Training Adaptations—Fitness Fatigue Model

By: Josh Bryant

Meeting of the Minds at an Undisclosed Location

As a teenager I remember this 35-year-old bodybuilder we will call Jimbo who lived in his van. This cat was a total disaster and did 70 sets per body part in training; “Two sets for each year” was his mantra and at 14 years old, I could think of 70 reasons this would backfire.

But, one day one, a faithful member of Arthur Jones’ flock preached the low volume HIT gospel to Jimbo.  

Over the next eight weeks, Jimbo gained substantial size!

 Jimbo did not realize this was simply because supercompensation took place by a de facto reload.

After this eight-week period, the gains ceased due to insufficient stimulation and because supercompensation from overtraining was no longer a factor.

Poor Jimbo, who in this short time became a full-fledged HIT Jedi, flew the HIT coop and like Moses had a glimpse of the promise land but never got to enter.

How did this happen?

The GAS Principle— not to be confused with the result of binge eating tacos at your favorite Tex-Mex joint.

Josh discusses periodization  

General Adaptation Syndrome, or GAS, is a single-factor model that describes your body’s short-term and long-term response to stress.

Josh discusses the Grandaddy Laws

GAS is the foundation for periodization and one of Dr. Fred Hatfield’s Seven Granddaddy Laws.

Simply stated, if stress (training stimulus) is great enough, fitness decreases for a time and then “supercompensates” to its original state, then beyond.

The Fitness Fatigue model is an expansion of GAS.

The Fitness Fatigue is a two-factor model of training and looks at the aftereffect of a training stimulus.

For example, let’s say you increased thigh mass from a cycle of heavy squats.

The gain in mass is the fitness component. The fatigue effect is the short-term after effect from training stressors; multiple sets of heavy squats caused fatigue.

Significant delayed onset of muscle soreness (DOMS) is one example of fatigue. Legendary sprint coach, the late Charlie Francis, at his seminars used to say that the CNS is like a cup of tea that you must never let overflow!

Every single stressor, whether it’s personal problems, interval training, power drinking, weight training, perpetual left swipes on tinder or lack of sleep, adds tea (in this case fatigue) to your cup. If the cup of tea (fatigue) does not overflow but is adequately stressed, supercompensation (fitness) takes place.

Strength Training

When it comes to pounding the pig iron, volume is a product of poundage lifted multiplied by repetitions multiplied by sets.

Stanley, a local debt collector by day and exotic dancer by nightfall, has a 400-pound bench press max.

Theoretically, Stanley executes three different bench press workouts; session number one is 300 pounds x 3 x 8 sets, resulting in more neural adaptations; session two Stanley does 300 pounds x 8 x 3 sets, a more hypertrophic response is induced; and finally, Stanley does 100 pounds x 24 reps x 3 sets, this is active recovery.

An active recovery/flushing workout can immediately increase fitness, without fatigue. All three of these set-and-rep schemes 7200 pounds of volume, BUT each workout has a totally different training effect.


The GAS Principle looks at total volume as the primary variable to influence fitness response from training, the Fitness Fatigue model expands on this by considering total volume and the intensity/magnitude of the training stimulus.

Squatting 1,000 pounds for a single ain’t the same as 100 pounds for 10 reps, even with total volume being the same!


Each individual training and lifestyle variable is independent of the others, but their total summation equates to total fatigue produced and fitness gained. If too much fatigue is produced, over time, a cumulative “snowball” effect takes place. 

Initially, this is overreaching, which can catalyze fitness gains during a period of deloading; but, if it goes beyond overreaching to overtraining, it can take months to recover.

Final Thoughts

No one has ever run a four-minute mile and bench-pressed 400 pounds!

Training needs to be purpose-driven and focused on specific goals so specific fitness and fatigue adaptations don’t fight against one another; instead, they concurrently merge for your success.

Before a major contest in track and other sports, athletes taper off training volume to peak at the contest. This idea is the delayed training effect and, in a way, is the whole premise behind the Fitness Fatigue model.

After stressful training, a period of lower volume and less intensity (deload/reload) is required for optimal performance. Remember, the same applies to you, as a bodybuilder, powerlifter or tactical athlete.

To gain the positive fitness effects after a period of stressful overreaching, a reload is called for to eliminate fatigue aftereffects and for you to get the gains you deserve from hard training.

In 1995, in his book, Science and Practice of Strength Training, Vladimir Zatsiorsky stated that in a workout of average intensity, the fitness effect endures roughly three times longer than the fatigue effect. That means, if the fatigue aspect from a training session dissipated after two days, fitness gains will persist for six days.

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