Acute Cardiorespiratory Responses to Exercise

Central command

Feed forward neural signal from the anterior cingulate cortex that triggers an anticipatory rise in heart rate.

Stroke volume

Blood pumped per beat. Calculated as EDV minus ESV.

Preload

End diastolic volume or myocardial stretch before contraction.

Afterload

Resistance the ventricle must overcome to eject blood, mainly systemic vascular resistance.

Frank Starling Law

Greater ventricular filling increases stretch which increases contraction force and raises stroke volume.

Cardiac output

Blood pumped per minute. Q equals HR times SV.

Parasympathetic withdrawal

Initial mechanism raising heart rate to about 100 to 120 bpm at start of exercise.

Sympathetic activation

Increases HR, contractility, and promotes vasoconstriction in large arteries during exercise.

Maximal heart rate

Highest achievable HR, largely influenced by age and genetics.

Systolic blood pressure response

Increases during exercise because of rising cardiac output and sympathetic vasoconstriction.

Diastolic blood pressure response

Remains stable or decreases because of reduced total peripheral resistance at working muscle.

Muscle Pump

Rhythmic muscle contractions that push blood toward the heart and increase venous return.

Total peripheral resistance

Resistance in systemic circulation which decreases during exercise due to vasodilation.

Trained vs Untrained stroke volume

Trained individuals have higher resting and maximal stroke volume due to greater ventricular filling and higher contractility.

Anticipatory rise

Increase in HR before exercise starts caused by central command.