Why HIT Training Works

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HIT Training and the Philosophy Behind It

Dr. Kenneth Cooper started the running/aerobics craze around the time Nautilus was founded in the early 1970’s. The HIT method originated from the original Nautilus philosophy espoused by Arthur Jones.

Only during the last three decades has resistance training been slowly becoming a major focus of exercise science. Philosophically speaking, the HIT philosophy represents the preferred technique to use for total body conditioning in a single workout in the safest, most effective and most time-efficient manner possible.

Arthur Jones Creator of Nautilus

Stretching and Warm-up

Why isn’t there any formal warm-up, stretching or cool-down? Contrary to popular belief, your muscles will perform better if you are slightly cooler. Heat contributes to fatigue and ultimately heat sickness if left to continue to rise. We actually want to keep you cool during a workout. A traditional warm-up can be more dangerous than the exercise itself because of the high forces involved which you’ll read more about shortly.

Your first two or three submaximal repetitions are the warm-up. It only takes a few seconds to bring your body temperature up. Usually walking around for a couple of minutes after a workout is sufficient to prevent any negative post-exercise effects. Stretching does not offer any protection from injury as previously thought.

We were able to rationalize this several years ago, but there is just now good research coming out that supports this. Most injuries are not caused by a lack of flexibility, but by trauma or too much force imposed on the systems. Stephen Thacker of the Centers for Disease Control (CDC) compiled a number of studies to look closely for any benefits that might be seen from stretching.

Thacker says “We could not find a benefit.” “And the injuries found in the study typically happened within the muscle’s normal range of motion, so stretching them would not have made a difference.” However, this is not to say that it is never done in HIT. Generally, we prescribe a full range of motion exercises which includes emphasizing the stretching portion of the range. This is one way, but not only you can enhance flexibility through strength training.

We frequently include a short stretching routine for those that feel it might prevent some later soreness and sometimes include 20-second stretches immediately after each exercise to stimulate a little more strength gain. Some recent research has shown this to be possible. Other research has shown a slight correlation with stretching before activity and an increased incidence of injury so we usually stick to doing it afterward if necessary. According to the literature, you should too.

Single Sets vs. Multiple Sets

One of the major differences of HIT is the low number of sets of each exercise we use, usually only one, but sometimes employ more especially for advanced techniques. Conventional practice by most people is to use at least three sets and usually more. In fact, in bodybuilding for much of it’s history, the more you could do the better. Athletes would literally spend hours on end at the gym sometimes making two or even three trips there per day.

However, over 96% of the research on this topic does not support or justify the idea that more sets are better assuming loads and intensity are the same. According to Jack Wilmore, a prominent exercise physiologist and author of my college textbook, Physiology of Sport and Exercise, “…it appears that a single set is just as effective as multiple sets for increasing muscle size and strength.

In fact, of the studies that used appropriate controls, only one study demonstrated an advantage of multiple sets over a single set, and the magnitude of the difference in strength gains between three sets and one set was small.” This being known and employed will instantly cut your workout time by 2/3. This alone should help convince some as to how it can be done in such a short amount of time.

No Rest Between Sets

We also use a circuit approach which implies no rest, or very little time between exercises as I laid out in previous chapters, preferably, 30 seconds or less. This keeps the heart rate elevated for the entire workout. Or there may be slight dips in heart rate between exercises and spikes during the exercise resembling interval training which has been shown to be very effective for cardiovascular conditioning.

The cardiovascular benefit is the same as if you were jogging down the street except you are not exposing yourself to high acceleration forces and high impact forces that cause injury. You have to move your muscles to get a response from your heart. Your heart does not know if you are pushing on a leg press or running. In a study more than twenty years old, a running and circuit weight training (RUN-CWT) program was compared to a circuit weight training (CWT) the only program.

In the conclusion of the study the authors state, “Statistically, one training program was not shown to be superior to the other; thus, both programs of RUN-CWT and CWT were effective in improving measures of physical fitness.” Does this mean that the running was just superfluous activity? Yes! Why wasn’t the running and circuit training better? Your body cannot tell the difference between the two modes of activity. All it knows is that it is under stress so you better make sure that stress is safe and effective and not exposing you to injury either acutely or at some point in your future.

Addressing More Than One Component of Fitness

This leads me to probably the most controversial of all the points in our philosophy, which is that we get our cardiovascular work primarily from the circuit weight training, itself. You don’t have to avoid so-called aerobic activity completely if you don’t want to, but it will be a negligible effect and possibly a detrimental one if you choose to engage in these activities beyond the scope of our guidelines.

We have designed HIT to be all-inclusive. Sending your body different physical messages can inhibit, not improve your results. What I mean by that is that with the circuit approach, your cardiovascular work is taken care of while you are doing stimulating muscular work at the same time. And according to most of the research, becoming “muscle-bound” and “tight” is a myth and you will actually have enhanced flexibility especially from full-range weight training.

