Football players don't lift to increase their strength during the season.. no athlete in any sport does that besides power lifting. They lift to maintain their strength and prevent injury. If they were lifting to get stronger during the season they would get hurt a lot more than they already do. There is a point when you plateau, you don't just keep getting stronger. If that were the case guys could bench 1,000 pounds. It doesn't work like that. Genetics plays into your strength as well.