Exercise Physiology

“Fitness is a journey, not a destination. It must be continued for the rest of your life.” - Dr. Kenneth Cooper, the Father of Aerobics

http://www.bodyfitnt.com.au/exercise-physiology.php

Exercise physiologists are experts who study how the body functions during rigorous activity. They can test how hard an athlete is working, and then can create training programs to enhance his or her performance.

One of the most useful measurements for an exercise physiologist is the VO₂ max of an athlete, usually measured in milliliters per kilogram of body weight per minute. It is defined as the maximum amount of oxygen a person can take in while exercising. As we run, our need for energy increases. Oxygn helps the body react ADP (adenosine diphosphate) with another phosphate in order to make ATP (adenosine triphosphate), the body's main source of energy. Since oxygen is a contributor to energy production, our oxygen uptake must increase to meet the demand. Having a higher VO₂ max signifies better endurance and thus better fitness. Exercise physiologists work to increase the VO₂ max by challenging athletes to perform at or near their recorded oxygen uptake.

There is a small amount of ATP within the myofibrils of muscles, but there's only enough for one explosive reaction. Therefore, it must be replenished by constantly reacting ADP and phosphate. This is done through a number of energy pathways. Sports that require short explosive moments only need the ATP already reserved in muscles, so athletes who participate in power-lifting rely on ATP splitting as their energy pathway.

http://www.emc.maricopa.edu/

At my high school, I'm a sprinter on the track team. Sprinting requires quick repeated muscular contractions, so it uses CP (creatine phosphate) splitting to resynthesize ATP. There is a certain reserve of CP molecules in the muscles that can be used for this process, but there is only enough to last a few seconds. Luckily, that is exactly how long many short sprint races last. However, I have also run the 400 meter dash before, which is the longest sprint at a track meet. For that race, another energy pathway must be utilized, known as anaerobic glycolysis. In glycolysis, a polysaccharide known as glycogen stored in the muscles is used to create more ATP molecules. Turning the glycogen into ATP creates a byproduct known as lactic acid, and when lactic acid builds up, it causes a painful sensation in the muscles. However, athletes can be trained to perform despite this pain. One of my least favorite workouts during Track season is called "Broken Quarters." In this workout, I sprint to build up lactic acid, and then I continue to run as hard as I can so that I can train my body to handle that much lactic acid in the muscles. By doing this, I increase my anaerobic threshold, the point at which the buildup of lactic acid exceeds its removal.

http://www.lollylegs.com/training/SprintTech.aspx

If the body is too fatigued from the lactic acid, then anaerobic respiration is no longer a viable source of energy. Aerobic respiration is used to sustain long-distance running by using the circulatory system to transport the oxygen in the blood to the muscles in order to create ATP in muscles. In team sports, athletes often have to utilize multiple pathways at times to replenish ATP; in other words, these energy pathways are not mutually exclusive. They form an energy continuum, and exercise physiologists will often create workouts that help an athlete's use of the pathways more efficient.

Besides exercise, an athlete's diet is critical to their success. Most exercise physiologists would agree that a typical athlete's diet should be 30% fat, 55% carbohydrates and 15% protein. Both fats and carbs are necessary to replenish ATP and CP reserves in the body. Fat is important to the diet, because there is a high concentration of fat in the body which is used as long-term energy storage. Carbohydrates, however, make up the majority of the diet because they are used for short-term energy storage, which is what athletes rely upon if they are going to be active for more than a couple minutes. Protein is not typically used as an energy source, but it is still important to consume so that the muscles in which all of these energy pathways take place can remain healthy.

http://healthguide.howstuffworks.com/

While conditioning is crucial to a proper training program, more studies are beginning to show that weight training is an effective way to improve athletic performance. Weight lifting is by far my favorite physical activity. Not only does it help me during Track season, but it also releases endorphins in the body that make me feel better. The principles of weight lifting are straightforward: first, there is the overload principle. This means choosing to lift weight that is challenging but not dangerous for the body. By doing this, you successfully tear muscle fibers, so that during the recovery stage when you are not lifting, they can repair themselves bigger than before to accomodate heavier weight. This is known as hypertrophy.

