It's not always necessary to know how far you ran during a workout. Sometimes the time spent on your feet is more important than the distance traveled. Mostly, however, you will want to know your mileage so you can enter it in your logbook. You also need the information to monitor your shoe wear. There are several ways to keep track.

If you often run a particular course, perhaps in your neighborhood or on a trail nearby, you can measure it once and always know how far you went. That keeps you from having to do anything special to measure each time.

There are also fancy pedometers that keep up with your mileage. Some can be calibrated for your gait and will measure distance traveled whether you are walking, running, or doing something in between. Some will also time your run and, based on information about your age and weight, will calculate the calories burned during your run.

Then there are the GPS devices, which are just the ticket for the triathlete who likes toys. Each year, although the devices seem to grow smaller, they continue to add features. The unit you wear on your wrist when you run works like the device in your car that gives you directions.

The device, which looks like an oversized watch, is in touch with a global positioning system — a series of satellites orbiting the earth — and it knows where you are and tracks you as you go. As with other high-tech devices, the available features are impressive. Some of the GPS devices keep track of your entire run and can even help you find your way back to the start if you become disoriented or get lost. Some of the more sophisticated models are made for biking and running, allowing you to toggle between modes.

Whatever you use, make it a habit to log your mileage and time. You keep the log, after all, in part to compare similar workouts from week to week. How else will you know if you have progressed?