Effects of Exercise

Mariam Kalsoom

Effects of Exercise

Trial Analysis and Evaluation

Hypothesis

Generally the fitter the person the shorter the heart rate recovery period since a fit person has a larger stroke volume and should therefore clear their oxygen debt more quickly after exercise than an unfit person.

Effect of exercise on cardiovascular and respiratory systems

When exercising or competing in sports, the body undertakes a number of changes. You breathe heavier and faster, your heart beats faster, your muscles hurt and you sweat. These are all normal responses to exercise whether you work out regularly or only once in a while or whether you are a trained athlete..

The body has an incredibly complex set of processes to meet the demands of working muscles. Every system in the body is involved. In my trial analysis I will look at how the body responds to strenuous exercise -- how muscles, blood circulation, breathing and body heat are affected.

Your Body's Response to Exercise

Any type of exercise uses muscles. For example, running, swimming, weightlifting all use different muscle groups to generate motion. In running and swimming, muscles are working to accelerate the body and keep it moving. Exercise means muscle activity!

When you use muscles, they begin to make demands on the rest of the body. In strenuous exercise, nearly every system in the body either focuses its efforts on helping the muscles do their work, or it shuts down. For example, your heart beats faster during strenuous exercise so that it can pump more blood to the muscles, and your stomach shuts down during strenuous exercise so that it does not waste energy that the muscles can use.

When you exercise, your muscles act like electric motors. Your muscles take in a source of energy and they use it to generate force. An electric motor uses electricity to supply its energy. Your muscles are biochemical motors, and they use a chemical called adenosine triphosphate (ATP) for their energy source. During the process of "burning" ATP, your muscles need three things:

They need oxygen, because chemical reactions require ATP and oxygen is consumed to produce ATP. They need to get rid of metabolic wastes (carbon dioxide, lactic acid) that the chemical reactions generate.

They need to get rid of heat. Just like an electric motor, a working muscle generates heat that it needs to get rid of.

In order to continue exercising, muscles must continuously make ATP. To make this happen, the body must supply oxygen to the muscles and get rid of the waste products and heat. The more strenuous the exercise, the greater the demands of working muscle. If these needs are not met, then exercise will stop, the body will become exhausted and won't be able to keep going.

To meet the needs of working muscle, the body has an arranged response involving the heart, blood vessels, nervous system, lungs, liver and skin.

ATP

For every cell in your body -- the source of energy that keeps everything going is called ATP. Adenosine triphosphate (ATP) is the biochemical way to store and use energy.

ATP is required for the biochemical reactions involved in any muscle contraction. As the work of the muscle increases, more and more ATP gets consumed and must be replaced in order for the muscle to keep moving.

Because ATP is so important, the body has several different systems to create ATP. These systems work together in phases.

Aerobic Respiration

By two minutes of exercise, the body responds to supply working muscles with oxygen. When oxygen is present, glucose can be completely broken down into carbon dioxide and water in a process called aerobic respiration. The glucose can come from three different places:

remaining glycogen supplies in the muscles
breakdown of the liver's glycogen into glucose, which gets to working muscle through the bloodstream
absorption of glucose from food in ...

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Because ATP is so important, the body has several different systems to create ATP. These systems work together in phases.

Aerobic Respiration

remaining glycogen supplies in the muscles
breakdown of the liver's glycogen into glucose, which gets to working muscle through the bloodstream
absorption of glucose from food in the intestine, which gets to working muscle through the bloodstream

Aerobic respiration can also use fatty acids from fat reserves in muscle and the body to produce ATP. In extreme cases (like starvation), proteins can also be broken down into amino acids and used to make ATP.

For example if you’ve started running. The body will undergo the following stages:

The muscle cells burn off the ATP they have floating around in about 3 seconds.
The phosphagen system supplies energy for 8 to 10 seconds. This would be the major energy system used by the muscles of a 100-meter sprinter or weight lifter, where rapid acceleration, short-duration exercise occurs.
If exercise continues longer, then the glycogen-lactic acid system supplies ATP. This would be true for short-distance exercises such as a 200- or 400-meter run or 100-meter swim.
Finally, if exercise continues, then aerobic respiration takes over. This would occur in endurance events such as 800-meter run.

