4 Improving Cardiovascular Fitness
Chapter 4 - Improving Cardiovascular Fitness _____________________________________________________________________
Did You Know That… The heart is a muscle, and it responds to progressive resistance training in much the same manner as skeletal muscle. You could jog every day and not develop cardiovascular fitness. Any physical activity can be used to develop cardiovascular fitness…as long as the individual elevates his heart rate sufficiently for a long enough period of time. Individuals who have properly trained for cardiovascular fitness will have larger and stronger hearts than untrained individuals. Strenuous exercise will not damage the healthy heart. Many athletes perform far below their physical capabilities because they have over trained. Some world-class marathon runners have resting heart rates as low as thirty two beats per minute. There may not be any such thing as “second wind.” There is a training technique used by endurance athletes to increase the glycogen (energy) stored in their muscle tissues. When engaging in cardiovascular training, it is best to abstain from eating solid foods for two to four hours before exercising. Walking is a poor exercise for developing cardiovascular fitness. The greatest non stop run is 352.9 miles in 121 hours and 54 minutes by Bertil Jarlaker (Sweden) on May 26-31,1980 (Guinness Book of World Records, 20th ed.).
After reading this chapter you should be able to answer the following questions What is physical fitness? How do I measure my cardiovascular fitness level? If I have good cardiovascular fitness, will I also have good muscular endurance and strength? Which component of fitness is most important? What are some ways that fitness can be developed? What is the overload principle? What is progressive resistance? What is cardiovascular endurance? Do women have the same capacity as men for developing fitness? What is required to make fitness gains? When is an exercise steady state reached? How is a target heart rate calculated? What test can and cannot measure cardiovascular fitness? What is Maximum Oxygen Consumption? What is the 600 Yard Run Walk Test? What is the 1200 Yard Run Walk Test? What does reliable and valid mean?
Key Terms Overload principle Maximum heart rate Frequency Duration Training effect Progressive resistance Training sensitivity zone Aerobic Training Heart rate range Tolerance pulse rate Marathon training Circuit training Oxygen debt
Synthesis Lactic acid Homeostasis Training sensitivity zone Intensity Adaptation Tolerance pulse rate Interval Training Karvonen Method Capability range African method of training Fartlek training Blood Doping
Creatine phosphate Steady state Pyruvic acid Lactate threshold
Chapter 4 - Improving Cardiovascular Fitness _____________________________________________________________________
Cardiovascular Fitness _____________________________________________________________________
Cardiovascular fitness refers to the health and adequacy of the heart and the circulatory system. It is generally defined as the ability of the heart and respiratory system to supply oxygen to the tissues of the body. As was mentioned, cardiovascular fitness is probably the most important component of physical fitness. There are numerous benefits that can be derived from cardiovascular training. First of all, it can significantly enhance the efficiency of the lungs in processing oxygen. Trained individuals are capable of processing almost twice as much air per minute as untrained individuals (Powers & Howley, 2003). This efficiency allows trained individuals with more oxygen for the energy producing process. In other words, the more oxygen you get to the muscles of the body, the more work you can do. In short, good cardiovascular fitness will afford you the ability to exercise longer and harder. Another advantage of cardiovascular training is that it strengthens the heart muscle and increases the heart’s stroke volume and cardiac output. An individual who is in good condition may have a heart rate twenty beats slower (or more) than a sedentary person or someone who is in poor cardiovascular shape. The reason for this difference is that the heart pumps more blood with each beat and with less effort. Keep in mind, if it takes your heart twenty beats more per minute to do the same workload as another individual, which means that in one hour your heart will beat 1200 times more (20 beats x 60 minutes); in one day, it will beat 16,800 times more (1200 beats x 24 hours); and in a year, 588,000 times more than a trained individual’s heart. That’s not good! A lower heart rate means that the heart is conserving energy and that it has built-in protection against beating too fast or being strained. Cardiovascular training will also increase vascularization (the number and size of blood vessels) of the heart. The heart, as with other muscles in the body, needs oxygen in order to do work. Thus, a healthy heart is both strong and well supplied with blood vessels…the better the vascularization of the heart, the better the oxygen supply, and the better the endurance of the heart. Cardiovascular training not only strengthens the heart muscle, it also increases the heart’s ability to do work over a prolonged period of time. In addition, cardiovascular training also increases vascularization of skeletal muscles and causes an increase in total blood volume. Both of these effects provide the means for delivering more oxygen to the tissues of the body. And remember, the more oxygen, the longer the cat stays on the conveyor belt before falling off.
