Fatigue Masks Fitness! - Back to Basics of Strength & Conditioning Pt. 2

In part 1 of the Back to Basics (B2B) series, we reviewed the concepts of General Adaptation Syndrome and the Stress, Recovery, Adaptation cycle. To recap, Dr. Hans Selye observed a phenomenon in organisms which he called General Adaptation Syndrome (GAS). Organisms attempt to adapt to a stress, such that it can withstand the stress at a subsequent exposure. There is a range of stimulus that needs to be applied to generate a stress, followed by a requisite amount of recovery, needed for an organism to adapt. Imposing too much stress with little recovery over prolonged periods of time will lead to the exhaustion stage of GAS, where the organism's resources become depleted, which can result in systemic or chronic fatigue, suppressed immune response, burnout or worse.

From the perspective of Strength & Conditioning or Health & Fitness, the goal of training is to recover from stress by spending enough time in the resistance stage to drive adaptation and achieve a new level of fitness, but not so much time that we enter the exhaustion stage. Moreover, we can think of stress and stimulus as two sides of the same coin; if each training session delivers a stimulus, we can think of stress as the individual's biological and psychological response to the stimulus, so the terms stress and stimulus will be used interchangeably. The process of repeatedly exposing a person to stress, allowing them to recover, and eventually adapt is known as the Stress, Recovery, Adaptation (SRA) cycle. See Figure 1 below.

Figure 1: Stress Recovery Adaptation Cycle + General Adaptation Syndrome

The next concept that we will cover in Part 2 is the Fitness-Fatigue Model (FFM). While GAS and SRA provide a general overview of how people adapt to training stress, the FFM provides the lens through which we can further evaluate and develop training plans to achieve health & fitness goals.

THE FITNESS-FATIGUE MODEL

Figure 1:  The Fitness Fatigue Model - Conceptual

All training stimulus produces a certain amount of fitness and a certain amount of fatigue both acutely and over the duration of a training cycle, and across multiple macro cycles. For example, if you did barbell back squats for a set of 10 reps with 2 Repetitions in Reserve (RIR), i.e. 10 reps at your 12 rep-maximum, intuitively you know you probably cannot repeat the same weight for the same repetitions at the same level of effort and movement quality with just 30 seconds of rest. However, you may be able to repeat that same weight for a set of 10 at 2 RIR with similar technique after 5 minutes of rest, depending on how trained you are in that specific task. Over time, you will be able to increase the amount of weight you can do for 10 reps with 2 RIR, although it may not occur as fast as you like.

The Fitness-Fatigue Model (FFM) is an expression of what you know intuitively from the example above. It is a two-factor model which correlates Performance (P) to Fitness Potential (FP) and Fatigue (F) as follows:

P = FP - F (Equation 1)

Where the variables are defined as follows:

Fitness Potential (FP): The absolute physical capability we develop through training over time. The longer we effectively train, the more fitness potential we can accumulate up to our maximum genetic limit, all else being equal. While most texts simply refer to this as Fitness, I prefer "Fitness Potential" because it is very difficult to express one's full capabilities, as we are always carrying some amount of fatigue, and external factors need to be near perfect for full expression. Furthermore, for sports requiring high technical prowess at maximum intensities, being in a zero fatigue state can lead to technical decay, which in turn decreases fitness. Also, I needed an easy way to differentiate fitness from the the next variable, fatigue.

Fatigue (F): In addition to Fitness Potential, training also generates negative acute training effects which hinder our ability to express fitness. This negative effect is generally called fatigue, but can be comprised of multiple and or compounding negative effects. If fatigue accumulates beyond the ability to recover or dissipate fatigue, then a state of chronic fatigue or stress may be reached where performance is severely impacted. Further accumulation of this fatigue leads to the Exhaustion stage of GAS which can have negative effects beyond just performance degradation.

Performance (P): Performance is the ability to express Fitness Potential. In the classical definition, Performance is Fitness minus Fatigue; hence the saying "Fatigue Masks Fitness." In actuality, there are other factors that come into play which impact the ability to express fitness. One factor is the technical decay as mentioned in the definition of FP above. However, many other factors can impact performance such as the environment, time of day, altitude, equipment issues, general life drama, etc., which can all detract from one's ability to express theoretical Fitness Potential. This "X" factor is difficult to quantify in practice, which is why the classical definition is usually what's referenced in Equation 1 above. However, I DO think it's important to point out that there ARE external factors which can also mask fitness, and so this factor "X" has been added into Equation 2 below. X would be some value between zero and 1, with zero being the worst possible conditions and 1 being absolute perfect conditions.

P = (FP - F) * X (Equation 2)

Using Equation 2, if all conditions are perfect, then Performance is simply Fitness Potential minus Fatigue as in Equation 1. As conditions become less ideal, then Performance decreases as X goes from 1 to zero.

Performance is the ability to express Fitness Potential. In the classical definition, Performance is Fitness minus Fatigue; hence the saying "Fatigue Masks Fitness."

GENERAL APPLICATION OF FFM

While it would be great if we could just plug numbers into an equation to predict performance, things like Fatigue and the X factor noted above are not something that can be directly measured. Furthermore, the same exact training stimulus will generate different amounts of stress and fatigue for different individuals. To further complicate matters, exposing the same individual to the same exact stimulus at different points in their training career can also generate different amounts of stress or fatigue, because that individual is not the same person they were the first time they were exposed to said stimulus.

