As the saying goes, if your feet aren’t happy, your trip won’t be happy.
As you begin your training, you will need well-fitting, comfortable shoes. Early on, you can probably get away with your tennis shoes but as you add distance and/or weight to your pack, that footwear is no longer built tough enough to protect your joints and back from the impact of hiking. You may want to consider a water-resistant shoe if you are hiking on backcountry or primitive trails (as opposed to “urban hiking” on sidewalks). There can be streams, mud, even horse manure (It’s happened to me- thank goodness for Gore-Tex) that you don’t want seeping into your socks. If you’re not concerned about precipitation, think about sweat. If you’re the sweaty-foot type, bring a change of socks for your midway point. Wet feet are more prone to blistering and, of course, trench foot.
The terrain you hike will dictate the type of footwear you should be wearing. Big rocks on trail might require you to wear a more heavy-duty boot, with a reinforced toe box. Gravel may mean you want a stickier sole on your shoe. Lots of brush could point you toward a higher boot so as to avoid morning moisture, stickers and scrapes. You don’t need a shoe for every possible obstacle you might encounter, just a pair or two depending on what you aspire to. Also, the more weight you carry, the more important it becomes to have good ankle support. Your local reputable gear shop can assist you in figuring out which type of shoe will be the most well-rounded for what you’re hoping to accomplish in training.
Please don't purchase new boots and jump into a 50 mile hike the next day. Start by wearing them around the house to make sure they fit and feel comfortable. Work them into your shoe rotation with low mileage hikes, building over time to that 50 miler. The stiffer the sole, the more time you need to spend breaking in your footwear. If you're headed out to hike the Inca Trail, buy your boots early in your training so they fit like a glove by the time you arrive in Peru. Here is where we have to break "new school supply" thinking. Remember when you were a kid and every August you got to pick out those shiny new crayons, Lisa Frank folders and pencils? You compared them against your friends new stuff on the first day. Yeah, don't do that with hiking gear. New is not better on trail. In fact, more broken in is usually better. No one will be impressed if you arrive at a trail head with clean, white shoes as they will see that it probably means they'll be stopping for your blistered and sore feet often.That said, have a well worn pair of boots re-waterproofed, check the treads and sole structure and perhaps get some new laces before you take them out again (or pack an extra pair-they can have many backcountry uses). If we're talking the ancient pair, it might at least be worth your time to get a new pair of insoles to revive their support. Take care of your feet and they will carry you many miles.
When we're talking footwear, just remember you don't want any surprises, no matter how old/new your boots are. Try them out close to home before trekking them abroad.
