Despite much existing information, a thru-hike of a major trail (2,000 miles+) does not have to be a life-disrupting event. It is possible and very enjoyable to thru-hike cheaply (less than $4,000 including ALL costs) and in a reasonable amount of time (3-4 months) that can easily coincide with a summer-vacation or a reasonably short leave of absence at work.
Note: Most hikers don't include initial gear costs or travel expenses when they give the costs of their thru-hikes. A $4000 hike including gear/travel costs would be considered a low-budget thru-hike.
Let's take a look at what's required financially to thru-hike. We'll use the Appalachian Trail for an example, since it's the most popular trail and makes the most sense for a first thru-hike for most people. We'll also assume a northbound hike (from Georgia to Maine), as that is also the most popular option. Firstly, you'll need to get to the trail and be able to get back from the trail (transportation), secondly you'll need gear, and thirdly, you'll need food. Finally, you'll also want entertainment, or town money. Then we'll take a look at what's required physically to thru-hike and make sure that you show up in shape, and can avoid costly injuries or a miserable start. To finish it all off, we'll talk about how thru-hiking in 3-4 months is possible for most anyone.
Getting to Springer is usually easy. You'll be flying to Atlanta. Since it's a large airport tickets will usually be cheap. Start looking at prices on orbitz 3-4 months in advance, and book a flight as soon as you can. Give yourself a 5-10 day range, and check the prices for every day--a one day difference can make a huge difference in price . I've bought three tickets to Atlanta, all were under $100 (two from Chicago, one from Baltimore).
You'll also need to get to the nearest airport. Public transit is the cheapest, if available ($20 or less, usually). Airport shuttles are also usually cheap ($40). Having a friend drive you can theoretically be cheap, but remember that your friend also has to drive back, and take into account how many miles and hours worth of gas, car expenses, and time your friend will be spending.
You'll also need to get from the Atlanta airport to the trail. You have three options here (in order of increasing expense). The first is to take the MARTA (public transit train) to the far north end of the line ($5) and then hitchhike (free) to Mt. Springer. Your second option is to put a post up on the Internet asking for a shuttle. There are lots of hikers near Atlanta that will shuttle you cheaply. This year my shuttle is costing me one bottle of scotch. The third option ($60) is to schedule a thru-hiker special with the Hiker Hostel (www.hikerhostel.com). For $60 they pick you up from the north end o the MARTA line, give you a bunk for the evening, feed you breakfast, and then drop you off at the trail in the morning. The Hiker Hostel, ran by Josh and Leigh (both thru-hikers) is without a doubt the cleanest and nicest hostel on the trail. I used the hiker hostel in 2006 and 2007, and would do so again on if they weren't already full on the date I booked my flight for.
You'll also need to get from the northern end of the trail (Mt. Katahdin) to home. When you have about a month left to your thru-hike book a flight. Look at all the surrounding airports. Remember that once you finish your thru-hike everything will find a way of working out. There will be a ton of section and thru-hikers at Baxter, and you'll find a way to get to where you need to be. By this point you'll be comfortable hitching and hiking around. Flying from the northeast was more expensive than flying to Atlanta for me.
For the sake of this article, we'll assume that you took an airport shuttle and used the hiker hostel to get to springer ($200), and that you managed to get home for $300.
Secondly, gear. Most people spend a lot of money on gear simply because they buy a whole setup of useless crap and have to replace everything along the way. What follows are my recommendations. You can find cheaper stuff if you really want to dirt bag it, and everyone has their own hiking style. YMMV (your mileage may vary).
a. Time frame
You'll save a lot of money if you can start between the 20th of April and the 10th of May--you can avoid the cost cold-weather gear, and you'll be behind lyme disease season once you hit the northeast. There's no need to start in March. We'll assume a start on the 1st of may. Let's go over some techniques to stay warm. The cheapest and lightest thing you can carry is knowledge. If we're starting May 1st, we should have few, if any, problems with cold nights.