So, does this mean we should throw our hands up and just do nothing? Not necessarily. While we can't directly measure fatigue or the X factor, we can quantify the stimulus, measure performance, and obtain feedback from the athlete regarding symptoms of fatigue. Further, we can assign fatigue or stress values to a given training stimulus, and adjust future training based on the athlete's response, which is way beyond the basics and won't be covered in the B2B series.

ACUTE APPLICATION OF FFM

Going back to the squat example above, during the first working set, if you did a set of 10 at your 12 rep-max, your Fitness Potential (FP) for that specific training session was 12 reps at some amount of weight, lets just say 135 lbs. Due to the Fatigue (F) accumulated from that working set, you may only be able to repeat that effort, i.e. 135x10 with 2 RIR for one more set after 5 minutes of rest. Any subsequent sets of 135 lbs. may not be for 10 reps with 2 RIR, they may be for 1 to 0 RIR or you may not even get to 10 reps depending on how trained you are at this task and depending on your fatigability. This would be an example of acute Fatigue, and should dissipate relatively quickly, as in several days, if the rest of the training for the week is programmed reasonably.

Figure 2:  The Fitness Fatigue Model - Acute

LONG-TERM APPLICATION OF FFM

FFM is very useful in evaluating and developing training plans for long-term development. Rarely, if ever, does fatigue reach zero without the associated fitness adaptation also decreasing. This means, in order to get faster or stronger, get bigger, go further, or go longer, you will always have to carry some amount of fatigue. The Fitness-Fatigue Model helps to illustrate why "deloads" or reduced periods of training are important, and why other fundamental approaches to training like "Periodization" become more important the more trained an individual becomes.

Figure 3:  The Fitness Fatigue Model - Long-Term

It's important to note that while performance increases over time, so does the accumulated effect of fatigue. Within any given week or cycle, the task-specific fatigue will vary along with task-specific fitness potential. Moreover, if we are trying to train multiple fitness qualities concurrently, fatigue from one goal can overlap with that of another. Going back to the original example, if the person back squats 135x10 with 2 RIR for multiple sets on Monday, they may not be able to repeat this effort on Tuesday or Wednesday. If the person is not training to develop other movements like the barbell deadlift, or qualities like a faster mile time, they may be able to repeat or improve by doing 140x10 with 2 RIR on Thursday for multiple sets. If the person is training other movements or qualities concurrently with the back squat, then they may not be able to repeat or improve on this performance until the following Monday.

While you may be able to dissipate enough fatigue from week to week, to obtain increased fitness potential and performance, you likely won't be able to do this in perpetuity due to the increased stimulus and stress required to keep driving adaptation for several reasons:

1. Adaptive resistance

2. Overreaching or overtraining

   
   

Adaptive resistance in this context is the body's inability to derive further adaptation from a given training stimulus, which will be covered in more detail in Part 3 when we review Progressive Overload. Overreaching and overtraining are essentially different stops on the Exhaustion stage of General Adaptation Syndrome.

OVERREACHING AND OVERTRAINING

As previously stated, every training session generates some amount of fitness and some amount of fatigue. The amount of fitness and fatigue you carry can be thought of like the rolling balance in your checking account. Let's say the amount of money in your account is your fitness potential, your pay check and other deposits are training sessions, while all the things you need to pay for day-to-day and regularly are acute doses of fatigue. The amount of money in your checking account is always changing, and ideally, your rolling balance is increasing over time until you achieve a new level of financial fitness where you can save or invest more money, while still maintaining a similar rolling balance in the account.

When the accumulated fatigue outpaces your rate of fitness potential, performance begins to suffer as you are no longer able to train as intensely. The magnitude of how much fatigue has outpaced fitness potential will determine how close you are to the exhaustion stage of GAS. If you are in an "overreached" state, you should be able to lower the stimulus/stress for a few days or weeks, performance returns and hopefully improves to a level not previously achievable. When performance returns to baseline, it is generally referred to as "non-functional overreaching." Conversely, if performance returns to a higher baseline, this is generally referred to as "functional overreaching." If the magnitude of fatigue generated from training is so high that we return to a lower baseline and continue to regress, then we have reached a state of "overtraining" which represents our last stop in GAS. Don't worry though, just because you are overtrained doesn't mean you are going to get sick or worse, but it does mean it will take a while for you to get back to your previous levels of performance.

Going back to the bank account analogy, overreaching would be like going negative in your checking account and having to pay some overdraft fees. Hopefully, you learn from the experience and find ways to make sure that never happens again, leading to an increase in your financial fitness. Overtraining would be like if you go negative in your checking account, max out all of your credit cards, take a second mortgage to pay off predatory loans, and eventually file for bankruptcy. While you may be able to reset your life and pay for basic needs afterward, it may take years before you are able to enjoy previous levels of financial fitness.

PUTTING IT ALL TOGETHER

Whether you are new to training or an elite athlete, the Fitness Fatigue Model provides a lens through which we can evaluate and develop training plans to achieve health & fitness goals. If you are hitting a wall or a plateau in training, you can troubleshoot using the concepts provided above and in B2B Part 1. For example, if performance is decreasing but you are getting sufficient calories, nutrients, and sleep, it may suggest that the amount of fatigue being generated during training is outpacing the fitness potential you are able to obtain from the current training stimulus, i.e. your program. So then, how do we plan training programs to ensure fatigue doesn't outpace fitness?

To find out, stay tuned for Part 3!