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The Case for Using RX’d Weights

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When defining fitness it is a matter of doing so based on the individual characteristics of a particular sport.

CrossFit defines the goal of its methodology and programming as improving fitness, which it defines as “work capacity across broad time and modal domains.”

https://en.wikipedia.org/wiki/CrossFit

What is work capacity?

Work capacity has been defined as “the total amount of work you can perform, recover from, and adapt positively to.”

How does one test an increase in fitness and work capacity?

Weightlifting and powerlifting; the amount of load successfully lifted within parameters of the defined sport. i.e. Load used.

Kettlebell competitions: the number of reps performed in a certain time with a designated load. i.e. Maximum reps possible within a time constraint.

Running, cycling, swimming: the amount of time needed to complete a specific task; distance over which one travels. i.e. Time to complete a task.

Within CrossFit and the variety of its workouts one finds a combination of these definitions applied to “benchmark workouts”.

https://library.crossfit.com/free/pdf/13_03_Benchmark_Workouts.pdf

Fran is one of the best known examples:

Fran consists of a 21-15-9 rep scheme of each of the following movements; thrusters performed at 95 or 65 pounds and pull ups, both of which are to be done within the standards of the defined movement, completed as fast as possible, for a score. The score being the time to complete all of the prescribed reps at the prescribed weight. Hence combining a “load used” and a “time to complete a task component”.

In order to have quantifiable test results one needs to reduce the number of variables. The movement standards need to be exact as well as the loads used.

Too many independent variables can and will change the dependent variable which is the specific result we are measuring.

Here are several definitions of variables.

“The two main variables in an experiment are the independent and dependent variable. An independent variable is the variable that is changed or controlled in a scientific experiment to test the effects on the dependent variable. A dependent variable is the variable being tested and measured in a scientific experiment. The dependent variable is ‘dependent’ on the independent variable. As the experimenter changes the independent variable, the effect on the dependent variable is observed and recorded.”

https://www.thoughtco.com/i-ndpendent-and-dependent-variables-differences-606115

“A variable is any factor, trait, or condition that can exist in differing amounts or types. An experiment usually has three kinds of variables: independent, dependent, and controlled. The independent variable is the one that is changed by the scientist.”

http://www.sciencebuddies.org/science-fair-projects/project_variables.shtml

Assuming that we as coaches are the “scientists” in the above definition, we need to keep the independent variables constant and fixed when quantifying whether or not our athletes/members are getting more fit.

“Dependent Variable: A dependent variable is what you measure in the experiment and what is affected during the experiment. The dependent variable responds to the independent variable. It is called dependent because it “depends” on the independent variable.”

https://www.ncsu.edu/labwrite/po/dependentvar.htm

Here is the case for using RX’d weights, or at the very least, the same weights (variables) within a specific WOD.

The following are hypothetical examples used to illustrate variables in testing and do not represent actual results. Being hypothetical does not diminish the idea behind differences in variability and the results not being quantifiable. 

Subject A does Fran multiple times with the following loads and records the subsequent results.

Assume the following: “blue” bands level of assistance >”red” band. This is the particular case at CrossFit Hell’s Kitchen.

1) 35 pounds and a “blue” band–6:22

2) 45 pounds and a “blue” band–7:08

3) 45 pounds and a “red” band–7:25

4) 55 pounds and a “red” band–7:43

5) 55 pounds and a “red” band–7:22

Result 1 would show a baseline

Results 1 vs 2 shows an increase in time, 6:22 to 7:08 with an increase in load 35 to 45 pounds on the thrusters. Not a quantifiable change in performance.

Results 2 vs 3 show an increase in time, 7:08 to 7:22 with the same load used on thrusters but a decreased load used on pull ups. Not a quantifiable change in performance.

Results 3 vs 4 show an increase in time 7:25 to 7:43 with an increase in load 45 to 55 pounds on the thrusters. Not a quantifiable change in performance.

Results 4 vs 5 show a decrease in time 7:43 to 7:22 with the same load used on thrusters and the same color band used on pull ups. Not a quantifiable change in performance.

The results of 4 vs 5 are still not a quantifiable change in performance due to the fact variables within bands need to be taken into account; manufacturer of band, age of band, amount of usage of band. The same band would need to be used each time with no other usage between testing in order for it to remain a constant variable. Again, reason for the RX’d testing which does not allow for any assistance during the pull up portion of the workout and therefore no variable.

Question: Has this person increased their fitness of level based on the above recorded workouts?

Answer:  No. Not a quantifiable change in performance or empirical evidence to support any change but rather only anecdotal as variability is too high.

Subject B does Fran multiple times with the following loads and subsequent results.

1) 65 pounds and a red band–8:47

2) 65 pounds and a red band–7:53

3) 75 pounds and red band–7:53

4) 75 pounds and no band–7:21

5) 75 pounds and no band–6:56

Assuming same band variables as listed above.

Result 1 would show a baseline

Results 1 vs 2 shows a decrease in time with the same load on thrusters and pull ups. Not a quantifiable change in performance taking into account variables within bands.

Results 2 vs 3 show an increase in load used in thrusters, 65 to 75 pounds and the same time to complete the task. Not a quantifiable change in performance taking into account variables within bands.

Results 3 vs 4 show both an increase in load on pull ups, red band used for assistance to no band as well as a decrease in time to complete the task. Quantifiable change in performance with a measurable increase in fitness.

Results 4 vs 5 show the same loads used for both the thrusters and pull ups and a decrease in time to complete the task. Quantifiable change in performance with a measurable increase in fitness.

These results are finally empirical and quantifiable, showing a measurable increase in work capacity and therefore fitness.

RX’d weights are a commonly used standard and goal that is used as a constant variable in order to measure the dependent variable/results.

It isn’t necessary to use RX’d weights to ascertain measurable results in an individual’s fitness as one can obtain measurable results using the same parameters in testing. However on a global scale and within the worldwide community it has been the way of standardizing the testing of, and measuring of, the empirical, quantifiable and measurable results that CrossFit has been founded on. It is this very model that Greg Glassman wrote about in “What is Fitness” in October 2002.

http://library.crossfit.com/free/pdf/CFJ_Trial_04_2012.pdf

It is this very principle quoted below that CrossFit was founded on and which has allowed it to repeatedly prove itself as well as stand the test of time.

“This model suggests that your fitness can be measured by your capacity to perform well at these tasks in relation to other individuals.”

This can only be done so by eliminating the variables and using RX’d weights as a standard of movement, testing and results.

Hence, in this author’s view, the case to use RX’d weights.