SACHA PFEIFFER, HOST:
Time now for some science news with our friends at NPR's science podcast Short Wave. Emily Kwong and Regina Barber host the podcast, and they're here now for our biweekly science roundup. Hi to both of you.
REGINA BARBER, BYLINE: Hello.
PFEIFFER: Hi.
EMILY KWONG, BYLINE: Sacha, so good to be with you.
PFEIFFER: Good to have you. So, Emily and Regina, the two of you have been combing through headlines, journals, social media. You have picked out three science stories for us to hear more about this week. Is that right?
KWONG: That's right. We've got kind of a fitness, recreation, health theme going on today, so I hope you're ready to become your best self.
BARBER: Yeah, we've got stories about counting steps, ice baths and something known as virtual reality sickness.
PFEIFFER: Let's start with that last one first, virtual reality sickness. Is that similar to motion sickness?
BARBER: Yeah. VR sickness, for short, is a lot like motion sickness, which I get in cars and boats when I read.
PFEIFFER: Same.
BARBER: What's happening in our bodies, though, is that we're noticing inconsistencies between what we're seeing and what our bodies are feeling. Our bodies are actually accelerometers, and there's structures inside our ears and our joints that tell us when we're speeding up and slowing down. But if your visuals don't line up with what you're actually feeling, you can start to feel sick.
PFEIFFER: Oh, yes, this definitely happens to me. It's why I can't read in cars, which is really frustrating when you're looking for ways to pass a lot of time, but you just end up feeling queasy.
BARBER: I know. Long car rides - it's just a struggle. It's horrible.
PFEIFFER: So have scientists gotten interested in this because gaming has gotten so prevalent and more people end up in these virtual reality situations where they don't feel great?
BARBER: Yeah, absolutely. There is just VR games and training, and there's a large population that just can't experience this because they just get too sick. So scientists are trying to figure out why some people are more susceptible than others.
PFEIFFER: This sounds like there could be some fun experiments involved. How do scientists study this?
BARBER: Yeah, so it actually is. So I talked to one researcher, Michael Barnett-Cowan at University of Waterloo, about this. And he says they asked people to take a visual test before playing a VR game for 30 minutes. And this test involved looking at a luminous vertical line when your head is tilted, and this creates an optical illusion. And they asked if that vertical line looked tilted or straight up and down.
MICHAEL BARNETT-COWAN: And then they play their game, and they come back.
BARBER: And they report whether they feel sick, and they retake this visual test to see if their perception of that visual line has changed.
BARNETT-COWAN: And if they didn't really change at all in those two settings, those were the people who got more sick. The people who changed were less sick, and it didn't matter the direction.
PFEIFFER: So, Regina, what is the scientific takeaway there?
BARBER: So basically, people who had no change in how they perceived things before and after - their bodies never got the time to kind of reconcile the difference between their visuals and their bodies' accelerometers. Researchers are still trying to figure out why some people can adapt to this kind of VR experience quicker than others. There's also still so many unknowns. Like, how do you figure out how to mitigate these effects? So we really need more studies to get to that one goal to make VR accessible for many more people.
KWONG: Yeah. I mean, what's interesting about health, period, is that everyone's body is so different. Everyone experiences the world in a different way. The VR story is a perfect example. And the example I have has to do with updating a long-held popular health claim, which is that we should be taking 10,000 steps a day. It is a number built into all kinds of apps and wearable fitness trackers as this daily aspiration. But, Sacha, that 10,000 step claim is not based in science. It's actually based in marketing.
PFEIFFER: Oh, why am I not surprised?
(LAUGHTER)
PFEIFFER: So what's the marketing history of this?
KWONG: It's pretty fascinating. In 1965, a Japanese company was selling pedometers. And the Japanese character for 10,000 just so happens to look a bit like a person walking. So the company sold their pedometer as the 10,000-step meter, and that number kind of stuck without much research to support it.
PFEIFFER: Wow.
KWONG: The person to piece together this history for public health purposes is Dr. I-Min Lee, Harvard Medical School professor and epidemiologist at Brigham and Women's Hospital.
