What Does the Word "Fitness" Really Mean?

Let's examine what exactly we mean when we refer to ‘fitness,' or when we talk about someone ‘being fit.’ Or, in my case, what I mean when I say that I am going to ‘get you fit.'

Brock Armstrong
5-minute read
Episode #345

The word ‘fitness’ is a bit of a catch-all, seeing as there are no less than three distinct components to fitness: cardiovascular fitness, strength, and flexibility. Summing those rather complicated topics up in one word is a bit reductionist, to say the least. If you look up the word "fitness" in a dictionary (pick a dictionary, any dictionary will do!), you will find a plethora of definitions, depending on what category (medical, historical, or biological) you choose.

These are the definitions that resonate well with me, and work best for our purposes here:

  • The capability of the body of distributing inhaled oxygen to muscle tissue during increased physical effort
  • The state or condition of being physically sound and healthy, especially as the result of exercise and proper nutrition
  • The degree of adaptation of an organism to its environment, determined by its genetic constitution

Interesting that none of the definitions include 6-pack abs, the ability to run 42.2 km (or 26.1 miles) in a herd, or having less than 6% body fat as criteria. Personally, I am happy and relieved to see that. If being fit required looking like the Photoshopped model on the cover of a Shape magazine, well I would hang up my coaching hat right now.

As a way of unearthing the truth, let's examine each of those definitions to see how they apply to us mere mortals.

Definition #1

First, the most clinical of definitions: “The capability of the body of distributing inhaled oxygen to muscle tissue during increased physical effort.“

This definition refers to that fact that when you exercise, your muscles move vigorously and that causes their metabolic rate to increase. When that happens, your muscles need more energy so they produce more of the chemical energy molecule called Adenosine triphosphate (ATP). You need oxygen to produce ATP, so the more ATP you produce, the more oxygen your body requires.

Using this definition of fitness, we can say that as our fitness increases we become more and more efficient at the process of using oxygen to produce energy. We can also say the direct and measurable result of this process is that we become more comfortable exerting ourselves at higher levels, can go faster, move heavier objects, or last longer at certain activities.

That definition is certainly straightforward but I think it lacks the nuance that we are looking for. Surely there is more to the concept of fitness than just a biological process.

Definition #2

The second definition: “The state or condition of being physically sound and healthy, especially as the result of exercise and proper nutrition” is a little closer to what I am looking for but is also a little more sticky.

This definition uses words like “sound, healthy and proper” that fall squarely into the subjective category. This definition also requires that we as a population have some opinions or ways to measure what it means to be “physically sound” and “healthy”. Not to mention the use of the phrase “proper nutrition,” which I am sure would make even our very own Nutrition Diva shake her fists at the sky.

Sure, we can test for things like VO2 Max, Blood Lactate Threshold, Body Mass Index (BMI), and even Resting Metabolic Rate to give us an idea of whether or not someone is “physically sound” but each one of those tests and measurements carries with it its own set of subjective issues and judgement calls. We can often determine when someone is unhealthy but there is much more debate when we try to differentiate between what is normal, average, and (especially) healthy.


All content here is for informational purposes only. This content does not replace the professional judgment of your own health provider. Please consult a licensed health professional for all individual questions and issues.

About the Author

Brock Armstrong Get-Fit Guy

Brock Armstrong was the host of the Get-Fit Guy podcast between 2017 and 2021. He is a certified AFLCA Group Fitness Leader with a designation in Portable Equipment, NCCP and CAC Triathlon Coach, and a TnT certified run coach. He is also on the board of advisors for the Primal Health Coach Institute and a guest faculty member of the Human Potential Institute.