This is Part II in a series of articles about Getting Faster.
Part I discussed Repeat workouts and explained these points.
- Repeats are generally shorter distances, e.g., 200s, 400s, 600s run at faster speeds that we can repeat multiple times without sacrificing intensity; we “repeat” the distance with the same quality at the end as at the beginning of the workout
- Repeats improve our anaerobic capacity, develop new muscles, build speed, and make us familiar with more rapid, efficient, and fluid leg turnover
- Recovery between repeats is subjective, giving ourselves enough recovery to hit our time goal on the next repeat
- Recovery guidelines for repeats are generally two to four times the amount of time spent running the repeat
Interval training is what many runners have in mind when we talk about speed work.
The key difference between repeat training versus interval training is the recovery period. In repeat training we allow full recovery; in interval training we limit the recovery time.
Contrary to popular belief, the “interval” is not the distance we run, but the time between runs spent recovering. So if you say you’re heading to the track to do 800s, that doesn’t make them intervals. Again, the “interval” actually refers to the time spent recovering, not running at a high intensity.
The goal for interval training is to “accumulate” time spent running at a very high level and increase our body's ability to adapt and eventually run at a sustained, higher anaerobic pace for longer periods. Over time interval training helps us string together multiple demanding efforts into that dazzling 5k or half marathon PR .
Interval training is marked by running at a challenging pace, stopping to rest—but only partially recover—and then resume running while our heart rates are still elevated—and while we’re still sweaty. Let’s say we’re doing 800m interval training. By running five 800s at 4-minute pace, we accumulate 20 minutes of anaerobic training (high heart rate).
For interval workouts, a general guideline for the amount of recovery time between runs should be equal to or less than the time spent running. For example, if we’re running those interval 800s at 4 minute pace, then our recovery time is also four minutes or less before starting our next 800. Between runs, active recovery, a blend of walking and jogging, helps prevent stiffness and keeps heart rate elevated. I remember as a high school and college runner our coach would holler for us to step up to the line for the next 800, while we would cling to and plead for every last second of recovery.
When designing our interval workouts, we can choose any distance we prefer ranging from 400 meters to 1200 meters, or a better rule of thumb might be runs ranging three to five minutes. Regardless of the distance, we run roughly the same pace. If we run our 800s at 4-minute pace, we would run our 400s at 2-minute pace, 600s at 3-minute pace, 1000s at 5-minute pace, etc. The challenge and the benefit of running intervals always comes back to controlling the recovery time, not running faster.
I like to schedule intervals into my training after three to four weeks of building up my speed by running repeats. I’m ready to ramp up my interval workouts when I’ve successfully run my workouts for three to four weeks or if I’ve proven my fitness level in a race.
The biggest unanswered question is “how fast?” To learn what pace to run your interval workouts, check out this training pace calculator, which is based on the research and expertise of Jack Daniels, recognized as “the world’s greatest running coach." As for how much, interval running is typically limited to no more than 8% of weekly mileage.
In his book Daniel's Running Formula, he provides a great deal of useful information about all forms of training, including tables and charts of what paces and intensities to run speed workouts, and tips for when to include speed work into your training schedules. He also provides sample training schedules for popular racing distances for all levels of runners from beginner to elite.
Next in this Getting Faster series: Threshold Training
Interval recovering on Flickr by Gordon McGregor