When I used to do the occasional "fun run", the sheer number of people at the start meant that unless I wanted to duck and weave through the crowd, I _had_ to s

When I used to do the occasional "fun run", the sheer number of people at the start meant that unless I wanted to duck and weave through the crowd, I _had_ to start slowly and then gradually speed up as everyone spread out. Even when I did a run without much training leading up to it, that forced slow start meant I'd ease into a sensible cruising speed and be fine for hours, as opposed to being wrecked inside of 20 minutes of running alone.