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Nathan DeMetz Personal Training

What is fitness?

Updated: May 27

Fit people working out

Fitness is the ability of the body to do work. It is also a reflection of no health issues. A person cannot be considered fit if they are unhealthy.

The textbook definition of “fitness” is: the condition of being physically fit and healthy.

Healthy is defined as: in good health

These definitions are relatively straightforward but are still open to wide interpretation. Let me dig in a bit further to help you better understand what fitness is.

The current health crisis

According to the National Institutes of health heart disease and stroke are the leading cause of death for men and women in the United states. This should come as no surprise since the topic has been a strong talking point for decades.

In fact, you probably know somebody who has heart disease or who has suffered a stroke. This may be a condition that runs in your family and something for which your doctor screens.

If you suffer from heart disease you cannot be considered healthy or fit. It does not matter how much you can bench press, how far you can run, or how many Pilates classes you take; you are not healthy if you suffer from a chronic heart condition.

In this logic somebody who has a heart condition cannot be considered fit broadly speaking. Now there are many ways to categorize a person's fitness level and I'm going to speak to the fitness categorization that I use for myself and clients.

This is how you define fitness

First and foremost in order to be considered fit a person must lack health conditions. They should not have a heart condition, diabetes, be obese, or some other similar health condition. In the absence of such conditions we can now consider the idea that a person may be fit.

However, a lack of health conditions does not in an of itself make someone fit. By that logic, being able to lift heavy weights, run a marathon, do handstands, be extremely mobile, or any similar singular physical expression of fitness does not in and of itself make someone fit.

Fitness encompasses 4 basic categories:

  • Strength

  • Conditioning

  • Skill

  • Mobility

Simply put, strength is the ability of the body to apply resistance. This can be measured in a variety of ways including a one rep max on the bench press or the ability to hold a plank.

Conditioning is the ability of the body to do work repeatedly. For example, the ability to do 100 reps on the bench press or to run a marathon are examples of conditioning.

Skill is technical ability. That is, the ability to do different movement patterns is a representation of skill. For example, the ability to bench press with good form, to run with good form, to hold a plank with good form, and other similar movement patterns is representative of skill.

The ability of the joints to move through range of motion is mobility. In order for these joints to be mobile, the tendons, ligaments, muscles, and the bones themselves must be free to move. Limitations in any of these can reduce mobility.

How to measure fitness

The way that you measure fitness is by looking at if you have health conditions and what's your ability is in each of the four categories of fitness. The more that you can do in each category be fitter that you are.

The more you increase your ability in any one category while maintaining the other categories the fitter you become. By that logic a loss of ability in these areas make you less fit. However, this is a nuanced subject.

A moderate degradation that leaves you at high per centage of best in one category while simultaneously increasing the other three would arguably still leave you fitter than you were before. One high-level way to look at this is are you presenting the best overall package compared to any period before.

For example, perhaps you were really strong at one point, but lacked conditioning, skill, and mobility. Now let's say you lose about 10% of your strength, but improve your mobility, skill, and conditioning significantly.

You are not less fit overall because you lost the strength. In fact, you are still very strong relative to how strong you were, but you have improved every other metric of fitness, making you the fittest you have ever been.


Again, this is a nuanced subject and I will flesh out more of this in future blogs. In the meantime, if you have any questions let me know. You can comment on this post, send me an email, or even contact me on social media.




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