You’re killing three birds with one stone. For busy people or people that don’t like to exercise, this should be good news. You cannot make your heart and lungs do anything unless you move your muscles first. You might be able to if you get scared suddenly, but that’s not exercising. The function of the cardiovascular system is to support the working muscles. Your muscles are the window into the rest of your body’s systems. I want you to remember that. The heart, lungs, and blood vessels are secondary in any activity.

They are the intake and hoses, the muscles are the engine. The only reason that they get so much attention is that it has been the part that is most disease-ridden, but nevertheless, they are affected by what your muscles are doing.

Knowing all of this, why not design the activity so that all 3 components are addressed at the same time to a maximal gain. Nautilus clearly demonstrated this in Project Total Conditioning performed at West Point in 1976.

As far as I’m concerned, this is the most comprehensive study ever performed in exercise science’s short history. An occasional jog, some activity for mental reasons, playing flag football, or practicing a sport is perfectly OK. There are two ways you can overdo it, either by too much intensity in any given exercise between HIT sessions or by too much volume.

In other words, too much time running or too many days of the week (also known as frequency). Overreaching and overtraining is easier than a lot of people think.

Endurance exercise has been shown to cause muscle wasting or loss of lean tissue in some cases. Think marathon runner versus a sprinter.

For someone trying to lose fat and raise their metabolism, this is not smart exercise. You may burn a few calories doing the activity, but only while doing it. You risk losing the biggest calorie-burning engine in your daily life…your lean muscle tissue which burns far more in a 24 hour period whether you are exercising or not.

For smart exercise application, we want to preserve and increase lean mass to increase metabolism while losing only fat tissue while controlling our calorie intake. The HIT method coupled with calorie control is the way to do this.

Although an elevated heart rate is probably necessary to accompany muscular work, trying to use a formula to get into a steady-state range is a step in the wrong direction.

Recent articles have shown the arbitrary establishment of the Heart Rate (HR) formulas. Specifically the HR=220-Age. This was never scientifically established and the resulting exercise prescriptions may not be effective and in some cases dangerous. In addition, all other tests that rely on heart rate training zone values will be flawed as well.

It is inaccurate, too unreliable, and there is too much variation among populations. In addition, the tools used such as elliptical machines are frequently inaccurate too. You don’t want a deconditioned middle-aged man trying to get his heart rate up higher using a flawed formula and a flawed exercise tool.

What if I told you that science has NEVER proven that aerobics will prevent heart disease or rehabilitate a diseased heart or any other disease or condition? You’d think I was crazy, but only because of what has been drilled into your head for the last 30 plus years. Early on in the research, the authors concluded that people who were more active had less heart disease and it was assumed that it was because of the activity.

That is a wrong assumption and this is what I would call bad science. What happened was that the authors of that research got the cause and effect exactly backward. They used people who chose to be more active so the sample size was filtering itself. Diseased, sickly people are not going to be engaging in much activity. They will self select themselves to jobs and lifestyles of less activity. This happens all the time in corporate wellness programs.

The fit/healthy ones do it, the diseased/sickly ones don’t. This is called selection bias when using a sample of people as subjects to study. It’s like saying playing basketball makes a person tall. Of course, it doesn’t. It’s the other way around. And so began a three-decade-long misapplication of ideas in the form of the “more is better” philosophy. It isn’t better. There is no way to attain super health, but you can improve your general fitness and manage diseases and conditions to a marked degree.

Safety Oriented

As professionals, we are looking for the safest, most effective, and most efficient designs of programs possible to prescribe to clients. Most activities do have some benefits but are usually outweighed by the negatives. Anabolic steroids are probably the best way to build muscle tissue, but overdoing it with them is not a safe option so you can toss it out the window right away.

According to Dr. Ellington Darden, “More than 20 million injuries are sustained each year in the U.S. as a result of sports and fitness activities. To put this number in perspective, 20 million are more casualties than the people of our country have suffered in all our wars to date.

Which activities are the most dangerous?

There is an 86 percent probability of being injured each year if you play tackle football. That’s self-evident because football is a combative sport.

At 83 percent is gymnastics, which seems unjustified until you understand the very high forces involved and the great flexibility required to do many of the competitive events. Following 80 percent is the popular aerobic activity, jogging or running. In the top ten is also aerobic dancing.

At one time, in the high-impact years, aerobic dancing was at the 70 percent level of injury. Introducing the low-impact style lowered it to the mid-40 percent level.

But with the arrival of step classes and the return of high-impact dancing, now called high-energy in many places, the numbers are moving back toward 70 percent”. Not only are these activities not safe, they are not necessary because the body’s systems are so interconnected. It is not more effective or even desirable to break up training into strength and cardio or aerobics. It is entirely possible to combine the two for the most effect.

