PHYSICAL ACTIVITY MAY BE THE MOST IMPORTANT thing you can do to improve your health. Want to lower your risk of cancer? Looking to drop your cardiovascular risk or all-cause mortality? The list goes on and on: While there is a lot of ambiguity about optimizing health, there is little debate that physical activity promotes health. Today we explore the optimal exercise volume.
“I grow old … I grow old …
I shall wear the bottoms of my trousers rolled.”
― T.S. Eliot, The Love Song of J. Alfred Prufrock and Other Poems
Recently, a kind reader pointed me to the podcast of a brilliant physician (with a perfect radio voice). If you haven’t listened to Dr. Peter Attia, the best gift I can give you today is to point you to his podcast, in which the Stanford-educated podcaster, now retired from medicine, in favor of understanding longevity, address exercise volume and longevity. I will share some of Attia’s insights, along with my own.
Is there a most effective dose of exercise? Before we get to the pertinent research, let me re-frame the question: I am not asking what is the minimum dose required to achieve a long health span, but rather if you want to optimize your lifespan and health span, how much physical activity should you pursue?
Today, we explore exercise volume and health.
Defining longevity, lifespan, and healthspan
Before we get too deeply into the topic, it is important to clarify some definitions. Let’s look at the meaning of lifespan, healthspan, and longevity.
- Lifespan. This is the duration of an individual’s existence.
- Healthspan. Healthspan is the period of life spent in good health, free from the chronic diseases and disabilities of aging. Healthspan is a length of chronological time beginning at birth and ending when an individual is no longer in good health or is suffering from diseases or disabilities of aging.
- Longevity. Longevity is a balance of lifespan (living longer) and health span (living better).
A broad body of scientific literature illustrates the remarkable therapeutic benefits of physical activity for cardiovascular health, quality of life, longevity, and more.
Exercise and cardiovascular health – THE OPTIMAL EXERCISE VOLUME
Being sedentary is an independent risk factor for the early development of heart disease involving the coronary arteries. The sedentary behavior: heart disease relationship is not new; scientists reviewed the clinical literature in 1987, performing a comprehensive review.
Today, we are not surprised that the researchers discovered an inverse association between physical activity and the incidence of coronary heart disease. This relationship appeared especially clear in the better-deigned studies.
In summary, physical activity appears inversely and causally related to better heart health. Moreover, the relative risk of being sedentary appears similar in magnitude to high blood pressure, high cholesterol, or smoking. Given the high number of sedentary Americans, we need a robust public policy that encourages regular physical activity.
The US Surgeon General offers some disturbing statistics: More than three in five adults in the United States do not engage in recommended activity levels. Worse yet, 25 percent are not active at all.
Sedentary behavior is more common among women, older adults, African American and Hispanic adults (compared with whites), and less affluent individuals. Regular physical exercise can be a primary and secondary means of reducing cardiovascular risk.
Can too much exercise hurt your heart?
Now that we have established that some physical activity is good for your heart, is more always better? Does chronic excessive endurance activity negatively impact your heart health or longevity?
I remember James Fixx, a famous American runner credited with helping to launch America’s fitness revolution by advocating for the sport of running and the health benefits of regular jogging. You may read his 1977 best-selling The Complete Book of Running.
Fixx died of a heart attack at age 52 while jogging. Admittedly, the runner’s genetic predisposition for heart problems and other lifestyle factors (including a two-pack per day smoking history) likely contributed to his death. His father died at age 43 of a heart attack.
Regular exercise helps prevent many chronic diseases while promoting longevity. Still, long-term excessive endurance exercise can induce pathologic restructuring of the heart and its large arteries.
In the short-term, chronic training for (and competing in) extreme endurance events such as ultramarathons, regular marathons, and ironman distance triathlons can result in temporary acute volume overload of the heart (more specifically, the atria and right ventricle). The result drops in how much blood the right ventricle pushes out (right ventricular ejection fraction), and rises in heart biomarkers return to normal within one week.
But with continuing repetitive injury over months or years, some folks may develop apathy scarring of the heart muscle, creating a higher risk for arrhythmias such as atrial fibrillation (an irregular and often very rapid heart rhythm). In addition, if we exercise excessively for sustained periods, we may develop coronary artery calcification, large artery wall thickening, and more.
But take these observations with a healthy dose of skepticism: the clinical literature is inconsistent. Fortunately, lifelong vigorous exercisers typically have low early mortality rates and excellent overall functional capacity. Still, it would be nice to identify the at-risk individuals to create individualized management plans.
J-shaped curves and public health
Most of us know that there is not a good dose of tobacco regarding health. The risk curve is linear; the more you smoke, the higher the risk of health problems such as cardiovascular disease, cancer, and early death.
The relationship between the number of cigarettes smoked daily and lung cancer incidence is linear. We would expect it to be quadratic, but the observation explains the anomaly that users of very high numbers of cigarettes inhale less smoke from each cigarette.
On the other hand, I frequently hear from my patients that they heard that a little bit of alcohol is good for us. Some risk factors do not have the same linear relationship between exposure and mortality that we see with cigarette use. For example, alcohol consumption shows a J-shaped association when we plot mortality on the vertical axis of a graph against the magnitude of the risk factor on the horizontal axis.
A comprehensive review and analysis of 34 prospective studies included more than one million individuals and nearly 100,000 deaths. Here’s what you need to know:
Consumption of up to two alcohol-containing drinks per day in women and four drinks per day in men appeared to be associated with lower mortality than zero consumption, with about one-half drink per day associated with the lowest mortality risk.
The J-curve can make communicating risk more challenging, for example, to the women that I see in the clinic who offer that they have heard that a couple of drinks daily is good for us.
What about weight? If we adjust for confounding variables (such as smoking or alcohol consumption), we again encounter the J-curve.
A prospective investigation of nearly 1.5 million white adults revealed a J-shaped association between body mass and early mortality. The lowest mortality rates generally occurred among those with a body mass index of 20 to 24.9. Those lower or higher than that range had a higher risk of early death.
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