I'm going backpacking in about a week. It is going to be about 4 miles, mostly flat but some ups and downs, at a higher altitude than I am used to working out at. We are camping out the night there and coming back the next day. I'm not in fantastic shape, but I've been on these trips before and done okay. I need some tips on what kind of pants and underwear to wear to prevent chafing? I may be on my period, how do I handle that? General guidelines from woman who do backpacking trips? How can I physically prepare for the hike, since that is more than I usually do, and I have a bad cardio system? Thank you