I-MIN LEE: For many folks who are older, I think 10,000 steps can be very daunting.
PFEIFFER: I think 10,000 steps is - what? - five miles. So I can see how, for - especially if you're older, that would feel like a big distance.
KWONG: Yeah, it's a lot. So to figure this out - and I read about this in a recent article from Scientific American - Dr. Lee and fellow researchers a few years ago tracked more than 16,000 women 45 years and older who all wore a pedometer over four years, OK? And they found that at 4,400 steps a day, study participants did have significantly lower mortality rates. But after only 7,500 steps, it kind of leveled out.
PFEIFFER: Meaning suddenly they weren't seeing as much health benefit from it.
KWONG: Yes, exactly.
PFEIFFER: Why?
KWONG: So as we get older, our movements become less efficient, and each step requires more energy.
PFEIFFER: Aging. Every time I hear more news about aging, it seems bad. Here's some more.
KWONG: No, no, no. But here's an upside. Think of it this way, right? It means that you need fewer steps to reap the same health benefits.
PFEIFFER: Oh.
KWONG: So Dr. Lee's ultimate recommendation if you're older - if you're over, say, 65 - is getting between 6,000 and 8,000 steps a day is more than enough to result in real health outcomes. And if you're sedentary or your area isn't safe to walk in, even a modest increase, just some walking every day, will significantly improve your cardiovascular health and your life expectancy.
LEE: Getting some steps is always better than getting fewer steps.
KWONG: And this nuance matters to me. It just means that as our bodies change, our expectations for ourselves should change, too. And ranges are better than hard and fast numbers.
PFEIFFER: All right. So we've covered virtual reality sickness. We've covered counting steps. You said you also wanted to talk about ice baths.
BARBER: Yeah. So we're talking about cold water immersion. That's the phenomenon where people are jumping into cold lakes, taking freezing showers or sitting in tubs of ice cubes.
PFEIFFER: I have an older - I had; he's no longer alive - an older Finnish friend who loved to do that. He would dunk himself into cold water. I always thought it must feel excruciatingly uncomfortable, but he really thought it was good for him.
KWONG: Yeah, it scares me a little bit. But people have been promoting this on social media, saying that it gives them, like, more energy and it improves their mood.
BARBER: It definitely causes a rush and gets your heart rate up. My fiancé and I are hosting a polar plunge the morning of our wedding next month. We're getting 100 people to run straight into the main ocean for fun.
PFEIFFER: (Laughter).
KWONG: Oh, my gosh.
BARBER: So I'm there for the social benefits, you know?
PFEIFFER: And are there actually any health benefits to this?
BARBER: Yeah. Even though the practice is old and traditional, there's a lot of people that do it around the world, like your Finnish friend, the research on cold immersion is new. There's just not a ton of studies to back up these anecdotal claims of health benefits.
KWONG: Yeah, most of the research that's been done on cold water immersion is on elite athletes. And we do know that cold water affects blood flow. When you get in the bath, your blood vessels constrict. And then when you get out, they enlarge. And that kind of supercharges the removal of lactic acid and other waste products because that blood is full of oxygen and nutrients and it lowers inflammation. But the thing is we don't know if cold water immersion is better at healing muscles than, say, active recovery, like walking or cycling between workouts. It seems like there's lots of things that can help our muscles heal.
BARBER: And there's just not a clear consensus because in a lot of these studies, you just can't clearly say that they have health benefits because the people might have been already healthy.
KWONG: But my consensus is that doesn't mean it isn't fun. It's actually, I would argue, more fun than a bouquet toss at your wedding. So maybe you should try it.
BARBER: I would not argue that.
PFEIFFER: Different definitions of fun for different people.
BARBER: Indeed.
PFEIFFER: That's Emily Kwong and Regina Barber. They host NPR science podcast Short Wave. That's where you can learn about new discoveries, everyday mysteries and the science behind the headlines. Emily and Regina, thanks, and see you next time.
BARBER: It's been fun. Thanks, Sacha.
KWONG: Thank you, Sacha.
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