After scouring the web for resources on the subject, I have come to the following conclusions:
High intensity interval training ("HIIT") programs are typically defined by a 2:1 ratio of work to rest/recovery periods, with anywhere from 4 to 10 cycles of work/rest, for a total workout session between 4-15 minutes depending on its structure ([source]).
An example program would be: 30 seconds of hard sprinting alternated with 15 seconds of walking, repeated 6 times for a total workout time of 4 minutes 30 seconds.
Another example would be the Tabata method (one of the more popular forms of HIIT), and is structured as 20 seconds of intense cardiovascular work followed by 10 seconds of rest, and repeated continuously for a period of 4 minutes or 8 total sets.
The primary benefit of HIIT/Tabata style workouts is a substantially improved VO2 Max, compared to that of gains from moderate intensity long duration aerobic activities. Additionally, it is thought that HIIT also improves fat loss compared to standard cardio ([source]) via the "afterburn effect," although critics cite that while HIIT has the highest caloric burn / exercise time ratio, traditional exercise can provide a much higher caloric expenditure at the expense of increased exercise duration.
As for specific exercises to do during HIIT/Tabata, that largely depends upon your goals. HIIT is best designed for aerobic activities such as boxing, sprinting, jumping (rope, boxes), so it is best to pick one or more of your preferred exercise and iterate between those during your 4-6 minute session. Some programs recommend barbell/dumbbell exercises, however those are not ideal because HIIT is an endurance/aerobic workout, and thus does not translate well into either the strength training or body building world ([source]).
Finally, when starting a HIIT program you should be mindful of the fact that--if you are doing it correctly--the exercise will be extremely intense; so much so, people often vomit after the first couple of sessions. Due to the intensity of the program, it is recommended that you consult your doctor first, and that you incrementally buildup intensity over time. For example of the latter, instead of starting Tabata off as 20/10 x 8 (20 work seconds, 10 rest seconds, 8 total sets), you build up to that instead. For example, below is a incremental HIIT structure taken from t-nation:
- Week 1 — 10/20 x6 (10s work, 20s rest, 6 sets)
- Week 2 — 15/15 x4
- Week 3 — 10/20 x8
- Week 4 — 15/15 x6
- Week 5 — 20/10 x4
- Week 6 — 15/15 x8
- Week 7 — 20/10 x6
- Week 8 — 20/10 x8