According to Dr. Richard Lieber, “Since muscle represents about three-fourths of the body mass, a healthy muscular system is usually associated with healthy cardiovascular, pulmonary, and endocrine systems”. Your muscular system is the one thing in your control (trainable) that you can use to elicit the desired response from your body as a whole for improvement.

You may not care about getting stronger, but it is probably the best indicator of improved fitness and health as a whole that we can measure. You can combine your efforts, save time, and not expose yourself to any of the dangerous forces such as the ones described in the activities above. Who doesn’t want that? Isn’t that what we’re all looking for?


How do you expect to improve your body with only two or three exercise sessions per week when everyone else says to do four, five, six, or even seven days per week, 60-90 minutes at a time? The exercise itself is not a good thing as far as the body’s systems are concerned. Again, this is where it went awry with regard to volume. Think about it, you don’t get more fit while you workout so when does it happen? It happens when you are at rest.

Work and rest are of equal importance, it’s just that the rest time is disproportionately long compared to the work. Essentially you have to heal from the severity of the exercise. You can cut your skin in one second, but take two weeks to let it heal. In addition, exercise is stress, nothing more. It makes you breathe heavy, your heart race, it burns, and you want to do all you can to stop it.

How could that be good? It’s not! But the adaptation the body makes as a result of the stress is good.

I suggest someone working out on their own do three days a week. I’ll settle this controversy with a quote from my own exercise physiology professor from college. He said, “Tell your clients to come five or six days a week and you can only count on them showing up three days a week which is all they need”.

That is the wrong approach because it will turn people off immediately to exercise because they think they have to do so much they will never find the time and will never get anything out of less frequency. Time is not an issue at all. Wayne Westcott, who is considered the country’s most respected exercise scientist, and a member of S.P.A.R.T.A.’s Medical advisory board, is an advocate of high-intensity training.

He recently performed a study in which 19 elderly adults performed a five exercise routine twice per week. They averaged 80% greater leg strength, 40% greater upper body strength, 4 pounds more muscle and 3 pounds less fat all in a 14-week span. That’s only 28 workouts total lasting approximately 5-10 minutes. The participants averaged 40-70 seconds per exercise.

So over the whole span of the study, at most, they were actually exercising for approximately 4 ½ hours out of 14 weeks. Dr. Westcott even did a study where the participants only engaged in 3 exercises with similar results. According to Kathryn Luttgens, “Once muscular strength and endurance are developed, they may be maintained with less frequent workout sessions as little as once every week or two provided maximum contractions are used”.

Athletes in a short pre-season phase could do as much as 6 days per week of split routines along with your conditioning to maximize fitness going into a competitive time period, but the average person should not need to do this and probably could not do it for very long.

Train to Fatigue vs. Sets of 10 Reps

Trainees sometimes have a hard time conceptualizing the idea that you have to train to muscular fatigue. Or in other words, you cannot perform another rep in good form. Exercise might be the only thing in your life in which you are trying to fail. Achievement driven people will focus on the actual movement so much so that you may not get the best result possible because you are constantly struggling, wiggling, and thrashing to move the weight.

If it was the movement that made you improve, then we would not need resistance. Think of working up to a high effort level your accomplishment, not mindlessly moving a bar up and down. The fact that your muscles are exposed to something that is unmanageable is what causes the improvement. It is very hard for trainees to grasp sometimes that the very idea of training is to attempt something that you cannot perform and this will, in turn, stimulate improvement.


To try a HIT workout on your own, follow these principles, give it a few weeks and see how you progress. Principles to apply:

  • Select a resistance that allows you to perform an 8-12 rep range. If you can perform more than the prescribed number of reps, continue until muscular fatigue and increase the resistance next time.
  • Use the first couple of workouts to determine appropriate resistances if prescribed amounts are off. Equipment will vary.
  • Train with a high level of effort until no more reps in good form are possible.
  • Exhale as you lift resistance. As the set progresses and heart rate increases, let your breathing increase too. Do not hold your breath during exercise.
  • Use a 2/4 lifting speed. Lift in 2 seconds on the positive and lower in 4 on the negative unless other speeds are prescribed.
  • Accentuate the lowering or negative portion of the rep.
  • Move slower, not faster if ever in doubt.
  • Concentrate on flexibility by slowly stretching comfortably through the first 3 reps.
  • Do everything possible to concentrate on and exhaust each targeted muscle or group.
  • Use double progression. Always try to do another rep in good form or a little more resistance over the last workout. But, stay in position and do not sacrifice form.
  • Record your workout results.
  • Move quickly between exercises to maximize cardiovascular involvement.
  • Employ advanced techniques as needed.





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