Getting Oxygen to the Cells

If you are going to be exercising for more than a couple of minutes, your body needs to get oxygen to the muscles or the muscles will stop working. Just how much oxygen your muscles will use depends on two processes: getting blood to the muscles and extracting oxygen from the blood into the muscle tissue. Your body has several ways to increase the flow of oxygen-rich blood to working muscle:

increased local blood flow to the working muscle
diversion of blood flow from nonessential organs to the working muscle
increased flow of blood from the heart (cardiac output)
increased rate and depth of breathing
increased unloading of oxygen from haemoglobin in working muscle

These mechanisms can increase the blood flow to your working muscle by almost five times. That means that the amount of oxygen available to the working muscle can be increased by almost 15 times!

During exercise, the blood vessels in your muscles dilate and the blood flow is greater, just as more water flows through a fire hose than through a garden hose. Your body has an interesting way of making those vessels expand. As ATP gets used up in working muscle, the muscle produces several metabolic by-products (such as adenosine, hydrogen ions and carbon dioxide). These by-products leave the muscle cells and cause the capillaries (small, thin-walled blood vessels) within the muscle to expand or dilate. The increased blood flow delivers more oxygenated blood to the working muscle.

When you begin to exercise, a happens. Blood that would have gone to the stomach or the kidneys goes instead to the muscles, and the way that happens shows how the body's processes can sometimes override one another. As your muscles begin to work, the sympathetic nervous system, a part of the automatic or autonomic nervous system stimulates the nerves to the heart and blood vessels. This nervous stimulation causes those blood vessels (arteries and veins) to contract or constrict. This contraction reduces blood flow to tissues. Because the rest of the body gets the message to constrict the blood vessels and the muscles dilate their blood vessels, blood flow from nonessential organs (for example, stomach, intestines and kidney) is diverted to working muscle. This helps increase the delivery of oxygenated blood to working muscle further.

The heart gets a workout during exercise too, and its job is to get more blood out to the body's hard-working muscles. The heart's blood flow increases by about four or five times from that of its resting state. The body does this by increasing the rate of your heartbeat and the amount of blood that comes through the heart and goes out to the rest of the body. The rate of blood pumped by the heart (cardiac output) is a product of the rate at which the heart beats (heart rate) and the volume of blood that the heart ejects with each beat (stroke volume). In a resting heart, the cardiac output is about 5 litres a minute. As you begin to exercise, sympathetic nerves stimulate the heart to beat with more force and faster. Also, the sympathetic nerve stimulation to the veins causes them to constrict. This, along with more blood being returned from the working muscles, increases the amount of blood returned to the heart (venous return). The increased venous return helps to increase the stroke volume by about 30 to 40 percent. When the heart is pumping at full force, the cardiac output is about 20-25 litres per minute.

The lungs and the rest of your respiratory system need to provide more oxygen for the blood. The rate and depth of breathing will increase because of these events: Sympathetic nerves stimulate the respiratory muscles to increase the rate of breathing.

Metabolic by-products from muscles (lactic acid, hydrogen ions, carbon dioxide) in the blood stimulate the respiratory centres in the brainstem, which, in turn, further stimulates the respiratory muscles.

Slightly higher blood pressure caused by the increased force of each heartbeat and by the elevated cardiac output, opens blood flow to more alveoli in the lungs. This increases the ventilation and allows more oxygen to enter the blood. As the lungs absorb more oxygen and the blood flow to the muscles increases, your muscles have more oxygen.

The body has increased the flow of oxygen-rich blood to the muscles, but the muscles still need to get the oxygen out of the blood. An exchange of oxygen and carbon dioxide is needed for this. Haemoglobin, which is found in red blood cells, carries most of the oxygen in the blood. Haemoglobin can bind oxygen and/or carbon dioxide; the amount of oxygen bound to haemoglobin is determined by the oxygen concentration, carbon dioxide concentration and pH.

As you exercise, the metabolic activity is high, more acids (hydrogen ions, lactic acid) are produced and the local pH is lower than normal. The low pH reduces the attraction between oxygen and haemoglobin and causes the haemoglobin to release more oxygen than usual. This increases the oxygen delivered to the muscle.

The exercising body is using energy and producing waste, such as lactic acid, carbon dioxide, adenosine and hydrogen ions. Your muscles need to get rid of these metabolic wastes to continue exercise. All that extra blood that is flowing to the muscles and bringing more oxygen can also take the wastes away. For example, haemoglobin can get rid of the carbon dioxide.