A Fantastic Voyage Through Your Lungs and Heart ____________________________________________________________________________________________________________________________
Before you can fully benefit from a fitness program, we believe it is imperative that you have a working knowledge of how your body functions. Once you acquire an understanding of your cardiorespiratory functions, you
∞ WELLNESS FOR LIFE ∞ __________________________________________________________________
What is Coronary Circulation? There is a subdivision of the circulatory system that supplies the heart itself with blood… thereby providing oxygen and nutrients while returning waste products. The coronary arteries leave the aorta and return to the outside of the heart. Approximately 10% of the blood leaving the left ventricle of the heart flows through the coronary system (roughly 300-400 ml per min.). Incidentally, the blood within the cavities of the heart nourishes only the lining of the heart.
Chapter 4 - Improving Cardiovascular Fitness _____________________________________________________________________
will develop greater appreciation for the benefits that you can derive from your training. So, let’s take a look at your cardiorespiratory system and how it functions. It always amazes us how many people don’t have the slightest idea as to how they breathe or worse yet, why they breathe. Incredibly, some students believe that oxygen goes in your mouth and then just sort of diffuses through the body…like osmosis or something. With all the misinterpretation and incomprehension concerning the cardiorespiratory system, we thought it would be a good idea to give you a cursory explanation as to how it really functions. The basic organs concerned with respiration are the nose, trachea, bronchi and the lungs. Air coming in through the nose and mouth leads through a pathway into the bronchial tube, then to the two bronchi (major pathways leading to the lungs), then to the bronchioles (smaller tubes branching from the bronchi) and finally, to the tiny air sacs called alveoli. Check out the diagram we made for you in Figure I. Just don’t glance at it…really check it out. If you understand the parts and how they work, this is simple stuff. So look at it closely and understand it before going on. Now, the question arises, “How does air get from the nose all the way to the alveoli?” It doesn’t suck in the same way you suck soda through a straw and it doesn’t get there by magic. Actually, air is exchanged by creating a pressure differential. The basic principle underlying the movement of air or gas is that it will travel from a high pressure area to an area of lower pressure. It will also travel from an area of greater concentration to an area of lower concentration. The process is called diffusion and takes place as a result of the pressure gradient or difference. The respiratory muscles and the elasticity of the lungs create the pressure differential that first allows air to flow into the lungs and then allows air to be expelled from the air passages. Let’s begin with inspiration, or the act of taking air into the lungs. First, the diaphragm (that big muscle in the lower portion of your stomach) and the external intercostal ∞ WELLNESS FOR LIFE ∞ __________________________________________________________________ muscles (those little muscles that are connected to your rib cage) contract What is Systolic and Diastolic Pressure? expanding your thoracic (chest) cavity. Allow us to explain further. It’s not all Systole corresponds to the contraction of the that hard to understand. When the ventricles. Ventricular systole causes blood to enter the arteries diaphragm contracts, its dome moves and blood pressure is at its highest during this period (it averages downward, expanding the thoracic cavity between 110-120 mm of mercury at the brachial artery in a from top to bottom. When the intercostal healthy adult). muscles contract, they pull the ribs During ventricular diastole (when the heart momentarily relaxes) blood pressure in the heart decreases and outward and slightly upward. This reaches a minimum just before the start of the next systole. This movement also enlarges the thoracic minimum is called diastolic pressure (it averages between 65-80 cavity from side to side and from front to mm of mercury at the brachial artery in a healthy adult). back. The enlargement of the thoracic Blood pressure will be affected by the position of the cavity causes a decrease in pressure. Air body. It is standard practice to measure blood pressure while the pressure outside the body is then greater individual is seated and the arm is about level with the heart. than the air pressure inside the body,