Because muscles will eventually adapt to meet the challenge required by repeated lifting, it is important to fulfill the principle of progression. This means constantly finding new challenges for the body to meet so that it can still tear those strengthened muscle fibers, thus inducing stress. When experiencing muscular fatigue, the body releases many hormones, including testosterone and endorphins. For overall health, it is essential to work out all of the various muscles in our body. The principle of specificity, which states that to increase strength and/or size in a certain muscle, that muscle must be trained, helps meet this need. Because muscles pull, never push, they must work in antagonistic pairs (for example, biceps and triceps). Therefore, in order to allow for the body to function properly, it is important to work both sides of the pair evenly. Lastly, it is essential to give the muscles rest (around 45-60 seconds in between 2-3 sets of an exercise) in order to give them time to repair.

Heart Surgeries

Fun Facts about Heart Surgeries:

- The first heart transplant was performed in South Africa in 1967 by Dr. Christiaan Barnard. The patient lived 18 days.
- In 1980, 80% of patients survive a year after a heart transplant.
- Robert Jarvik made the first artificial heart in 1982.
- Barney Clark, a retired dentist, was the first person to receive an artificial heart.
- Today, surgeries used to correct congenital heart disorders have about a 95% success rate.
- To make heart surgery as minimally invasive as possible, we can use surgeon-operated robots to make small incisions

http://www.dreamstime.com/

Heart Patient Case History: Baby Fae

Stephanie Fae Beauclair, more commonly known as Baby Fae, was the first infant to receive a non-human heart transplant procedure. She was born three months prematurely, and was only two weeks when the surgery was performed. Baby Fae was born in 1984 with hypoplastic left-heart syndrome, a fatal condition in which the left side of the heart, the side that pumps oxygenated blood throughout the body, is severely undeveloped. Knowing that this was a life-or-death situation (most children with this disorder die within two weeks), Fae's doctor, Dr. Leonard Bailey, frantically searched for an infant donor heart. However, there was no way he could find one in time to save Fae. In an act of desperation, Bailey examined prior research about cross-species transplants and found that perhaps a baboon heart would be his last hope. Fae would be the perfect opportunity to carry out his experiment on a human. After 20 hours of contemplation, Fae's parents finally agreed to let Dr. Bailey try his procedure.

A considerable amount of tests had to be performed to figure out which baboon heart would be a match for Fae's, and there was no time to waste. Eventually, a donor was chosen. However, a major difference between human and baboon hearts is that human hearts have three major arteries that extend from the aortic arch; baboons only have two. To combat this, Dr. Bailey joined two of Fae's arteries together. Then, he connected her to a heart-lung machine to lower her body temperature, slow her metabolism, and allow her blood to continue pumping. Any transplant procedure is tricky, because the intricate wiring of blood vessels has to be disconnected and then reconnected again. And even if the surgeon is able to reconfigure the vascular pathways, there is still a chance that the patient's immune system will reject the foreign tissue. Dr. Bailey used cyclosporine, a drug that suppresses the immune system without taking away its ability to fight infection, which helped Fae accept the heart. Once the heart began beating on its own, both the medical community and the general public were astonished by the miracle and potentially life-altering decision Dr. Bailey had performed on Baby Fae.

