Sure, it sounds easy enough: Settle into the perfect speed for your given effort and hold it. But whether you're a seasoned veteran or an eager newbie, it can be hard to know if you're going slow enough on easy days
and fast enough on hard days. "You can't go as hard as you want every time you work out, or you'll have nothing left to race with," says Greg McMillan, M.S., an exercise physiologist and founder and coach of McMillan Running in Flagstaff, Arizona. "The goal is to train at various paces--usually at 50 to 70 percent effort--so you can race at 100 percent. This is difficult for most runners to follow." (Find the pace of your last race using the Pace Calculator
.) It's hard in part because not every runner knows the speed from which to base those paces. Here's how to nail the right pace for every workout.