Not swinging your arms makes it 12% more difficult!
A new study explained why it is that we swing our arms when we walk. It's because they make waking a much easier effort. In fact, the experiments conducted for the study found that not swinging your arms increased the effort of walking by 12%.
To put that number in different terms, if you don't swing your arms, you exert the same amount of effort as if you were walking 20% faster or you were carrying a 20lbs backpack.
Why would anyone spend their time researching this, you ask? Well, they hope that these findings will help develop better walking robots and also aid in physical therapy.