The controversy came quickly. Some experts questioned whether Bailey's intentions were pure, and if he was just using Baby Fae and her family to perform medical experiments. Religious individuals were outraged that a Christian doctor would try to undermine God's creation, and animal lovers wre equally upset at the slaughter of a baboon for her heart. However, as the days passed, slowly more faith was shown towards the work of Dr. Bailey as Fae became independent from oxygen masks and intravenous fluids. Unfortunately, after two weeks, signs of rejection were becoming apparent. The most traumatic incident was when Fae's kidneys started to fail. Fae died three weeks after her surgery, but the impact she has had on heart transplant research was enormous. Perhaps one day a human with a simian heart will be capable of sustaining life.

http://www.viewingspace.com/genetics_culture

Heart Beats and Electrocardiograms (EKG):

When the heart is at rest, blood flows into the atria. The right side collects oxygen-poor blood while the left side collects oxygen-rich blood. Clusters of cells called the sinoatrial node send out electrical impulses to make the atria contract, thus forcing blood into the ventricles. Then, the atrioventricular node is triggered, causing the ventricles to contract. This phase is called systole. This releases blood from the right ventricle to the lungs, and from the left ventricle to the rest of the body. The blood pushes against mitral valve on the left and tricuspid valve on the right, which shuts them closed to prevent blood from flowing backwards. This makes the "lub" sound of a heartbeat. The ventricle relax in diastole, causing the pulmonic and aortic valves to shut. This sound is known as "dub."

http://www.nhlbi.nih.gov/

Every time the heart beats, tiny electrical impulses are discharged. Using a process called electrocardiography, those electrical discharges can be recorded and used to measure the heart's condition. Several thin wires are attached to the body. The wires conduct the electrical charges into a machine that measures them and produces a readout that can be interpreted as a series of waves, defined as follows:

P wave - sinoatrial node fires electrical impulses to make the atria contract
QRS complex - atrioventricular node fires electrical impules to make the ventricles contract
T wave - ventricles relax

Types of Heart Surgeries:

Coronary bypass - A healthy blood vessel is removed from another part of the body, such as the leg or chest wall. Surgeons then build a shortcut around a blocked coronary artery. One end of the vessel is attached below the blocked vessel, while the other end is grafted right above it. If it is successful, then blood flow can continue without interruption. Multiple grafts can be built in one surgery, potentially leading to double, triple and even quadruple bypasses.

Heart transplant - A diseased heart is removed from a patient, and then the healthy donor heart is attached. The operation is complicated because so many blood vessels have to be detached and re-attached. After the operation, there is still a risk that the patient's systems may reject the new heart. Tissue types have to be perfectly matched in order for the transplant to be successful. As a result, the number of transplants performed is quite low.

Angiocardiography - Doctors can find where an artery is blocked through coronary arteriography. This means that the coronary arteries are mapped using a procedure called cardiac catheterization. The doctor uses a catheter (a thin plastic tube) and moves it through an artery in the arm or leg and traces it into the coronary arteries. A liquid dye is poured through the catether, and when exposed in an x-ray, the liquid appears white. If there are dark sections of the x-ray of arteries, then the doctor knows that the dye did not pass through, so something must be blocked. Angiocardiography is especially suited for determining the extent and location of coronary artery disease.

Artificial Organs

http://www.creatingpositivelives.co.uk/

Regenerative medicine is a rapidly growing field that offers endless possibilities for doctors and patients alike. While there are still many discoveries to be made and technology to be developed, there have already been incredible advances. For example, doctors have created an extracellular matrix, which is a powder made from pig bladders. It is a mix of proteins and connective tissue, which means it can regenerate tissue by mobilizing the cells that maintain and repair injuries in the body. This has already been shown to help regenerate a part of a man's finger, and scientists believe that, if studied further, they can create new limbs and skin for amputees and burn victims respectively.

Sangeeta Bhatia has had a huge role in advancing regenerative medicine. She specificially studied manufacturing a liver by taking liver cells out of the body - the problem was these cells quickly died once removed. Bhatia hypothesized that the arrangement of these cells is crucial to their survival, and ultimately their function. Similar to how the complex networks of a computer chip are built through light, Bhatia used a chemical reaction with light to manipulate the placement of liver cells outside of the body. Although it took over a year, Bhatia eventually had the proper formation. In addition, these cells maintained life for an unprecedented six weeks. With enough time and support, enough networks of tissue can be built to construct an entire functioning liver. Procedures to build artificial bladder, skin, and even valves of a heart have been successful as well.

http://eecsfacweb.mit.edu/

There are many benefits for artificial organs, which can replace, restore or enhance organ function in a sick individual. First, being able to construct an organ decreases the need for transplant surgeries, which are risky because the organs have a short amount of time to be delivered and not every organ is a match for a recipient. With artificial organs, however, we do not need to worry about rushing the procedure to keep the organ alive, and if an organ is made from the recipient's cells, then it would be a guaranteed match. Another benefit is that these artificial organs can be made as subjects for testing the toxicity of new drugs, thus reducing the need for animal testing.

