I'm hiking the grand canyon in june, however I'm slightly out of shape. I've had a busy month so I've slacked off on exercising. I could probably walk 5-6 miles on level ground before I'd need a break, and maybe 3 if I was going uphill.Do I have enough time to get in shape for the hike(14 miles down, sleep, 9 miles out)? What routine can I use to get the most out of my time?