The fearsome tyrannosaurus rex likely walked at a speed slightly slower than humans, according to a new study from Vrije Universiteit’s Human Movement Sciences student Pasha van Bijlert. The reason for this slow walking speed mostly had to do with the giant dinosaur’s equally big tail, which would have swung back and forth as the creature roamed prehistoric Earth. According to the new study, animals and humans naturally stick to certain walking speeds that are based on their resonance, which is essentially the rhythm one gets into based on their body that enables them to save energy while walking. This is why someone may find it exhausting to walk at a slower speed than usual in addition to walking faster than usual.