How a Phone Breaks Your Stride When we walk and use a phone at the same time, Giang said, we reflexively adjust how we move."You see several 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.And if walking makes up a big portion of your daily physical activity, strolling with a phone may have repercussions for your fitness, said Elroy Aguiar, an assistant professor of exercise science at the University of Alabama.