Simply put, nothing is better than interval training for improving your speed at distance.
Peak Performance newsletter, a monthly publication put out mostly by trainers, coaches, and physical therapist for the top professional English soccer teams and top British runners, reported a study comparing the top Kenyan 10K (6.2 miles) runners to those that were second-rate—meaning they were only as good as the top runners from other nations.
Do you know what the only significant difference was between the two sets of runners?
The best runners did intervals for their speed work, while the 2nd-tier runners used tempo runs.
Okay, now I'm going to explain interval training, but don't miss the two excellent tips on how to do intervals in the last section.
Intervals are high-speed, short-distance bursts separated by recovery runs of equal or lesser distance.
Interval training varies. A marathoner may do sets of 1/2-mile runs at race pace separated by 1/2-jogs at a slow pace. A miler, on the other hand, may do 220 yard bursts at or above their mile pace, separated by 1 minute of jogging or walking.
Here's two examples that might apply to an amateur runner wanting to run a 5K or marathon.
For marathoners, a Runner's World editor recommended working up to 10 half-miles run in the same number of minutes as the goal hours of the marathon with slow half-mile jogs as the rest in between.
So, if you are shooting for a 4-hour marathon, you would work up to 10 half-miles at 4 minutes each. In between, you would jog a half mile very slowly, maybe at a 5- to 6-minute pace.
I tried that for a half marathon, and I shot for 5 half miles at that speed, rather than 10 as I would do for a marathon. The result? A 2:04 half marathon, 4 minutes off my dream pace.
Not bad. Next time I'll work up to 7 half-miles at the recommended pace.
I adapted that marathon interval suggestion from Runner's World by mixing half miles and quarter miles. I would do 3 half-miles at the goal pace for the 5K, and then I would follow those up with 3 quarter-miles at however fast I could run without hating the training and not wanting to do it the following week.
The result? I beat my goal by 15 seconds. I pulled that off even though I paced two younger friends through a first mile so that they wouldn't ruin their own race pace. They were faster than me, so I ran the first mile 15 to 20 seconds too fast for me in order to help them. I made my goal nonetheless.
(Running the first mile too fast in a 5K is a really bad idea for most people. There are some folks who don't seem to get a rapid lactic acid buildup from starting too fast, but I'm not one of them. Most others aren't, either. You will run a faster 5K if you run the first mile at or below your goal pace.)
I read an article on interval training once that interviewed several world-class coaches. I picked up two main themes in their advice:
Khalid Khannouchi, trying to make a comeback in 2010
The second tip is obvious and needs no further explanation. On the first one the coaches said that runners underestimate the power of intervals that are not done to exhaustion. It simply needs to be hard, not exhausting.
Shortly after that article, I read an article on Khalid Khannouchi, who was the top marathoner in the world and the world record holder at the time. He recommended really pushing the intervals, in absolute contradiction to what the coaches said. Shortly after, he was injured, and I've never seen his name on the marathon circuit since.
So don't overdo it. Interval training should be hard, but intervals do not need to be run to maximum effort.