re: I lied to a girl I'm trying to impress, told her I can run a 5k in under 29 minutes (DONE)

Just skip it and then tell her you were on a late call manning a teen suicide hotline....you already have the lying part down. Or...just show up to the run with a puppy. The topic about your (lack of) running will never be brought up. If she doesnt dig it some other girl will ....which will probably retroactively cause the original girl to dig it.