If u are crossfiter, powerlifter, weightlifter or bodybuilder, I would highly recommend the Tuscherer scale of effort.
Adaptation
As noted, training intensity is often described as the percentage of 1-rep max for a particular lift. But there are issues with this method, namely that the body doesn't know or particularly care about how much weight is on the bar. The adaptations that occur from training are a result of tension and duration.
Performance
The body responds to things like the force of the muscle's contraction, how long the contraction lasts, and how many contractions there were. A percentage isn't necessarily a precise way to describe this as different lifters will perform differently.
If two lifters perform 3 reps with 85%, one lifter may find the task to be moderate effort while the other may find it to be next to impossible. The ratio of fast-twitch to slow-twitch fibers, training history, and other physiological issues all play a role here.
Next, there is the matter of having accurate maxes to work with. Such accurate data isn't always available, especially for assistance lifts.
RPE
For these reasons, I prefer to describe intensities in terms of reps-per-set and the RPE (rate of perceived exertion). This allows for greater individualization of training.
The RPE scale is described in the following chart:
@10: Maximal Effort. No reps left in the tank.
@9: Heavy Effort. Could have done one more rep.
@8: Could have done two or three more reps.
@7: Bar speed is "snappy" if maximal force is applied.
@6: Bar speed is "snappy" with moderate effort.
With this chart, not only can we describe the intensity of a lift with more accuracy, but RPE charts are also auto-regulatory in nature, meaning that they help us to modulate our training on a given day.
Tracking your progress is key to success.
