High Intensity Interval Training

High Intensity Interval Training (HIIT) uses short, high intensity intervals. HIIT has been shown to improve both anaerobic and aerobic fitness in trained athletes. It is one of the most efficient work outs in terms of improvement for time committed, as well as being a lot of fun.

1 The Tabata Workout

Main article: Tabata

The Tabata workout is 8x (20 seconds maximum effort with 10 seconds recovery) for a four minute workout. Before starting the Tabata it is important to warm up thoroughly as this work outs a lot of stress on the body. The 'maximum effort' nature of the Tabata intervals creates significant risk for injury. I would strongly suggest that you start doing the Tabata structure, but instead of doing the 20 seconds 'all out', do them as comfortably hard. Over the course of a few weeks, build up to doing them as fast as you can. Another alternative is to do the workout on a bike, riding out of the saddle to use similar muscles to running, but without the increased range of motion required by this level of intensity.

2 The Little HIIT

A variant on the Tabata workout is the Little HIIT, named after Jonathan Little, one of the researchers. The Little HIIT uses 4 or 6 repeats of 30 seconds 'all out' with a 4 minute recovery after each interval.

3 Benefits

HIIT has been shown to improve VO2max, mitochondrial activity and performance in cycling time trials. HIIT has also been shown to shift muscle fiber types from type IIb (fast twitch) to type I (endurance) with type IIa unchanged.

4 Caveats

There are some caveats to be aware of with HIIT

• It is remarkably easy to get injured with running HIIT unless care is take to build up the intensity over time.
• HIIT has shown to provide similar benefits to longer periods (90-120 minutes) of steady state exercise. I have not found any studies showing the effect of adding HIIT to an existing training program.
• The changes with HIIT include an increase in the size of type I muscle fibers, whereas endurance training often results in smaller type I fibers that are more efficient.
• If the rest periods are long enough (15-20 minutes), then the training produces adaptations to sprinting rather then endurance.

5 HIIT on a Treadmill

HIIT can not reasonably be done on a treadmill. This is partly because the intervals are very short, with a dramatic change in pace between interval and recovery, so a treadmill acceleration becomes a problem. The other issue is that 'all out' is not a pace you can program into a treadmill.

6 See Also

• Introduction to Workout Types
• Introduction to Interval Training