The body heats up during exercise. Working muscle produces heat in two ways:

The chemical energy used in muscles contracting is not efficiently turned into mechanical energy. The excess energy is lost as heat.
The various metabolic reactions (anaerobic, aerobic) also produce heat.

The body needs to remove this excess heat. The heat produced by exercising muscle causes blood vessels in the skin to dilate, which increases the blood flow to the skin. This high blood flow to the skin and the large surface area of the skin allows the excess heat to be lost to the surrounding air.

However, if exercise is done in a hot, humid environment, then sweat does not evaporate. This reduces the efficiency of this system and the person is subject to heat stroke. Heat stroke is a life-threatening condition and can cause a person to collapse, lose consciousness and die.

Oxygen Debt

Oxygen debt is the physiological state produced by vigorous exercise, in which the lungs cannot supply all the oxygen that the muscles need. In other words, the lungs and bloodstream, pumped by the heart, cannot supply sufficient oxygen for aerobic respiration in the muscles. In such a situation the muscles can continue to break down glucose to release energy for a short time using anaerobic respiration. This partial breakdown produces lactic acid, which results in a sensation of exhaustion when it reaches certain levels in the muscles and the blood. This explains why you can run faster in a sprint than you can over longer distances. During the sprint, your muscles can respire anaerobically. Once the vigorous muscle movements stop, the body breaks down the built up lactic acid on top of the normal breakdown of glucose in aerobic respiration, using up extra oxygen to do so. Panting after exercise is an automatic mechanism to pay off the oxygen debt.

Training Your Body

Your body can get more out of exercise and can exercise more easily with training. Athletes spend a great deal of time training. It allows the body to adapt its basic response to exercise and to improve athletic performance. Training can:

make your muscles perform better
match what you eat with what your body will use in energy
improve the efficiency of oxygen delivery to working muscle
get you used to the competition environment

Getting More Oxygen Quickly

To become a world-class athlete or to get the most out of exercise, you want your muscles to get the oxygen they need most efficiently. To do that you need to increase:

cardiac output
respiration
the amount of oxygen carried by the blood

The main effects of training on the cardiac output are an increase in stroke volume (a larger heart) and a decrease in the resting heart rate. The increased stroke volume allows the heart to pump more blood with each beat. Because there is a limit to the maximum heart rate (180-190 beats/min), then a slower resting heart rate (50-60 beats/min in the trained athlete vs. the normal 70-80 beats/min) allows the heart to have a greater increase in heart rate during exercise. The greater increase in heart rate during exercise along with the large stroke volume increases cardiac output and blood flow to working muscle.

Training can help the respiratory system by decreasing the resting rate of breathing, increasing the respiration rate during exercise and increasing the volume of air exchanged with each breath (tidal volume). These changes allow the lungs to take in more air during exercise. Training can also boost the amount of oxygen that the working muscles take from the blood.

Evaluation

My hypothesis is supported by the data I have collected. The fitter the person the shorter their heart recovery rate is. The data I have collected states that the greater increase in heart rate during exercise along with the larger stroke volume, increases cardiac output and blood flow to working muscles. The lower the recovery rate was the better the fitness of the person.

Although I believe that my experiment produced fairly valid results, I am not sure that my experiment was particularly accurate. For instance, I cannot be sure that the step-up exercise was done at the same rate throughout the experiment. Also, I am not sure that the 30-second intervals were kept exactly to this timing.

If I were doing this experiment again I would have to look closely at the method of exercise I used. I think that exercising on a piece of equipment like a running machine would produce more accurate results because I would be able to guarantee that the exercise remained constant throughout this experiment.

Finally, a ‘pulse-meter’ might have helped the experiment to be more accurate. This is simply strapped round the chest of the exercise and it measures your current heart rate. I believe that this would produce a more accurate heart rate.

The graph tells me that the heart recovery rate for fit people is a lot lower than unfit people. This is because during the exercise, anaerobic respiration begins to take place therefore the body has to pay back that oxygen back when it is resting. When exercise is complete the body’s heart rate does not immediately return to the normal resting pulse rate. This is because of the pay back the body has to complete first. After two minutes after the exercise is complete the decrease rate then begins to gradually fall as the pay back becomes complete.

I have some anomalous results, for example, there is a result for the heart recovery rate for an ‘unfit’ person (circled on graph) which doesn’t quite match with the others.