Dear Doctors: I meet up with friends a few days a week to go running. One of them always skips the cooldown and hops right into his car to drive to work. A trainer once told me that’s a recipe for sudden cardiac death. Do you know if that’s a myth, or is there something to it?

Dear Reader: The term “sudden cardiac death” is used to describe a medical emergency that, because it compromises the cardiovascular system, results in the person’s death within an hour of the onset of symptoms. Most often the problems directly involve the heart. These include various types of heart arrhythmias, cardiac arrest, heart attack, cardiomyopathy or stroke. Although not as common, sudden cardiac death can occur due to a drug overdose, trauma or poisoning. Sometimes a cause for the sudden cardiac death cannot be determined. The death occurs because something has caused the heart to stop altogether, or to function so poorly that it was unable to deliver enough blood throughout the body to sustain life.

The most common factor in sudden cardiac death is the presence of coronary artery disease, or CAD. This is a condition in which the interior walls of the arteries that deliver blood to the heart grow narrow, or become completely blocked, due to a buildup of plaque. In younger adults, a heart arrhythmia, such as ventricular or atrial fibrillation, or ventricular tachycardia, is often the cause. These are conditions in which the electrical signals that coordinate the heartbeat go awry, which swiftly disrupts the flow of blood throughout the body.

The good news is that sudden cardiac death during or after exercise is rare. However, the trainer you spoke with is on the right track in discussing the importance of a cooling down period after exercise. When you exert yourself in any way, your heart begins to beat faster and more forcefully in order to deliver the additional oxygen and nutrients needed by the muscles. This, in turn, leads to an increase in systolic blood pressure, which is the force of the blood on the walls of the vessels during a heartbeat. Both the added demands on the heart and the increase in systolic blood pressure will persist for as long as you maintain the pace and intensity of the exercise you are doing.

A cooldown period immediately following prolonged vigorous exercise is beneficial to the heart. It lets you slowly reduce the demands you have been making on your muscles, and thus on your heart. As the muscles work less, their need for oxygen decreases. This allows a return to a slower and less vigorous heartbeat, which in turn begins to ease systolic blood pressure. A cooldown doesn’t have to be elaborate or prolonged. Simply taking the time to slow the pace of your run, to jog for a bit as you regain your breath and then wind down to a few minutes of brisk walking should be enough for both the heart and your blood pressure to have a safe and gradual recovery.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: My sister has been diagnosed with myasthenia gravis. It started last year, when she turned 38, and it has been getting worse. I would like to know more about the condition. Also, I have heard that a study says the gut microbiome is involved. Can you please talk about that?

Dear Reader: Myasthenia gravis, also known as MG, is a somewhat rare autoimmune disorder. It occurs when the immune system mistakenly attacks compounds produced by the body that are integral to allowing muscle fibers to contract. MG disrupts the communication pathways between the skeletal muscles and the nerves that animate them. This causes weakness in those muscles, along with fatigue, each of which can intensify throughout the day. MG can occur at any age, but it becomes more common among women at about age 40 and in men after about age 60.

The condition often begins with progressive weakness in the muscles around the eyes. This is known as ocular myasthenia gravis. One or both eyelids may begin to droop, it can become difficult to keep the eyelids open, and the person may experience blurred or double vision. About half of cases of ocular MG progress to include the muscles of the legs, hips, arms, face or neck. This is known as generalized myasthenia gravis. It can become difficult to rise from a chair, navigate stairs, raise or use the arms, control facial expressions and chew or swallow. Generalized MG can also affect the muscles that control the diaphragm and those that connect the ribs, which can interfere with breathing.

At this time, there is no cure for myasthenia gravis. Treatment depends on the scope and severity of each person’s symptoms and how quickly the disease is progressing. It can include medications to improve neural activity, corticosteroids to dampen immune system response or immunosuppressant drugs. None of these is completely effective, and each has the potential for side effects. That’s what makes studies like the one you are asking about so important.

A growing body of research continues to find that the gut microbiome and the immune system work together to maintain the health of the body. There is also persuasive evidence that an imbalance in the populations of microorganisms in the gut can contribute to a range of diseases, disorders and conditions. This includes myasthenia gravis.

When scientists in Spain and Italy explored the role of the gut in MG several years ago, they saw intriguing results. They compared fecal samples from 10 adults living with MG with those from 10 adults of the same age and sex who do not have the disorder. All participants lived in the same region. When the researchers analyzed the types and quantities of microorganisms present in the fecal samples, and ran their genetic profiles, they found striking differences between the two groups. Specifically, unusually large populations of certain bacteria were associated with an elevated risk of developing MG. The researchers hope that further research will lead to the development of prebiotics or probiotics that can modulate the microbiota of MG patients and improve, or even eliminate, symptoms.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Hello, dear readers, and welcome to a bonus edition of our monthly letters column. We are receiving a lot of questions about the various respiratory tract infections that become common this time of year and will have columns on them soon. In the meantime, with such full inboxes, we’ll dive right into your letters.

-- We heard from a reader regarding a column about gastroesophageal reflux disease, or GERD. Commonly known as heartburn, it occurs when acid surges up from the stomach and into the esophagus, where it causes irritation and damage. “I was prescribed antacids to help with discomfort from GERD, but they were of minimal help,” he wrote. “Then I read that drinking alkaline water would neutralize the pepsin in the esophagus. I did that and have been much more comfortable ever since.”

Pepsin, which digests protein, is one of the acids produced by the stomach. During episodes of acid reflux, pepsin can become lodged in the tissues of the esophagus. It has been found that when you drink alkaline water with a pH of 8.8, it can help neutralize the effects of pepsin. However, it is important to understand that GERD is the reason pepsin has reached the esophagus. That makes the lifestyle changes discussed in the column important. These include reaching a healthful weight; eating smaller meals; minimizing high-fat, acidic and spicy foods; and avoiding eating before bed.

-- A recent column about how going for even a short walk after a meal can help with blood sugar control has received a lot of positive responses. We heard from a reader in California who used the column to persuade his wife to get out of the kitchen and into the neighborhood. “I often go for a walk after dinner. It’s a chance to visit with our neighbors and spend some time outdoors. When I tried to get my wife to join me, she would say that she had to get the kitchen cleaned up instead,” he wrote. “Well, her latest A1C test came back as pre-diabetes. I remembered what I read in your column about walking after a meal and shared it with her. Long story short, she comes for a walk with me now, and afterward I help her with the dishes. Win-win across the board.” Thank you for sharing such a good outcome. We think you’ll be happy to know that two other aspects of your evening walk -- socializing and spending time in nature -- have been shown to contribute to improved emotional and cognitive health.

-- Another reader interested in the idea that walking soon after a meal can help with blood sugar control asked us to provide the source material. The information was published in the Feb. 11, 2022, issue of the journal Sports Medicine. It can be found online.

We love hearing from you, so thank you for taking the time to write. If it occurs to you, please let us know your city or region. And a quick reminder -- we cannot review personal medical information, offer a diagnosis or second opinion or comment on specific medications or treatment plans.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)