Remember to camp at lower elevations, and near/underneath trees. Avoid camping in meadows. Also, avoid camping in Katabatic troughs. Cold air flows downhill at night--you can sometimes even feel it! If water is flowing downhill, that means that the cold air from the upper elevations will also be flowing down in that area. Don't camp near rivers or streams, or anywhere else that looks like it might be a katabatic trough. Shelters are noisy, cold, and hard; it's usually best to avoid them. Also, plan your day intelligently. If you want to have a few hours a day when you're not hiking, enjoy them in warm mid-afternoons basking in the sun and the views on a mountaintop. Don't spend them trying to stay warm once the evening chill has set in. Also, get up and get hiking right away in the morning--the coldest hours are right before and after dawn.
Proper nutrition is also important to staying warm. Fatty foods are very helpful. If it's a cold night I like to keep a snack ready in case I am cold in the middle of the night. It will really make a difference.
Clean yourself once you're done hiking for the day--some people say that a quick cleanup with some water and a bandanna really helps stay warm at night. Also, if you expect to have a cold night it's generally better not to wear a lot of clothing. Wearing something like a down vest or long johns/a base layer can help, but a raincoat or a sunshirt will not help. Ball up the clothing that you're not wearing and use it to eliminate dead-air space in your sleeping bag (I tuck these items between my heels and butt). You want your body to have to keep as little space as warm as possible
c. Sleeping Bag
Alright, let's talk about the gear itself now. Most important is your sleeping bag. Don't skimp here. Buy a first-rate product. You'll want a nice, 30-35 degree sleeping bag. Myself and most hikers prefer down. It's lighter, has a more comfortable-warm feeling, breathes better, is more comfortable in a wider range of temperatures, and compresses to a smaller package. The chief, and only real advantage of synthetic is that it lofts faster. That is to say, once you take a synthetic bag out of your backpack, it will provide warmth right away. If you have a down bag you'll have to hang on a branch for 15 minutes then turn it so the top (part that would be on top of you as you sleep) is facing towards the ground and shake the loft/down so that it will actually be on top of you, keeping you warm at night.
I actually prefer blankets/quilts over sleeping bags. Since trapped air insulates, the underside of a sleeping bag will become compressed by your weight and won't accomplish anything (other than costing money and weight). Also, when you have a warm night it's a lot more comfortable to hang an arm out of a blanket than to try to sleep comfortably in a sleeping bag.
Here are some great options (in order of increasing weight)
16 oz: Nunatak arc ghost, 32 deg. (www.nunatakusa.com), $300. I have the 20 degree arc alpinist from Nunatak and I love it. I used it for my 07 AT section hike and 07 PCT thru. I'll use it again for my 08 AT section and 08 CDT thru attempt. I would recommend this bag.
19 ounces Golite Ultra 20 (20 degrees) www.golite.com $225
If you're starting a bit earlier, are worried about being a cold sleeper, or want a quilt for a bit cheaper price, this is a great option.
19 ounces: Western Mountaineering summerlite (32 degrees) $290
. 25 oz: Western Mountaineering cloud 9 twin sized comforter, 35-40 degrees. If you're starting more like early/mid may this quilt may be a good option. I used one for most of my 06 AT thru and use it as the comforter for my bed at home now. $225
25 ounces: Fanatic Fringe 30 degree quilt (synthetic) http://www.fanaticfringe.com $160
Do it yourself quilts are also a great option if you enjoy making gear. I'd rather pay a professional myself.
d. Shelters, insect protection, and rain gear.
For the AT, I recommend a flat tarp. The AT is a warm, wet, wooded trail. We want a shelter that won't have condensation problems, and we aren't that afraid of high winds, since we won't be camping above treeline on the AT. 6x10 feet is the perfect size.
Etowah makes great flat tarps. You can get a silnylon (9 oz) tarp for $89.00. You can get a coated nylon (18 oz) one for $40. Spend the extra $50 if you can; 9 oz is a lot of weight to carry for thousands of miles. You'll need 12 light/cheap aluminum Y stakes ($10, 3.5 oz), and a package of some lightweight, thin guy-line cord such as kelty triptease ($10, .5 oz). If anyone wants more information on getting one of these set up, message me and I'll add the information into this article.
