Runner's backpack

I bought new backpack for runner yesterday. Until then, I used backpack which was not for sports. So, it moved when I was running. And, it made my balance bad. So, it was difficult to run.
I tried it in this morning. It was fit my back as if it was a part of myself. I could run only for 37 minutes from Hiroshima station to my office in Dejima. I like it.