Just about everyone and his mama has heard about High Intensity Interval Training, or HIIT for short. HIIT has been found to have various advantages over other forms of exercise for both fat loss and retaining muscle mass. It sees everyone has jumped on the HIIT bandwagon and regularly talks about how they do 40 minutes or so of HIIT and so on. The problem is, most of the people who claim to be doing HIIT are not. A quick hint: if the person was doing true HIIT, they would not be able to do 20 minutes of it, much less 40!
Many, if not most, people seem to confuse HIIT with regular interval training. HIIT is in fact a form of interval training, but not all interval training is HIIT. Put simply, Interval training is a variation of intensities within the same workout, where you alternate a low intensity bout with a higher intensity bout. That's the general nature of interval training, but it is not HIIT training folks. HIIT training, is a low intensity / no intensity bout alternated with a maximal intensity bout. By maximal, I mean 100% effort, which of course, no one can achieve for more then 20-30 seconds at a time.
There are various ways to perform HIIT, but all have that in common, and what most people think they are doing for HIIT is really just old fashioned interval training. For example, the other day I did 4 minutes of walking on a treadmill at 3.5mph hour followed by 1 minute of running at 8.5mph (which for my short legs is pretty fast pace!) And repeated the cycle 5 times, which meant I was doing a 1: 4 run / walk that measured about 30 minutes including warm up and warm down. Was that HIIT? No, it was not. It was interval training, which is effective and productive training, but it's not HIIT.
There are many ways to perform HIIT training, from Tabata protocols (the most intense form of HIIT) which may only last 4-5 minutes to other versions. For example, my current HIIT protocol goes like so: after a brief warm up – 5 minutes or so on the treadmill – I will use a stair stepper type machine and will do 1 minute low intensity followed by 30 seconds all out, and repeat. I will do that for 10 minutes, which is literally all I can stand. When I say "all out" I mean 100% intensity, nothing held back, as fast and as hard as my legs can move me, similar to a sprint on a track.
I like the stair stepper because it's non-impactive on the joints and it's easy to speed up and slow down quickly, but there are many ways to do HIIT training. The fact is however, most people claiming to do HIIT are not … another essential point is, HIIT is not for everyone. It requires a higher level of fitness, and many people are better off starting with various interval programs similar to what I wrote above vs. HIIT. Done too often, and or combined with other forms of high intensity exercise (eg, weight lifting, etc.) HIIT can and will lead to over training and or injury, or as James Krieger concludes in his excellent review on the topic below
"HIIT carries a greater risk of injury and is physically and psychologically demanding, making low- and moderate-intensity, continuous exercise the best choice for individuals that are unmotivated or contraindicated for high-intensity exercise."
Do not gloss over that part.
Personally, I do HIIT training no more then once per week when combining it with weight training and will usually do the interval training above above, or something like it, and keep the HIIT to once per week, and as part of the Hybrid Training program I developed, is very taxing and intense. I will also take time off from the HIIT for a time, and then add it back in for a few months at a time. What follows is a nice review of the science of HIIT worth reading, but keep in mind the realities of HIIT training.