You have two options for raingear: 1. What I like to call 'paper raingear' Cheap, light raingear. The best option is the o2 rainwear hooded jacket ($25, 5 oz). I do not recommend rainpants; your legs will be generating plenty of warmth on their own. If you're a cold person I'd go with this option, but if you're a warm person waterproof raingear such as the o2 may be too warm for you to actually hike in. I
Your second option is to carry a wind jacket/shirt. Montbell makes some sick windjackets ($85, 2.5 oz) I lost mine on the PCT (Damn), but these are great items. They add a huge amount of warmth for almost no weight, and work well as raingear in warmer temperatures. EMS and REI also have their store-brand versions (5 oz, $40), but they are usually not available during the winter. You might also want to carry a dollar-store, 1 ounce emergency poncho in case a cold rain comes. You can put the cheap, light fragile poncho on underneath your windshirt.
A poncho-tarp is an ok option as a shelter/raingear combo (but makes more sense on a desert trail like the PCT than it does on the AT). Golite makes a good one ($50, 10 oz, 8.5 feet by 4.5 feet). I don't really feel like the 1-2 ounces of weight saved is worth it for the hassle of dealing with having a mediocre shelter on the AT. Frankly, after the beginning of May, I rarely wore anything while it rained. If you have a poncho-tarp you'll also want to carry a wind jacket.
We're not going to have insect problems for a while (I didn't have any until I got to New Jersey, and then they started very suddenly). You'll want to keep some no-seeum netting in reserve (either ready to be mailed out to you, or get ready to order it) for when the insects come out. Mosquito netting isn't fine enough to protect you from gnats. There are two great insect protection options. First is the equinox mantis(4.5 oz, $26). This product is a pyramid that hangs over your face/shoulders. You need to find a way to set it up (trekking pole/stick). The next is the Adventure 16 bugy bivy (or A-16 bug bivy). It is a little beefier, and has a wire that holds it in place above your face/shoulders (6 oz, $40). The wire looks like it'd be a hassle to carry. If I thru-hiked the AT again I'd probably take the mantis at Deleware Water Gap.
e. sleeping pads
Sleeping pads: You have a huge variety of choices here. You can carry anywhere from a 1/8" thick foam pad (2 oz), all the way up to 3.5 inch thick inflatable pad (Big Agnes, $35, 19 oz). If there's one item in your pack that is going to be on the heavy side the sleeping pad is a good one. Remember that your sleeping pad also insulates you, as well as keeps you comfortable. Good campsite selection (soft ground) helps eliminate the need for a sleeping pad. I use a 3/8" thick foam pad (ridgerest, $22) and trim it down so that it fits exactly the area that I use to sleep on. It weighs around 5-6 oz. I carried the 19 oz big agnes for most of my 06 AT thru, and it was definitely worth the weight before I was comfortable sleeping on the ground. You'll also want a ground cloth. www.gossamergear.com sells two good options. The spinncloth groundclothes (2 oz, $12, durable), or the polycryo groundclothes (1.5 oz, $6 for a two-pack, less durable). One of the spinncloth ones held up to 3500 miles of use and abuse for me, and has no visible damage (other than being really, really filthy)
Well, let's line up the items we have so far and see how much stuff we actually need to carry. So far, we have around 50 ounces of stuff. That's only three pounds and change. If you lined the stuff up, it'd take up almost no room. You don't need something big, nor do you need something with a hipbelt. We're barely carrying anything!
For part of my 06 AT thru and 07 PCT thru I used the jansport superbreak (http://www.jansport.com/js_product_d...id=10&pid=T501). It's just a basic, durable, school backpack. The only reason I got rid of it on the PCT was that people thought I was a hobo and I couldn't get a hitch for the life of me. I regretted getting rid of it every day. It is, without a doubt, the best pack I've used. I cut a bunch of useless stuff off of it (the loop to hang it up in the closet, the small foam padding and sleeve for it on the back, the pencil holder, the outside pocket, the jansport tags) 9 oz, $15-30, 23 L after modifications. Although it might look small, it was plenty for me on the PCT, which includes some long stretched without resupplies, and some long desert stretches where carrying lots of heavy/bulky water is necessary. I sewed some loops onto the outside to attach my sleeping pad to.
