Originally published in January 2009 at GroundUpStrength
This article is an attempt to clear up some of the misconceptions on the internet regarding the Bannister’s Fitness-Fatigue Model, the so-called “Dual Factor Theory”. Although it is simply a model it has been used to design one size fits all programs due to a misconception that it attempts to explain training responses for a typical trainee. Such programs are nonsense and a proper explanation is needed to counter such misinformation. Programs are not built from these kinds of theoretical models. These models, instead, are built to try to understand responses to training.
“Single Factor” Model: Supercompensation
The so-called single factor model of adaptation is a post-facto way of describing supercompensation. The idea is that the only factor the supercompensation model considers is “fitness” or preparedness. According to this model, if a stress (training stimulus) is great enough, fitness decreases for a time and then ‘supercompensates’ to return to baseline and then beyond.
While this certainly describes adaptations to training, it lacks explanatory power. If you look at supercompensation in terms of a curve, fatigue, the single factor considered, would cause the downward trending portion of the curve. Then rest and recovery should cause the curve to move upwards to supercompensation. However, the simple removal of fatigue should only cause a return to baseline if nothing else is working on the system.
Bannister’s Fitness-Fatigue model helps to illuminate the previous models and considers fitness and fatigue as two separate factors, thus we have the two-factor or “dual factor” model of adaptation.
Fitness-Fatigue Model for Real
According to the fitness-fatigue model, at any time preparedness is the difference between the positive effects of fitness and the negative effects of fatigue. But since fatigue although very great doesn’t stick around very long we can take advantage of the fitness gained without over-training. Intuitively it has to be this way or you’d never have any apparent progress. What it really means is that it allows us to take advantage of the fact that while the fatigue impulse may be twice as high as the fitness impulse the fatigue decays three times as fast. The fitness gained is still a result of the training impulse. This is a simplified explanation of the fitness-fatigue model.
Models versus Theories
A model is different than a theory. Models are used to understand a particular set of phenomena, but the model’s themselves are too simplistic to be called theories. They cannot predict all of the attributes of a system. The example most often used is the visualization of an atom as a planetary system where the electrons orbit around the nucleus similar to how the planets orbit around the sun. This is an over-simplified model of the atom and is only used to understand some aspects of the atom intuitively. It cannot predict everything about an atom. In the same way, the fitness-fatigue model cannot be expected to predict all of the outcomes of training, as the athlete system is too complicated to be explained so easily.
Fitness-Fatigue vs Supercompensation
How is super-compensation so much different than fitness-fatigue? At its heart, it’s not. You work out (the stressor) and performance decreases. How long performance decreases depends on training status and the degree to which homeostasis was disrupted. But after some period of time, you recover and performance theoretically increases past the point at which you started. This doesn’t go away because we have a fancier model to look at. You workout. You recover. You get more fit.
Earlier theories tend to look at the responses to training as a cause and effect relationship. Such as the SFRA concept (stimulus-fatigue-recovery-adaptation), which bears similarities to Selye’s GAS theory. These theories are supported by observations and it is important to note that these observations are not inherently wrong.
Fitness-fatigue theory or dual factor simply enhances our understanding of this. It doesn’t just consider the response to training but the factors involved and the interplay among them. It views fatigue and recovery as opposing forces rather than having a cause and effect relationship. What we had before with Selye’s GAS theory is simply an initial period of fatigue followed by adaptation. However, the initial fatigue of dual factor is very comparable to Selye’s Alarm Stage. Fitness-Fatigue then views the fitness response and fatigue response as two simultaneous but independent factors.
But the term theory is meant loosely. As stated above what the “theory” really is is a statistical model used by scientists to help predict exercise response. It is not in itself a physiological theory that relates to sports improvement. It is a model that gives rise to a qualitative measurement of exercise response in individual athletes. Banister, et al. proposed this mathematical model in 1975 (NOT Zatiorsky!) as a way to understand the fluctuation of athletic performance throughout periods of heavy training separated by taper periods. It is a way to mathematically model and study the effects of training on an individual by generating fatigue and fitness profiles. The model followed as a way to look at the training; not as a way to plan training.
