A lot of people enjoy running. I confess that I am not one of them. But I still find the construction of my brother in law's running shoes interesting. And I have tried on running shoes and found them immensely comfortable. And that is, of course, the point. When running, one expects to be wearing shoes for a long period of time. This means that running shoes have to be durable and comfortable at the same time.

Early running shoes

Early running shoes were hardly ideal for serious athletes. While there were shoes made with soft rubber soles in the early 20th Century, they almost always wore out too soon to be of much use. Indeed, running shoes (sneakers) grew out of the plimsolls which were made in the 19th Century for those who worked on ships. When people began to see their use in running, shoes began evolving.

At first, though, even with the rubber soles available, many runners preferred leather soles for their sneakers. The soft rubber simply fell apart too easily for professionals. Running shoes for sprinters had kangaroo leather for the soles, and they were spiked slightly for traction. Marathon runners chose heavier shoes, with thick and stiff leather soles. But, even with advances introduced at the 1936 Olympics, it wasn't until nearly 30 years later that we saw the first truly modern running shoes.

Modern running shoes are born

In 1962, an orthopedic shoe company introduced a novel design adjustment to running shoes. A rubber wedge was placed in the back of the shoe, between the upper and the sole. This allowed for increased comfort, since it change the position of the foot while running. Then, not too many years later, a University of Oregon coach, Bill Bowerman, got serious about designing an ideal running shoe for his track athletes. Some of the changes he introduced included:

• Nylon uppers (as opposed to leather or canvas).
• Sole made from urethane (instead of straight rubber or leather).
• Waffle sole, resulting in better traction without the need for spikes.

Bowerman started the company Nike, and the innovations of that company led to the creation of the midsole. The midsole in running shoes is an extra layer of cushion that lies between the sole and the upper. It adds to the stability and comfort of the runner -- and eases pressure. (After all, when a runner strikes the ground with his or her foot, the pressure is equal to three time his or her weight.) Today, midsoles are made from silicone gel or from some other type of cushioning material.

Today, as well, there are running shoes that come with pumps. These pumps allow you to fill bladders in the shoe with air, creating a tighter fit. This can increase comfort and stability. And, manufacturers of running shoes are always coming up with ways to increase your natural ability to run, while at the same time providing comfort. Mesh, lacing schemes, air cushioning and different sole patterns for traction are just a few of the ways that technology is constantly improving the design of running shoes.

One of the best pairs of shoes that I have -- and wear regularly -- is my pair of cross trainers. I do not run much, nor do I play organized sports. But, I do like to shoot around a little or play baseball or soccer with my son and husband. And I enjoy tennis. But I really can't justify spending the money for a particular pair of shoes for each sport. So instead, I wear cross trainers.

A pair of cross trainers can serve as a sort of all purpose athletic shoe. They are reasonably comfortable, and they are capable of providing support for the amount of activity that I do in them. Here are the parts of cross trainers, and what makes them ideal for all different sports.

Cross Trainer Outsoles

The key to the versatility of cross trainers is the part of the shoe known as the outsoles. (the bottom of the shoes) On most shoes, the outsoles are very wide, as to offer good stability, and is ideal for side to side movement. Most outsoles are made from some sort of carbon rubber (which is quite durable) for the sturdier varieties. These will hold up longer, and will work well for outdoor sports activities.

If you are looking for flexibility, however, look for cross trainers that have a mixture of carbon rubber and blown rubber. Blown rubber is lighter and softer. These shoes are ideal for frequent use and offer a higher level of comfort while playing sports. It is important to check to make sure that your outsoles are approved for indoor activities, since many gyms restrict the types of shoes you wear; they do not want your shoes marking up the gym's floor.

Midsoles

The midsole is that area between where your foot rests and the bottom of the shoe. One of the things that contributes to the comfort of cross trainers is the fact that there is cushioning at the heel and at the front of the shoe. You want midsoles that are fairly durable, yet somewhat flexible. Look for polyurethane, since it is more dense and will add stability to your shoe. EVA may provide for a lighter shoe, but it is less durable. In many cases, cross trainers will combine EA and polyurethane to produce a shoe that is lighter, but still durable and stable.

Uppers

One thing that I need in my athletic shoes is ankle support. Cross trainers usually have mid-tops that provide a degree of ankle support without the restrictiveness of high top shoes. Most uppers are made from leather, along with synthetic mesh. The leather offers stability, while the mesh provides breathability, so that there isn't a problem with your feet becoming uncomfortable from the moisture.

Another thing that many cross trainers come with is a lacing system that is secure. This provides additional stability and ankle support, especially for side to side movements.