causing air to flow into the lungs and alveoli until thoracic pressure is equal to the atmospheric pressure. If you understand all of that, raise your hand. If you don’t, the easiest way to understand this is to think about a balloon under water. What happens to a balloon when you put it under water? It shrinks because of the pressure that the water exerts on the balloon. Does the amount of air in the balloon change? No. It’s still the same. So, we have the same amount of air in a smaller space. So, the pressure in the balloon goes up. Consequently, when you take the balloon out of the water, the size of the balloon expands and the pressure decreases according the change in the size of the balloon. The lungs are like balloons such that as the space that holds the air expands, the pressure in them goes down. So, after your diaphragm drops and the intercostals lift the ribs increasing the space in the lungs, you will have air in your lungs…right? Right! Now, listen closely here. We want you to do well on your test. Now, let’s see how it gets back out. In other words, let’s look at expiration, or the expelling of air from the lungs. Expiration is nearly the opposite of inspiration. In this case, the diaphragm and the external intercostal muscles relax, thereby returning to their original position. When this occurs, the volume of the thoracic cavity decreases by all parameters, causing the pressure inside the lungs to increase. The pressure in the cavity and lungs now is greater than the atmospheric pressure, which causes air to flow out of the cavity and lungs until the external (atmospheric) and internal (thoracic) pressures are once again the same. If you don’t understand what we are talking about, Simon says, “Read it again.” Okay, now that you understand how air enters and exits the body, the next step is to understand how oxygen is delivered to the tissues of the body. In order to know how that works, you will first have to understand how the cardiovascular system functions. See, you’re getting a real education here. This system consists of the heart and blood vessels (let’s not forget arteries, capillaries and veins). Check out the picture we have for you on the heart. Look at it closely before you go on. The heart is a four chambered muscular organ that is roughly the size of your fist. The upper cavities are called atria, while the lower cavities are known as ventricles. Blood comes in from the lower extremities (legs, groin, & abdomen) into the right atrium through the inferior vena cava. Blood from the upper extremities (head, shoulders and chest) also empties into the right atrium, but this time through the superior vena cava. The blood at this time has a high concentration of waste products, such as carbon dioxide and carbon monoxide, and a low concentration of oxygen. From the right atrium, blood goes to the right ventricle. When the ventricles contract, the left ventricle forces blood through the pulmonary artery which leads into the lungs. From there, the connection goes off the pulmonary artery branch to smaller vessels called arterioles, and off the arterioles branch even smaller vessels called capillaries. These capillaries intermingle with the millions of tiny air sacs throughout the lungs. It is there in the tiny air sacs that the real work of the vascular system takes place. The carbon dioxide in the capillaries is exchanged for the oxygen in the alveoli. Remember, high concentrations always diffuse to low concentrations. The carbon dioxide in the alveoli is then exhaled.
