IV- Acute Responses to Aerobic Exercise (Heart Rate & Blood Pressure) PDF

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Summary

KNES320 Lab Notes...

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Blood Pressure - Blood pressure = the amount of pressure exerted by circulating blood on the walls of the arteries. -

Measured w/ a Sphygmomanometer

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What is Blood Pressure (BP)? Quantitative terms: product of arterial blood flow per minute (cardiac output or Q) and the vascular resistance to that flow (Total Peripheral Resistance or TPR). BP = Q * TPR Cardiac Output (Q): - The total volume of blood pumped by the left ventricle per minute (L/min) - Product of heart rate (HR) and stroke volume (SV): - Q = HR * SV - HR = beats per minute (bpm) - SV = the amount of blood pumped per contraction (L) Total Peripheral Resistance (TPR): - Cumulative resistance of thousands of arterioles in the body - Determined by the degree of their vasoconstriction/vasodilation and compliance/stiffness Systolic vs. Diastolic - Systolic Blood Pressure = force/pressure from the contraction of the left ventricle (systole) that pushes blood from the heart through the arteries. - Diastolic Blood Pressure = force/pressure exerted on the arteries during the heart’s relaxation phase (diastole) - Expressed as SBP/DBP (mmHg)

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Systole vs. Diastole - Systole – ventricles contract, ejecting blood - Diastole – ventricles relaxed, filling with blood

Why do we measure BP? - Primary purpose = to determine the potential risk for cardiovascular disease (CVD) BP is highly regulated within a narrow range of normal values. - Short-term regulation = Baroreceptors - Long-term regulation = Other organs (renin-angiotensin system, etc.) -

Maintenance of blood pressure within a normal range is important to protect both blood vessels and the organs they perfuse. Abnormal measurements above or below normal ranges could be considered pathological and indicate an elevated risk for CVD.

Blood Pressure Classifications BP Classifications (AHA, 2017)

Classification

SBP/DBP (mmHg)

Normal

in men than women (at all age groups?) - Difference between the sexes is significant in age groups except 60 and over.

Disparities in Hypertension – Race/Ethnicity - Prevalence: non-Hispanic Black > non-Hispanic Whits & Hispanic populations

Disparities in Hypertension – Education Level - Significantly more individuals w/ hypertension have an education in high school or less or more than high school or some college > college graduates. - For men, the difference in the prevalence of hypertension is not significant between men in high school, or less education & more than high school or some college. The difference -

however is significant when compared to college graduates. W/i college graduates, men are more likely to be hypertensive.

The GOOD NEWS Although you cannot control all of the risk factors for hypertension, there are several lifestyle modifications that can be used to prevent or control/lower high blood pressure: - Weight reduction - DASH diet (balanced diet reduced in fat & salt) -

Restrict sodium intake PA Moderate consumption of alcohol

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Sphygmomanometer: made up of a fabric cuff, w/ an air bladder, and pressure gauge.

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The valve for the gauge can be closed to allow the user to inflate the cuff w/o any air escaping. This in turn allows the cuff to partially or completely close off the brachial artery during measurement (also known as occlusion). Wrap the cuff around the upper arm about at heart level aligned with the brachial artery. Place a stethoscope below the antecubital space over the brachial artery to hear the LUB DUB sounds once the cuff is being deflated and blood flows through the brachial artery again. The cuff is inflated to ~ 200mmHg and then the pressure is slowly released. The first sound clear tapping noise is the LUB sound at which point the systolic pressure is recorded. The last point before the disappearance of the sound is the diastolic pressure.

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Acute Responses to Aerobic Exercise - Normal responses to BP during exercise - Systolic BP increases linearly with exercise intensity. As the heart works harder, the CO increases to deliver O2 rich blood to working muscles. - Diastolic BP remains ~ the same level & may decrease slightly. The slight decrease in diastolic BP is likely due to the vasodilation of the arteries from the exercise.

Heart Rate (HR) Classification Heart Rate = beats per minute (bpm) -

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Average resting heart rate (RHR) = 60 - 80 bpm - Tachycardia = above 100 bpm - Pre-tachycardia or tachycardia is usually a bad sign - Linked to increased risk for CVD & early death - Bradycardia = below 60 bpm - Not always a bad condition to have; cyclist Lance Armstrong has a resting HR of ~32bpm. - Aerobically trained individuals often have a lower HR because they have trained their cardiovascular system to be more efficient w/ an increased SV. - The heart doesn’t have to be as fast because it can pump more blood w/i each beat & effectively perfuse the vital organs w/ oxygenated blood. Normal RHR range = 60 – 100 bpm - RHR near the upper limit of this range is linked to increased risk for cardiovascular disease and even early death.

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Higher RHR is linked to lower physical fitness and higher blood pressure, body weight, and levels of circulating blood fats. Lower RHR implies more efficient heart function and better cardiovascular fitness. When is the best time to measure RHR? - Best time to get an accurate measurement is usually in the morning before you get out of bed & after a good night’s sleep.

Measurement of Heart Rate - Do not use the thumb to take HR! yields inaccurate measurements: - The thumb contains tiny arteries with their own pulse. - Gently place the index and middle fingers at the base of the thumb (under the wrist; radial side) of the underside of the wrist – alongside the tendons is best. This is the radial artery. - Once a pulse is located, count the number of pulses for 15 seconds and multiply by 4 to get the heart rate for 1 minute. Factors that can influence heart rate: - Activity level: high activity level requires the heart to work harder to meet the body’s demands for oxygen. - Fitness level: see Lance Armstrong - Air temperature: hot temperature: some blood is rerouted to the surface of the skin to cool off. - Body position: standing up or lying down, for example i.e the extent to which the heart is working against gravity. - Emotions/Stress - Body size: larger individuals tend to have lower RHR - In the case of an obese individual, excess fat/weight increases stress on the body and may cause the heart to work harder which will → increase HR -

Smoking: Caffeine: Medications:

Max and Target Heart Rate - 50 - 85% target zone of the age-predicted HR - From the table, max HR decreases w/ age -

To calculate age-predicted HR max: 220 - individuals age - e.g for age 20, age-predicted HR max = 220 - 20 = 200 bpm

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Aerobically trained individuals are sometimes able to exercise above their age-predicted HR max

Acute Response to Aerobic Exercise - HR increases linearly w/ exercise intensity. - As intensity increases, HR increases to meet the metabolic demands of the exercise until the point where the heart reaches its maximum and cannot beat any faster....