The routes vary in length from 107km on the Camino Ingles to over 1000km on the Via de la Plata. If you combine a route in France and a route in Spain to reach Santiago, you could be walking 1800km or more.
Most of the trails are cross country: on gravel, dirt, rocks, shale, mud, stones, grassy paths.This is not a walk in the park or on a sidewalk!
If you walk the 800km camino Frances, you will cross three mountain ranges, traverse valleys and riverine hills. The camino Primitivo is shorter (285km) but is one of the most arduous of the camino routes.
You really will need to do some training before setting off on any long distance trail especially one that might take over a month to walk.
People often ask about training: when to start, how much to do in a week, how far to walk. Any training should be specific to the event - i.e: cycling for a cycle race, swimming for a gala, running for a marathon. If you are going to walk the camino then you need to do WALKING training.
How much, how far, how often?
As a regular walker I walk every day with three longish walks of up to 13km each week and a few shorter walks of between 2 and 5kms.Twice a week I walk on the beach and on Saturday and Sunday, I either walk in the suburbs or go on a hike.
I don’t do much extra training until a couple of months before doing a long distance walk. In those months I do longer walks of about 20km each weekend and do back-to-back long walks and hikes over hilly terrain.
I test all my equipment, shoes, socks, shorts, shirts, backpack etc.
Some people think that just being active is
enough or that being a cyclist, swimmer or runner qualifies them physically to do an 800km cross-country trek with ease. Walking uses different muscles – you might get shin splints from walking, and sore quads from running. You will be on your feet for much longer than you are used to so you need to build up stamina and endurance. “Time on your feet” will be much more important than speed and even the fittest runner will be tested doing a long, day after day walk.
Here is an example:
Bruce Fordyce was one of 
ultra-distance marathon runners in the 1980’s. He won the Comrades marathon – a grueling 90km race between the two cities of Durban and Pietermaritzburg - eight times in succession, and nine times overall averaging an incredible 5:34. He also won the London to Brighton Marathon for the third time in a row in 1983, setting a world record for 50 miles (80.45 kilometres), and in the same year he set a United States all-comers record in the 50 mile, clocking a ridiculous 4:50:51 in Chicago.
In 1996 Bruce was invited to take part in the 2-day Superb Charity Walk along the 90km Comrades Marathon route to
“I thought that walking Comrades over two days would be a doddle. I’ve always said that walking is for people who can’t run and that runners do not walk, even up the steepest of hills. After 6 hours of walking I hadn’t even reached the half-way mark. Usually by now I have finished the race, had a shower, given an interview and had my first beer. 
Here I was, facing Inchanga hill and another 7km to go. At the end of the first day I was aching in places where I didn’t even know I had muscles. I wore my trusty running shoes but had blisters and hot spots that reduced me to a hobble. If I hadn’t made a pledge to walk this event for charity I would not have started the 2nd day.
When I finally reached the end of the 2nd day I couldn’t get over the numbers of middle-aged women all strolling around, smiling, chatting and greeting their loved ones. I could hardly walk let alone stroll and had to be helped into a car. I was in no state to chat and was certainly not smiling. I’ve come to the conclusion that running is for people who can’t walk!”
So you are planning on walking a camino.
If you are not a regular walker, a good walking training program could be the difference between a comfortable, pain-free walk or a hobbling, painful trek.
When to start? If you are a healthy, fairly active person, I think about 4 months before your walk should do the trick. If you are grossly overweight, inactive, or ill - see your doctor before embarking on any training program. You might want to lose weight, go on a course of vitamins or clear up an illness before you start training.
Wiki has these points for starting out:
Motivate yourself. You will have a much harder time walking if you don't want to be out there. You have to want to do this long distance walk.
Start out easy. Depending on the shape you're in, you might be starting with a walk in your local park, or a walk around your house. Start out with a distance you know you can easily walk.
Start building distance. Your walks should eventually start to increase in distance and time. Don't increase these too quickly though. You don't want to walk for fifteen minutes on one day, and then walk two hours the next day. (Buy a pedometer to measure your walks).
