IMPORTANT TERMS AND CONCEPTSINTRODUCTIONPHYSIOLOGICAL RATIONALEMEAN ARTERIAL PRESSURE (MAP)BLOOD PRESSURE DURING EXERCISE AND RECOVERYBLOOD PRESSURE DURING AEROBIC EXERCISEBLOOD PRESSURE DURING RECOVERY FROM AEROBIC EXERCISEEXPERIMENTAL PROBLEMPROCEDURECalculationsIMPORTANT TERMS AND CONCEPTS1. Blood Pressure (BP)2. Pulse Pressure (PP)3. Mean arterial pressure (MAP)4. Cardiac cycle5. Hypertension/Hypotension6. Cold Pressor TestINTRODUCTIONBlood Pressure is the force exerted on the walls of blood vessels by the blood. The forceis the result of the contraction and relaxation of the heart. Blood pressure is expressed inmillimeters of mercury (mmHg). Typical measurements for males and females are 120/80 and110/70, respectively. The higher number refers to systolic blood pressure (SBP), which isproduced as blood is ejected from the left ventricle during systole. The lower number indicatesdiastolic blood pressure (DBP); this represents the pressure being exerted on the blood vesselsduring the relaxation phase (diastole) of the cardiac cycle. In this lab blood pressure will be evaluated at rest and during exercise using a stethoscopeand a sphygmomanometer. Pulse pressure (PP) and mean arterial pressure (MAP) will bedetermined for one subject during rest, lying supine, exercise, and exercise with the cold pressortest. Blood pressure may be defined for laboratory purposes as the force of blood distendingthe arterial walls. Blood pressure is primarily dependent upon the volume of blood and theresistance of the blood vessels. Blood exerts pressure throughout the vascular system, but isgreatest within the arteries where it is generally measured and used as an indication ofcardiovascular function. Blood pressure is typically measured in the brachial artery at theantecubital fossa (anterior crease of the elbow). In this lab, we will measure blood pressureresponse to perturbations in body position and physical work.PHYSIOLOGICAL RATIONALEBlood 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 ahigh risk for cardiovascular disease, stroke, and kidney failure. High blood pressure results in agreater workload for the heart, which can lead to physiological changes, such as artery damageand narrowing, aneurysms, and enlarged left ventricles. High blood pressure may not be noticedoutwardly because there are no obvious symptoms until a fatal or near fatal heart attack or strokeoccurs. Therefore, the primary clinical purpose of measuring blood pressure is to determine theLABORATORY #4: BLOOD PRESSURE AND ACUTERESPONSEpotential 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 onheart 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 thatcorrespond to the highest pressures (systolic) and lowest pressures (diastolic) experienced by thevasculature during a cardiac cycle. Pulse pressure (PP) is the difference between systolic bloodpressure (SBP) and diastolic blood pressure (DBP). This difference is used to determine meanarterial pressure (MAP). Because arterial blood pressure under resting conditions is at systoliconly about 1/3rd of the time during a cardiac cycle, MAP is always closer to diastolic pressurethan it is to systolic pressure. The formula for MAP is shown below:MAP = [(SBP-DBP)/3] + DBPThis is during resting conditions. During exercise, the time spent in diastole and systole becomeequal 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 + DBPBLOOD PRESSURE DURING EXERCISE AND RECOVERYNumerous factors may affect blood pressure at exercise. These may includecharacteristics 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 beexpected to increase blood pressure more than rhythmic aerobic exercise such as cycling orwalking. 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 therate of increase and absolute levels of blood pressure during exercise. Blood pressure is mainly a function of cardiac output and peripheral resistance. Ingeneral, 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 increasedcardiac output more than makes up for the decreased peripheral resistance.BLOOD PRESSURE DURING AEROBIC EXERCISEIn general, systolic blood pressure is expected to increase rather linearly and diastolicpressure changes very little, if at all, during progressive aerobic exercise. Systolic pressure isexpected to increase by approximately 10-15 mmHg for each 300 kg.m/min (50 W) increase incycle power level. A higher rate of increase may be found in subjects who are less active.BLOOD PRESSURE DURING RECOVERY FROM AEROBIC EXERCISEBlood pressure often returns to the pre-exercise level within 5-8 minutes after thecessation of moderate exercise. It is not unusual for systolic pressure to drop slightly lower thanthe pre-exercise systolic pressure, due to prolonged systemic vasodilation. The return of bloodpressure to resting levels is affected by the type, intensity, and duration of the original exercise inaddition to the type of recovery.BLOOD PRESSURE DURING CHANGES IN BODY POSITIONThe body and vasculature can be thought of