Most people think of warming up as it relates to getting ready to play a sport: stretching, jogging, etc. For me, though, warming up means that it's getting ready for paintball to begin. Not in a matter of minutes or hours, but in a matter of weeks or months.
I'm well aware that people in the south and along the west coast of America generally never have a time of the year when they can't regularly play paintball in the great outdoors, but for those of us that live in the Midwest (and many other parts of the country and world), there's a long period when paintball is hard to play due to the cold. In fact, in Ohio where I live, there are about four months of the year (middle of November to the Middle of March) when paintball is almost impossible to play. It's not that it's too cold and snowy that whole time, but on the few days when it is a bit warmer, the field is so wet that it turns into a soggy mud puddle by about the second game.
Because of the long winter, it always gives me a little breath of fresh air when I can sense that the season is finally changing. It's not that there's just a warm day, but there's something in the air that makes it feel like the end is in sight. With the warming up period, it really feels like the weather is warming up for paintball season. Just like you warm up before you play, the season is getting ready to begin.