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.
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.
