My high school cross country coach always used to tell us that, as if it would make running a fast 5K more pleasant. I think a big part of improving race times is learning to push through the pain of running fast. But how do you do that?
Obviously, races are a great way to get used to running faster. But it's not realistic to run a race every single week. So what do you do? Tempo runs. There's not a whole lot I dread more than tempo runs, because they're definitely not easy. But I know they're an important part of getting used to running with discomfort.
I'm not going to go into a whole lot of detail about tempo runs, because there are many people with PhDs in Exercise Physiology who've written far more on the subject than most people would ever care to read. But basically the whole point is to stay at your lactate threshold pace (which is generally where discomfort begins) for a prolonged period of time (generally 20 minutes or more).
There are various ways to find your lactate threshold pace. One method I found through a quick google search says to add about 30 seconds to your 5K race pace. Since I did my last 5K in 22:25 (7:12 pace), my pace for a tempo run should be about 7:42 pace. If you have a heart rate monitor (which I don't), you can also shoot for about 85-90% of your maximum heart rate.
On my six mile run this morning, I did 3 miles of tempo running (which I may have done too fast, but it felt like the right pace - 7:30) plus 1 km at 4:15. I am hoping to run my 10K this weekend at 7:30 pace (for a finish time of 46:36), so we'll see how that goes. For the rest of the week, I'll be doing pretty easy runs in preparation for Saturday morning. I'm really hoping I'll be able to deal with the discomfort so that I can meet my goal!