Counting time or counting steps?

I caught a story on NPR’s Morning Edition that made me do a double take. Thanks to a new book, the decades old concept of getting 10,000 steps per day, as measured by a pedometer, is getting headlines.  This is great because pedometers have underpinned health research, including that in my lab, for years.  The NPR story argues the 10,000 step metric is wrong and we should focus on getting 30 minutes of moderate intensity walking (enough to ramp up yor heart rate) five days a week (150 minutes/week). So which one is right? How do you know if you’re doing enough? Turns out they are both right.

There is lots of evidence that people who get, on average, 30 minutes a day of walking, have lower rates of heart disease, diabetes, stroke and some cancers.  But most of that science hasn’t specifically studied 30 minutes per day.  Some of the people who expended that amount of energy did so by doing more intense activity for less time, or for a longer time on fewer days.  Does that make the 30 minute recommendation wrong? No! But it also isn’t the only way.  And remember that doing more is even better in those studies.  We call it a dose response – up the dose and you up the response ( in this case, lower the risk).  And that’s why the recommendation is actually no longer 30 minutes for 5 days, but 30 minutes for most days – ideally ALL days.

Now what about those 10,000 steps I’ve been recording on my pedometer? In the NPR story, they said you have to walk 5 miles to get there and it takes 2 hours to get it – four times that 30 minute walk.  Do the steps mean nothing? Or do you need to do so much more if you are using the step metric instead of the time one? Goodness no.  On BOTH.

The recommendations comes from much of the same science.  Here’s the science (& math).  The average healthy adult gets between 6000 and 8500 steps per day just going about her daily life (those who are sedentary or suffering from a chronic disease get 3500 to 5000 steps per day and younger adults more like 7-13,000 steps).  A brisk 30 minute walk accumulates about 3-4000 steps.  So an average adult going about her day who adds a 30 minute walk would get about 10,000 steps per day.  Making the recommendations about the same.

The benefit of the 10,000 steps per day recommendation is that it merges two distinct, but important concepts in science – being active and not being sedentary.  It turns out, regardless of how much exercise you get, people who sit more are at higher risk for disease.  So a person who is sedentary (getting 3500 steps per day) who adds a 30  minute walk will be at about 7000 steps per day.  Is this person better off, healthwise, than the one who didn’t take the walk? ABSOLUTELY.  But is he doing as well as the person who doesn’t sit all day AND gets a 30 minute walk? Nope.

Think about it like this.  If you drive to work and sit around the office all day, drive home, heat up dinner in the microwave and sit around for the rest of the evening (whether you are reading or watching TV provided you aren’t snacking, it doesn’t matter for the purposes of this example), you might get only 2500 steps the whole day.  I know this because I’ve had days like that.  Even if I add a 30 minute walk in there, I’m still largely sedentary.  But if I walk to the train and make an effort to go down the hall to discuss a project with my colleague instead of emailing her, if I get up and pace the hallway for a minute instead of checking the ESPN headlines, I’m over 5000 steps, maybe even 6000 steps before I even take a purposeful walk.

The pedometer also keeps people honest.  We don’t intentionally lie to ourselves about these things, but that 6 minute walk to and from the train becomes 10 each way and the 10 minute walk with the dog becomes a walk, not 2 minutes of walking and 8 minutes of standing around during sniffing and stuff.  Suddenly, 15 minutes is 30. But the steps are steps.

The ideal is both an active day and purposeful walking.  Not either or.  And saying the former is better ignores the science about the dangers of sitting.  Which shows not moving all day is bad, regardless of our exercise.  And if you read between the lines, the NPR story says as much, since their expert advocates for walking meetings, which might not be vigorous enough to “count” toward that 30 minutes of moderate intensity exercise the science says we need to reduce chronic disease risk.  Remember, it isn’t a 30 minute leisure stroll!

So if you’re taking a 30 minute walk and your pedometer is only at 6000 steps at bedtime – is that a failure? No. In our research, we know to tailor the goal to the audience.  And thanks to our understanding g of dose response, we know there’s a benefit to something over nothing.

In our cancer prevention segment on activity we introduced Virginia.  She’s closer to a 6-8000 steps per day person some days after our intervention (But working hard to keep doing more!). But her blood pressure is down and her glucose regulation is better. Do I think our intervention didn’t work because she didn’t hit 10,000 steps? Not even close.  Because the other thing about that step counting helps is the durability. More than a year after the intervention ended, she’s still walking and counting steps.  The pedometer gives her credit for what she does – she knows more is better but we also know something is better than nothing!  And for chronic diseases we know it is long term behavior change that matters most.

Advertisements