Intensity, intensity, intensity…the higher the better! Higher intensity means faster results! If you’ve been paying attention to the world of performance training in recent years, it’s a safe bet that you’ve seen this mantra repeated ad nauseam in countless articles, discussion forums, books, etc. It’s actually becoming difficult these days to find a training related article that doesn’t involve some discussion of the purported benefits of high intensity training.

Research showing greater results in less time from higher intensity methods is often pointed to as the evidence of the efficacy the high intensity training methods so frequently advocated in such discussions. In fact, everyone from research scientists, to CrossFitters, to the celebrity trainers seen on late night infomercials seems to agree that the secret to maximum results in minimum time is higher intensity.

Given this rather broad consensus and the unavoidable frequency of the high intensity message, it’s not difficult to see why so many athletes and fitness enthusiasts alike have replaced their miles with interval sprints and are flocking to high intensity programs like CrossFit. As Americans, we love to believe in the shortcuts, “get rich quick” schemes, and the promise of getting in the best shape of our lives with just twenty minutes of hard work.

Unfortunately, the harsh reality is that I don’t know anyone who has ever gotten rich from a get rich quick scheme. I doubt you do, either. I also don’t know anyone who has reached the peak of performance with only twenty minutes a day of hard work. I’m going to let you in on a little secret and show you why all of the “experts” out there preaching the high intensity message generally don’t understand the big picture of training.

I’m also going to discuss why their recommendations can often do more harm than good and how they can be keep you from reaching your fitness potential and performance goals. The principle of training that I’m going to discuss along the way is one of the most important you will ever learn, so let’s get started…

From the beginning

The best place to start this discussion on intensity is with a brief discussion on what training is really all about it in the first place. Getting caught up in all the details of training, it can be easy to lose sight of the big picture and forget that your body doesn’t care if you have big or small muscles, a high or low bodyfat percentage, or how many pull ups or kettlebell swings you can do. The only thing your body really cares about is its own survival.

On the most fundamental level, it is this innate drive of the body to stay alive and maintain equilibrium within all of its many systems that creates the opportunity for performance and/or physique improvements to be made. Adaptation to various training stimuli is nothing more than the body’s defense mechanisms at work, plain and simple.

You place a stress on the body by lifting weights, doing some form of cardiovascular exercise, etc., and the body in turn responds to this stress by adapting to it so that it is better suited to handle this stress the next time. The exact adaptations that take place, of course, depend on the specific type of training stress that you put your body under, but the end result is the same. The next time you train, the body is now better equipped to meet the physical demands you are placing on it.

Because of the body’s increased preparation, the same level of training now presents a relatively lower level of physical stress on the body and the body’s defense mechanisms will not be called into action like before. In order to continue to see results, you inevitably have to place a greater stress on the body to once again force it to respond by adapting.

This process of repetitive stress and adaptation provides the underlying foundation for improved performance as well as general health and fitness. And it is this incredibly adaptability of the human body in response to physical stressors that keeps us all alive in the first place.

What is Intensity?

In the context of training, the term “intensity” is generally accepted to represent a relative gauge of how hard you are working. Regardless of the specific exercise or activity you may be doing, higher intensities are closer to your maximum effort and lower intensities are, of course, a lower percentage of your capabilities. Running long distances at a slow pace, for example, is considered a low intensity effort, while interval sprints are high intensity because you are running at speeds much closer to your maximum effort.

While this simplistic definition of intensity is generally well accepted and understood, I think it doesn’t really paint the whole picture very accurately. A much more accurate way to think of intensity is not just as a gauge of relative effort, but rather as a gauge of the amount of stress imposed on the body.

Higher intensities represent a larger stress being placed on the body. The higher the level of stress, the greater the disruption of the body’s equilibrium and thus the more marked the body’s adaptive response will be.

In other words, the body perceives greater stress as more of a threat to its survival and will therefore adapt to it faster. In a nutshell, this simple principle is the reason why everyone has been jumping on the high intensity bandwagon in recent years. Higher intensity does, in fact, lead to faster results.

The Intensity Threshold

Given my last statement above, it would seem all the “experts” have been right. After all, you want the fastest results possible, so why not just train with the highest intensity? Although this idea may sound logical at first, the answer to this question becomes rather obvious if you take a step back for a minute and look at the big picture of training, intensity, and adaptation that we’ve discussed so far. Once you do this, you’ll find there are several reasons higher intensity is not always the answer it might at first appear to be.

First, it’s important to recall two points discussed above: 1) Adaptation to training only occurs when the body’s defense equilibrium (homeostasis) is disturbed and 2) each time the body adapts it becomes better equipped to handle the same level of stress. Taken together, these points make it clear that there is a certain level of intensity required to see improvements (adaptations to training) and that over time, this level rises. This level of intensity is known as the intensity threshold.

The concept of the intensity threshold is an important one because it offers valuable insight into why our progress inevitably slows the more we train. As a beginner, I’m sure you can remember how quickly the results came. Strength improved almost overnight, aerobic fitness seemed to be better with each workout, muscles were built and/or fat was lost easily, etc. When someone first starts training, it all seems easy and everything works.

Unfortunately, most people quickly find out that training isn’t always like this and sooner or later, the rapid improvements slow down dramatically. Now, instead of improving your lifts by 20-30lbs in just a few workouts, you’re lucky to do it in a few months. Sooner or later, the results even feel like they’ve stopped coming at all. This is what most people refer to as a plateau.

Although everyone who has trained for long enough has hit training plateaus, few realize that what really happened is that as they trained, their intensity threshold was getting higher and higher until finally the stress imposed by their training program was no longer enough to cross it. In other words, their workouts no longer had much of an impact on the body and thus the body had no reason to adapt and improve.

