Understanding Reversibility: If you don't use it, you lose it

The following post is the third installment in a five post series called “Understanding The Principles Of Fitness”. This post concerns the principle of Reversibility. Previous posts address Adaptation and Progressive Overload, and Specificity. Future posts will address the Principles of Variability, and Individuality.

Last week, I was working with a client who had taken a few weeks off of training for a holiday. Shortly thereafter, she got sick with a cold, which also put her back in her training schedule. When she finally was able to return to training with me, she was shocked at how hard everything felt and how much more winded she was becoming at exercises that had previously felt much easier.

”How can this be? I’ve only been gone 4 weeks? Why do I feel like I am starting over completely?”


I assured her that, while it might feel like she was completely starting over, this wasn’t the case. But I also had to explain that if she was feeling like her fitness had taken a pretty big step backwards, it was because it had.

In fitness, we talk an awful lot about progression, and about how we get stronger, faster, and more powerful when we train with regularity, consistency and intensity. However, we don’t always take the time to explain that the opposite is also true.

Of all the hard to swallow health pills there, the hardest one is very likely: if you don’t use it, you lose it. In fitness, we refer to this as the principle of reversibility.

In order to fully understand how reversibility works, it is first important to distinguish the necessary component of recovery from the less necessary and often harmful components of inactivity/ de-conditioning.

When the body trains, the muscles undergo damage. Don’t worry, it’s not a bad thing and the body is well equipped to deal with this damage and rebuild itself. As we saw in the post regarding progressive adaptation, this is actually a fundamental aspect of growth and it is the process of healing that actually allows us to grow stronger, faster, more powerful and more flexible.

Ensuring you get enough sleep can be a critical component of your training program.

Ensuring you get enough sleep can be a critical component of your training program.

Fundamental to understanding this process is the principle of recovery, or the period of time in which the body is at rest and able to focus its energy on rebuilding the damage done to the tissues. Recovery can take several forms, the most meaningful of which is sleep. (Yes, sleep is actually critical to your fitness and health goals. We will talk more about that in a future post!). Recovery can also be passive, where you take an entire day off of training altogether, or active, where you engage in lower intensity activities that are not designed to inflict significant additional damage to the working tissues. Failure to allow an adequate amount of time for tissue recovery can lead to serious health conditions, including over training syndrome,

Recovery is a fundamental aspect of fitness training, and absolutely critical to improving your over health. However, there is a relatively thin line between recovery and de-training. De-training occurs when we take prolonged breaks from our regularly training routines. This can happen as the result of an illness or injury, or just because life sometimes takes us out of the gym for a few weeks at a time.

How quickly a body begins to de-train depends on a large number of variables, including but not limited to age, fitness level, how long you have been training and the specific type of training. Well conditioned athletes who have structured periods of de-training (sometimes referred to as deloading) will generally feel the affects less intensely, whereas newer exercisers will feel the deconditioning effects in a faster, more profound way.

Not limited to losses in cardiopulmonary capacity (your ability to pump blood and circulate oxygen through your system effectively) and lean muscle mass, de-conditioning can also affect other physiological components of health including blood pressure, cholesterol levels, and blood sugar regulation.

When training for endurance performance, many athletes will include weeks in their program dedicated to strategically reducing their training l

When training for endurance performance, many athletes will include weeks in their program dedicated to strategically reducing their training l

According to Adam Tzur, author of The Science of Detraining: How long can you take a break from the gym before you lose muscle mass, strength, and endurance, detraining effects can be felt in as little as 2-3 weeks. Muscles start to atrophy after two to three weeks, though evidence indicates that these gains can be more quickly recovered with newer athletes. Simlarly, aerobic capacity can be impacted by up to 25% in four weeks, and flexibility can be decreased by up to 30% in as little as a month.

While there may be advantages to taking on a period of deloading, particularly for athletes or for people beginning to experience physical exhaustion, these should e executed strategically and with an understanding that there will be a cost to performance and progress.

Rather than completely stopping all training, most exercisers would benefit more from taking on a reduce maintenance training schedule in which typically involves training at a reduce frequency (less times per week), duration (less time per session), volume (less work load per session), or intensity (less difficulty in the work performed). A lightened training schedule can greatly preserve your fitness levels, either maintaining them entirely or significantly slowly the de-conditioning process.

So, long story short: Next time you decide to take a few weeks off from the gym, make sure you remember to include some activity during your break- even if it`s just short bouts of strength or aerobic training, to keep your progress in tip top shape!


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Zita Dube-Lockhart (BA/D. HS, CSEP CPT, NASM CES, AFAA GFI) is known for her voracious appetite for t̶a̶c̶o̶s̶ knowledge and her unquenchable t̶h̶i̶r̶s̶t̶ ̶f̶o̶r̶ ̶w̶i̶n̶e̶ passion for creating accessible fitness opportunities for every body and everyone.