American College of Physicians: Internal Medicine — Doctors for Adults ®

Thursday, May 14, 2015

Exercise: the luminous, latent potential of a little action

Mechanistically, exercise is entirely dependent on action potentials, while its incredible benefits may be characterized as the potential of action to enhance our lives. Ironically, perhaps, the luminous potential of action to promote our health is in a very fundamental way the exact opposite of the action potentials from which it derives.

I imagine that may be about as clear as the way through a Tough Mudder. No worries; I've got Windex.

An action potential refers to the mechanism that underlies the firing of our nerve cells, or neurons. Famously, action potentials are “all or nothing.”

At rest, there is a slight electrical gradient maintained across the cell membrane of a neuron. That slight charge is energy dependent, requiring the constant work of ion channels that traverse the cell membrane, shuttling positively and negatively charged ions in opposite directions. When we talk about “resting energy expenditure,” or “basal metabolism,” these are the kinds of functions represented; our cells are always working even when we are not.

That electrical gradient is, quite literally, an “action potential,” because it primes the cell to take the one action it owns: depolarizing. When a stimulus reaches a neuron, if it is strong enough, it reverses the electrical charge at the site of contact. That reversal of charge, or depolarization, then courses along the length of that nerve cell, rather like a fast moving wave.

If the nerve cell in question is a sensory neuron, the result of that wave is that we feel or perceive something, a caress, a color, a shiver, or a symphony. If it is a motor neuron, it ends at a muscle cell, which in turn is stimulated to contract. When a whole lot of muscle cells contract in unison, we have the familiar command over our moving body parts; such as my fingers, currently dancing over this keyboard.

We could, of course, go much deeper into the weeds, but that's the relevant gist. What matters for today's story is that the depolarization of every neuron, or muscle cell (myocyte) for that matter, is all or nothing. The stimulus reaching it is either enough to excite full depolarization, or it is not. There are no partial responses; there is no dose response curve*.

Exercise is just the opposite. There is an enormous benefit from even a little, more benefit from more, and then a threshold past which returns diminish, but don't decline. The take-away message is that there is enormous potential for even a little bit of action to make our health, and lives, better.

We have long known this, frankly. It is the reason why prevailing recommendations for physical activity rally around 30 minutes or so, roughly 5 days out of every 7. That's not really very much for a species that spent millennia as roaming bands of hunter-gatherers. It is, however, enough to generate decisive health benefits in an age when the clan is a distant memory, and the couch a constant temptation.

A new study reaffirms this. Just published on-line in JAMA Internal Medicine, the paper explores the relationship between weekly, average exercise and mortality in more than 650,000 men and women. The findings confirm our convictions, and validate our fervent hopes, about motion.

The risk of dying prematurely was reduced 20 percent in those who did “any” routine physical activity, as compared to those who did none. Those how met that recommended minimum of 150 minutes per week of moderate activity had more than a 30 percent reduction in mortality risk. Those who exceeded the minimum by a factor of two to three had a nearly 40 percent mortality reduction. Benefits went up as exercise increased, but they diminished; the mortality benefit was front-loaded.

While the new study looked at benefit in terms of mortality, the real rewards of routine exercise may be even better captured in considerations of morbidity, or its converse- vitality. Lack of habitual motion has long been atop the short list of factors contributing to both premature death, and chronic disease. Conversely, routine activity is a key factor on the short list associated with a lifetime reduction in the risk of all chronic diseases of roughly 80 percent.

Those of us who are active routinely probably all agree that motion is its own reward. We have vital, animal bodies made to move. Taking them off the leash and out of the cage of modern, sedentary living just feels good. For those who doubt it, a major reduction in the lifelong risk of any major chronic disease is a pretty good, alternative motivation.

Move, because your body was made to move. Move, because you will be less likely to die prematurely. Move, because you will be less likely to succumb to any major chronic disease, and more likely to recover from, or thrive despite, any you already have. Move, because it is vital to health. And strive for health not because I say so, but because healthy people have more fun.

The potential contribution of action to health is quite incredible, and accessible to almost all of us. Unlike the action potential with which it originates, the potential of action is considerable with even the first little bit; some is much better than none.

I invite and encourage you on that basis to take action; any kind, and any amount- and share the notion of motion with those you love. The luminous potential of it is at your disposal. Exploit it, and live a life likely to be both longer, and better.

*You may be wondering: how can we differentiate strong and weak signals, a caress from a smack, a whisper from an explosion- if our neuronal response is all or none? The answer is: it depends on the number, and variety, of neurons that get in on the action.

The response of any given neuron is all or none. However, the number of neurons activated does vary with the strength of the stimulus. Equally important, we have both excitatory neurons, that enhance our perception of a stimulus, and inhibitory neurons that dampen it (one of the more important functions of our nervous system is to squelch our awareness of superfluous stimuli bombarding us all the time). A strong stimulus will tend to overcome inhibitory neurons, whereas they will prevail when the signal is weaker.

