Study finds T-rex had a swing in her step Humans and animals have a preferred walking speed. This is, in part, influenced by the amount of energy required: they prefer to walk at the speed at which they use the lowest possible amount of energy. One of the ways to achieve this is using something called resonance. You already know how it works: when you are on a swing, you can’t just swing at any speed. If you want to do it properly, you have to get the timing right, and swing in the rhythm of the swing. In other words: you have to resonate with it. And when you’re on a nice relaxing walk, the parts of your body resonate, too. Walking slightly slower doesn’t require less energy: you notice that it’s actually harder.