Great that your girl wants to ride with dad, but remember, she is a young child. Keep it fun, don't make it a chore. There will be plenty of time for intervals and hill repeats when she is in grade school (just kidding . . . sorta). If she is losing interest, maybe it's time to back off a bit and do some other healthy activities with her for a while. I love to see parents who are actively involved with their kids, but as in all good things, practice moderation.