People worry about the PRECISE rep count. I hate to break this to people: reps don’t matter, like, at all.
In exercise physiology and biology, the definition of energy systems feeding into the citric acid cycle is all about time under tension. Your muscle fiber hasn’t clue one whether you performed 37 reps in 45 seconds or 3 reps each over the course of 15 seconds a piece.
It’s physics. Force times distance is work. Power is work over time. Reps don’t matter because you could lift MORE weight for MORE reps and still REDUCE the work and power performed by going a lot faster and/or decreasing the range of motion (the distance over which force must be produced).
That is, imagine person A can squat 100lbs for 10 reps over the course of 30 seconds at a greatest-depth of 90 degree knee flexion. If she increases the weight by 5lbs (5%) and the reps by 5 (50%), but reduces the knee flexion to 45 and completes the set in 25 seconds, not only will she have performed significantly far less work (more than 30% less as the force produced on the eccentric portion drops dramatically with faster reps) and power (at least 10% less), the improved leverages with reduced time will drop her perceived exertion by several factors. The weight and reps both went up a substantial percent. But the stimulus dropped by MAGNITUDES.
All the body knows is motor unit recruitment and sarcoplasmic adaptation. If you solely focus on rep counts, there is no obligatory need for the body to change.
Absolutely no one who understands exercise science cares about the rep count ALONE. What was the duration of effort? What was the perceived effort? What was the load’s percent of 1RM? What was the range of motion? These are some interesting questions.
But reps: 8 or 10? 20 or 30? 100 or 1000? No. Nothing valuable to be gleaned there.
From one point of view (that of “pushing” the human spirit), there’s always five more reps, no matter what. From another point of view, an effort is alactic when maximally handled for 0-15 seconds, lactate at 15-45 second, and aerobic after 45 seconds.
If an exercise program tells you a rep count, the proper response is to ignore entirely. The set demands 15 reps? Cool. What if you get to 15 and have more in the tank? Do more. What if you can’t get to 15? Cool. DON’T DO 15.
The asinine and endless rep recommendations from fitness enthusiasts don’t help laypeople. I’ve seen someone think they’re performing a productive set when they complete 12 reps but clearly have 70 more in the tank. I’ve seen people think they’re “failures” because they don’t achieve a made-up number.
No. No. No.
Just challenge yourself intelligently in a progressive manner. That could be 1. That could be none. It could be 17. In fact, I kinda like prime numbers exclusively for rep goals. They’re more trustworthy, since they’ve fewer escape routes when divided.
Without a lot of other reference points, reps don’t friggin matter.