When it comes to footwear, comfort and health are closely related. They depend on how the shoe is constructed, and what it's made of (see What Makes a Good Shoe), and, equally important, proper fit.
Many foot problems are caused by shoes that don't fit correctly. Shoes that are too short compress the toes and foot bones. Ones that are too narrow up front squeeze the toes together. Those that lack arch support and heel cushioning can cause heel spurs and an inflammation called plantar fasciitis.
The common consequences of poorly fitting shoes are familiar to many people: bunions, calluses, corns, and ingrown toenails to name a few. You may not be aware that they can also cause very painful pinched nerves, stress fractures, aggravated arthritic conditions, and plain old foot fatigue.
Incidentally, did you know that poorly fitting or designed shoes can affect your neck and shoulders? Your feet are the foundation for the rest of your body. If they can't function properly, your knees, hips, lower back, and spine try to compensate for the misalignment. That can lead to problems in all of these areas, and the cause can be as simple as your shoes.
The Fit
Shoes are built on models called lasts, which represent common foot shapes and sizes. The size 7 of one manufacturer isn't necessarily the same as another manufacturer's size 7. That's one reason why shoes labeled as the same size and width don't necessarily fit the same way. Regardless of style, here are a few general considerations.
The most common mis-fit is shoes that are too short. When you walk, your foot extends inside the shoe. That's why shoes that seem to fit just fine when you're standing in them or test-walking them in a store, turn out to be toe-crunchers when you get out into real life. From standing still to walking, you need up to a half-inch extra room in front of your longest toe.
You should also have room to wiggle your toes. While you don't want the toe area to be so roomy that you're sliding around inside it, you don't want the fit to be so tight that your toes get squeezed together. The widest part of the shoe should match the widest part of your foot. That seems like a no-brainer, but remember that lasts are "typical" foot shapes. While the widest span of most people's feet is across the base of the toes, yours may be different.
The part of the shoe that cups your heel is called the counter. This should fit snugly to keep your foot in the proper position within the shoe. When the counter fits well, you should feel even contact all around your heel. Extra pressure in one or two spots can lead to blisters and calluses.
Finally, the bed of the shoe should cradle your foot, providing support at all the correct points. The best shoes are anatomically designed to allow your foot to function the way it's supposed to when both resting and moving. The "high" parts and the "low" parts of the bed should match those of your foot.
By the way, the best time to try on new shoes is late in the day. You're likely to have been moving around a lot by then, and your feet will be slightly swollen. You'll get a better indication of the fit then. Also, practically everyone has one foot bigger than the other, so you need to make sure you try on both shoes. One last consideration: as we age, our feet get longer (not wider, as some people think), so your size will change over the years.
Beyond the Fit
Comfort and health depend on more than just the fit. The environment inside your shoe has a lot to do with how you feel, too, and depends on how the shoe is made and the materials used inside.
Stick your hand into shoes you're considering and feel around. You shouldn't feel anything that will stick into your feet, such as thick seams, wrinkles, or ridges. The lining should be smooth and soft. A padded tongue will allow you to tighten your laces without putting unnecessary pressure on your instep. Padding along the top edge of the shoe adds to the comfort in your ankle area, too.
Your feet can sweat as much as a half-pint each per day, so how a shoe handles moisture is very important. There are two considerations here, the material used inside the shoe, and the way the shoe is constructed. Inside the shoe, leather is best because it wicks moisture away from your feet and allows it to evaporate outside the shoe. Leather "breathes", too, which helps to regulate the inside temperature. This makes the shoes more comfortable while you're wearing them, and minimizes the breeding environment for bacteria. Bacteria growth is the source of "sneaker smell", and it happens mainly because shoes that use lots of synthetic material in their inner construction (like athletic shoes) don't allow moisture to escape.
Additionally, well-designed shoes often have removable footbeds. You can clean or replace them when necessary. By the way, removable footbeds also allow you to alter the fit if necessary.
