UMass Amherst KIN 470 - Lab 4 Handout_adjusted_ (7 pages)

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Lab 4 Handout_adjusted_

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Pages:
7
School:
University of Massachusetts Amherst
Course:
Kin 470 - Exercise Physiology
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LABORATORY 4 BLOOD PRESSURE AND ACUTE RESPONSE IMPORTANT TERMS AND CONCEPTS 1 2 3 4 5 6 Blood Pressure BP Pulse Pressure PP Mean arterial pressure MAP Cardiac cycle Hypertension Hypotension Cold Pressor Test INTRODUCTION Blood Pressure is the force exerted on the walls of blood vessels by the blood The force is the result of the contraction and relaxation of the heart Blood pressure is expressed in millimeters of mercury mmHg Typical measurements for males and females are 120 80 and 110 70 respectively The higher number refers to systolic blood pressure SBP which is produced as blood is ejected from the left ventricle during systole The lower number indicates diastolic blood pressure DBP this represents the pressure being exerted on the blood vessels during the relaxation phase diastole of the cardiac cycle In this lab blood pressure will be evaluated at rest and during exercise using a stethoscope and a sphygmomanometer Pulse pressure PP and mean arterial pressure MAP will be determined for one subject during rest lying supine exercise and exercise with the cold pressor test Blood pressure may be defined for laboratory purposes as the force of blood distending the arterial walls Blood pressure is primarily dependent upon the volume of blood and the resistance of the blood vessels Blood exerts pressure throughout the vascular system but is greatest within the arteries where it is generally measured and used as an indication of cardiovascular function Blood pressure is typically measured in the brachial artery at the antecubital fossa anterior crease of the elbow In this lab we will measure blood pressure response to perturbations in body position and physical work PHYSIOLOGICAL RATIONALE Blood pressure measurement is a common component of a physical clinical examination It is recommended that persons of all ages should periodically check their blood pressure Elevated blood pressure hypertension 140 90 mmHg and greater has been associated with a high risk for cardiovascular disease stroke and kidney failure High blood pressure results in a greater workload for the heart which can lead to physiological changes such as artery damage and narrowing aneurysms and enlarged left ventricles High blood pressure may not be noticed outwardly because there are no obvious symptoms until a fatal or near fatal heart attack or stroke occurs Therefore the primary clinical purpose of measuring blood pressure is to determine the potential risk of cardiovascular disease Medications that function to decrease blood volume vasoconstriction and cardiac contractility are typically prescribed to reduce blood pressure While lifestyle and medications have chronic effects of blood pressure by their effects on heart function and the peripheral vasculature blood pressure is also subject to acute influences In this lab we will examine the acute effects of exercise and body position on blood pressure This is done to demonstrate the influence of changing oxygen demands and gravity on the body Pressure changes within the thoracic cavity can also influence cardiovascular function MEAN ARTERIAL PRESSURE MAP Blood pressure is expressed in millimeters of mercury mmHg with two numbers that correspond to the highest pressures systolic and lowest pressures diastolic experienced by the vasculature during a cardiac cycle Pulse pressure PP is the difference between systolic blood pressure SBP and diastolic blood pressure DBP This difference is used to determine mean arterial pressure MAP Because arterial blood pressure under resting conditions is at systolic only about 1 3rd of the time during a cardiac cycle MAP is always closer to diastolic pressure than it is to systolic pressure The formula for MAP is shown below MAP SBP DBP 3 DBP This is during resting conditions During exercise the time spent in diastole and systole become equal due to increasing heart rate A change in the calculation for MAP reflects this The equation for MAP during exercise is MAP SBP DBP 2 DBP PP 2 DBP BLOOD PRESSURE DURING EXERCISE AND RECOVERY Numerous factors may affect blood pressure at exercise These may include characteristics of the subjects such as their age muscle mass fitness level and smoking status Also the type of exercise may affect blood pressure For example weight lifting would be expected to increase blood pressure more than rhythmic aerobic exercise such as cycling or walking Differences are found even among types of aerobic exercise cycling for example elicits higher blood pressures than treadmill exercise The exercise protocol itself may affect the rate of increase and absolute levels of blood pressure during exercise Blood pressure is mainly a function of cardiac output and peripheral resistance In general the increase in blood pressure during exercise is due to the increased cardiac output Despite a decrease in peripheral resistance due to dilation of muscle arterioles the increased cardiac output more than makes up for the decreased peripheral resistance BLOOD PRESSURE DURING AEROBIC EXERCISE In general systolic blood pressure is expected to increase rather linearly and diastolic pressure changes very little if at all during progressive aerobic exercise Systolic pressure is expected to increase by approximately 10 15 mmHg for each 300 kg m min 50 W increase in cycle power level A higher rate of increase may be found in subjects who are less active BLOOD PRESSURE DURING RECOVERY FROM AEROBIC EXERCISE Blood pressure often returns to the pre exercise level within 5 8 minutes after the cessation of moderate exercise It is not unusual for systolic pressure to drop slightly lower than the pre exercise systolic pressure due to prolonged systemic vasodilation The return of blood pressure to resting levels is affected by the type intensity and duration of the original exercise in addition to the type of recovery BLOOD PRESSURE DURING CHANGES IN BODY POSITION The body and vasculature can be thought of in some respects as a vessel of fluid The distribution of fluid within this vessel is subject to the effects of gravity For this reason it is important to be mindful of an individual s body position and the site of pressure recording relative to the heart when measuring blood pressure Pressure will be taken with a subject supine and while seated Brachial blood pressure typically drops substantially when standing after laying supine due to the sudden shift of blood volume to the vasculature of the lower limbs This phenomenon is known as


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