--TRAINING & YOUR FEET--
If you have decided to walk the pilgrimage, you need to hear this at least once — this is not a pleasant walk in the park. While not difficult for someone who has been hiking and walking in the mountains on a regular basis for a while, for those whose idea of a hike is getting from the parking lot to the office, you are in for a surprise.
I think that some people go into this thinking: "How hard can this be? Granted it's about 900 miles (1,400 km) if you walk to the Bangai as well as the main 88 temples, but it's only walking and that just can't be that hard." That might be true if it weren't for the fact that a lot of the temples are on the top of one or another mountain, and that to get from one temple to another you have to climb that mountain, descend back down to a much lower altitude, and then climb back up to the top of the next mountain. Sometimes 3-4 peaks a day. And that, my friends, is the part that catches so many people. It's the climbing and descending that kills the feet and causes blisters.
Several years ago i switched to socks that have a separate pocket for each toe. I happen to use Injinji brand socks, but there are probably other brands available. Once i made the switch to this type of sock, i have never had a blister since. I had one hot spot once, but put tape on it as soon as i felt it and the blister never developed. I removed the tape that night at the minshuku and it never came back. I can't recommend this option highly enough. If you do switch, you'll be poorer, they're expensive, but you'll thank me for the recommendation anyhow.
To increase your odds of not getting blisters, or to reduce the number and/or severity of the blisters that you do get, you need to prepare your feet before you even leave for Shikoku. You do that by practicing exactly what you will be doing while on the island — walking. Several months before you leave get in the habit of walking at least several times a week. You need to toughen up your feet so a half-hour on Saturday and another on Sunday just isn't going to suffice. The more walking you do, the better your chances of beating the blister problem.
As i said before, most of your walking on Shikoku will be up or down a hill. This is completely different from walking on flat ground. Going uphill your heels are pushed into the back of your boots. Going downhill your toes are crammed into the toes of your boots. Since very few people actually do this type of walking at home, even if you walk for months on flat ground before leaving, your toes and heels are still soft and tender. You may never get a blister on the balls of your feet or in the arch area, but your toes and heels are still very vulnerable.
When walking at home, find the hilliest area you can find and practice there. Only this will actually get the toes and heels the exposure to the inside of your boots that they will need to toughen up. If there are just no hills in your town, go to the local multi-level public parking lot and walk up and down the ramps every weekend.
Almost everyone is going to get blisters at sometime during the trip, even with pre-training. Accept that before you even leave and plan accordingly. Bring plenty of your favorite variety of Band-Aids, and lots, and lots of that white adhesive tape that doctors use to tape bandages to various parts of your body (i think it's just called Adhesive Tape).
When you first notice a blister forming, forget the bandaids and head straight for the tape. Put the tape directly on the skin, right over any sore or tender areas AS SOON AS YOU NOTICE IT. Do it before the blister fully develops and the tape will act like a second skin, preventing further friction from exacerbating the situation. If the blister is between two toes, tear the tape into narrow strips and wrap a strip around the toe. Again, the key is, the tape has to be flat with NO wrinkles.It takes time to do this if you are trying to wrap a toe, but take your time and you can do it.
If you train yourself to be aware all the time, you can catch potential blisters early, even just as the skin is starting to get hot. If you do, and immediately stop and tape them, there is a good chance a full blister will never form, and after just a few days the tenderness will go away and you can remove the tape. The key is not being stubborn and saying "Ah, i think a blister is developing, i better tape it tonight when i get to the minshuku." No, no, no, no, no, no, no! (If you're not sure what i mean, pull out your dictionary and look up the definition of immediately in your language.)
If you are like the rest of us, however, you will end up with full-fledged blisters on both feet and on both the heels and the toes. They will hurt terribly every morning when you put your boots on. They will hurt miserably as you set off each morning. They will make life a living hell on some days. But, always remember, they do get better.
When this happens, you have to perform surgery. Take a clean sewing needle and puncture the blister in two or three places so that the pus drains out. If you poke the skin and not the foot it won't hurt, you won't feel a thing. After you soak up all the pus with a tissue, tap it dry, and then put tape over it just as explained above. Try and put the tape on so that there are no wrinkles or ridges in the tape. Make the tape as close to a second layer of skin as possible. This prevents making the situation worse while you walk during the day.
Each night, or at least every other night, take the tape off and put a bandaid loosely over the blisters to keep them covered in your futon. The purpose of this is to protect their futon while still exposing the blister to the air as this will help it heal, so make sure the bandaid is solidly attached, but loose enough to allow air to reach the blister. Before leaving the next morning, remove the bandaid and put fresh tape on. (I see people from time to time who never take the tape off or put bandaids on at night. That may be fine, but i can only recommend what has worked for me for many, many decades.)
Continue this until the blisters are healed or until you finish the pilgrimage and return home ;-). No, joking aside, if you do as i suggest, a blister can be gone in a week or less.
It's Not The Feet, It's The Legs...
This brings up another problem area that most people don't think about. Your quadriceps and your hamstrings. The hamstrings are the muscles on the back of your legs between your butt and your knees. Your quadriceps are on the front. You use the hamstrings to climb and walk uphill. You use the quadriceps to go downhill.
We use our hamstrings often enough in everyday life that, while they will get tired going uphill if you don't train them, at least you will survive the trip without screaming. On the other hand, very few of us walk downhill all that often. Our quads are very weak compared to our hamstrings. You would be surprised how weak they are. And let me tell you right here and right now, if you don't find a hilly area where you can practice walking downhill and strengthen your quads before you leave, you will learn that they exist very early into your pilgrimage. As you go downhill you will be amazed at how sore your legs will get and how quickly the condition will set in. I have seen people with quadriceps so sore that they could barely continue walking. They would have to take a few steps downhill, take a break, take a few more steps downhill, and continue like this in misery for hours.
Before leaving, i implore you to go out and exercise. Find the hilly area or parking garage in your town and walk regularly. Do it until your legs are tired and then you know you are making progress. I promise, if you do this you will thank me after you get to Shikoku and see the hills you will be walking on.