Now, here’s something interesting. Did you ever notice that when you walk around campus, all of those little green trees and shrubs follow after you? What do you think they want…your bootie? No! What they want is your carbon dioxide…not your phone number. You see, we have ∞ WELLNESS FOR LIFE ∞ this little arrangement with them. We __________________________________________________________________ give them carbon dioxide and in turn they give us oxygen. If they don’t get carbon How is Blood Pressure Measured? dioxide they will die, and if we don’t get oxygen, we will die. If you take all the A rough estimate of systolic pressure can be made by greenery off the face of the earth, we using a finger to take a pulse (usually at the radial artery of the would all die. If you take all the animals wrist). If the artery is easily compressed and stops the pulse, it is a sign of low pressure. If the artery is relatively incompressible, and humans off the earth, all the greenery it may indicate hardening of the arteries and/ or high blood would die. We keep the trees alive by pressure. supplying them with carbon dioxide and More sophisticated methods of measuring blood they keep us alive by supplying us with pressure involve using an inflatable fabric cuff. The cuff is oxygen. They take our carbon dioxide wrapped around the arm and inflated until the pulse is no longer and through a process called felt. The cuff is deflated until the pulse can just be felt. This photosynthesis, convert it to the oxygen pressure is indicated on a gauge and is approximately equal to that we breathe. In brief, we need each the pressure that the blood exerts on the walls of the artery other to coexist. (systolic pressure). The device is called a sphygmomanometer. In the auscultation method, a stethoscope is used and The oxygen that the blood and the inflated cuff is slowly deflated until a pulse is first heard. The the capillaries pick up is then taken back corresponding pressure reading is systolic pressure. The cuff is to the heart through three pulmonary now deflated further. The pressure just before the last sound of veins and emptied into the left atrium. the disappearing pulse indicates diastolic pressure. For an adult, From the left atrium, the blood then goes systolic pressure of 110 or 120 millimeters of mercury and to the left ventricle. When the heart condiastolic pressure of 65 to 80 is normal. Hypertension is tracts, the oxygenated blood in the left suggested by a systolic pressure of 150 or above. ventricle is forced into the aorta which in turn leads into systemic circulation. As the blood moves through the body, the tissues of the body absorb the oxygen and use it in the metabolic process. It is good to remember that normally arteries in the body carry oxygenated blood while veins carry deoxygenated blood. The only exceptions are the pulmonary artery that carries deoxygenated blood from the heart to the lungs and the pulmonary veins that carry oxygenated blood from the lungs back to the heart. Now here is something else you may not know. The heart does not get its oxygen from inside its chambers. The blood actually leaves the heart and then returns to “feed” itself through coronary vessels. There is a subdivision of the circulatory system that supplies the heart with blood, providing oxygen and nutrients while returning waste products. When the blood leaves the heart, coronary arteries branch off from the aorta and return to the outside of the heart. This is called coronary circulation. Approximately 10% of the blood leaving the left ventricle of the heart flows through the coronary system (roughly 300-400 ml per minute). By the way, the blood within the cavities of the heart nourishes only the lining of the heart.
Why Do We Need Oxygen? ___________________________________________________________________________
Why do we need oxygen? This is a question our students mull over in their brains hour after hour until the Madonna video’s come on ∞ WELLNESS FOR LIFE ∞ __________________________________________________________________ MTV every night. Some of the Oxygen Debt. answers we’ve gotten are…well… Oxygen debt is a condition in which the amount of oxygen needed for optimal cute…things like functioning of the muscles is less than what is available or being supplied. Typically, the “You need oxygen oxygen debt is made up after you stop exercising. That is, as you are still gasping for air to breathe,” or following the completion of an exercise bout, you body is making up for oxygen that was “You need oxygen unavailable during the activity. to make the blood During light exercise, the need for oxygen is constantly satisfied, but strenuous or vigorous exercise produces an oxygen demand that may be greater than the supply, go through the and oxygen debt is said to occur. Oxygen debt stimulates anaerobic metabolism and body.” Of course, increases the demand for glycogen. Synthesis of ATP is reduced and there is a reduction the standard answer of creatine phosphate. The strength of muscle contraction is progressively diminished, is “You need fatigue results, and eventually the muscle will not respond to further stimulation. This oxygen to