My cadence is 3-1-3 on sets where my workload 75% of 1 rep max. a 75% workload translates to 8 to 12 reps. The enrgy system employed is the latic acid system that provides 45 seconds to 120 seconds of energy at this workload before failure. This wide range for the general population reflects conditioning, genetics, and possible transient personal factors. For workloads of 90 to 95% of 1 rep max, where ATP is the body’s primary primary energy source, I will use a faster, 2-1-2 cadence to engage more of the faster twitch fibers in my muscles. The ATP energy source typically lasts from 8 to 15 seconds before failure at near maximum workloads occurs. One can divide how long their various energy systems last by their cadence to get an idea of the rep range they may be able to accomplish on that set. Of course, they need to either know their 1 rep max or use a chart to derive it. ATP replenishment / recovery time is mostly complete (a little more than 90%) at the two minute mark.
Interesting post, but I'm not sure about this part: I'm not convinced that speed necessarily dictates more fast twitch muscle fiber recruitment. I would think it's more a matter of effort/intensity, which is not necessarily either weight or speed dependent. https://www.cbass.com/Carpinelli.htm
During the last couple of months have I used a “3 sets, 12 reps per set” approach for all exercises I do. Using three counts as cadence. Depending on the exercise have I usually one rep left after the first set, none after the second and am hardly able to complete the third set. Once I’m able to complete 3x12 on an exercise will I step up the weight the next time I do this exercise.