When you have reached your target distance repeat it once a week. This will only make your long distance walk seem easier.
Keep walking, and when it is time for your walk, you will be ready.
Other tips:
· listen to your body, let your breathing and heart rate recover before hard efforts;
· be disciplined, make sure you put the effort in;
· try to incorporate hills into your walks and use them for hard walks, not for recovery;
· do not expect immediate results, persevere and improvements will follow.
· Remember to take days off to rest to let your body recover.
· Find a good pair of walking shoes/boots to use on your walks - break them in.
· Keep yourself well nourished and hydrated. Eat high carb foods and drink plenty of water.
· Feel free to use a treadmill, but remember to get outside. Your long distance walk is mostly outdoors.
· Work out to build the other muscles in your body especially shoulders and back.
· Walk with a buddy. Talking to someone during your walk will make it more enjoyable.
· Listening to music on a personal music player or singing marching songs often encourages you to walk further, as you concentrate on the music instead of the distance.
Here are some old favourite walking songs to keep in time whilst you are walking.
Remember to include stretching in your program. Walkers are subject to the same kinds of pulls strains and other problems that runners get. Warming up is usually not a problem as you can get a perfectly fine warm-up by just beginning your walk at a slower pace. It's important to remember that muscles respond best to stretching when they are warm: think how pliable salt water taffy is when it's warm and how brittle and breakable it is when it's cold. Your muscles are like that too. So don't go out on a cold day and begin to stretch. Your stretches are best done either after the workout, or after a thorough warm-up (or both). Remember to take days off to rest to let your body recover.
Here is a16 week training schedule from a trek - training guide: (Click to downlaod the full guide)
Week 1 - 6:
2 x 30mins walks.
1 x 2 hour walk. Full stretch after each walk.
Week 7 & 8:
Sat or Sun: 4 hour walk and stretch
Mon: Rest Day
Tues: 1 hour walk, stretch, exercise circuit x 3, stretch.
Weds: Rest Day
Thurs: 1 hour walk, stretch, exercise circuit x 3, stretch.
Fri: Rest Day
Week 9:
Sat AND Sun: 4 hour walk and stretch. (Back-to-back walks).
Mon: Rest Day
Tues: 1 hour walk, stretch, exercise circuit x 3, stretch.
Weds: Rest Day
Thurs: 1 hour walk, stretch, exercise circuit x 3, stretch.
Fri: Rest Day
Week 10 & 11:
Sat or Sun: 6 hour walk and stretch with backpack
Mon: Rest Day
Tues: 1 hour walk, stretch, exercise circuit x 4, stretch.
Weds: Rest Day
Thurs: 1 hour walk, stretch, exercise circuit x 4, stretch.
Fri: Rest Day
Week 12:
Sat AND Sun: 6 hour walk and stretch. (Back to back with backpack).
Mon: Rest Day
Tues: 1 hour walk, stretch, exercise circuit x 4, stretch.
Weds: Rest Day
Thurs: 1 hour walk, stretch, exercise circuit x 4, stretch.
Fri: Rest Day
Week 13 & 14:
Sat or Sun: 8 hour walk and stretch
Mon: Rest Day
Tues: 1 hour walk, stretch, exercise circuit x 5, stretch.
Weds: Rest Day
Thurs: 1 hour walk, stretch, exercise circuit x 5, stretch.
Fri: Rest Day
Week 15:
Sat AND Sun: 8 hour walk and stretch. (With backpack).
Mon: Rest Day
Tues: 1 hour walk, stretch, exercise circuit x 5, stretch.
Weds: Rest Day
Thurs: 1 hour walk, stretch, exercise circuit x 5, stretch.
Fri: Rest Day
Week 16:
Sat or Sun: 4 hour walk and stretch
Mon: Rest Day
Tues: 1 hour walk, stretch, exercise circuit x 3, stretch
Weds: Rest Day
Thurs: 1 hour walk, stretch, exercise circuit x 3, stretch
Fri: Rest Day
Here you will find more on preparing for your pilgrimage.
Buen Camino!!
