Four things to think about when planning your interval training:
1. Keep it simple
Even if 15s work 15s recovery would be the best method, this type of workout may be difficult to execute. This is especially true if you are training by yourself or running on roads versus the track. The most important thing to consider in your training regimen is that is has to be something that you can actually do. Your training environment and schedule are all things that need to be considered. For example, if you are training in the dark how often do you want to look at your stopwatch? If you are training on the road, how ridiculous do you want to look stopping and starting every 15 seconds? What can you do if you get to the track ans realize you forgot your watch? (…or does that only happen to me?)
2. Remember that this is an aerobic workout
The goals is to increase the amount of time you spend processing the maximum amount of oxygen you are capable of without increasing lactic acid. If you feel sore during or the day after your training, this indicates that you accumulated too much lactic acid. Adjust by doing fewer intervals, decreasing your intensity, or increasing the length of the recovery times.
I firmly advise running only at speeds and volumes in which you can maintain good form. By good form, I mean that you should be landing on the midfoot or forefoot, and you are able to remain tall in your core. Both speed and fatigue will affect your form.
If you experiment with running at different speeds, you will notice that your form subtly changes. Sprinting, you will naturally be contacting the ground with the balls of your feet. As speed is decreased, the point of contact with the ground tends to shift farther back on the foot. Some people even strike the ground with their heels at a slow jog. The amount of time your foot spends on the ground should be minimized. Think of each step as its own plyometric event. The foot should tap the ground, not stick to it.
The second contributor to form is level of fatigue. If at any point there is flailing of the arms, or slouching in the trunk, I will stop running. Every repetition done with poor form is practicing a motor pattern you don’t want to learn. Running with poor form also invites overuse injuries.
Pick intervals at which you can fun fast enough to maintain good form. Stop your interval training session if your form starts to break down.
4. Rest intervals
Deciding on the intensity/time/duration of work intervals is only part of an interval workout. The next thing to decide is the intensity and duration of the rest intervals. Studies show that complete rest does not clear lactic acid from the bloodstream as well as active rest intervals. Some people prefer jogging intervals. I recommend walking intervals for two reasons.
First there is the form issue. Jogging usually results in lollygagging accompanied by plodding or shuffling feet. I cannot think of a less efficient, more awkward form of movement. Please stop! Jogging in the way I’ve described also uses a very small range of motion in the hip. Walking is actually more similar to sprinting than jogging in hip range of motion. This is why so many long distance runners experience tight hamstrings and hip mobility issues. Walking can help prevent this tightening up because the range of motion in the hip is larger.
Second, some studies show that clearance of lactic acid between bouts of work is more efficient at 40% velocity VO2 max versus 60% velocity VO2 max. I don’t know about you, but my velocity at VO2 max is slow enough that 40% , or maybe even 60% of that pace is better accomplished at a walk than a jog.
Until next time…
I hope these suggestions were helpful. In Part III of this series, I’ll give you examples of interval workouts I’ve used with a lot of success. I’m still experimenting with my interval workouts so I’ll also talk about how I’m modifying my workouts based on my prior training.
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By the way, my knowledge of interval training comes mostly from reading a studies by Veronique Billat.
Her comprehensive review of aerobic interval training research is a fantastic read.