The balance between these Yin and Yang forces of neurology also changes with circumstance. For example, when you first put on your underwear today, you were quite conscious of the slight pressure of that elastic band against your skin. Until I made you think of it just now, however, you were entirely unconscious of it (if you are not wearing underwear, I don't want to know about it ...). That's because the signal in question is only useful to indicate a “change” in our condition; it is not of much use as continuous input over the course of our day. So, thankfully, the nervous system squelches it, and we are free to think loftier thoughts than: Yep, I've still got my underwear on!

David L. Katz, MD, FACP, MPH, FACPM, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care. He is a board certified specialist in both Internal Medicine, and Preventive Medicine/Public Health, and Associate Professor (adjunct) in Public Health Practice at the Yale University School of Medicine. He is the Director and founder (1998) of Yale University's Prevention Research Center; Director and founder of the Integrative Medicine Center at Griffin Hospital (2000) in Derby, Conn.; founder and president of the non-profit Turn the Tide Foundation; and formerly the Director of Medical Studies in Public Health at the Yale School of Medicine for eight years. This post originally appeared on his blog at The Huffington Post.

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Members of the American College of Physicians contribute posts from their own sites to ACP Internistand ACP Hospitalist. Contributors include:

Albert Fuchs, MD
Albert Fuchs, MD, FACP, graduated from the University of California, Los Angeles School of Medicine, where he also did his internal medicine training. Certified by the American Board of Internal Medicine, Dr. Fuchs spent three years as a full-time faculty member at UCLA School of Medicine before opening his private practice in Beverly Hills in 2000.

And Thus, It Begins
Amanda Xi, ACP Medical Student Member, is a first-year medical student at the OUWB School of Medicine, charter class of 2015, in Rochester, Mich., from which she which chronicles her journey through medical training from day 1 of medical school.

Ira S. Nash, MD, FACP, is the senior vice president and executive director of the North Shore-LIJ Medical Group, and a professor of Cardiology and Population Health at Hofstra North Shore-LIJ School of Medicine. He is Board Certified in Internal Medicine and Cardiovascular Diseases and was in the private practice of cardiology before joining the full-time faculty of Massachusetts General Hospital.

Zackary Berger
Zackary Berger, MD, ACP Member, is a primary care doctor and general internist in the Division of General Internal Medicine at Johns Hopkins. His research interests include doctor-patient communication, bioethics, and systematic reviews.

Controversies in Hospital Infection Prevention
Run by three ACP Fellows, this blog ponders vexing issues in infection prevention and control, inside and outside the hospital. Daniel J Diekema, MD, FACP, practices infectious diseases, clinical microbiology, and hospital epidemiology in Iowa City, Iowa, splitting time between seeing patients with infectious diseases, diagnosing infections in the microbiology laboratory, and trying to prevent infections in the hospital. Michael B. Edmond, MD, FACP, is a hospital epidemiologist in Iowa City, IA, with a focus on understanding why infections occur in the hospital and ways to prevent these infections, and sees patients in the inpatient and outpatient settings. Eli N. Perencevich, MD, ACP Member, is an infectious disease physician and epidemiologist in Iowa City, Iowa, who studies methods to halt the spread of resistant bacteria in our hospitals (including novel ways to get everyone to wash their hands).

db's Medical Rants
Robert M. Centor, MD, FACP, contributes short essays contemplating medicine and the health care system.

Suneel Dhand, MD, ACP Member
Suneel Dhand, MD, ACP Member, is a practicing physician in Massachusetts. He has published numerous articles in clinical medicine, covering a wide range of specialty areas including; pulmonology, cardiology, endocrinology, hematology, and infectious disease. He has also authored chapters in the prestigious "5-Minute Clinical Consult" medical textbook. His other clinical interests include quality improvement, hospital safety, hospital utilization, and the use of technology in health care.

Juliet K. Mavromatis, MD, FACP, provides a conversation about health topics for patients and health professionals.

Dr. Mintz' Blog
Matthew Mintz, MD, FACP, has practiced internal medicine for more than a decade and is an Associate Professor of Medicine at an academic medical center on the East Coast. His time is split between teaching medical students and residents, and caring for patients.

Everything Health
Toni Brayer, MD, FACP, blogs about the rapid changes in science, medicine, health and healing in the 21st century.

Vineet Arora, MD, FACP, is Associate Program Director for the Internal Medicine Residency and Assistant Dean of Scholarship & Discovery at the Pritzker School of Medicine for the University of Chicago. Her education and research focus is on resident duty hours, patient handoffs, medical professionalism, and quality of hospital care. She is also an academic hospitalist.