Theories enable the use of controlled experiments designed to measure outcomes. Calling fitness-fatigue a theory is a stretch by that definition. Others have called the model a paradigm instead of a model, probably in an attempt to cover their own confusion with a bit of jargon.
But let me be very clear about something. As I mentioned above the fitness gained from training is STILL a result of the training stressor. It is not a result of the degree of fatigue. Greater fatigue does not LEAD to greater fitness as has been suggested. This kind of thinking could actually lead to regressions in performance rather than improvements. This is especially true once you consider that increasing the frequency between similar training bouts gives rise to an exponential accumulation of fatigue and a progressively greater and longer duration of fatigue while the fitness response to a single bout goes down. In other words, if a certain amount of work would give rise to a fitness response, adding to that and accumulating fatigue would only lessen the impact of each successive bout past that point.
Disrupting homeostasis to the point that we initiate an adaptive response results in more fitness. But there is more to it that allows us to manipulate our training at various stages of our career.
The model was contrived as a way to study training response and thus maximize training effectiveness for an INDIVIDUAL. It takes into account the fatigue and fitness response of individual bouts as well as long-term response overloading periods and taper periods. It is thought necessary to schedule successive training bouts when fatigue is dissipating in order to maximize the fitness response and to prevent the exponential accumulation of fatigue. Then a taper period is undergone to dissipate any accumulated fatigue. Accumulation of fatigue is not a goal in itself. It is simply that once it does accumulate a tapering period is necessary to realize the full fitness potential of a training period. Training is scheduled according to the needs of the individual athlete and the competitive season.
I stress the importance of the individual because the fitness-fatigue model does not treat all fatigue after training the same. Different things cause different levels and durations of fatigue and fitness. So the two-factor model suggests ways in which we can periodize our training. It is NOT in and of itself a method of periodization. I myself hold on to strength gains for a long period of time. This allows my to organize my training in a different way than those who tend to lose apparent gains in strength quickly.
The training load, total work performed, and training economy changes the magnitude and duration of the after-effects. Different types of work do as well. High volume initiates a much larger and immediate fatigue response than maximal intensity. High volume could be compared to the repetitive-effort days of Westside and maximal intensity to the max effort days. ME days must always precede RE days because of this. For DE days they fall differently depending on the status of the trainee. But from a simple perspective, we can see that the weekly scheduling of a Westside routine will take into account facets of the two-factor model. It is scheduled to minimize accumulated fatigue for the individual. But a taper or deload period may be necessary when fatigue does accumulate, again, according to the needs of the athlete and the competitive season. This is the dual-factor model at work. What you must see is that if the program is sound, the model should help predict responses to it. The model itself does not predict the program. Depending on your goals, it may be better to schedule high-volume days earlier in the training period. Again, the model would predict the results of this scheduling.
At whatever level of training you are, your preparedness is still the difference between fitness and fatigue and the effects of fitness cannot be displayed unless fatigue has dissipated. This is really the central point.
This is true whether you are a beginner or advanced athlete. There is no “single factor training” as such. There is simply effective and less effective ways of training, just as there always have been. The effects of fatigue and recovery, their interplay, become more apparent the more advanced you get.
What is the real primary difference between looking at training in terms of “single factor” or “dual factor”? If you look at it in terms of single factor thinking you do not view fatigue as an independent factor but only consider recovery. Therefore if you fail to make progress your assumption is you did not fully recover. Obvious conclusion? More time to recover. How many people actually work this way? Not many.
Where Did This Idea of Fatigue Accumulation Come From?
