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How marathon affects the body

Before the race, the brain shifts into fight/flight mode, diverting blood from the stomach and digestive tract to the muscles. This causes butterflies-in-the-stomach and twitchy, tingling feelings in the arms and legs.
When nerves in the eyes and ears tell the brain that the race has started, the decision-making parts of the brain tell the motor cortex to trigger nerves that make the leg muscles contract. The pattern of contracting and relaxing is embedded in the brain stem, and is easily influenced by outside rhythms - this is why many people listen to music while running.
Other parts of the brain evaluate pain signals and the anterior cingulate cortex determines the cause. Higher centers in the cortex can suppress some of pain signals if a runner so chooses. The cortex is dependent on mood - a depressed runner feels more pain, and a happy one has higher thresholds.
The lungs are the only organ that receives a full blast of all the blood pumped by the heart. A rise in the volume of blood leads to increased blood pressure in the lungs. Through training, runners can achieve an "increased lung capacity". This means cellular changes in the muscles make them more efficient and able to move more blood through the lungs faster.
At rest a typical heart might pump five liters of blood per minute. But during strenuous exercise, such as a marathon, the heart pumps 15-20 liters. As the marathon progresses, the heart's squeezing strength remains the same, but its ability to relax lessens, particularly in the right ventricle.
One common problem is the thickening of the heart walls, which can impede blood flow and squeeze less efficiently. Blocked or constricted coronary arteries carry less blood to the heart and impede its ability to function.
Pain behind the kneecap can be caused by overuse or a misalignment of the kneecap that leads to wobbly strides and a loss of cartilage.
An awkward step or unexpected dip can roll the ankle and stretch or tear ligaments, usually but not always, on the outside of the ankle.
Pain around the shins can be caused by inflammation or tears in connective tissue.
The iliotibial band is a thick connective tissue that runs from the hip to just below the knee. It can rub against the lower end of the thigh bone and become inflamed.
Even a well-trained marathoner can expect low-level pain and joint soreness during the race. Stress fractures can happen to any bone, especially hip, lower leg, and small foot bones. Stress fractures are most worrisome because they require a long recovery period.
Alternately contracting and relaxing muscles move the body along the race course. Glycogen (derived from carbohydrates), fat, and protein provide fuel to keep the contractions going. Muscles contract when thin filaments grab and crawl up the thick filament. Thin filaments slide apart when the muscle relaxes.
CRAMPS

While the exact cause of cramps is unclear, fatigue, dehydration, and depletion of electrolytes are all involved. Stretching before the race helps prevent them and massaging and stretching a cramped muscle will release the cramp and ease pain.

Running a marathon beats up your feet. The average runner will land with full weight up to 20,000 times on each foot. Blisters are inevitable. Socks will help.
Many runners traumatize their toenails to the point that they fall off. Keep nails trimmed and smooth to avoid damage.
Common injuries such as fractures of weight-bearing bones in the foot and inflammation or tearing of tendons and ligaments can be prevented with shoes that fit and are not worn out.
Before the race, the brain shifts into fight/flight mode, diverting blood from the stomach and digestive tract to the muscles. This causes butterflies-in-the-stomach and twitchy, tingling feelings in the arms and legs.
When nerves in the eyes and ears tell the brain that the race has started, the decision-making parts of the brain tell the motor cortex to trigger nerves that make the leg muscles contract. The pattern of contracting and relaxing is embedded in the brain stem, and is easily influenced by outside rhythms - this is why many people listen to music while running.
Other parts of the brain evaluate pain signals and the anterior cingulate cortex determines the cause. Higher centers in the cortex can suppress some of pain signals if a runner so chooses. The cortex is dependent on mood - a depressed runner feels more pain, and a happy one has higher thresholds.
The lungs are the only organ that receives a full blast of all the blood pumped by the heart. A rise in the volume of blood leads to increased blood pressure in the lungs. Through training, runners can achieve an "increased lung capacity". This means cellular changes in the muscles make them more efficient and able to move more blood through the lungs faster.
At rest a typical heart might pump five liters of blood per minute. But during strenuous exercise, such as a marathon, the heart pumps 15-20 liters. As the marathon progresses, the heart's squeezing strength remains the same, but its ability to relax lessens, particularly in the right ventricle.
One common problem is the thickening of the heart walls, which can impede blood flow and squeeze less efficiently. Blocked or constricted coronary arteries carry less blood to the heart and impede its ability to function.
Even a well-trained marathoner can expect low-level pain and joint soreness during the race. Stress fractures can happen to any bone, especially hip, lower leg, and small foot bones. Stress fractures are most worrisome because they require a long recovery period.
Pain behind the kneecap can be caused by overuse or a misalignment of the kneecap that leads to wobbly strides and a loss of cartilage.
An awkward step or unexpected dip can roll the ankle and stretch or tear ligaments, usually but not always, on the outside of the ankle.
Pain around the shins can be caused by inflammation or tears in connective tissue.
The iliotibial band is a thick connective tissue that runs from the hip to just below the knee. It can rub against the lower end of the thigh bone and become inflamed.
Alternately contracting and relaxing muscles move the body along the race course. Glycogen (derived from carbohydrates), fat, and protein provide fuel to keep the contractions going. Muscles contract when thin filaments grab and crawl up the thick filament. Thin filaments slide apart when the muscle relaxes.
CRAMPS

While the exact cause of cramps is unclear, fatigue, dehydration, and depletion of electrolytes are all involved. Stretching before the race helps prevent them and massaging and stretching a cramped muscle will release the cramp and ease pain.

Running a marathon beats up your feet. The average runner will land with full weight up to 20,000 times on each foot. Blisters are inevitable. Socks will help.
Many runners traumatize their toenails to the point that they fall off. Keep nails trimmed and smooth to avoid damage.
Common injuries such as fractures of weight-bearing bones in the foot and inflammation or tearing of tendons and ligaments can be prevented with shoes that fit and are not worn out.

SOURCES: Dr. Jordan Stewart, podiatrist; Dr. Kerry Stewart, director of clinical and research exercise physiology at Johns Hopkins School of Medicine; Dr. Malissa Wood, co-director of the Corrigan Women's Heart Health Program at MGH and assistant professor of medicine at Harvard Medical School; Dr. Aaron B. Waxman, Director of Pulmonary Vascular Disease Program at the Brigham and Women's Hospital; Dr. Alice Flaherty, neurologist at MGH and assistant professor of neurology at Harvard Medical School; Dr. George Theodore, Director of Foot and Ankle Sports Medicine Center, MGH; Vic Brown, associate strength and conditioning coach at BU; National Library of Medicine, NIH; Dept. of Physiology and Biophysics, Univ. of Calif., Irvine.

Monica Ulmanu, Javier Zarracina and David Butler/Globe Staff

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