The Rodney Dangerfields of Races

Races of 15K (9.3 miles) through the half-marathon (13.1 miles) get no respect. The half-marathon doesn’t even get its own name; it’s just half of another distance. Imagine if people called 5Ks “half-10Ks.”
This range of races, which also includes 10-milers and 20K (12.4 miles), is almost never the focus of a runner’s races. Runners usually use these races as tune-up races a month or so before a marathon. Or some runners will run one of these races at the beginning of a racing season to build strength, and then drop down in distance to 5Ks and 10Ks for the rest of the season. But you almost never hear a runner say, “This fall, my goal is to be the best 10-mile runner I can be.”
That’s too bad. These hybrid distances can be some of the most satisfying in running. They’re plenty long, so you’re not going to get through one by running a few miles a few times a week, as you could with a 5K. But they’re not so long that they’re going to knock you down for too long. Most of the soreness and lingering fatigue that people have from marathons comes from what happens after 18 or 20 miles. Should you try a 15K, 10-miler, or a half-marathon? Why not? For people who are thinking about trying a marathon someday, building up to one of these races is a good idea. You learn the routine of training for longer distances by gradually extending your distance. Anyone running a marathon should have experience with other races first. These longer races will give you a better idea of what you’re going to experience if you try to tackle a marathon.
If you usually don’t run farther than five miles, keying on one of these races is a good motivation to extend your distance. To do that, increase the distance of your long run by one mile two out of every
three weeks. For 15Ks and 10-milers, work up to running that far two weeks before the race. Take it easy for the next two weeks, and then run the race at a strong but reasonable
pace that you know you can maintain to the end. If you’re going to do a half-marathon, then build up to 10 to 12 miles at a time, again doing your last long run two weeks before the race.
But if you’ve been running a bit more and think that you can not only cover the distance, but also run a good notch faster than on your usual training runs, you can improve your performance at these distances by entering the strange world of the lactate threshold.