When I did the JMT a couple of years ago, at 63, I was a little discouraged at first that my months of training did not pay off better right away. After struggling for four of the first five days, something clicked, and suddenly I was kicking it as I had hoped to from the start. Over the next few days I realized that what I was suffering from was not a lack of physical training, at least not in the sense of hiking harder or faster or even higher than I had in the weeks prior, but that I had imposed other changes suddenly that I did not work up to as I had the physical exertion: diet, sleeping arrangements, hydration come to mind.
Lessons learned: if your usual morning routine consists of throwing off a couple of goose feather pillows and sliding out of your good old familiar bed around 830 and padding downstairs to 3 big cups of fresh dark roast caffe au lait for breakfast, then getting right to work on your email, don't expect that waking up at LYV at first light and creaking up off your self-deflating BA Thinset and having one cup of really shitty coffee and half a pound of oatmeal and raisins with honey is suddenly going to be the start of a really good day involving a climb of 4000 feet.
If your usual lunch is a tomato and ham sandwich with sparkling water or a smoothie, don't expect your body to switch right over to handfuls of gorp every 20 minutes, tortillas with ghee at 1100 am or in fact anything at all. If you have been eating really healthy - a bed of baby greens, sliced tomatoes, fresh mozzarella, avocado, minced garlic and balsamic vinagrette with a seared 3 oz salmon filet for a typical summer dinner, do not expect dehydrated beef stroganoff on egg noodles with mashed sweet potato compot to be irresistible after that last 8-hour, 3,000 foot, 90 F. slog up to Sunrise camp.
You gotta sneak up on this, work up to it, and there are only two possible strategies. One is to carry that bed you have been sleeping in for a hundred years on the trail and the other is to start sleeping on your BA Self Deflatable on the floor for a few days to a few weeks before your first night on the trail.
The latter is more realistic.
Take a canteen and a bag of trail mix to work, and practice sipping and munching constantly through those mid morning meetings. Get up at first light for at least a week before your trip. Eat exactly the same breakfast you will eat on the trail. I dare ya. Go to bed with the sun. If you have to read a little, try out that headlamp.
You will have plenty of surprises on the trail. Most of them should be of the 'will you look at that sunset!" variety. Try to minimize the "Damn, why didn't I try this pack WITH the hernia belt?" sort.
