HIIT, or high-intensity interval training has been in the top five fitness trends during the last few years. Lots of bootcamp classes and HIIT specific workouts are flooding the workout scene. HIIT training is a method that involves short, intense bouts of high amounts of work followed by a short recovery. It's been used in training both anaerobic and endurance athletes and considered a necessary principle leading to athletic improvements. But amateur and professional athletes aren't the only ones using this technique. You can find these same principles with CrossFit and Tabata training.
Is this the best technique for everyone? ACSM researchers found significant evidence that backs aerobically-based interval training (running, cycling, etc.) but body weight/resistance training interval benefits remain to be seen. Since bootcamp-style HIIT has only been around (in the grand scheme of fitness) for just a few years, more data needs to be collected to measure any long-term physiological improvements. However, it's easy to feel the benefits while fitness professionals collect evidence.
In general, current recommendations for aerobic training call for 150 minutes of moderate exercise or 75 minutes of vigorous exercise each week. HIIT workouts tend to be shorter but more intense which fulfills recommendations for vigorous exercise. For lots of participants, especially those busy with work and family, this is an efficient solution.
My biggest complaint about HIIT workouts, especially those that require olympic-style lifting is that these should be supervised by a professional. I've heard too often that some participants who are entry-level athletes or undertrained enter into intense workouts, load exercises too soon, and end up with a serious injury that impairs their movements and/or keeps them out of all activities.
It's best to start these kinds of fitness programs much like any other. Start with low to no weight and higher reps and increase the intensity by decreasing repetitions and increasing weight. HIIT training is popular for a reason -- it can make you stronger and help you increase the quality of how you move.