Heart Rate, Blood Pressure, and Exercise

Blood Pressure Made up of two numbers: –systolic blood pressure –diastolic blood pressure. Written as: Systolic/Diastolic Spoken as: Systolic Over Diastolic Measured in mmHg

Measuring Blood Pressure Sphygmomanometer and stethoscope Normally, inflate cuff to 180 mmHg –Allow pressure to drop at a rate of 3 mmHg/second Three Conditions –No Flow –Turbulent Flow –Laminar Flow

Cardiac Output and Exercise Q = HR x SV Q is cardiac output (L/min) HR is heart rate (beats/min) SV is stroke volume (ml/beat) Cardiac output must increase in exercise to meet the metabolic demand of the active tissues.

Total Peripheral Resistance Describes the resistance in vessels Change it via physiological response or by physical measures Vasoconstrict or Vasodilate in response to exercise. –Active Skeletal muscles: Vasodilate –Non essential organs & Non-active skeletal muscles: Vasoconstrict

Systolic Blood Pressure Refers to the arterial pressure during the contraction phase of the heart Corresponds with the onset of turbulent flow through the arteries Pressure at first Korotkoff sound (a beating sound with each heart beat) Average value is around 120 mmHg Reflects Cardiac Output, but is not equal to it

Diastolic Blood Pressure Refers to the arterial pressure during the relaxation phase of the heart Corresponds with the onset of laminar flow through the arteries Pressure at last Korotkoff sound (a beating sound with each heart beat) Average value is around 80 mmHg Reflects total peripheral resistance, but is not equal to it

Blood Pressure Must Be Regulated Low Blood Pressure Blood will not reach all tissues Specifically those where gravity is acting against flow Most importantly the brain High Blood Pressure –Heart is placed under great stress –Excess plasma leakage –At the extreme, capillaries burst

Rate Pressure Product RPP = HR x Systolic BP / 100 Has no units An estimation of the total work of the heart Also known as the double product

Two Types of Exercise Dynamic –Involves repetitive motions –What we typically think of as exercise Static –A held position with little or not muscle movement –Still requires energy

What happens during exercise? Exercising tissues require an increase in blood flow Cardiac output (Q) must increase Cardiac output = heart rate (HR) x stroke volume (SV) Q = HR x SV

But how does that affect blood pressure? MAP = Q x TPR Mean Arterial Pressure (MAP) Cardiac Output (Q) Total Peripheral Resistance (TPR) MAP = Diastolic +1/3 (systolic-diastolic)

Effects of Exercise on Blood Pressure Dynamic Exercise –Need increased Q –Increased HR –Decreased TPR –Diastolic BP stays ~ the same –Systolic BP increases and then levels off or slightly decreases Static Exercise –Need increased Q –Increased HR –Increased TPR –Increased MAP –Increased DBP/SBP