Obviously, the longer you can keep this from happening, the longer you will continue to see improved results from your training efforts. Rather than hitting plateaus and seeing your progress grind to a halt, you will instead see steady improvements because your body is continuing to adapt to the stress level imposed by your workouts. The key to ensuring this happens lies in understanding the real difference in intensity and designing your training program accordingly.

A Difference in Intensity

By now, you may be getting the idea that the other side of high intensity training that you aren’t seeing the “experts” out there talking about relates to the intensity threshold. You see, while it is true that the higher stress levels imposed on the body from higher intensity training compared to lower intensities do produce faster results, they come at the cost of raising the intensity threshold much faster. Ultimately, this means that the improvements you see from high intensity methods are much shorter lived and you will plateau much faster when using them.

This principle makes sense when you consider the previous discussion about the body’s response to the stress of training in the first place. The higher the stress level, the greater the perceived threat, the more the body’s defense mechanisms kick into action and the greater the resulting adaptations. Because of this, the body is now prepared to handle this higher level of stress and your intensity threshold has been subsequently raised to a much higher level. If your training program no longer crosses this higher threshold, your progress will quickly stall.

This governing principle of how the body works provides the foundation for the most important piece of training advice you’ve probably never been given: always use the lowest intensity necessary to stimulate adaptations to training. Yes, contrary to what many of the so called experts in the field out there are preaching, I am advocating the use of the lowest intensities that you can use that will get the job done. Use intensities higher than necessary and you are sacrificing your long-term development for short-term gains.

Unfortunately, this is exactly what is happening in gyms and training centers all over the country. Following the advice of the latest magazine article or CrossFit Journal about the magic of high intensity, athletes and fitness enthusiasts alike are racing to use the most advanced and most intense methods they can find. Beginners are doing 1-3 rep maxes for training, fighters are foregoing age-old roadwork for sprints and Tabata intervals, and boot camp classes have exploded all over the US in recent years.

This approach, however, is very shortsighted and founded in marketing hype and selling products, articles, and programs. Ironically, much of the very same science people are citing to support their high intensity advice actually demonstrates how short lived the results can be! Even the now famous Tabata research comparing the effects of high intensity interval sprints to lower intensity methods tells a different story than you’ve likely read.

The Research

If you examine the Tabata research that is so often pointed to as the holy grail of high intensity training in greater detail, it becomes clear that the higher intensity (intervals) group did, in fact, see almost all of their improvements within the first 3 weeks of the study and then their results slowed dramatically. According to the study itself, “After 3 wk of training, the VO2max had increased significantly by 5 ± 3 ml·kg-1·min-1. It tended to increase in the last part of the training period, but no significant changes were observed.” This means they basically spent half the study training without seeing any significant improvements in VO2 max from their high intensity intervals. Not to mention that they started with relatively low VO2 maxes to begin with, so it should have been easy to see steady improvements for 6 weeks.

The lower intensity group, by contrast, saw slightly less improvement in VO2 max, but the gains were steadily seen throughout the entire 6-week duration. It should also be pointed out that the gains in VO2 max between the high intensity and low intensity groups were not nearly as dramatic as people like to report and at the end of the study, the low intensity group still had a higher average VO2 max than the high intensity group. It’s also worth noting that the high intensity group actually included 30 minutes of low intensity cardio each week, though this is almost never mentioned in articles.

I could go on, but I think you get the idea that research is often extrapolated well beyond its original limitations and used as a marketing tool without being fully understood by those referencing it. The majority of research out there is done over fairly short periods of time, often 6 weeks or less, and fails to take the big picture of long-term training into account. Most serious athletes and fitness enthusiasts train year round, not just 6 weeks at a time.

Recommendations

Regardless of whether you train for a sport or just want to stay in shape and be healthy, the most important part of reaching your long-term goals is having the right plan. By now, I hope I’ve convinced you that having the right plan means looking at the big picture of training when it comes to intensity.

Rather than jumping on the high intensity bandwagon and sprinting before you’ve even tried jogging, the most important thing I hope you take away from this article is that intensity is a powerful tool that must be wielded wisely. Too much intensity, and you may see quick results, but they will come at the expense of long-term gains. Of course, you may end up overtraining as well, but that’s a whole other discussion for another time.

Too little intensity, on the other hand, and your efforts will not be rewarded with the progress you are looking for or could be achieving. The real key to long-term success is using the right amount of intensity at the right time. The best way to do this is to constantly examine the intensity you are using and the results you are seeing and make adjustments as necessary.

If you’ve been using the same training program for 3 months but haven’t really seen any changes in the last 6 weeks, it’s probably time to up the intensity. If you’re a relative beginner to training or getting back into it after a long layoff and you feel like you’re going to die during each workout because you’re practically killing yourself, it’s probably a safe bet you’re doing too much.

Save the more advanced methods and the higher intensity training until you really need them. Using them prematurely is a huge waste of their effectiveness and will inevitably short change your development. Far too many people hit plateaus far too soon in their training because they were in such a hurry to see results that they used far more intensity than necessary.

If your goal is to increase your vertical jump, you don’t need to be doing depth jumps off a 48” box or deadlift for single reps, especially if you’ve never even squatted before. If you just want to get in the best shape you can and improve your general health, you don’t need to be sprinting until you feel like you’re going to pass out or try to find out how many times you can swing a kettlebell before you feel like you want to throw up, especially if you can’t even jog a mile.

The take home lesson is that higher intensity is only better when it’s what you need to continue improving. Anyone who tells you otherwise is most likely trying to sell you something.