Treadmills don't only provide the cardio workout benefits of walking or running - treadmills also have the same positive and negative issues for the human body.

Walking and running, whether on treadmills or pavements, are weight bearing activities. Weight bearing activities such as running on treadmills helps strengthen your bones by causing them to produce new cells. When your feet impact harder surfaces, the bone-building happens more quickly. The less give in the ground surface, the stronger the impact - and so, potentially, the stronger your bones. Treadmills with firm running beds provide more impact than softer beds.

Hard surfaces, whether sidewalks or firm treadmills, are better used for walking than jogging or running paces, because while impact helps build strong bones, too much impact can hurt your joints. For less impact, use treadmills that have belts with some give. If you have problem joints, you can get similar cardio workout benefits from elliptical trainers.

To work out on treadmills, no matter how firm or how fast, make sure you warm up for five minutes first. Start slow for one minute, then work for half a minute on your heels and half a minute on the balls of your feet; repeat. Speed up slightly and take longer strides for one minute. Increase the incline and walk for one minute, then return to your main workout level and increase the pace for a minute. Now it's time to do your stretching. And don't forget to wear quality shoes, which is important for cushioning impact as well as proper alignment.

When we talk about life in general, "being on a treadmill" implies monotony. But while in the outside world "going nowhere" is a negative, for a cardio workout not having to go anywhere is treadmills' advantage You can run without dealing with weather or traffic - and, if you're one of the many who have treadmills in their homes, without even getting dressed.

For those who find working out on treadmills boring, there are plenty of things that will help the time pass more quickly. If you want distraction from your workout to make it go more quickly, you can read - but only if you're walking at a reasonably slow pace.

Watching TV or movies is a good choice - that's why you see many health club treadmills facing a TV screen. If you want the illusion of being outdoors, try one of the many available videotapes that are made for simulating running or walking indoors.

Listening to music is another good distraction for treadmills. If you need help keeping your pace, you can buy CDs or audiocassettes that keep specific beats. Books on tape are another good choice for making the time go by when using treadmills. If you set aside an audio book, or movie, to only use when it's treadmill time, it will give you an added incentive to jump back on.

If you are a home-treadmill user, how you situate your treadmill can also make your treadmill time more pleasant. If you don't want to face a video screen, face a window and watch the world go by. If that's not possible, surround yourself with plants, art, or family photos to create a pleasant setting.