The great thing about running is that you only need one piece of equipment. The bad thing is that the equipment, your running shoes, is so important that it gets buried under millions of dollars of hype, advertising and confusing techno-babble.

Because running, while it's a simple sport that almost everyone can do, forces your feet and legs through a fairly complex series of movements - with all the high-tech running shoes available today and all the special features that each shoe claims to have, picking the right pair can be a daunting task.

 Running is a complex bio-mechanical process in which you strike the ground first on the outside of your heel. Next, your foot rolls downward and inward slightly as it meets the ground. And lastly, the heel lifts from the ground, and you push off from the ball of the foot to move forward.

The rotation of the foot downward and inward when your land on the ground is called pronation, and it's a completely natural, normal process. Everyone should pronate to some degree. Pronation is a good thing in that it helps the foot absorb the chock of impact.

Some runners overpronate, their feet roll too far inward. This is a common problem that can lead to injuries, particluary of the lower leg and knee. Other runners supinate (or underpronate); their feet roll inward only a little after contact. These runners are said to have feet that don't absorb shock very well. This,too, can lead to injury overt time.

 Most runners can determine whether they are supinators, overpronators, or normal pronators by checking their arch heights. The easiest way to figure out your arch height is with the "wet test."

Wet the bottom of your bare foot, then make a footprint on a flat, dry surface - a piece of white pater laid on a hardwood floor works well to shoe the shape or your foot. If your footprint is very full and wide and shows no arch, your have a low arch and a flat foot. If the print shows your entire foot with a moderate curve where the arch rises off the ground, you have a normal arch. And if the footprint is very slight and curved, showing mostly the ball and heel of your foot but very little of the middle of your foot, you have a high arch.

 Your foot type and degree of pronation determine the characteristics that you'll need in a running shoe. One of the most important characteristics to look for is shape. You can see the shape most clearly by looking at the bottom of the shoe.

In general, running shoes come in three shapes - straight, semi-curved, and curved - which correspond to the three types of footprints revealed by the wet test.

Overpronators (Flat Feet) - Straight Shape Shoe

You will need a shoe that will prevent your foot from rolling in too far, that is, a motion-control shoe. These types of shoes give maximum support to your foot. Also look for a firm rather that a soft mid-sole, a dual density mid-sole with the denser material along the inner edge of the shoe to prevent excessive pronation, and a firm heel counter to minimize rear-foot motion.

Supinators (High-Arched Feet)  - Curved Shaped Shoe

Your feet do not absorb shock very well, so you need a cushioned shoe. Also, you want a shoe that allows your feet to roll inward, since this helps absorb shock. Cushioned shoes tend to be less supportive and work with the foot rather than try to control it. Shoes with a soft, cushioned mid-sole and a curved or semi-curved shape permits foot motion as you run.

Normal Pronators (Normal Arches) - Semicurved Shape Shoe

If you have normal arches and pronate normally, you're lucky. You don't need to search out a shoe with special features. You might want to begin by considering shoes that lie somewhere between the motion-control and cushioned types. Manufacturers often refer to such shoes as stability shoes. These shoes, which often have a slightly curved shape, don't control foot motion as much as motion-control shoes.

As running shoes have gotten more complicated, so has the terminology used to describe them.

Upper: The part of the shoe that wraps around and over the top of the foot. It's most of what you see when you look at a running shoe.

Heel Counter: A firm cup that is encased in the upper and surrounds the heel. It controls rear-foot motion.

Outsole: The under-surface of the shoe, usually mad from carbon rubber.

Midsole: The most important part of a shoe, it is the cushioning layer between the upper and the outsole. It is usually made of ethylene vinyl acetate (EVA), polyurethane ( a synthetic rubber that's heavier and longer-lasting than EVA), or a combination of the two. Dual density midsoles have a firmer material on the inside of the shoe. This helps limit pronation. Many shoe companies also put patented technologies in their midsoles, such as gel and high-tech plastics.

 A running shoes that fits will be snug but not tight. Buying running shoes that are too small is a common problem. Your running shoes may need to be half to a full size larger that your street shoes.

• Check for adequate room at the top by pressing your thumb into the shoes just above your longest toe. The edge of your thumb should fit between the end of your toe and top of the shoe
• Your heel should fit snugly into the rear of the shoe and should not slide up and down as your walk or run.
• The upper (the part of the shoe that wraps around and over the  top of the foot) should fit snugle and hold your foot securely, but it should not irritate or press too tightly on any area of your foot.
• Take the shoes for a test run. Most speciality stores allow - even encourage- you to run down the street or around the block so that you can feel the shoes in action. The knowedgeable people who work in these stores will be able to tell you if you're a special case who needs extra attention when it comes to shoe selection.
• Once you've found a shoe that works for you, stick with it!