Track Coach

Confusion vs. Habituation

By Jason R. Karp, MBA, PhD

Excerpted from Jason Karp’s new book, Running Periodization: Training Theories to Run Faster.

Legend has it that the ancient Greek wrestler Milo of Croton trained by carrying a newborn calf on his shoulders every day until it grew into an adult bull. This training enabled Milo to become one of the strongest men around and win six Olympic titles. While Milo probably didn’t articulate to the curious onlookers that carrying a growing bull on his shoulders around town was an example of progressive overload, this training theory became the basis for developing muscle strength.

Because a calf grows slowly into a bull, it wasn’t every day that Milo lifted a heavier animal than the day before. The training stress didn’t drastically change from day to day or even week to week. Milo’s muscles had time to adapt to the animal’s current weight, slowly progressing to heavier and heavier weights as the animal aged.

Many years later, in 1950, Hungarian endocrinologist Dr. Hans Selye discovered that laboratory animals exposed to various stressors, like drugs, cold, or surgery, and individuals with various chronic illnesses, like tuberculosis and cancer, display a common set of symptoms and pattern of responses. From his observation of the stress response pattern, Selye developed the General Adaptation Syndrome, which represents the chronologic development of the response to stressors when their actions are prolonged.

Selye discovered that giving a rodent a small dose (one-quarter) of an alarming/toxic stressor (e.g., drugs, cold, exercise) prior to a full, alarming dose of the same stressor protected the rodent from the alarming/toxic dose. Applied to a runner’s training, introducing a small dose of a specific type of workout is beneficial for adaptation before introducing a larger dose. Selye also discovered that an organism appears to possess a finite amount of “adaptation energy,” with adaptation to a specific stimulus decreasing resistance to other stimuli. As Selye described, “…anything to which adaptation is possible eventually results in exhaustion, that is, the loss of power to resist.”

Using different types of workouts (e.g., aerobic, anaerobic, intervals, strength, power, etc.), training introduces a variety of unique stressors. How your athlete’s body reacts and adapts to those stressors determines the amount of work that he or she can tolerate, how much he or she can adapt to other types of workouts at the same time, and, pure talent notwithstanding, how much he or she can progress. Following a training stress, the athlete’s body adapts and physiologically over(super)-compensates, so that when the same stress is encountered again, it doesn’t cause the same degree of physiological disruption. In short, the athlete’s body adapts to be able to handle the stress. Following the adaptation, he or she can do more physical work. The aim of training is to introduce training stimuli in such a fashion that greater and greater levels of adaptation are achieved while avoiding exhaustion (and, ultimately, until your athletes’ genetic potential is reached, if so desired). A fundamental understanding of stress and adaptation is imperative to fully understand how and when to prescribe different amounts and intensities of training.

After repeated or prolonged presentation of a specific stimulus, your athletes become habituated to it, and their bodies decrease their response to that stimulus. Confusion, on the other hand, keeps their bodies guessing by constantly varying the stimuli.

Variation is an important concept in training. It’s important to manipulate training parameters, such as intensity and volume during the training process. Variation of training, which is the cornerstone of modern training theory, alters the expression of genes that results in greater adaptation. However, if you vary the training too much that your athletes’ adaptation energy is too widely distributed across many fitness targets, their ability to adapt diminishes and they can stunt their progress.

Conversely, focusing on a single aspect of fitness at a time with repeated training stressors can induce rapid improvement in that single target, but if your athletes prolong such a concentrated focus, that can result in unremitting monotony, staleness, and overhabituation. Doing the same training repeatedly can blunt expression of key molecules involved in endurance adaptations, which can result in stagnation.

While “confusing” your athletes’ bodies can be useful to avoid plateaus in fitness and performance, variation in training must be scheduled, organized, and carefully controlled—enough to avoid monotony and overhabituation, but not too much to avoid inadequate adaptation.