For my 07 AT section I used the REI flash. I attacked it with scissors and got it down to around 6.5 oz, $25, 17L. This pack is what I would use if I thru-hiked the AT again.
Another option is a pack from www.zpacks.com. I'll be using the zilch for my 08 AT section (as a test run on my CDT gear) and CDT thru attempt. The zilch weighs 3 oz with no options. I'd recommend getting it constructed from the more durable 1.9 ounce fabric, and getting the daisy chains down the shoulder straps (these are great for hanging watches from). You could also have a hipblet added if you feel that one is necessary. The way I had it constructed weighs more like 6-7 oz, but this is set up to get me through conditions I haven't encountered on either the AT or PCT.
g. Miscellaneous gear
Cooking? It takes a bit of time out of every day, and requires a bit more gear. It is possible and enjoyable to go cold. I didn't cook for my 06 AT thru, and I won't cook in 08.
You'll want a pot slightly larger than 1 liter. You can get an aluminum one from snowpeak for 11 oz and $23. You can get a titanium one for 7.5 oz and $45. You can also lighten your pot up by removing the handles and using aluminum foil instead of a lid. I think my titanium 1.4L pot weighs a bit under 5 oz. When I cook, I make myself enough at dinner so that I can also eat leftovers for my first meal of the next day.
As far as a stove goes, alcohol and canister stoves are both viable options on the AT. Alcohol stoves are lighter, but the fuel is heavier. As a package, alcohol will be cheaper and a little lighter. Storebought alcohol stoves end to be very poor in quality. I'd recommend making your own (it is less than a 5 minute project, costs around $1, and is pretty idiot-proof. Even I could do it). Here are some instructions: http://timberwolf.us/SuperCat/. The snowpeak giga: $40 is a good canister stove, 3.25 oz. Canister stoves may prove to be cheaper in the long-run if you are on the AT because half-empty canisters are frequently abandoned in shelters and hiker boxes. You'll want a plastic or titanium spoon as well. I carry 2 bic lighters, just in case one dies/gets lost.
Headlamp: There are many options options . Anything in the 2-4 ounce and $20-$40 range is reasonable. If you LOVE night hiking (I hate it), then you might want something more towards the heavy/expensive end. A headlamp isn't necessary, but you won't want to hike without one unless you have some miles under your belt. I didn't carry any light source for most of the PCT, but I got into a pretty set routine and knew where everything was.
Guidebook: You can print one off for free: http://www.aldha.org/comp_pdf.htm. But if you buy one the $20 cost goes to AT charities....
Maps: Expensive, heavy, most AT thru's don't buy or carry maps or any navigational tools other than a guidebook. Some people consider maps and compasses to be essential safety equipment in the backcountry. I personally don't consider anything on the AT to be the backcountry, and so I don't carry maps on the AT. I did carry maps on the PCT, and they were quite useful. I will of course, also carry 2-3 sets of maps for the CDT.
Water: Usually, you don't have to carry water on the AT. A 3L carrying capacity is a good amount (enough to camp away from water and/or to only make 1 trip to an off-trail spring). I'd just buy three 1L bottles of Gatorade. If you have the zilch backpack you can just keep bottles in the side pockets--they're reachable while walking so that you don't' have to stop to drink water. If you get a backpack without easily accessible side pockets you can get some elastic shock cord and a cord lock and attach them to your backpack straps. If you get a very small pack such as the flash, you'll need to attach the water bottles in this manner.
Water purification: Most hikers use Aqua Mira chemical drops. The aqua mira website makes no claim that their product effectively treats water. Some people use clorox unflavored bleach. The red cross website says that clorox actually works (cheapest effective option). Iodione also works. Polar pure, a small glass jar of iodine crystals, will have enough iodine for an entire hike. I just drink the water, but I would be careful downhill of or near shelters, campsites, or agricultural areas. If you're really worried I would get a UV pen (Steripen adventurer, 4 oz, $100). I can't see how poisoning your body 10 times a day for 4 months with chemicals could possibly be a good idea, and filters are heavy, slow, and just kind of silly to me. I've read studies showing no correlation between different treatment methods (including 'none') and getting waterborne illnesses. I've also read studies saying that 99.96% of all backcountry water sources are safe to drink from. I'd be more worried about town water than water from a mountain spring, but if you choose the just drink treatment method realize that you are exposing yourself to some risk. YMMV.
