There are many theories on HIT, and many HIT workouts such as Max-OT among others, but I'm here to talk about a new HIT philosophy.
High intensity training or HIT is a training philosophy where intensity is the primary concern of the workout. HIT training was originally developed by Arthur Jones and popularized by Mike Mentzer. Since intensity will fall as the muscles begin to fatigue, HIT workouts keep the duration short and thus the volume low. There are many theories on HIT, and many HIT workouts such as Max-OT among others, but I'm here to talk about a new HIT philosophy. It seems that the intensity in HIT is often gauged by how much weight one can lift.

If weight was the deciding factor in HIT, then HIT workouts where all one did was perform 1 rep maxes or even negatives would be the most intense workouts. Since most of us are working out to build muscle rather than win powerlifting contests, most HIT workouts seem to utilize the lowest rep ranges that are effective for building muscle. For example, Max-OT recommends staying in a rep range of 4-6. While these rep ranges may stimulate the fast-twitch muscle fibers more than higher rep ranges, the tendons may be compromised and recovery may begin to suffer. The body is also extremely adaptive, and may adapt to lifting more efficiently in a particular rep range and therefore not changing (growing) as much over time. Powerlifting is a classic example of where an athlete may become stronger without becoming larger.

Changing The Definition Of HIT

I think our definition of intensity needs to be changed. Anyone who's ever squated will most likely agree that it is much harder to do a set of 20 to failure than it is to do a set of 6 to failure. The set of 6 will tax the fast-twitch muscle fibers more than the set of 20, but the set of 20 will tax the slow-twitch muscle fibers, heart, and lungs more than the set of 6. So why is the set of 6 considered more intense than the set of 20. I propose that each set is equally intense since they are both taken to failure.

Higher rep ranges may target the slow-twitch muscle fibers, which are seen as less conducive to growth, more so than the lower rep ranges, however training these fibers will increase overall growth. Training in a higher rep range gives the tendons a break from heavier weights. It also increases recovery by bringing more blood into the muscle. And it increasing the mitochondrial content of the muscle, which is a limiting factor of growth.

So now that intensity has been redefined, what rep range should you use. I would suggest using a variety of rep ranges. And instead of using them haphazardly, why not use them in a methodical way that will maximize progression and recovery. For instance, I would begin with a rep range between 18-30 reps for the first week, switch to a range of 13-17 reps the second week, 8-12 reps the third week, and 3-7 reps the fourth week. After the 4th week, I would go right back to the 18-30 rep range and repeat the cycle 2 more times before giving myself a total week off.

By lowering my rep range each week, I am progressively using heavier weight and thus accustoming my muscles to become stronger. However, instead of continuously trying to lift heavier and heavier weights week in and week out in the same rep range, I return to a higher rep range after my heaviest week. This gives my tendons time to recover as well as pushes more blood into the muscles to improve recovery from the heavy week. I'm also stronger than I was 4 weeks before and can lift heavier weights for the same 18-30 rep range. Thus I am dramatically improving my strength every 4 weeks without compromising my tendons or my recovery ability.

Why This Is Different!

Now that I've explained how this routine differs from other HIT protocols, I'm going to explain what I feel to be the most important aspect of HIT, and why I feel it's superior to high volume workouts. Since HIT workouts keep the duration short and the volume low, the questions arise how short and how low. I believe in keeping the duration of a HIT workout underneath an hour. To keep my workouts short, my workouts consist of a warm-up set or two to get started, but then I only do one set for each exercise.

I may do one set each using different variations of the same exercise, but I rarely do more than one set to failure for any movement. I will occasionally use drop sets, rest-pause, supersets, and other high intensity principles, but I believe that a second set taken to failure will never be as intense as the first set, and is not time well spent. So therefore I opt for variety rather than banging away at the same movement for multiple sets.

My philosophy is why do 3 sets on 1 exercise when I can do 1 set on 3 exercises and hit the muscle from multiple angles for greater development, stay more intense because I am using different areas of the muscle, and get through my workouts much quicker.