Doesn’t the pump heat up as you inflate the balls to begin with? So you could be dumping warmer than room temperature air into the balls before sending them out in the cold.
“Doesn’t the pump heat up as you inflate the balls to begin with? So you could be dumping warmer than room temperature air into the balls before sending them out in the cold.”
True but a negligible effect since the volume of air being pumped into a football is small. It’s the difference between filling a bicycle tire and a car tire. The bike tire reaches rated pressure very quickly. The heat content of that volume of air is less even if the temperatures are the same.
Pumps could ad a little, probably very little if the balls were anywhere near end pressure level.
This could do a lot more:
http://espn.go.com/video/clip?id=12221498
Note the dirth of measuring gauges, and the method of approving the balls.
This is what the Patriots claim they determined added about a PSI temporarily. The pumping probably added significantly less than just holding the balls in human hands.