However, there are also reasons to be cautious when dealing with artificial organs. There is a possibility that undiscovered diseases or defects in the cells used to build artificial organs could lead to fatal consequences if left unchecked. Also, similar to the stem cell debate, there is a question of whether or not it is ethical to create the systems of life in a laboratory. Some believe that only God has the ability to create life, and humans should not have this capability.

Stem Cells

http://www.amyshah.com/

Embryonic Stem Cells (ES) - Cells taken from unused human embryos at IVF (in-vitro fertilization clinics) that can become any type of cell. However, using these cells destroys the human embryo.


Induced Pluripotent Stem Cells (iPS) - Cells taken from the skin that are reverted back into embryonic cells by switching certain genes on and off (there are 4 out of 20,000 that can help reprogram cells). These cells are implanted in a virus and sent back into the body. This treatment may carry a high risk of cancer.


Adult/Somatic Stem Cells - Undifferentiated cells taken from certains areas of the body that can be manipulated to become differentiated like surrounding tissue. There is thought to be specific areas of tissues and organs that are "stem cell niches," rich in this type of stem cell. There is a phenomenon called transdifferentiation, in which these stem cells can create cells that perform a different function than what is expected.

http://stemcells.nih.gov/

How do scientists get stem cells to specialize in a lab?


Scientists remove the outer layer of a blastocyst and put the inner layer in a petri dish. Only a few survive, but the ones that do can create colonies. These colonies go through self-renewal: they are immortal and can continue to grow indefinitely. At some point, these cells differentiate: they begin to become ectoderm/mesoderm/endoderm cells. To control this differentiation, we add growth factors (Retinoic Acid, Sonic hedgehog and Activin are a few examples) to give the cells specific functions. By simulating the environment of a cell, we can induce it into becoming a certain type.


What are some uses of stem cells in curing diseases?


Stem cells are useful in a variety of circumstances. One of the most well-known areas of stem cell research is hematopoietic cells, which create blood and immune cells. Sickle Cell Anemia is a disease where red blood cells are sickle-shaped, instead of donut shaped, so they are less efficient in delivering oxygen to the body. This results in excruciating pain. Stem cells can replace the genetically-fault hematopoietic cells to create properly-shaped RBC. Neurodgenerative diseases, like Parkinson's, can also be improved by replacing dead neurons. And if we can get stem cells to become beta cells that produce insulin, we can finally find a cure for diabetes. The possibilities for cures are virtually endless, although stem cells are not necessarily the final solution for all diseases.
 The types of cells that scientists can manufacture are:

Hematopoietic stem cells create blood cells: red blood cells, B lymphocytes, T lymphocytes, natural killer cells, neutrophils, basophils, eosinophils, monocytes, and macrophages.

 Mesenchymal stem cells create: bone cells (osteocytes), cartilage cells (chondrocytes), fat cells (adipocytes), and connective tissue cells.

Neural stem cells create: nerve cells (neurons) and two categories of non-neuronal cells—astrocytes and oligodendrocytes.

Epithelial stem cells in the lining of the digestive tract create: absorptive cells, goblet cells, paneth cells, and enteroendocrine cells.

Skin stem cells are located in the basal layer of the epidermis and at the base of hair follicles. The epidermal stem cells create keratinocytes, which leads to the formation of a protective layer in the epidermis. The follicular stem cells can help create both the hair follicle and the epidermis.