In a continuing collaboration with Scott over at Straight to the Bar, we will be writing about timeless exercises in different disciplines throughout the month of May. This week I would like to talk about one of the most important types of workouts for any competitive runner.

What is interval training?
According to the Merriam-Webster dictionary, fourth definition, an interval is “one of a series of fast-paced exercises interspersed with slower ones or brief rests for training (as of an athlete).” Intervals can be practiced across sports, but in running an interval workout is any workout where you run for a specified distance or time at a specified pace with a specified amount and type of rest.

Most intervals in an interval workout will be run between 90% and 110% of your race pace. Some workouts will call for running slower or even faster than that. Your race pace could be for any distance. Once you have determined a goal race and what time you want to run at that race, you can decide what sorts of interval workouts you want to do. If your goal race is a 4 hour marathon, you might run mile intervals between 8:30 pace and 10 minute pace. If your goal is a 4 minute mile, you might run 400 meter intervals between 54 seconds and 66 seconds. An interval effort is relative to your level of fitness, your goals, and what race pace you are currently working towards. You may even mix up your training, and do your shorter distance intervals at your 5k race pace and your mile or two mile intervals at your marathon race pace.

How does interval training help you?
Interval training puts you in oxygen debt and teaches your body what it is like to run at speeds near or above what you expect to race at. You can get your body used to moving fast for a specified distance without having to run that entire distance at once. This allows you to concentrate on your form, maintain your rythm, and teach your muscles how to deal with excess lactic acid and less lower fuel reserves.

Running intervals at your race pace allow you to work out your mind as well as your body. You can get a feeling for what pace you should be running so that you can make adjustments if you are running too fast or too slow during the race. They can also make you tougher and more resistent to the pain and distraction of running at your peak performance.

Interval training is also great for burning fat. The actual number of calories burned while exercising may be equal or even less than the number of calories that a moderate effort steady state run may burn, but your metabolism gets cranked up and you continue to burn calories for many hours after the workout. Be sure to eat and drink water after interval training; you can keep your metabolism going much faster and much longer when your body knows that it has the fuel to break down the fat to aid recovery.

What do you do between intervals?
Running fast is only half of the equation in interval training. Just as important as the interval itself is the (passive) rest or (active) recovery that follows.

Rest is a measured period before between intervals that breaks up the periods of fast running. Rest usually entails standing, stretching, or light walking where you do not travel from a specified area. Rest tends to be passive, and can even include sitting on the ground or hunching over your knees or a fence. Rest is designed to bring your heart race down as quickly as possible. Rest is usually measured either by duration (in seconds or minutes) or by your pulse.

Recovery is a measured amount of activity between intervals. Recovery tends allows your heart rate to drop, but keeps it elevated at a higher level than rest does. Recovery could include a jog or walk back to your starting position, some other type of activity such as pushups and situps, or any other active movement that prevents you from remaining stationary. Recovery can be measured by duration, but is usually measured by distance.

Rest and recovery can be mixed and matched in an interval workouts. Some workouts will call for just rest or just recovery between each interval. Other workouts will mix them together, usually by following each interval with some sort of active recovery with rest right before the next interval begins. Higher repitition intervals may include a period of recovery to help loosen you up again after the rest, however.

What are popular interval workouts?

1. Repeats are the most popular type of interval training. A set number of intervals over a set distance at a set pace with a set rest or recovery. For example, 4 by 1 mile repeats at race pace with 2 minutes rest between each interval, or 20 by 400 meter repeats faster than race pace with a 200 meter active recovery between intervals.
2. Ladders are a variation of repeats where you do not run the same distance for each interval. Common ladders will climb up or down in distance, or will climb up and then down. For example, 1×400, 1×600, 2×800, 1×600, 1×400 is a common ladder where you start at 400 meters and climb up to 800 meters and then back down to 400 meters. The “x” replaces the word “by” and means that you run the distance on the right of the “x” as many times as appear before the “x”. Not all ladders are progressive, and this type of workout could be any changing distance for each repeat. Rest and recovery between the intervals of a ladder may remain constant or may change based upon the distance of the interval that you just ran.
3. Fartleks are a form of interval training where you never stop running throughout the workout, and will normally (but not always) run your intervals and recovery for a set duration rather than for a set distance. For example, you may run 10×1 minute repeats with 3 minutes of recovery running between each repeat. The name “fartlek” comes from the Swedes and means running play. Fartleks don’t need to be timed; one of my favorite runs is to just go out and randomly choose a target to run fast towards at regular intervals without rhyme or reason. I might sprint to a telephone pole or after a pedestrian up ahead of me or an intersection, with however much recovery between each interval as it takes me to find a new target that peaks my interest.

How do you integrate intervals into your training plan?
You should always give yourself an adequate warm up and cool down before and after each interval workout. Treat interval training like you would a race, because you can easily pull a cold muscle and injure yourself. By adequately cooling down, you will relax your muscles gradually and will prevent cramping and soreness in the hours and days following your interval workout.

If you are new to interval training, start slowly. Do not rush into high repetition workouts at a pace that is faster than your race pace. Working your way up to progressively more difficult workouts will help get your body used to the high intensity workload without causing an injury. You will still realize great gains in your races from any sort of interval training. Start with fartleks; they are much easier to reign yourself in from advancing too fast.

Each season and every few month or so throughout a season, cut back a little. Do half the number of intervals that you are used to. You will still get some training in at pace, but you will give your body a chance to recover. Go back to your normal intensity and number of repetitions the next week. If you have not done interval training for a few months, then work your way back up from a lower number of repeats.