What is HIIT?

I know this probably a dumb question but, what exactly is HIIT?  I keep hearing people talk about it, but what does it mean exactly?

High Intensity Interval Training

thanks claudius. 

HIIT (High intensity interval training) It is excellent for you. I do it in the form of sprinting 3 times a week. It is going all out for 30 seconds to a minute, however long you can last, then bringing it back down for 30 seconds to a minute and going all out again. The actual time may be different but close because if you are truly doing HIIT you cannot last much longer than a minute. IT depends on your physical condition.

It gets your heart rate up. You can do it many different ways, bike, jump-rope, lifting, sprinting, swimming and so on. It burns calories while you are doing it and for hours after, unlike regular cardio that burns calories only while you are doing it. HIIT is also one of the only types of activities that naturally releases HGH (Human growth hormone) which declines as we age.

It also increases resting metabolic rate (RMR) for up to 24 hours because of excess post-exercise oxygen consumption, it also improves maximal oxygen consumption (VO2 max) more-so than doing long steady state cardio.

It is an excellent activity to burn fat.

Original Post by jessicasbc:

I know this probably a dumb question but, what exactly is HIIT?  I keep hearing people talk about it, but what does it mean exactly?

Definition:

High-intensity interval training (HIIT) or sprint interval training is an exercise strategy that is intended to improve performance with short training sessions.

A HIIT session involves a warmup period, several short, maximum-intensity efforts separated by moderate recovery intervals, and a cooldown period. The period of alternating effort and recovery intervals typically lasts a total of 15 minutes.

Studies by Tabata[1], Tremblay[2] and others have shown this method to be more effective at burning fat and maintaining, or building, muscle mass than high-volume, lower intensity aerobic work-outs. A study by Gibala et al[3] demonstrated 2.5 hours of sprint interval training produced similar biochemical muscle changes to 10.5 hours of endurance training and similar endurance performance benefits. According to a study by King [4] , HIIT increases the resting metabolic rate (RMR) for the following 24 hours due to excess post-exercise oxygen consumption, and may improve maximal oxygen consumption (VO2 max) more effectively than doing only traditional, long aerobic workouts.[5][6][7][8] Long aerobic workouts have been promoted as the best method to reduce fat, as fatty acid utilization usually occurs after at least 30 minutes of training. HIIT is somewhat counter intuitive in this regard, but has nonetheless been shown to burn fat more effectively. There may be a number of factors that contribute to this, including an increase in RMR, and possibly other physiological effects.

Ok laymans version short bursts (or sprints) during your cardio workout to achieve better results....btw I do HIIT training all the time its really great.

I do cardio 6 days a week...My cardio consists of modified HIIT (walking mainly)

Some additional benefits to HIIT training include building tolerance for, and more efficient disposal of, lactic acid. This is of particular interest to people involved in sports that revolve around relatively short periods of intense, largely anaerobic exertion, ie: competitive swimming, hockey, lacrosse, etc, but is also very handy to anyone who finds themselves needing to do occasional anaerobic activity: to push hard and get up that brutal hill on the bike, to shovel out your walk in winter, or help a friend move into a new house.

Consult your doctor before starting a HIIT regimen. For real.

... and be advised, when you start HIIT, you will know pain. Pain and yourself will be close, personal friends for a good while. You'll send each other cards with pictures of the SO and kids at hollidays. In the end though, it's worth it, and after a while you'll be able to trounce even nominally healthy people who stick to the more mainstream low-medium intensity cardio/resistance training.