Thursday, December 13, 2012

How Much Exercise is Too Much?

About two weeks ago the Wall Street Journal published an article that further rocked the world of endurance sports, that is, the one inhabited by millions of people who put in millions of miles running, cycling, rowing, swimming, and otherwise conveying themselves via high mileage across the landscape. The article was called "One Running Shoe in the Grave." It basically expressed the notion that running anything but very low mileage is unhealthy, especially for the heart, and will lower lifespan.

A fast-emerging body of scientific evidence points to a conclusion that's unsettling, to say the least, for a lot of older athletes: Running can take a toll on the heart that essentially eliminates the benefits of exercise.

The article derives its claims partly from a recent British Medical Journal review called "Run for your life…at a comfortable speed and not too far," so I grabbed a copy of that to read and write about.

By the way, although the article refers to running, I think the basic concept of the potential risks posed by long duration, high-heart-rate exercise applies to those other endurance sports as well (e.g., hard cycling).

To put everything into perspective, you may also want to read these two cardiologist's blogs (one a cyclist who races) – here and here – which help you step back from the more inflammatory tone of the WSJ article.

I've looked into this issue about extreme training being bad for you – as in marathons and long triathlons (maybe even as short as two hours, if you do a lot of them) – since at least five years ago when I cut way back on my own mileage and virtually ceased racing.

I'd seen enough evidence, in well-reasoned arguments on the web as well as anecdotely (i.e., really bad things happening to men around my age), to make a change in my own exercise regimen. Because my goal is healthy longevity, not "dying young and leaving a pretty corpse." By the way, that latter approach would be pretty irresponsible considering that I have younger kids.

Although it's only anecdotal, the recent death of the Born To Run ultramarathoner Micah True at age 58 has only raised more eyebrows and added fuel to the fire. I knew a wonderful man here in New England, a coach who was adored by his athletes, who was getting ready to challenge age-60+ long distance running records (he had recently run five miles in 30 minutes) when he dropped dead after a training run at age 63.

This evidence and research for Fitness For Geeks has led me to embrace the conclusion that there is a dose:response relationship to exercise.

This means that if you exercise in the "sweet spot" you're getting healthier (e.g., jogging less than 20 miles per week), but if you push it too much (a heavy dose), you get the heart scarring and calcification of the artieries (essentially, converting your arteries to bone), not to mention the immune suppression (cancer? MS?) that some of these articles and reviews talk about.

But where you do draw the line? What level of running and cycling is healthy? If you look at the comments beneath the WSJ article, you can see how perplexed we all are. Is my routine hurting me? would be the crux of the issue. For example, you can't tell me that a lifelong bicycle commuter (and occasionally racing through that intersection will elevate the heart rate) is putting themselves at risk. Or simply a 5k runner?

I think we can reasonably conclude that years and years of extreme training can shorten your "healthspan" (and probably will). Buit It's impossible to make more fine-grained recommendations than the BMJ article does (see ahead), because all the data and analysis isn't in yet.

Everyone is different and has varying tolerance levels. It also seems reasonable to conclude that nutrition, length of rest periods and patterns, stress management, sleep, and other lifestyle aspects have to play a role in the "survivability" of heavy endurance exercise. For example, are you up to speed on vitamin K, which "takes calcium from where you don't want it" (e.g., your arteries) and puts it where you want it, your bones?

Here's a big quote from the BMJ essay, which seems to conclude that anything more than 40-50 minutes of strenuous exercise in most days has diminishing returns.

Indeed, regular vigorous exercise is probably the single best step a person can take to ensure robust CV health. In a study of 416 000 adults followed for a mean of 8 years, 40–50 min per day of vigorous exercise reduced risk of death by about 40% (figure 1).7

In that study, at about 45 min, a point of diminishing returns is reached whereby longer exercise efforts do not appear to translate into lower death risk. Light to moderate physical activity reduced death rates too, albeit not as strongly, but in this case more physical activity appeared to be better, with no plateau out to 110 min daily.

Indeed, if we had a pill that confers all the benefits of exercise, many physicians might be looking for work. Approximately 30– 45 min of daily vigorous exercise significantly reduces risks for many maladies including early death, Alzheimer’s disease, CHD, diabetes, osteoporosis and depression. 4 5 Yet, as can be expected with any potent drug, an insufficient dose will not confer the optimal benefits, while an excessive dose can cause harm, and even death in extreme overdoses.


In fact, the review claims that there is no health advantage beyond the ability to run eight-minute miles (meaning that if you can go faster, you're doing it for another reason other than health).

There are analogies to make in this area. We think (and my book points out) that one glass of wine at night might confer health, compared with none or multiple glasses. One of the running study directors says, "The relationship appears much like alcohol intakes—mortality is lower in people reporting moderate jogging than in non-joggers or those undertaking extreme levels of exercise."

One reassuring note: although the heart, as an organ, is not particularly great at repairing itself (that would take stem-cell technology) some of the studies show (including with mice) that some of the damage of extreme training is reversible if followed by months of rest and not undertaken anymore.

Another long interesting quote you might ponder (and echoing some of the stuff I wrote about "chair living" and the like in Fitness For Geeks):

Hippocrates, the father of medicine and a contemporary of Phidippides in ancient Greece, taught, ‘The right amount of nourishment and exercise, not too much, not too little, is the safest way to health’.1 If you listen to your body, this is just common sense.

Yet, nothing we have published previously has stirred so much controversy, especially among the general public. Increasingly our culture is one of extremes: during the past 30 years, obesity has tripled in the USA and has increased in much of the Western World, while during the same time the number of people completing a marathon has risen 20-fold.

On one side of the U-curve, the couch loungers/channel surfers embrace this message as justification for continuing their sedentary lifestyle. And, on the far end of the U-curve, the extreme exercise aficionados want to ignore the message and instead kill the messenger. As with many things in life, the safe and comfortable zone at the bottom of the U curve—moderate exercise—is the ‘sweet spot’ for which most should try to aim.

Sitting is the new smoking; a sedentary lifestyle will cause disability and disease, and will shorten life expectancy. We are not so much born to run as born to walk.

Ethnographic research indicates that, in the environment of human evolution, our ancient ancestors walked 4–10 miles a day.

Walking is superior to running for mechanical efficiency and musculoskeletal durability. Indeed, we advise our patients that they can walk or garden hours a day without concern about CV overuse injury. So while it is true that exercise confers powerful health benefits, the common belief that more is better is clearly not true.


The take home message for most is to limit one’s vigorous exercise to 30– 50 min/day. If one really wants to do a marathon or full-distance triathlon etc, it may be best to do just one or a few and then proceed to safer and healthier exercise patterns.

Reference: "Run for your life…at a comfortable speed and not too far," James H O’Keefe, Carl J Lavie; British Medical Journal, http://heart.bmj.com/