Glass Hospital
John H. Schumann, MD, FACP, provides transparency on the workings of medical practice and the complexities of hospital care, illuminates the emotional and cognitive aspects of caregiving and decision-making from the perspective of an active primary care physician, and offers behind-the-scenes portraits of hospital sanctums and the people who inhabit them.

Gut Check
Ryan Madanick, MD, ACP Member, is a gastroenterologist at the University of North Carolina School of Medicine, and the Program Director for the GI & Hepatology Fellowship Program. He specializes in diseases of the esophagus, with a strong interest in the diagnosis and treatment of patients who have difficult-to-manage esophageal problems such as refractory GERD, heartburn, and chest pain.

I'm dok
Mike Aref, MD, PhD, FACP, is an academic hospitalist with an interest in basic and clinical science and education, with interests in noninvasive monitoring and diagnostic testing using novel bedside imaging modalities, diagnostic reasoning, medical informatics, new medical education modalities, pre-code/code management, palliative care, patient-physician communication, quality improvement, and quantitative biomedical imaging.

Informatics Professor
William Hersh, MD, FACP, Professor and Chair, Department of Medical Informatics & Clinical Epidemiology, Oregon Health & Science University, posts his thoughts on various topics related to biomedical and health informatics.

David Katz, MD
David L. Katz, MD, MPH, FACP, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care.

Just Oncology
Richard Just, MD, ACP Member, has 36 years in clinical practice of hematology and medical oncology. His blog is a joint publication with Gregg Masters, MPH.

Kevin Pho, MD, ACP Member, offers one of the Web's definitive sites for influential health commentary.

MD Whistleblower
Michael Kirsch, MD, FACP, addresses the joys and challenges of medical practice, including controversies in the doctor-patient relationship, medical ethics and measuring medical quality. When he's not writing, he's performing colonoscopies.

Medical Lessons
Elaine Schattner, MD, FACP, shares her ideas on education, ethics in medicine, health care news and culture. Her views on medicine are informed by her past experiences in caring for patients, as a researcher in cancer immunology, and as a patient who's had breast cancer.

Mired in MedEd
Alexander M. Djuricich, MD, FACP, is the Associate Dean for Continuing Medical Education (CME), and a Program Director in Medicine-Pediatrics at the Indiana University School of Medicine in Indianapolis, where he blogs about medical education.

More Musings
Rob Lamberts, MD, ACP Member, a med-peds and general practice internist, returns with "volume 2" of his personal musings about medicine, life, armadillos and Sasquatch at More Musings (of a Distractible Kind).

David M. Sack, MD, FACP, practices general gastroenterology at a small community hospital in Connecticut. His blog is a series of musings on medicine, medical care, the health care system and medical ethics, in no particular order.

Reflections of a Grady Doctor
Kimberly Manning, MD, FACP, reflects on the personal side of being a doctor in a community hospital in Atlanta.

The Blog of Paul Sufka
Paul Sufka, MD, ACP Member, is a board certified rheumatologist in St. Paul, Minn. He was a chief resident in internal medicine with the University of Minnesota and then completed his fellowship training in rheumatology in June 2011 at the University of Minnesota Department of Rheumatology. His interests include the use of technology in medicine.

Technology in (Medical) Education
Neil Mehta, MBBS, MS, FACP, is interested in use of technology in education, social media and networking, practice management and evidence-based medicine tools, personal information and knowledge management.

Peter A. Lipson, MD
Peter A. Lipson, MD, ACP Member, is a practicing internist and teaching physician in Southeast Michigan. The blog, which has been around in various forms since 2007, offers musings on the intersection of science, medicine, and culture.

Why is American Health Care So Expensive?
Janice Boughton, MD, FACP, practiced internal medicine for 20 years before adopting a career in hospital and primary care medicine as a locum tenens physician. She lives in Idaho when not traveling.

World's Best Site
Daniel Ginsberg, MD, FACP, is an internal medicine physician who has avidly applied computers to medicine since 1986, when he first wrote medically oriented computer programs. He is in practice in Tacoma, Washington.

Other blogs of note:

American Journal of Medicine
Also known as the Green Journal, the American Journal of Medicine publishes original clinical articles of interest to physicians in internal medicine and its subspecialities, both in academia and community-based practice.

Clinical Correlations
A collaborative medical blog started by Neil Shapiro, MD, ACP Member, associate program director at New York University Medical Center's internal medicine residency program. Faculty, residents and students contribute case studies, mystery quizzes, news, commentary and more.

Interact MD
Michael Benjamin, MD, ACP member, doesn't accept industry money so he can create an independent, clinician-reviewed space on the Internet for physicians to report and comment on the medical news of the day.

PLoS Blog
The Public Library of Science's open access materials include a blog.

White Coat Rants
One of the most popular anonymous blogs written by an emergency room physician.

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