If you want to shape up, walking, jogging and running can all provide a step in the right direction. Experts say these activities are not only excellent aerobic exercise but they can be the easiest and natural route to fitness.

Running or walking outside, however, may not always be a natural choice. If you're not enthusiastic about running or walking in winter weather or summer humidity, or if you live somewhere where there are few sidewalks or where there's a lot of traffic, you may want to invest in a state-of-the-art treadmill.

A treadmill can make it easier to achieve fitness goals and the latest treadmills offer many fun, motivating features that let you track progress.

Not all treadmills are created equal and a badly designed treadmill may ultimately do more harm than good.

It's important not to settle because a bad short-term choice could have serious long-lasting health consequences.

Since exercise should be a life-long habit, you want a treadmill that will protect potentially fragile joints.

When you exercise on concrete sidewalks, for example, the impact shock is "bounced" back to your knees and hips, because concrete is a rigid material.

This can also be true of rigid, heavy steel treadmills.

When choosing a treadmill, look for one with active shock management features like those featured on PaceMaster treadmills. The tri-flex system uses three components to protect joints:

? A custom-designed deck flexes with every foot strike.

? Elastomer cushions further absorb the impact shock.

? Aluminum frames provide strength but also flex more than steel.

As a result, your joints can stay healthier for longer.