Photo from Kilo Classic III by PhotoLab.
When it comes to programming strength training, there are two common ways of prescribing intensity: percentage (or fixed numbers) and RPE (rate of perceived exertion).
At first glance, they can seem like completely different approaches. One tells you exactly what to lift; the other asks you to decide how hard a set feels.
In reality, both are simply different ways of communicating intensity, and both have strengths and weaknesses.
Fixed numbers
Fixed-number programming gives the lifter a specific load, or sometimes a range, to work with.
For example: Squat: 3 reps @ 180kg
The obvious advantage is clarity. The lifter knows exactly what they are expected to do, and the coach has a clear target to build the programme around.
This can make progression easier to visualise. Some lifters enjoy opening their programme and seeing that they are meant to squat 180kg this week and 185kg next. It removes some of the decision-making from training and allows the lifter to simply execute the plan.
It can also make programming more predictable. If a coach has spent years working with similar lifters, exercises, volumes and intensities, fixed numbers can provide a consistent framework for building and progressing training.
But there is an obvious problem:
180kg is 180kg, but a percentage of what?
A percentage is only useful if the number it is based on is appropriate.
If you take an old one-rep max and prescribe percentages from it for months without accounting for changes in strength, the numbers eventually stop representing the athlete's current ability. The same problem occurs when the context changes. A competition squat in knee wraps isn't necessarily an appropriate reference point for a safety-bar squat performed several months later.
There can also be large individual differences between rep ranges. Someone might be exceptionally good at singles and doubles but struggle with sets of eight. Another lifter might be the opposite. A percentage that works perfectly for one type of training may not translate neatly to another.
Fixed numbers can also create psychological problems when the numbers are wrong. Missing a programmed weight can make a lifter feel like they are getting weaker, even when the problem is simply that the programme was too aggressive.
The key point is that the input number matters less than the quality of the output numbers. A good coach needs to continually assess whether the numbers being produced by the programme still make sense.
RPE
RPE is essentially a way of communicating how difficult a set was.
An RPE 10 is maximal effort. An RPE 9 might mean you had roughly one rep left. An RPE 8 might mean you had around two reps left.
The exact application can vary, but the principle is simple:
Instead of only asking, "What weight did you lift?", we also ask, "How hard did that weight feel?"
This makes RPE extremely useful as a shared language between coach and lifter.
A coach can see a lift, but they cannot directly feel it. Two lifters can perform the same weight at the same number of reps and experience completely different levels of difficulty. Over time, RPE gives the coach a way to understand that difference.
If a lifter is having a terrible day, the weight can come down while still achieving the intended level of effort. If they are having an unusually good day, they can potentially lift more.
This can be particularly useful when someone's current strength is difficult to predict: returning from time off, during a peak, when changing exercises, or whenever external factors are likely to affect performance.
RPE can also teach lifters to become more aware of their own training. Instead of blindly moving weight from one set to the next, they learn to assess how something actually felt.
However, that is also where the biggest problems with RPE occur: the subjectivity.
A lifter needs to be able to accurately judge their effort, and they need to be honest about it. Someone might call a set an RPE 8 because they genuinely misjudged it, because they are inexperienced, or simply because they wanted it to be an RPE 8.
That can lead to undershooting or overshooting.
It can also create an opportunity to talk yourself out of a lift. If your warm-up feels slow, you might decide that the planned weight is impossible when, in reality, you could have completed it. Conversely, you might feel fantastic and push beyond what the programme can realistically support.
RPE therefore requires education. A coach can't simply write "3 reps @ RPE 8" and assume the lifter automatically knows what that means.
So, which one should you use?
This is where the distinction becomes less important.
The advantages of one system are often the disadvantages of the other.
Fixed numbers provide structure, predictability and clarity, but can become rigid if the underlying numbers are no longer appropriate.
RPE provides flexibility and autoregulation but requires the lifter to make accurate decisions. And, importantly, we are already using both whether we realise it or not.
Every time you lift a weight, that weight represents some percentage of a reference number. At the same time, your brain is automatically registering how difficult it felt.
You might finish a set and think: "That was heavy." Or: "That moved really well."
That is essentially RPE in action. The most useful approach is therefore not necessarily to choose one system and reject the other. Both can be used together.
For example, a coach might prescribe a specific weight and an expected RPE:
180kg x 3 (RPE 8)
Now there is both an objective target and a subjective measure of how the set should feel.
This can be particularly useful around competition, where the coach may have a good idea of the numbers the lifter should be capable of but still needs to account for how they are actually performing on the day. Ultimately, neither fixed numbers nor RPE is inherently better. They are tools for managing training intensity.
The important skill is understanding what each tool tells you, what it doesn't tell you, and when you need to adjust the plan.
A good programme isn't one where the lifter blindly hits every number. It's one where the prescribed training continues to produce the intended stimulus as the athlete changes over time.
Want a programme that adjusts as you do? Our online coaching is built around exactly this balance of structure and autoregulation.
