To understand the purpose of aerobic interval training and my opinions on it (like seriously, why is this chick walking all the time?) please see Part I: What is it?  Why do it? and Part II: Planning your Interval Program.

A brief overview

These interval protocols should be primarily stressing the cardiovascular system.  I have developed (and borrowed) a few methods of interval training I like.  These types of workouts take the place of long steady state running.  If the workouts feel exceedingly difficult, that means that you are probably increasing the percentage of anaerobic metabolism you are using.  Feeling sore the next day also indicates that the workout may have been at a higher than optimal intensity.  This can become a problem if you are doing these types of workouts every day.  If you are only doing them two days per week, the intensity can be a little higher.  All workouts are preceded by a dynamic warmup.

My experience, your experience

The following are examples of workouts I used last year as I went from a very low level of fitness in January to being extremely fit by tryouts in April.  The frequency with which I used aerobic intervals varied depending on the focus of my program at different points in the year.  Your starting point will depend on your current level of fitness.  Your progression should take into consideration the other workouts you're doing during the week.

Three Interval Protocols I've Used and Liked

1. 20/40 at 80% sprint

This workout involves doing 80% of your max sprint speed for 20 seconds followed by 40 seconds of recovery.  I walk during the 40 seconds.  I like this workout because of its simplicity.  And it feels great to run fast! The first 3-4 intervals I'm usually still warming up.   I feel fully recovered between working intervals.   After about the 8th interval I can feel each interval becoming progressively more difficult.  The last three intervals feel stressful.  I never go until exhaustion. Never sacrifice your running form for the sake of doing more.   I started doing this workout at ten intervals adding about 2 reps per week.  Now I can easily do twenty.  This was by far my favorite endurance workout last year.

2. The 30/30 workout

Thirty seconds is run at about your timed mile pace followed by thirty seconds of walking.  The 30/30 protocol is less stressful than the 20/40 option.   I have often used this workout the day after a tournament or a weekend practice as a recovery workout.  I'll go anywhere from 20-40 minutes depending on the circumstances.

3.  Distance intervals:  200 m/100m workout

Half a lap is run at my timed mile pace followed by walking a quarter lap.  For me, this works out to being about 50-55 seconds on, 1 minute off.  I use this workout once in awhile for variety.  Also good for when I lose, misplace, forget my watch.  (which happens more often than you'd think!)

Modify the above suggestions to suit your needs

I like simple workouts but you might prefer increasing the variety by including different interval lengths within the same workout.  Using a variety of interval length would have the added benefit of more closely resembling what happens on the field.

This year, my favorite 20/40 workout is no longer challenging so now I'm doing 25/35 instead.  About eight of those feels about right.  That seems like a good starting point.  Another modification is to do some longer intervals first to more quickly arrive at the point where I feel like I'm working.  A few 200m/100m reps before I start the 20/40 intervals does the trick.

A great modification for team practice:

Do the 80% sprints from the back of one endzone to the back of the other, walk the width of the field, and repeat.

Closing thoughts

I don't believe that interval times and distances need to be extremely precise as we are not training to be middle distance runners. The most important thing about endurance work is that you do it. Find a type of interval workout you enjoy, stick to a consistent schedule for about 6 weeks and see what it does for you.

I hope that you've found this series of articles to be not only informative but also applicable.  Consider subscribing to the blog (the RSS button is above the "Categories" heading on the right side of the page) and look forward to coverage of other training principles and how to apply them to your ultimate fitness!

If you try any of these workouts, let me know what you think!  Was it harder or easier than you expected?