Hiking poles: If you have knee issues, get them. Otherwise, realize that it's just going to take a month for you to get into hiking shape, and poles will only be crutches. Keep your body weight and pack weight down, and you won't need them. They take up far more energy over a long day. If you do choose to get poles, wal-mart sells pairs for around $20 if you can stomach wal-mart. You can also go to a used sporting goods store and buy a pair of used ski poles.
Clothing: You need enough clothing to stay warm while hiking. You should plan on hiking during the cold parts of the day. If you want to have a few hours of a day while you don't hike, it is best to plan these hours during the hottest part of the day. You will avoid either sitting around idle during cold weather or hiking during the oppressive heat.
If you need clothing to stay warm in camp, this is a result of one of two things: 1. Poor day planning (hiking during warm weather and doing nothing during cold) or 2. Wanting to hang out around shelters (where drug/alcohol abuse is standard behavior). If #2 is your gig, then by all means carry some sort of warm clothing (western mountaineering flight down vest, $200, is a good option)
Otherwise, the following should suffice: running shorts/hiking kilt, sun t-shirt (www.railriders.com makes good ones), visor (a visor is very optional), warm fleece or wool hat. If weather gets really cold for a stretch, you can simply pick up a $10 fleece from a store near the trail until the weather improves. You'll likely have this stuff at home already. If you are cold while hiking a rainjacket or windjacket will provide a lot of warmth.
mp3 player: Look for a player that runs off of batteries. I found one that runs for 80 hours off of one AA, but I don't think the same model exists anymore. Shoot for at least 40 hours off of a AA.
Extras: Be reasonable. I carried a 2 pound mandolin on the PCT. I practiced a lot in the desert, waiting for the snowpack in the sierras to melt, and not much after that. You have some wiggle room if you want to carry some extra warm clothes, a book/journal, a stuffed animal, or whatever.
Socks/Shoes: Real hikers use running shoes, not boots, for nearly all conditions that can be called hiking. You're going to need to replace your shoes every 500 miles or so (4 pairs for the trail), and they'll cost $80/pair. Shoes are mostly personal preference, but look for the following features:
1. Make sure that your shoes are breathable. Gore-tex shoes are a joke; don't bother unless you love having blistered feet that stay wet for days.
2. Provide ample protection and cushioning. The AT can be rocky. Step on a corner or a rock or something when you try your shoes on, and see how it feels. Also, look for shoes that will protect you from stubbing your toe. You'll find out where the pressure points in your feet are--once you know, make sure that your shoes are thick in that area.
3. Stiff heel cup: I don't like my heel moving around in my shoes when I hike. I've also heard that it's bad for the knees.
4. Plenty of room in the toes and forefoot. Remember that this area will expand as you drive off it, especially hiking uphill.
5. Are a little big. Your feet will swell up a bit as you hike and with increases in temperature.
DO NOT pre-buy shoes. You'll learn a lot as you hike, and the size/shape of your feet will change a little bit.
Socks: Personal preference as well. Generally coolmax nylon socks are the best. I've had good luck on the AT with darn tough socks (although the desert ate them) and good luck on the PCT with ultimax socks. Get 1/4 length or mini-crew length socks. Ankle length socks collect dirt. Some people prefer the thin wool socks such as the smartwool adrenalines as well. I'd buy a pair of each and see what you like. Expect to spend $50-$150 on socks for an AT thru-hike, depending on what socks you choose and how fast you go through them. Keeping them clean can help make them last longer, as can keeping your toenails clipped.
The thick wool sock+nylon liner sock combo is a throwback to old-fashioned wool socks and hiking in boots. It isn't really necessary anymore.
