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  • Writer's pictureAaron Adams

Why is 21/15/9 a thing?

Why 21/15/9?

I remember the first time I saw a rep scheme like 21/15/9. I thought it was the silliest way imaginable to attain 45 reps. Why not 3 sets of 15? Or even 20/15/10. Why the arbitrary reduction of 6 reps after each set. I pondered that thought for years, and in the early stages of creating Deep with my business partner, and friend, Dave, he posed a very interesting thought. He said “a computer doesn’t care if you reduce by 13, what it cares about is the difference between a reduction of 13 and a reduction of 3.” I remember this blowing my mind.

A computer or even your body for that matter does not care what the rep scheme is. It only sees data. But what we see as humans is very different. We create stories. We see numbers and want very simple orders, 5’s, 10’s, 3’s. Small simple numbers that are “round” to us. But in reality, your body is responding to a stimulus regardless of the reps done or the breakdown of sets.

This is where coaching comes in.

What these reps schemes do in reality is challenge the way you approach a workout from the mental side. Most people see a 21/15/9 rep scheme and understand that the work is front loaded and will therefore get easier as more is completed. In reality, you end up mentally baiting yourself into coming out very fast and petering out quickly over time. Coaches love to see these workouts completed by their athletes because it allows them to witness the “test of will” that comes along at the end of a workout like this. It shows them the grit and perseverance of an athlete. From the computational perspective though, it’s quite different. By seeing how athletes manage these different reduction rep schemes, lots of data can be used to not only see where and how an athlete physically falters, but it can also tell us about where they mentally falter. The Deep algorithm gives predictive times to finish a workout in an allotted time. This is done by a variety of predictors that can inform us on what workouts athletes have more difficulty completing and how those workouts differ from what was previously done.

Coaches do this same thing but in a more intuitive fashion. It also requires them to not only witness the workout currently, but also previous workouts leading up to it. Context is also very important. If this workout is done early in the cycle you would expect the times to be greater than later in the cycle. This is because the coach typically assumes the athlete will be in the most “complete shape” before competition, meaning they will be able to complete both high and low intensity workouts to greater effect.

What does this mean to the average person, well not a lot and a whole lot at the same time. While most people don’t need to reach such a high intensity, it can show things like relative recovery days after the workout as well as how accustomed they are to fast bursts of work. Imagine a person who can get a sub 2 min Fran but only 5 rounds of Cindy, that should tell you a whole lot and it can be further nuanced as these two examples reach a more realistic state.

Deep can calculate lots of variables like the ones listed above in seconds. And it can make adjustments on the fly, and as time goes on. Coaching is a great nuanced skill, but with Deep we can help you be even better.

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