​This series of blog posts is a quick guide to different types of interval training and focuses on the fundamental principles involved. Armed with this and a few examples, you’ll be ready to start adding intervals into your training week, whatever your event. The principles of High Intensity Training (HIT) or High Intensity Interval Training (HIIT) apply to everyone, so you can use these workouts on the running track or turbo trainer.
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This time we’re focusing on short intervals.

​Short intervals last just 15-60s. This isn’t long enough to reach your maximum rate of oxygen consumption (VO2max) in a single interval so they rely on using a very short recovery period and blocks of intervals lumped into sets. This means your heart rate will keep climbing through the first few intervals before you max out. Despite this, you can accumulate a long time at VO2max through the workout.

These intervals have a long history but have also received a lot of attention in recent years as “magic” training, with research showing they might be more effective than standard long intervals (see our last blog post for more on these).
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In their excellent review of interval training methods, Paul Laursen and Martin Buchheit (2013) talk about intervals of 15s up to about 60s and recommend using recovery periods equal to, or shorter than, the work interval. This means something like blocks of 15s on, 15s off, written as 15/15. Other research by Ronnestad and colleagues has focused a 30/15 protocol and found benefits for a range of athletes, from recreational up to elites. Eminent sports scientist Stephen Seiler has also talked about these intervals, noting that they are physiologically very similar to long duration VO2max intervals, but may have some additional benefits resulting from the higher intensities reached.

​Short intervals are designed to increase your maximum aerobic capacity by having you accumulate significant total time at or close to your VO2max. They may also benefit your anaerobic capacity because they involve working well above your anaerobic threshold.

Interval training is typically described as sets of intervals or work and rest, where 10 x 30/30 means 30s of work followed by 30s of recovery, repeated 10 times. Usually these intervals will be arranged in sets with a longer recovery period between them. Runners can do these over any terrain running at around 3k effort or faster. For cyclists, these are perfect for indoor training on the turbo or rollers. Good targets to aim for are about 120-130% of your FTP or 100-120% of your 5-minute power. Effort level will be higher for the shorter intervals and bit lower for the longer ones. Having said that, the best way to pace these is probably by feel. Just go as hard as you can manage without having to drop your intensity. You’ll learn pretty fast what you can do!

Try this progression of workouts, including just one in your training plan each week:

• 2 x 5 x 30s hard / 30s easy with 5 mins easy between sets
• 2 x 16 x 15s hard / 15s easy with 5 mins easy between sets
• 3 x 4 x 60s hard / 60s easy with 5 mins easy between sets

Always make sure you bookend the interval session with a thorough warmup and cooldown.

Alternatively, you could try the “Ronnestad” intervals:

• 4 x 13 x 30s hard /15s easy with 2-3 min rest between sets

​Other combinations of duration, reps and sets are just as valid. Don't feel you have to follow this prescription exactly to get the benefit.

You can download a free Zwift workout for the Ronnestad intervals developed by Espresso Performance Coaching!

Long interval are performed at a high intensity for long enough for you to reach and spend significant time at your maximum rate of oxygen consumption (VO2max). Typically, that will mean intervals of 2-5 minutes with a total work duration of between 12 and 30 minutes. Recovery periods will be about as long as the work interval. If you monitor heart rate, you should be getting up to 90-95% of your maximum heart rate after a minute or two.
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However, there is also some interesting research from Stephen Seiler that suggests accumulating more time at a slightly lower intensity might by even more effective. More on this below!

​Long intervals are designed to increase your maximum aerobic capacity by having you spend as much time as possible operating at or close to your VO2max.

Interval training is typically described as sets of intervals or work and rest, where 10 x 2min / 2 min means 2 minutes of work followed by 2 minutes of rest, repeated 10 times. Runners can do these over any terrain running at around 3k to 5k effort. For cyclists, these are perfect for indoor training on the turbo or rollers. Good targets to aim for are about 120% of your FTP or 90-100% of your 5-minute power.

Try this progression of workouts, including just one in your training plan each week:

• 5 x 2 min hard / 2 min easy
• 5 x 3 min hard / 3 min easy
• 4 x 4 min hard / 4 min easy

Always make sure you bookend the interval session with a thorough warmup and cooldown.
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Alternatively, you could try the Seiler approach, which involved a slightly lower intensity but longer intervals. It’s been shown to be more effective than the traditional 4x4 session, so definitely worth considering as a part of your toolbox:

• 4 x 8 min hard / 2-3 min rest

Try these free Zwift workouts developed by Espresso Performance Coaching and let us know what you think in the comments below!

• ​4x4 minutes
• 4x8 minutes