There are a gazillion sports watches on the market today. (Unfortunately for women, it seems like a lot of them are designed for men, and so are pretty large.) You’ll probably want to purchase a watch with a 50-lap memory. This means you can record up to 50 time intervals (you’ll need 27 if you want to record the pace for every mile, and the last .2 mile, during your race). Most watches will also come with a regular timer, interval timer (you can program it to beep when you need to speed up and slow down for an interval workout) and alarm clock. But you don’t have to use those features if you don’t want to.

Lately, watches with GPS sensors have become more popular. These combine regular running-watch features with Global Position Satellite technology that measures how far you’re running. This can be helpful if you need to do a 15-miler, for example, but don’t have a measured course. However, sometimes the satellite feeds aren’t strong, and your watch can temporarily stop recording mileage. And when you’re training for a marathon, time is generally more important than actual mileage. If you were planning to run 15 miles at a 10-minute pace but didn’t have a measured course, you could simply run for 150 minutes and get the same benefit.

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