exercise due to centrally generated CV motor signals

• signals set the “general” pattern of the CV response

Central Command Theory - Signals From Periphery That Contribute

• mechanoreceptors

• chemoreceptors

• baroreceptors (exercise pressor response)

• important for fine tuning to exercise

CV Control During Exercise

illustrates redundancy in the system

• ensures BF consistently matches the metabolic needs of muscles

CV Control - Initial Drive

• centrally generated motor signals

• “central command theroy”

• sets the pattern of CV response

CV Control - Fine-Tuned By Feedbacl

• heart mechanoreceptors

• muscle chemoreceptors

• muscle mechanoreceptors

• baroreceptors

Sudden Death During Exercise

unexpected, natural, and nonviolent death occuring within the first 6 h following the beginning of exercise

• not all are cardiac

• fewer than 20 cases per year

Cause of Sudden Death During Exercise in Children/Adolescents

• lethal cardiac arrhythmia

• genetic anomalies

• myocarditis (heart inflammation)

Cause of Sudden Death During Exercise in Adults

• CAD

• cardiomyopathy

Regular Exercise Is

cardio-protective

• decrease incidence of MI and increase survival from heart attack

Exercise Decrease Damage From

MI

• increase antioxidant capacity

• increase ATP-sensitive K+ channels