Proper nutrition is essential. Poor nurtition will make you miserable. It will slow you down, and it will give you irrational, irresistible urges to spend lots of money at restaurants
When I thru-hiked the AT in 2006 I bought food along the way. I ate around 7,000 calories a day, hiked far fewer miles than I did on 5,000 calories a day on the PCT, and had a never-ending appetite 24/7.
I'm certainly not qualified to give nutritional advice, but pay attention to what you eat! If you read information from past thru-hikers you can end up with some terrible advice. Thru-hiking on pop tarts, peanut butter, bagels, and mac'n' cheese is very common. Most thru-hikers on such a diet struggle to do short mileages, are constantly hungry, and get worn down and depressed towards the end of their hikes. And they wonder why!
I recommend maildrops. That is to say, you will mail yourself packages of food to post offices (care of general delivery) and businesses that are near the trail. They are cheaper, more reliable, quicker, and they provide better nutrition when compared to buy as you go. The best way to mail yourself food is to use priority flat rate boxes. You can usually fit around 4 days of food in one of these, and you can send any reasonable amount of weight to anywhere in the US for $9. The post office will send you the boxes, tape, and labels for free if you are using priority mail. Let's assume that we have 40 total packages, an average of a package for every three days for 120 days. I try to send mail drops every 3-5 days, and the 5 day packages usually take up 2 boxes. So we spend $360 (rounded up to $400) on postage.
Here is a sample of my 2007 food. I ate the same thing every day on both my 850 mile AT training hike and my 2,700 mile PCT thru-hike. A typical day for me for the bulk of my PCT hike was 37-42 miles, and I weighed around 170 during that period. I spent around $11/day on food. Plan food according to mileage and your weight. $1000 should be plenty for an AT thru-hike.
These websites are both good bulk suppliers: www.harmonyhousefoods.com and www.bulkfoods.com. Costco is usually cheaper, because you won't be paying for shipping. If you buy a dehydrator and do it yourself you can probably pay off the cost of the dehydrator and a little more in one hike.
Wakeup snack: Energy bar (I won't use these again, even bought in bulk they're expensive!) 3 oz, 300 calories, $1.25 (I have a friend that bought expired luna bars in bulk from e-bay to save money on his thru-hike. I don't think I need to tell everyone how bad of an idea this was)/
Meal 1: Leftovers from dinner (925 calories, 8.5oz, $1.85),
Meal 2: 8 oz instant oatmeal, 2 oz powdered milk, 2 oz dried fruit in a ziplock, 2 oz nuts 3 oz of salty-crunchy snacks (pretzels, peanut butter filled pretzels, sweet and salty chex mix, etc.) (17oz. 1850 calories, $3.30)
(high-quality mixed grain oatmeal at $2/lb, powdered milk at $6/pound, dried fruit at $3/pound, nuts at $5/pound, salty crunchy snacks at $3/pound,)
Meal 3: 3 oz fruit, 3 oz nuts, 4 oz of salty crunchy foods (10 oz, 1200 calories, $2.25)
Dinner (925 calries, 8.5oz, $1.85)
2 oz olive oil ($6/lb=$.75)
8 oz quinoa ($2.5/pound)=(1.25)
2 oz dehydrated (not just dried) beans (8 different types, $6/lb, $.75)
2 oz TVP ($2/pound) =12 cents
1 oz dried veggies (tomatos, corn, peas, carrots, red peppers, and spinach, $4/lb, $0.25)
2 oz flavoring (duck sauce, sweet and sour sauce, etc $0.50/day)
2-3 cubes of bullion (for the salt $.10/day)
Total: 47 ounces, 5200 calories
When I pick up a resupply package I usually pick up a snack of fresh fruit and dairy to eat right then. Sometimes I go to a restaurant instead, but I usually just eat what's in my mail drops: I'll feel a lot better hiking out of town than if I pig out on junk food, and I save money.
IV. Town expenses
So, let's assume that we spent around $1,500 on socks, shoes, and gear, $500 for travel expenses, and $1400 on food and shipping. You should be able to get by with far less, but I always like assuming spending the maximum amounts for financial costs.