I’m not exactly sure but as far as I can tell a bunch of influential “bro-scientists” got together on some bodybuilding boards and ‘interpreted’ fitness fatigue to mean that the more fatigue you can accumulate (via ‘planned overreaching’) the stronger you’ll get. They then came up with a quasi-scientific ‘method’ as to how this could be done. The definition of dual factor or “fitness-fatigue’ itself, I.E. the one developed by some writers on bodybuilding boards is on its surface an advanced periodization method and NOT a definition of the adaptation model itself. The so-called “dual factor program” is simply an aggressive loading protocol given a fancy name.
The idea is that the dual factor theory basically necessitates a long period of peaking fatigue (say 4 to 6 weeks) and then a peak. If you don’t do that you are “using single factor theory”. The developers of these programs think that dual factor has replaced super compensation and has therefore spelled out a superior way of training for every athlete. This is complete nonsense.
In reality, you do not need to load for extended periods until you can no longer make progress during a shorter period. So an advanced athlete certainly cannot always make progress on a workout to workout basis in a realistic manner. This does not mean that it is impossible for apparent progress to occur after one training day, it simply means that, by and large, longer periods of training are needed as we advance. Why this is true is beyond my scope since there are so many parameters that would make different ways of training workout to workout fail for the advanced. And let’s forget all the comparisons to HIT, shall we, that’s a whole other can of worms. Let’s just suffice to say that an advanced lifter can’t make any real good progress on the squat every workout.
So what would be the next step? Logically he would switch to making progress on the shortest time period possible for as long as possible. Instead of making progress every 36 to 72 hours he switches to a week (or 4 or 5 days or whatever). What has this got to do with single factor vs dual factor? Not a damn thing. A lot of confusion has been caused that is causing beginners to jump into advanced programs.
Advanced programs are for the advanced. Quite frankly that excludes most trainees. But those programs take advantage of one of the facets of the dual-factor model of adaptation. Programming and the theory that allows it to work are TWO DIFFERENT THINGS. Regardless, if they work it is because they are founded on experience and knowledge of advanced periodization. If they work it is because they coincide with how the body adapts (the theory) but ALSO because they coincide with the particular athlete’s needs at that time.
The athlete has been referred to as a dynamic machine and never a static model. You know a lot of people don’t realize that you can react to a program one way in one stage of training and later on derive completely different results from that same program because of the state of the “adaptive system” at THAT PARTICULAR phase of development.
Hope that doesn’t sound all “sciency” because it’s not. It’s just the opposite. Science the way it has traditionally been done would have you believe that the athlete IS a static model and that mathematical means can be used to measure adaptation across a population. The fact is that a reliable model can only be developed for a test pool of one.
To say that an adaptation theory tells us there is a superior way of programming for everyone, even among a population of advanced athletes, is to say the same thing: we are static models instead of dynamic machines. But we are not. EVERYTHING changes. The ability to recover changes. The amount of work or stimulus that it takes to create an adaptive response is different for a beginner and an advanced athlete. And pretty much everyone falls in between that. Everyone is not the same.
But the theory does not say this so there is really no conflict. There is no single-factor versus dual-factor. Super-compensation still plays. The GAS model is not incorrect and opposed by the fitness-fatigue model. The program a person should be on still depends on their training status just like it always has. And at each stage of the game recovery must be planned.
A load that is too stressful at any time can overwhelm the recovery process resulting in the need to re-plan recovery. This process doesn’t change for the beginner through advanced athlete. Only the time periods involved and the degree of the stressor needed does. The physiological process of adaptation is basically the same. Training gives rise to simultaneous fatigue and fitness manifestations and at any time preparedness is the difference between those two forces.
Much too much has been made of the dual factor theory for the average trainee looking to increase his strength and performance. It is the province of scientists looking to understand human performance and adaptation and it is not the only game in town. We can look at the concept and learn things about training but the idea of a bunch of coaches or trainers sitting around coming up with “dual factor programs” is just ridiculous. If you have been influenced by any of these so-called dual factor programs floating around the internet then you are basically looking at a sledgehammer being promoted to hammer a nail. Don’t fall for it.