Spend time on any crowded sidewalk and you’ll see heads bent over and eyes cast downward. One recent study of college students found that a quarter of people crossing intersections were glued to a device.

“I don’t think people are aware of how much they’re distracted and how much their situational awareness changes when they’re walking and using a phone,” said Wayne Giang, an assistant professor of engineering at the University of Florida who has examined the link between phone use and walking injuries.

Indeed, our devices can cause what some experts call “inattentional blindness.” One study found that participants were half as likely to notice a clown on a unicycle — a cheeky touch — while walking and talking on a phone.

But that screen in your hand isn’t just diverting your attention. It also changes your mood, your gait and your posture — and hinders your ability to get from point A to point B without running into trouble.

How a Phone Breaks Your Stride

When we walk and use a phone at the same time, Dr. Giang said, we reflexively adjust how we move. Video footage of pedestrians has shown that people on phones walk about 10 percent slower than their undistracted counterparts.

“You see a number of gait changes that reflect slowing down,” said Patrick Crowley, a project manager at the Technical University of Denmark who has studied the biomechanics of walking while using a phone. “People take shorter steps and spend longer time with both feet on the ground.”

These changes can gum up traffic on the sidewalk. And if walking makes up a big portion of your daily physical activity, strolling more slowly may have repercussions for your fitness, said Elroy Aguiar, an assistant professor of exercise science at the University of Alabama.

Looking down at a smartphone while walking — as opposed to standing up straight — can also increase the amount of load, or force, placed on the neck and upper back muscles, which can contribute to symptoms of “text neck.” And research in the journal Gait & Posture suggests all this could reduce balance and increase the risk of stumbles or falls.

How It Affects Your Mood

When scientists want to study stress, they often ask people to perform several tasks at once. That’s because multitasking is a reliable way to stress people out.

There’s evidence that walking while using a phone functions this way too, even if we’re not aware of it in the moment. One experiment found that the more people used a phone while walking on a treadmill, the more their levels of cortisol, the so-called stress hormone, tended to rise.

A 2023 study examined the psychological effects of walking in an outdoor park while looking at a phone — or not. “Generally, when people go for a walk, they feel better afterwards, and this is what we saw in the phone-free walking group,” said Elizabeth Broadbent, one of the authors of the study and a professor of health psychology at the University of Auckland in New Zealand.

“In the phone-walking groups, these effects were reversed,” she added. “Instead of feeling more positive after walking, people felt less positive — less excited, less happy, less relaxed.”

She and her study coauthors attributed these negative effects to a diminished connection with the surrounding environment — it’s now widely accepted that walking in natural spaces is good for your mental health. “It appears that to get these benefits, it’s important that your attention is on the environment, rather than on your phone,” she said. It’s also possible, she added, that walking and trying to use a phone is simply annoying, and that’s why it sours your mood.

The Dangers of Distracted Walking

Most of us understand that walking and using a phone can be risky. Some cities, like Honolulu, have even passed laws to rein in distracted pedestrians. But research on those dangers has turned up some surprises.

Dr. Giang’s work has looked at the connection between “phone-related distracted walking” and emergency department visits. Using government data spanning the years 2011 to 2019, he and his colleagues turned up nearly 30,000 walking injuries occasioned by phones. While many of those accidents occurred on streets and sidewalks, almost a quarter happened at home. Tripping over something or falling down the stairs is a real risk, Dr. Giang said.

Age was one of the major risk factors for phone-related walking injuries, his study found. Young people from the ages of 11 to 20 had the highest proportion of injuries, followed by adults in their 20s, 30s and 40s — perhaps because younger people use their phones more than older people do, he said.

So how do you stay safe? If you want to check your phone, Dr. Giang recommended just stopping for a moment — preferably out of the path of other pedestrians.

If you do walk and use your device at the same time, he advised refraining when you’re around stairs, crosswalks and cluttered or uneven terrain — all settings where, according to his research, accidents are more likely to occur.

“Even alert and aware people are injured walking,” he added. “If you’re distracted by a phone, you’re definitely putting yourself at some risk.”