You then have $600 to blow in towns on a $4000 budget. That's around $0.30/mile. That means if you hike a 75 mile section, you have a little less than $25.00 to spend. On that budget you can afford a few fresh items from a grocery store and a restaurant meal at nearly every town, and an overnight hostel/shared hotel stay with a shower and laundry every 2nd or 3rd town. I typically spend far less (I'm actually allergic to the indoors--dusts and molds. I much prefer sleeping outside when I can, unless it's been between 30 and 40, windy, and rainy for a while I hate cold rain). Since I plan my trail meals carefully I don't have the hiker-huger that most hikers get. Obviously if you save up an extra $600 and have a $4600 budget you'll have more than twice as much money to blow in towns. Be realistic about your expenses: If you like going to bars once a week and sleeping in hotels after, that adds up to a lot of money, and you'll need to save up a lot more money.
Why train before a thru-hike? Don't you have the chance to get in shape along the way? I've done it both ways. I started my 06 AT thru right after a college wrestling season--in very good shape for most anything. It was wonderful. In 07, I started out of shape and 30 lbs overweight. It was miserable until I got in shape. Hiking is not much fun if it's a painful struggle, but it's great if the hiking comes easy and naturally, as it should. Humans are built to be long-distance hiking machines.
Cross training is really the key. No one activity (other than hiking) can get you prepared for hiking. Run, jump rope, and bicycle. Do a stair-stepper, run up hills, take a hike one a week, etc. Lift lower body weights (proper technique is key or else you're wasting your time at best). People that only run tend to be injury-prone as hikers. Be careful not to over-train and start your hike injured.
Find out your weight and your bodyfat percentage, and set a goal for what weight/bodyfat % you want to be at when you begin. Before you leave for your hike, know what weight you shouldn't be dropping below, and try to keep an eye out for excessive weight loss. Excessive weight loss is fun to correct (I have to go to the pizza buffet again, and then get a gallon of ice cream after? DAMN! I lost way to much weight when I had lyme disease in 06)
VI. Finishing up in 4 months
To finish the AT in 4 months, you would have to average 18 miles a day, or 126 miles a week. 126 miles a week might sound like a lot, and it will be a lot the first week or so, but it's really not difficult! The mileages sound intimidating, but they're only tough for normal people. You're not a normal person--you're a thru-hiker now. Your life for the next four months is going to be hiking*, and you're going to be damn good at it.
If you have a four month schedule you'll still have plenty of time to mess around and take side trips. You'll have plenty of time to explore the little towns you come across, and to check out all those side trails to waterfalls, and take days off when you feel like it. I tend to dislike total rest days (zero days) as they break my rhythm and make me wonder why I'd want to go hiking instead of hanging out in town.
There are a multitude of ways to split the mileage up and get it done, but if you are on the trail to hike, then it isn't ever really a matter of getting it done. Just spend your time doing what you enjoy, and you'll be at Katadhin before you even notice. If you dread hiking and just like hiking from town to town along with big groups, then a four-month time frame isn't possible (nor is a thru-hike a good idea. Go join a commune or something)
Efficient town stops are key to both finishing up in time and on budget. I try to look 2-3 towns ahead and plan so that I will be able to make all of my maildrops. I don't want to come into town Saturday afternoon and have to wait in town until Monday to get my maildrop! It's not that tough to adjust your schedule by a day or so when you know 10 days in advance where you need to be.
I try to come into town in the late-morning (9-10 AM, or so), pick up a few fresh things from the grocery store or treat myself to a restaurant meal, pack up my maildrop, take a shower if I can, call my family, and then hit the trail. An early entry time into town lets me get everything I need done without having to spend the night. Eating first allows the food to settle in my stomach before I go hiking. If I'm in a hurry, I can usually get everything done in 1-2 hours, but I often like to spend a bit more time in town lounging.
Is there a mental aspect to successfully completing a long distance hike? Of course. You're not going to finish unless you're having fun--that is the only secret. And if you do finish without havening had fun, you didn't really succeed at anything! A thru-hike is not a resume builder, it accomplishes nothing concrete, although I have found myself to be a much better person in many ways after every hike I've done.