If you have been following fitness news at all in the last few months you have probably encountered headlines like these:
Couch potatoes rejoice! Too much exercise may be bad for you
OVER-EXERCISING CAN SPEED YOU TO THE ‘FINISH LINE OF LIFE’
Running Too Far Too Fast Will Make You Dead (Eventually)
They all stem from a Wall Street Journal article with the wonderful headline “One Running Shoe in the Grave” and that article stems from a couple of papers all written by the same two authors over the last few years. The basic premise is if you run more than a few miles a day and if you run more than 8 minute per mile pace running stops being good for you, and in fact becomes bad for you. Now there are a lot of problems with this premise. First is how they manipulated the data to get a result they wanted. Science journalist Alex Hutchison breaks it down much better than I can so I’ll just quote him (please read his full article here.)
(1) One of the major pieces of evidence the group cites is a study that was presented at a conference over the summer. The WSJ description: In a study involving 52,600 people followed for three decades, the runners in the group had a 19% lower death rate than nonrunners, according to the Heart editorial. But among the running cohort, those who ran a lot—more than 20 to 25 miles a week—lost that mortality advantage.
But here, from the actual abstract, is the part they never mention: Cox regression was used to quantify the association between running and mortality after adjusting for baseline age, sex, examination year, body mass index, current smoking, heavy alcohol drinking, hypertension, hypercholesterolemia, parental CVD, and levels of other physical activities. What this means is that they used statistical methods to effectively “equalize” everyone’s weight, blood pressure, cholesterol, and so on. But this is absurd when you think about it. Why do we think running is good for health? In part because it plays a role in reducing weight, blood pressure, cholesterol, and so on (for more details on how this distorts the results, including evidence from other studies on how these statistical tricks hide real health benefits from much higher amounts of running, see my earlier blog entry).
They’re effectively saying, “If we ignore the known health benefits of greater amounts of aerobic exercise, then greater amounts of aerobic exercise don’t have any health benefits.”
The second and more troubling problem with the premise is that they use, as part of their paper, data from a study involving 400,000 people that doesn’t in fact show a problem with exercising up to 2 hours a day or vigorous exercise. In fact, what the data actually shows is a leveling off of benefit at around 2 hours a day but does not show a turn toward negative impact, just no more positive impact. (again you can see this in the Hutchinson article.)
To me the most ridiculous part of the scaremongers claim is that they are using mortality rates as their sole indicator of whether prolonged vigorous exercise is good or bad for you. They take a group of people and find out over a span of 30 years how many of them died. That is your mortality rate. So setting aside the obvious fact that every person who ever lived or will ever live is either dead or is someday going to be dead, I’m more interested in the quality of that life. Lets pretend they weren’t screwing with data, and cherry picking information to get a result they want. Lets pretend for a minute that they are right, and running 7 hours a week and doing speed workouts, and races means that you have a higher chance of dying in the next 30 years than someone who goes for a few mile jog a few times a week. Are you really going to stop running the way you want to run? Is it worth giving up your running life for 30, 40 , 50 years just so at the tail end you can squeak out a few more years in a nursing home? Given the choice of doing what I love and dying at 80 or not doing what I love and dying at 83 I know what I’m going to pick. Luckily it isn’t really a choice I have to make.
Hot on the heels of the too much excerise is going to kill you news is the, too much excercise will make you depressed news. This latest paper has been published in the most recent Journal of Preventive Medicine. If you don’t have access to the full text you can read a pretty good summary of the article here by Scott Douglas. This article hasn’t been hyped nearly as much as the running will kill you article, but I say give a month or so before newspapers and websites pick up and on it and start splashing the alarmist headlines. If you don’t want to read the origonal or even the Douglas summary I will break it down for you very quickly.
No exercise= sad
2-25 hours a week of exercise= not sad
More than 25 hours a week of exercise= sad
There is even this handy chart.
So the lesson here is very clear. If spend twice as much time running as the best marathoners in the world you will not be happier than someone who doesn’t run at all. If you spend triple the time running as the best marathoners in the world you have mental problems. Yah science.