What is Fitness?

The classic article, “What is Fitness?” by Greg Glassman is a staple of CrossFit theory and practice. It’s such a staple that all affiliates are required to link to it from their homepages. You can find our link on the very bottom right of your page that says “CrossFit Journal free issue.” Being such an important article, and understanding how little visibility it gets, I want to get it into our resources section for quick and easy reference, and open the topic for discussion. So download the article from the link above, check out the below primer, and tell us what you think.

First, CrossFit is the only fitness program that has defined fitness in a way that is measurable, observable, and repeatable. That’s a big deal. What if your business was tuning and repairing cars but you couldn’t define a “car?” That sounds ludicrous, but other programs claim to chase the goal of fitness without ever clearly defining what they seek to achieve. Unacceptable! Furthermore, how can we measure our results and compare them against a standard if we do not define that standard?

Coach Glassman’s exposition of the multiple ways CrossFit defines fitness sets our standard. These multiple definitions also give us different contexts for understanding fitness, which is welcome, because fitness is a very complex topic. CrossFit’s three definitions of fitness are

  1. 10 general physical skills. Strength. Stamina. Endurance. Flexibility. Power. Speed. Coordination. Agility. Balance. Accuracy. These ten words describe the predominant characteristics of almost any activity you are likely to encounter, and therefore your capability in each describes your fitness. We humans are usually pretty good in a couple, mediocre in most, and horribly deficient in a few. Improvement in some of these skills comes through training: stimulating physiological changes in your body. Others are developed through practice: developing your nervous system to accomplish tasks within your current physical capability. Finally, power and speed are developed through a combination of both training and practice.
  2. Capability at random physical tasks: The hopper. Put every conceivable workout (not just CrossFit WODs–every conceivable workout) into a hopper. Spin the hopper and then pull out a workout at random. He/she who is fittest will perform the best over a large number of these random tasks. What’s the task you dread coming out of the hopper more than anything? A long run? Pullups? Single rep strength? Could anything reasonably come out of the hopper that’s completely a non-starter for you? Fixing that weakness is the single best thing you can do for your overall fitness. CrossFit has found that you can make more progress by devoting yourself to improving your deficiencies rather than continuing to improve your strengths. Furthermore, improving your deficiencies seems to have an amplifying effect on all of your non-deficient skills. This is both unexpected and very cool. We don’t understand it, but we know it happens.
  3. Capacity in the three metabolic pathways: phosphocreatine, glycolytic, and oxidative. A metabolic pathway is just a method your body uses to produce ATP, the body’s currency of energy which is spent by your muscles. You are as fit as your capacity in each of these pathways. The phosphocreatine pathway is for short, explosive ATP production. The glycolytic pathway provides energy during medium-duration exercise from ~30 seconds to ~4 minutes. The oxidative pathway is your capability to produce energy aerobically (from oxygen). This pathway provides low amounts of energy for very long durations. Many people are fit in a single pathway. CrossFitters seek to be fit in all of them.

In addition to CrossFit’s three standards of fitness, the article touches on a few more important concepts:

  • The continuum from sickness to wellness to fitness. It’s all a measure of the same thing. Fitness is just an advanced state of wellness, and a hedge against sickness. Sickness is the absence of fitness. This doesn’t apply as much to sniffles as it does to degenerative diseases. In essence, it’s difficult for grandma to break her hip if she’s got the bone density and connective tissue strength of Conan the Barbarian from three decades of weight training.
  • A Practical Guide to Fitness in 100 Words: Eat meat and vegetables, nuts and seeds, some fruit, little starch, and no sugar. Keep intake to levels that will support exercise but not body fat. Practice and train major lifts: Deadlift, clean, squat, presses, clean and jerk, and snatch. Similarly, master the basics of gymnastics: pull-ups, dips, rope climb, push-ups, sit-ups, presses to handstand, pirouettes, flips, splits, and holds. Bike, run, swim, row, etc, hard and fast. Five or six days per week mix these elements in as many combinations and patterns as creativity will allow. Routine is the enemy. Keep workouts short and intense. Regularly learn and play new sports.
  • CrossFit seeks to improve work capacity across broad time and modal domains. Practically, this means improving your performance at many different physical tasks that require many different amounts of time to complete. This spans max effort lifts lasting less than five seconds to hero workouts that might require more than an hour. Graphically, this is the area under the curve on a plot of your power output in all of those time domains. Check out the graph below for a hypothetical athlete. If you assume we have data on this athlete’s capability in many different workouts at an instant in time then you can plot her time and power output for each workout.  Power is just a function of the load she used, the distance it traveled, and time required. Then we draw the blue line, which is a best-fit trendline formed by all of the plotted workout data. This is the athlete’s work capacity across broad time and modal domains–on a single given day of her life. Click on the graph to open a slightly larger version.

graph of work capacity across broad time and modal domains

We achieve fitness by building the area under this curve, hopefully by shifting it upward and developing capacity in all time domains. By the way, the area under a curve of force vs. time (a similar but not identical concept) is known as impulse, which is part of the genesis of the name “CrossFit Impulse.”

Coach Glassman has also proposed an interesting theory as a corollary to the idea of work capacity across broad time and modal domains: the three dimensional model of fitness and health. Here’s how it works. Take the 2D plot of an athlete’s work capacity at a snapshot in time and extend it along a third dimension representing the duration of her life. The resulting 3D plot is “health.” Coach Glassman has proposed defining health as the integrated work capacity over a lifetime. Sure, it has some kinks and limitations, but is pretty interesting nonetheless. If we had perfect data available about someone’s performance in all time domains, and recorded this data over the course of the athlete’s life, we could construct a plot like the 2D graph above for every year of her life. The graph would shift up and down and change shape as she grew up, developed work capacity, developed strengths and weaknesses, and aged. If we connected all of those plots in three dimensions then we would get a graph like the one below. Click on it to open a slightly larger version.

three dimensional model of health over a lifetime

This blue dotted line is just the 2D plot of Work Capacity Across Broad Time and Modal Domains we examined first, taken at the age of 40.

All the 2D plots at every age of the athlete’s life comprise the 3D graph of her health. The three-dimensional model of health is still in the formative stages. It isn’t as canonical as work capacity across broad time and modal domains, but one day it might be. The above graphs have a couple limitations. First, the units of average power output are just a general order of magnitude guess and are not accurate. The graph is not meant to show the precise power output of any workout, or the relationship between power output in different workouts, so don’t use it this way. Second, it’s impossible to know an athlete’s capacity in all of these workouts on any given day, so while we assume the data is for a single point in time, it must necessarily be taken over a long period of time.

Can you find any problems with these concepts? Does a better model exist? Are these models truly scientific (measurable, observable, and repeatable)? Is work capacity over a lifetime an accurate measure of “health?” What is “health?”All of this is still up for debate, so get into the discussion below.

5 thoughts on “What is Fitness?

  1. Looks like I need to be training the glycolitic pathway for the FFCC. That’s a really cool article.

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