live.” hurts! Kind of like giving birth or perhaps a little more like having gas but either way it’s Yet, few students no fun when you experience oxygen debt. The muscle will recover after a period of rest really understand that provides time for the blood to carry away waste products and restore the supplies why. We are going oxygen and nutrients to the muscles. Isn’t that good news! to tell you why it is It is primarily the accumulation of the waste products of metabolism that brings on fatigue by inhibiting enzyme actions involved in the utilization of glycogen, but you imperative that you knew that, right? The heavy breathing and accelerated heart rate that occurs during get oxygen without oxygen debt reduces oxygen deficiencies, supplies the muscles with nutrients, and clears embarrassing you. away accumulated waste products. What the heck, you Also interesting to note is that when the glycogen stored in the specific muscles paid for the book so is depleted, the individual is unable to continue the exercise even though there is an we are going to cut adequate supply of glycogen in inactive muscles that are not involved in the exercise. In you some slack. other words, there is little transfer of glycogen from one muscle to another. Let’s do it this way. You go over to McDonald’s restaurant and order one of those 99 cent Big Macs that sells for $2.50 nowadays. You know the kind…two all beef patties, special sauce, lettuce, cheese, pickles, onions, on a sesame seed bun. You take a big bite and chew it up into this icky substance call bolus. This process is called mastication, not masturbation as some of our students seem to think. After you chew your food up, you swallow it and it goes down into your stomach, where it is churned up into this gummy substance called chime. Your pancreas then squirts out hydrochloric acid that breaks the chime down to a complex sugar called glycogen. The glycogen is then converted to a simple sugar called glucose and the glucose is circulated through the body by way of your blood stream. The pancreas then secretes insulin, which gives your cells the ability to absorb the glucose. Now, here is something you may not know. Every cell in the body has a manufacturing company called mitochondria. Once this cell absorbs the glucose, it is taken to this manufacturing company and converted into an energy rich compound called adenosine triphosphate (ATP). ATP serves as the fuel for the cells’ energy requirements. ATP molecules represent stored chemical energy. Energy is released when the bonds of the ATP molecules are broken. The breakdown of ATP serves to power all biological work. So, what does this have to do with oxygen? We’re glad you asked. Let’s use another analogy here. When it gets cold, we go out and chop wood to build a fire. The log goes into the fireplace and then we stand next to it. Now, does that make us warm? Of course not! In order to get heat from the wood, the wood has to burn. So, the wood is potential energy but it is worthless to us unless we can light it. Then, we get energy from the wood. ATP is like the wood. It is potential energy but you can’t get the energy from it unless you light it. And, guess what lights it? Get a grip now, because this is the $64 million question. If you said oxygen, you’re right. You win $64 million…use your imagination here. When oxygen mixes with ATP, a phosphate is released and used for energy! In short, nutrients in consumed food supply the energy that powers all biological functions. In order for the cells (which are like chemical factories) to use these nutrients, they must first be converted to ATP and then oxidized.
Aerobic and Anaerobic Metabolism __________________________________________________________________________________________
Okay, now that you understand all of that, we are going to throw a monkey wrench into this mess. The breakdown of ATP molecules can occur anaerobically, in the absence of oxygen. I know we said it couldn’t, but we lied…sort of. The cells can break down ATP without oxygen for immediate energy. However, there is only enough ATP stored in the body to provide energy for a few seconds (about 5-8 seconds) of all out strenuous activity. Consequently, exercises that are high intensity and short duration (such as a 100 yard dash) can be performed anaerobically. At the other extreme, long duration activities (such as marathon running) require a constant aerobic energy source. In order to perform such exercises, a continuous source of energy ATP must be used constantly, requiring a constant supply of oxygen. The relative contribution of anaerobic and aerobic metabolism to the energy needs of the individual depends on the type of activity being performed. Many sports activities require particular combinations of aerobic and anaerobic metabolism for maximum effectiveness. Therefore, athletes usually have to use different training routines in order to develop both components of the metabolic system. …
Why the Heart is so Important __________________________________________________________________________________
