It’s OK if you only hit 8,500 steps today — and sit while you work. Fitness myths, debunked.

You've probably heard fitness experts say that 10,000 steps — about 5 miles — should be your goal if you want to reap the daily benefits of exercise. And if your desk job makes a pedometer routine tough to keep, one of your co-workers may have already recommended you try out a standing desk.

Both the 10,000 steps adage and the standing desk are popular additions to modern fitness regimens, but have you ever wondered why? As it turns out, both are probably better for you than sitting in a cubicle, but neither is completely backed by cold, hard science.

To begin with, counting steps. Why do we — and our fitness devices — call 10,000 the magic number?

“It was made up in Japan in the 1960s,” says Euan Ashley, a professor of cardiovascular medicine and genetics at Stanford. “There was a pedometer that became very popular there. Its nickname was ‘manpo-kei,’ which literally means ‘10,000 steps.’ And from there, the Japanese health ministry took it on, and it became kind of almost like a meme.”

Ashley, who has worked with Apple on its suite of fitness apps, says the appeal of 10,000 daily steps may be its simplicity. It’s a round number and a relatively achievable goal. But his team at Stanford is now digging deeper into the link between steps, fitness and even mental health with a study-turned-app called MyHeart Counts.

“If you consent to take part in the study, it will upload the number of steps that the phone thinks that you do into the cloud, allow us to analyze it along with the rest of the population, and we can study exactly what effect exactly how many steps are on your happiness, on your fitness and other things,” Ashley says.

But for the moment, at least, 10,000 remains the number many of us are stepping toward. Ashley says that number is reasonable — and close to current recommendations from health professionals.

“I mean the current American Heart Association, American College of Sports Medicine recommendations are to do moderate exercise for 30 minutes, five times a week,” Ashley says. “And if you add that about 3,000 or 4,000 steps to your sedentary steps, it takes you to about 8,000 or 9,000 [steps].”

Now, what about that other healthy habit, using a standing desk? As it turns out, the fad just might have legs — if only because we now know that prolonged sitting can be bad for us. Bethany Barone Gibbs, a professor of health and physical activity at the University of Pittsburgh, says that all the sitting we do now is a new phenomenon.

“With computers and video streaming, we sit for hours on end sometimes without getting up,” Gibbs says. “In theory, it makes sense if we replace some of that sitting with standing up it would be better, but we actually don't really know that right now.”

Instead, Gibbs says there’s evidence that people who sit more can experience more cardiovascular disease, more Type 2 diabetes, more pain and shorter lifespans. But there aren’t yet clinical trials that have shown how changing that sitting into a different behavior — like standing — improves our health.

“We’re really interested in it, but we don't have the proof yet,” Gibbs says. “So I'm looking forward to that developing over the next five to 10 years.”

Gibbs’ team has found that desks offering both sitting and standing options get some people to stand more — in some cases for hours a day. But Gibbs is careful to add that standing at a desk doesn’t do much to increase movement, which we already know is good for us.

“The extra movement — although we do see a little bit, it's not very much,” Gibbs says. “And some recent data we had showed maybe about 12 extra minutes a day.”

As researchers like Gibbs try to tease out the health benefits of standing at a desk against other possible options, they also face a surprising social pressure: expectations about what “busy” looks like.

“In our current American office culture, if you stand at your desk you can still be working, and that's valued,” Gibbs says. “And if you have to walk away, you're not necessarily still working.”

Recently, Gibbs’ team published its findings about how many extra calories are burned by just standing. Alternating 30 minutes standing, 30 minutes sitting, burns about five to six extra calories per hour.

“Over a day, that's going to be 40 or 50 calories, which is not a ton,” Gibbs says. “But it could build up, and it's just one small change that you can easily make that could contribute to preventing weight gain.”

That, and approximately 10,000 daily steps. Just don’t ask science to prove it — yet.

This article is based on an interview that aired on PRI's Science Friday.