Thanks to WNET's Nature for supporting this episode.

Check out The Serengeti Rules on PBS and pbs.org/nature and follow the career journey and discoveries of five pioneering ecologists! According to fitness trackers and pedometers, people — if possible — should take at least ten thousand steps each day to live a healthy lifestyle.

But… why? I mean, I know exercise is good for you, but what's so special about ten thousand steps? How did doctors and scientists figure out this was the perfect number for maintaining health and fitness?

Well, as it turns out… they didn't figure this out. In reality, this nice, round number just isn't backed up by science. As far as anyone can tell, this figure can be traced to the mid-1960s in Japan, when the world's first wearable pedometer came out.

Its developers named their device Manpo-Kei, which translates to “ten thousand step meter.” Then, they took advantage of the hype around the 1964 Tokyo Olympics to promote it. Now, decades later, people are trying to walk this massive number of steps thanks to some ingenious marketing and… not much else. Because again, there's no conclusive evidence that ten thousand steps a day should be your ultimate health goal.

Instead, many studies suggest that how fast you move — whether you're walking or doing something else — is much more important. Papers have shown that moderate or vigorous exercise is associated with fewer depression symptoms, reduced feelings of anxiety, better sleep quality, higher bone strength, and more. That explains why many public health guidelines recommend a certain amount of time for an activity like this, not a certain number of steps.

For example, the Physical Activity Guidelines for Americans states that the average adult should get a minimum of one hundred fifty minutes of moderate exercise or seventy-five minutes of vigorous exercise each week. If you really want to translate those guidelines into steps, though, you can do that. Like, let's say you want to get in some moderate activity.

For an exercise to be considered this intensity, you need to burn at least three times the amount of energy you would at rest. And research has shown that, for some adults, that's equivalent to walking at a pace of about a hundred steps per minute, or roughly four kilometers per hour. So to satisfy those U.

S. guidelines, you'd need to walk around fifteen thousand steps at this pace over the whole week, or approximately twenty-one hundred steps per day. That number won't make your pedometer happy, but it will likely get your heart rate up. This being said, though, don't worry if you can't get in those steps.

There are tons of other ways to exercise if walking a certain amount just isn't a possibility. Like, there are plenty of people with mobility issues and disabilities that lead healthy and active lives without keeping tabs on a step counter. But in any case, if you can fit in some moderate or vigorous activity, your health will likely be better for it.

If you enjoyed watching this episode of SciShow, we've got something else you'll probably enjoy: a new documentary from PBS Nature. The film is called

Nature: The Serengeti Rules, and it follows the story of five unsung heroes of modern ecology. Beginning in the 1960s, these researchers headed out into the wilderness, driven by an insatiable curiosity about how nature works. And while they were immersed in some of the most spectacular places on Earth — like the Serengeti in Africa — they discovered a single set of rules that governs all life and offers hope for the fate of our planet. In the documentary, the ecologists share the stories of their adventures, and how their pioneering work on keystone species flipped our view of nature on its head.

This film premieres /tonight/ — that's October 9th, 2019 — at 8PM Eastern Time on PBS. But if you're watching this video in the future, you can find it at pbs.org/nature or on the PBS video app. If you watch it, let us know what you think! ♪♪♪.