Personally the best way for me to get ready for a trip is to do a series of day hikes with full pack (including water). My wife and I start day hiking every day (even if its just a mile or two on our local county park land) at least two weeks prior to leaving on a trip. I find that my legs and feet are usally fine, but the pre-trip dayhikes prepare my shoulders and lower back.
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"Pain is just weakness leaving your body!"