Variation to cause confusion must be balanced with mastery of the skill. On one hand, you must vary your athletes’ training often enough to adapt and improve fitness, while, on the other hand, they must repeat the same training a number of times to master the volume and intensity (or to master the skill of a specific type of workout) so they can progress with their training, having each workload build on what came before.

The Confusion-Habituation Balance

And therein lies the secret behind the stunning success of smart training.

That secret is the Confusion-Habituation Balance.

It is in the Confusion-Habituation Balance that makes every smart training plan work.

It is in the Confusion-Habituation Balance that every successful runner builds his or her future.

Too much confusion or too much habituation won’t work.

Confusion and habituation must be balanced.

But, the Confusion-Habituation Balance is not a perfectly balanced see-saw.

The Confusion-Habituation Balance should be slightly unbalanced in favor of habituation.

That’s because habituation, a learning process that leads to mastery of a skill or workload, is a more effective training method than confusion, as long as the same stimulus is not repeated for too long that the physiological response begins to decrease.

Habituation leads to mastery. But only if the skill or workload is practiced. Over and over and over again. Like practicing the piano or practicing a golf swing. Over and over and over again.

Although the act of running is more physiologically-based than skill-based, mastering a given workload is a skill that is learned through physiological adaptation.

Give your athletes enough time to absorb and adapt to the training before changing it. For example, 40 miles per week should become a normal experience for your athletes’ bodies before increasing to 50 miles per week. Change the stimulus just as habituation occurs so that they continue to increase their response.

Like Milo of Croton, most runners would benefit from changing the training stimulus every four to six weeks (if your athletes run nearly every day; longer if they run a few days per week).

For example, if focusing on running volume, rather than increase mileage from 30 to 40 to 50 to 60 miles per week each week, use a pattern like 30-30-30-20-40-40-40-30-50-50-50-35-60-60-60 miles per week. After a few weeks at a higher volume, reduce the volume for a week so your athletes can recover and absorb the previous few weeks’ training, and then increase the volume again. Although they may still run at the same pace at the higher volume, the increased workload serves as confusion and necessitates a physiological response, at least up until they reach their genetically-determined response ceiling.     

Sustained Volume

Once your athletes reach a higher level of mileage, have them stay there for as long as they can. Sustained volume over time, rather than a short period of higher volume, is what makes them better runners, both physiologically and biomechanically. Physiologically, sustained higher volume leads to habituation and mastery of the training workload. The adaptations achieved—mitochondrial density, capillarization, running economy—stick with your athletes and become part of them. Biomechanically, sustained higher volume also leads to habituation and mastery of the skill. It optimizes movement patterns, which results in a more efficient application of muscle force and greater propulsive forces, and causes changes to running mechanics that can reduce the risk of injury. It takes years of sustained higher volume for its benefits to be fully realized.

Of course, endurance training is more than just about habituating to higher and higher doses of volume.

Endurance training is also about intensity and volume of intensity.

Your athletes need to habituate to those variables, too.

Once they have reached the volume you plan for them to reach in your current training plan, change the intensity.

But, don’t change it too much.

Change it just enough.

Then, have them habituate to it by repeating it for a few weeks. Over and over again.

Then, change it again.     

That’s the secret of the Confusion-Habituation Balance.

By balancing habituation with confusion, your athletes will become more skilled, accomplished runners. Their progress will be more consistent, and perhaps they’ll even be able to challenge Milo of Croton to a wrestling match.   

Few coaches are able to combine the knowledge of the science of human physiology with the art of coaching that Jason Karp brings to the table. He is a practicing coach, exercise physiologist, author of 12 books and more than 400 articles, speaker, and educator. He is the 2011 IDEA Personal Trainer of the Year and two-time recipient of the President’s Council on Sports, Fitness & Nutrition Community Leadership award. His REVO2LUTION RUNNING™ certification has been obtained by coaches and fitness professionals in 25 countries. Follow him @drjasonkarp on social media and learn more about his women’s specialty run-coaching company, Kyniska Running at