Use Interval Training to Hit Your 5K and 10K Potential

Most runners seeking to maximize their 5K or 10K potential will need to adopt some form of interval training. After a base of solid distance running has been established, runners can add interval training to complete the elements needed for optimal racing fitness.

Purposes of Interval Training

Understanding the principles and purposes of interval training will guide runners in developing workouts that are tailored to their particular situations. By interval training, I am referring to workouts in which hard running efforts of prescribed distances or time are repeated with intervals of rest between the repeated hard efforts.

The term "interval" actually refers to the rest interval, but will be used here, as elsewhere, to describe both the running and rest portions of the workout.

There are three main reasons to do interval training:

  1. Intervals are used to increase anaerobic threshold levels. By repeating sustained hard efforts at near anaerobic condition, the runner improves his ability to run hard without going into oxygen debt.
  2. Interval training also increases a runner's endurance. This means that the runner can continue at a certain pace for an extended period of time.
  3. Finally, interval training builds muscle strength. Typical distance running exercises the leg muscles in a certain range of motion, with the focus on slow-twitch fibers. By running at faster speeds, the runner exercises all leg muscles and improves flexibility during running, both of which will mean improved muscle performance in races. This makes running at a race pace easier and improves top speed for sprint finishes.

More: 3 Interval Training Plans to Build Fitness Fast

While these reasons can be summed up by the maxim, "If you want to race fast you have to train fast," they also indicate (at least reasons No. 2 and 3) that some small amount of intervals will also benefit even fitness joggers.

The amount and distance of the intervals, as well as the frequency of the training sessions, will be determined by the quality of mileage training, the type of runner involved, and personal preference. Two principles must be kept in mind when developing a training schedule that includes intervals:

1) The intervals must complement the distance mileage training (i.e., a runner needs to identify what is missing from the mileage running).

2) The type of workouts must suit the runner both physiologically and psychologically.

The latter point is important, especially for runners who are no longer part of a team. It is hard enough for a runner to motivate himself to do a tough workout, let alone one that the runner does not like or do well at. In short, for a runner to benefit from interval training, he has to show up at the track. And to reliably and enthusiastically show up at the track, the runner must have interval workouts that work for him.

Like many runners, I sought the perfect workout, or combination of workouts, to achieve ultimate fitness. It took me a while to click my heels three times to find my way home on this. Within a defined need for fitness development, there is a great deal of latitude in the type of workout that can provide that fitness.

Physiological Differences

Different types of runners will benefit from different mixes of interval training. A runner with a greater amount of slow-twitch muscle fibers will generally do better with longer intervals. Conversely, a runner with a higher percentages of fast-twitch muscle fibers will tend to do better with an interval mix that includes more shorter intervals.

The slow-twitch runner will generally need fewer interval sessions than the fast-twitch runner. Indeed, too many interval sessions can quickly fatigue the slow-twitch runner's limited number of fast-twitch muscle fibers, which results in no staying power in longer races, or the appearance of no endurance. Runners with more fast-twitch fibers will generally thrive on more interval sessions. For example, it is plausible that a slow-twitch runner would need no more than one well-designed interval session per week, whereas a fast-twitch runner would need three weekly interval sessions to maximize his ability.

More: Train for Your Muscle Fiber Type

That being said, for slow-twitch or fast-twitch, a runner who is seeking to maximize fitness for a 5K or 10K will need to have a significant amount of high-quality mileage or longer intervals. Most runners who have trained on a team have seen a "workout king" a runner who excels at interval training, especially shorter intervals, but fails to come close to the same level during races. The usual cause of this dissonance is a lack of endurance, which can only come from quality mileage or longer intervals.

Another caution when it comes to interval training is that runners can compete with other runners or themselves during these sessions and lose sight of what they are trying to accomplish. Three workouts come to mind: one where I ran 4 x 1-mile and averaged 4:19, one where I did 20 x 400 meters and averaged 64 seconds, and one where I did 20 x 200 meters and averaged just under 30 seconds.

These all sound impressive, and they were performance goals in my mind, but they were three of the most worthless workouts I ever did because they were too strenuous and did not help me build toward the three purposes of interval training anaerobic threshold, endurance, muscle development. Those workouts may have been appropriate other runners, but for me they were counter-productive. (Note that I was ill soon after each one of them.)

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