Smartphones can be a valuable tool for getting fit. They can count steps, play fitness videos, help us track our progress and connect us with workout buddies and coaches, both real-life and virtual. But when it comes to phone use during a workout, recent research suggests a few reasons to leave your device alone: Texting or talking on the phone while exercising can worsen your balance and workout intensity, according to recent research.One new study, published in the journal Performance Enhancement & Health, found that texting during exercise impacted balance and stability by 45%, compared to not using a phone. Talking on the phone made balance 19% worse—less than texting, but still significant enough to contribute to injuries, say the authors.“It could lead to you possibly falling off the treadmill, or if you’re walking outside, falling off a curb and rolling your ankle or tearing your ACL,” says Michael Rebold, lead author on both studies and assistant professor of integrative exercise science at Hiram College.Another study, published in Computers in Human Behavior last year, found that people who texted during a 20-minute workout spent almost 10 of those minutes in a low-intensity zone, and only seven minutes in high intensity. Those who worked out without a phone spent only 3 minutes in low intensity, and almost 13 minutes in high intensity.This might seem like common sense; it’s not news that cell phones distract us. But Rebold says he was a bit surprised by the extent to which cell-phone use messed with people’s performance. “The studies were done on college students, and you’d think that, being born in this digital age, they’d be able to multi-task somewhat better than that,” he says. “If we’re seeing these severe impacts even on younger generations, I can only imagine how older adults might be affected.”Both studies looked at very specific measures: One tested 45 people on balance platform, while the other tested 32 people on a treadmill. The researchers can only speculate as to how their findings may translate to other activities, but they say their studies call attention to the potential drawbacks of mixing exercise time with mobile screen time.The good news is that listening to music on a cell phone had no notable impact on balance, so exercisers should feel free to use their tunes, says Rebold. In fact, his earlier research has shown that listening to music during exercise can boost workout intensity and enjoyability.Just try to have your playlist planned out in advance, so you can avoid too much screen interaction while you’re actually moving. “Anything that distracts you from the task at hand, whether it’s texting or switching songs or entering info into an app, is going to take away from your performance and could potentially put you at risk for injury,” says Rebold.In other words, save your calls, texts, and any unnecessary fiddling until after your sweat session. And if the buzzing in your pocket is too tempting to ignore mid-workout, try leaving your phone behind.