Every business has key performance indicators (KPI’s).

Regardless of what gym you attend, every gym attempts to sell “results.” My contention, therefore, is if delivering results is the crux of your sales pitch, why do you track attendance, average revenue per member, length of engagment, and lifetime value above all else? Shouldn’t there be a greater KPI?

At RxFIT, our crowning KPI is your work capacity; more specifically, the score you put into Wodify every Monday when we retest a benchmark workout.

And here’s why:

What Greg Glassman Taught Me (2008 Lecture)

The workout Fran is 21-15-9 thrusters (95 lb.) and pull-ups. Complete the workout by doing 21 thrusters (front squat 95 lb., then drive it overhead), then 21 pullups (get your chin over a bar from a hang anyhow). Then go back to the thrusters for 15 repetitions, 15 pull-ups, 9 of each, stop the clock, and we get a total time for the effort.

Power is force times distance (work) divided by time. The work required to do Fran is constant (force times distance). It does not change unless your height changes (distance), the distance we travel (the movement’s range of motion) changes, the load changes (95 lb.), or your weight changes. This means that every time you do Fran or a specific benchmark workout, the work is constant.

So, you do Fran for the first time and have a Time 1 for it (T1). If you do it a year later, the same work was completed but you have a separate time (T2). In comparing the two efforts, we find that the work quantity cancels and the difference in time is the difference in power produced (see below).

There will be measurement error in this calculation. I can measure the force/weight with a scale, the distance traveled with a tape measure, and time with a watch. There is not a lot of error therein, but there are some concerns as we are calculating the body’s displacement by using the center of mass, for example. However, as long as the work is constant, the same error occurs with every effort. And in comparison from one effort to the next, the errors cancel each other out (zero order error).

This ratio of time (T2/T1) describes my progress to the accuracy and precision of the watch, which is the best of my three tools (stopwatch, tape measure, scale). By tracking the difference in time between workout attempts, we are looking at changes in power. Therefore, the collection of workout data points represented your work capacity across broad time and modal domains. This is your fitness.

With power on the Y-axis and duration of effort on the X-axis, the power output of any effort can be plotted. Take a handful of efforts that take approximately 10 seconds to do, measure their power output individually, and then get an average of these efforts. Repeat this exercise at 30 seconds, 2 minutes, 10 minutes, 60 minutes, etc. Plot these data points. With adequate scientific accuracy and precision, I have graphed mathematically an individual’s work capacity across broad time and modal domains (figure 1).

to be continued.

Tyler