The recent review by James Fisher, James Steele, Stewart Bruce-Low and Dave Smith should be on the “must read” list for everyone with an interest in exercise. In fact, you should download and read it before you read the rest of this post which is the third of several commentaries I will be writing on their review.
Rating of Perceived Exertion (RPE)
In addition to the problems with the designs of studies comparing RPE between different repetition methods and load and repetition combinations, its subjectivity makes RPE a poor choice for measuring intensity. The perception of intensity is relative, and even training to momentary muscular failure (maximum possible intensity) will be perceived differently between those who are and aren’t accustomed to it.
Even if it is a poor measure of intensity I have found RPE to be useful for determining the starting resistance for new trainees. When teaching a new exercise I purposefully set the starting resistance at what I estimate to be low. After going over proper performance and having the subject perform a few repetitions I instruct them to stop and unload or transfer the weight back to me and ask them to rate the difficulty of those reps on a scale of one to ten, with one being so easy it barely requires any effort and ten being so hard it can barely be done with a maximum effort. Depending on their answers I will increase or decrease the weight until they perceive it as being about a “five” or only moderately hard, since when learning a new exercise I want them to focus on doing it correctly rather than doing it intensely.
Since I do not perform or recommend one repetition maximum testing to determine starting resistance and the initial selection doesn’t have to be precise RPE is practical for this purpose.
Load and Repetition Range
Research shows a wide variety of repetition ranges can be used to effectively improve muscular strength, however some individuals may respond better to higher or lower ranges or set durations based on genetic factors such as predominant muscle fiber types. There is no validity to claims like those made by the proponents of periodization and similar training approaches that different set and rep ranges are required to improve different types of muscular strength or strength versus hypertrophy. Rather, as you get stronger all of these things improve proportionally (muscular endurance, speed, size, etc.), in a ratio that is mostly genetically dictated.
Other factors to consider include safety and bone density. If set duration is too short the resistance required may be too high for the subject to use with adequately strict form. If set duration is too long the resistance may be too low to stimulate meaningful improvements in bone density.
Note I wrote “set duration” and not “repetition range”. It is important to distinguish between the two since the duration of a set of a certain number of repetitions can vary considerably depending on the repetition speed. As I mentioned in Thoughts On Relative Volume Of Single And Multi-Set Workouts, “Most exercise research . . . doesn’t specify or standardize repetition cadence, and when it does it is usually not supervised and timed to ensure strict compliance. Instead, subjects are often self-supervised and most people without proper instruction will use relatively poor form, moving in a fast and sloppy manner not representative of what is often recommended for high intensity training.”
Unless a paper states otherwise I assume the reps were performed at typically fast speeds and the resulting sets are of relatively short duration. This is important to consider when extrapolating the results of these studies to prescriptions for exercises performed at the slower cadences typical of high intensity training protocols.
My personal preference is to use a moderate repetition range with most subjects after the initial learning stage; six to ten repetitions at a 4/4 cadence on compound pushing exercises and five to eight repetitions at a 4/3/4 cadence on compound pulling and simple exercises. This results in set durations of approximately 50 to 90 seconds which seems to be a good, conservative starting point for most people. Higher rep ranges may be prudent for exercises like squats and deadlifts for long term spinal health.
I do not recommend the method Darden uses to determine repetition range based on a fatigue response test mentioned in the paper due to the problems with one repetition maximum testing discussed in part 1. Instead, I prefer to start with a moderate range and adjust it based on individual response. I have observed subjects who tend to respond better to lower repetition ranges have difficulty progressing beyond some range but are able to consistently perform within it with small resistance increases, while subjects who tend to respond better to higher repetition ranges have difficulty staying within a range with small resistance increases unless it is higher.
Coming in Part 4: Muscular Endurance