Every living cell of the body is dependent upon blood for its existence because the blood transports all substances to and from the cells. That is, it carries oxygen and nutrients to the cells and carries away waste products (Remember carbon dioxide and carbon monoxide?). Now, here is the important part. The blood is contained in a system of tubes that are connected to the heart. The contractions of the heart cause the blood to circulate continuously throughout the body. In short, the function of the heart is to increase or decrease the velocity and volume of blood in accordance with the metabolic needs of the cells. The blood can’t circulate through the body unless the heart pumps it through. In laymen’s terms, no heart, no circulation, no circulation, no blood, no blood, no oxygen and nutrients, no oxygen and nutrients…no you. Do you get the point? GREAT! Okay, now you have to understand a few terms to get a real appreciation of the way all of this happens. The first term is heart rate. You probably already know what it is, but just in case you have been living in a cave for the last decade or so, we are going to explain it to you. Heart rate is the number of times the heart beats per minute. Heart rate is calculated by counting your pulse for a minute. You can also calculate it for 10 or 15 seconds and multiply that number by six and four respectively. We love math! The best place to take your heart rate is at your carotid artery. Don’t use your thumb to do this because it has a pulse and that will interfere with getting a correct count. All right, put your book down and take your heart rate. Do it now! We’re doing the coaching here. Now, write that on your sleeve with indelible ink because we are going to use that information later on. The next term you will need to know is stroke volume. Stroke volume is the amount of blood pumped out of the heart per beat. The heart contracts during systole (the contraction phase of the heart) and forces about 70ml of blood from the ventricle to the aorta. From the aorta, it is then distributed throughout the body. Here is something else you can write on your sleeve. Stroke volume is directly proportional to the
strength of the heart. The next term you need to know is cardiac output. Cardiac output is the product of the heart rate and the stroke volume. Again with the math! Multiply the stroke volume by the heart rate. So, for example, a man at rest has a pulse rate of 70 beats per minute and the amount of blood leaving the left ventricle per minute is 70 ml. 70 beats x 70 ml/min = 4,900 ml/min (4.9 liters) Consequently, cardiac output is defined as the amount of blood pumped per minute. Cardiac output will rise proportionally to increases in either stroke volume or heart rate. If you increase one or the other, you are going to increase you cardiac output. All right, it’s time for a little quiz. Take out a piece of paper. No cheating now. Are you ready? Here we go…there are two individuals. Let’s say…Jane Fonda and Richard Simmons. We picked them because they are aerobic experts… which is kind of funny because Richard’s legs are so skinny they look like a pair of pliers. That just goes to show you that you can be a fitness expert without looking like one. Anyway, let us assume that Jane and Richard are engaged in the same exact workload. You know sitting around and watching Oprah on the tube. During this time, Jane’s heart rate is 50 beats per minute and her stroke volume is 60 ml. What is Jane’s cardiac output? If you said 3000ml per minute, you were right! Don’t get too excited though; we’re not finished yet. Richard’s heart rate is 60 beats a minute and his stroke volume is 50ml. Consequently, his cardiac output is also 3000 ml. Incredible how that works, huh? For a smiley face, who is in better shape, Richard or Jane? Or are they both in the same shape? If you said Richard you are dead wrong. You can just look at him and tell that. No, just kidding. You can’t just look at someone and tell if they’re in good cardiovascular shape or not. It’s kind of like judging a book by its cover. You can do that, but you’re not always right. The same is true here. The reason Jane is in better shape has nothing to do with her being better looking than Richard either. The reason is that her heart is stronger. When Jane’s heart contracted, it pumped more blood than Richard’s, thus giving her a greater stroke volume. In general, stroke volume is directly proportional to the size and strength of the heart. If you don’t believe us, look on your sleeve. It’s all written down there. In general, a strong heart is larger and contracts more forcefully, thereby forcing a greater volume of blood. Strengthening the heart and consequently, increasing stroke volume reduces the number of times the heart must beat in order to supply the needs of the cells. In summary, with a greater stroke volume Jane’s heart does not have to beat as many times as Richards for the same cardiac output. In other words, her heart does not
have to work as hard has Richard’s to do the same workload. The obvious question now is, “How do you get a stronger heart?” That’s easy, but you will have to wait for the answer. The first thing you will need to do is learn how to evaluate the shape your heart is in now. So, let’s explore that first.