Whether it's to play music that motivates you to work out, to monitor your performance, or even just in case you need to call a loved one in the event of an emergency, many of us run with our mobile phones in our hands. While this habit is seemingly safe and mostly harmless, it can have a negative impact on your body and reduce the benefits of running.Is running with your phone in your hand harmful?Running with your cell phone in one hand and nothing in the other can create an imbalance and lead to pain in your hips, shoulders, and knees. Sports medicine specialist Victoria Tchaikovski explained to Madame Figaro:The weight of your phone will increase the range of your arm's rotation, and that can cause tense muscles, pain, or even tendonitis.If you regularly go for runs with your phone in your hand, the effects of doing so could be significant. Cécile Bertin, author, and creator of the blog Run, fit & fun says:Often times, people don't realize the imbalance holding their phone is causing in the upper limbs. But if you run for an hour 2-3 times a week, your body can tilt a few millimeters to the side you are holding it on, which is not negligible.Less significant fitness benefitsWhile running with your phone in your hand can create body imbalances and joint tension, it can also reduce your performance by reducing your speed. How come? Well, the momentum of your arms is what determines how fast you jog. If there's a weight in one hand (eg. a phone), it'll offset your balance and alter how you run. In other words, your running pace is instantly reduced and your physical activity becomes less efficient.Running with your phone in your hand can also be disruptive. All it takes is a call, a text, or a notification to interrupt or distract you from your run. Your respiratory rate and the consistency of your strides are also affected.Also, having your eyes glued to your phone screen prevents you from seeing potential obstacles ahead of time, thus increasing your risk of falling.Remember: going for a run is an opportunity to disconnect and blow off steam, so take a deep breath and try to unplug while you do it.