I like percentages.
They give training some structure.
I just do not like pretending the percentage knows how strong you are today.
A spreadsheet sees 80%.
It does not see the bad night of sleep. It does not know yesterday's run got harder than planned. It does not know you walked into the gym feeling unusually good either.
That is where RPE and RIR earn their place.
RIR is the one I find easiest to use
RIR means reps in reserve.
Finish a set and ask a simple question.
How many clean reps did I probably have left?
If the answer is two, that is 2 RIR.
If the set was an all-out grinder and another rep was not happening, that is 0 RIR.
I like it because the language is hard to misunderstand.
"Leave two reps" tells me more than "make it kind of hard."
RPE is basically the same idea from the other direction
On the common lifting scale, RPE 10 is an all-out set.
RPE 9 is roughly one rep left.
RPE 8 is roughly two left.
You get the idea.
I do not care which language somebody likes better as long as they can use it consistently.
Mass in Motion uses RIR because I think it maps pretty naturally to the question most lifters are already asking after a set anyway.
The first few weeks will be messy
This is normal.
People are not born knowing exactly what 2 RIR feels like.
Newer lifter says two reps left.
Then somehow does six more.
Okay. We learned something.
It gets better with practice, especially when you occasionally take a safe set close enough to failure to recalibrate what "one left" actually feels like.
I would rather have somebody improve that skill over time than pretend a fixed percentage solves all uncertainty.
Do not turn every set into a courtroom argument
You do not need to debate whether a set was 2.0 RIR or 2.7 RIR.
Close is useful.
If the program wanted three reps left and the set looked like a max-effort attempt, we know enough.
If it wanted one rep left and you could have done another five, we know enough there too.
The point is adjusting training with better information, not winning an accuracy contest.
Running makes autoregulation more useful
Hybrid athletes get days where the bar feels different for completely predictable reasons.
Long run Sunday.
Lower body Monday.
The planned weight might normally be easy. Today it feels like somebody welded another ten pounds to each side.
I do not think forcing the exact load proves anything.
If the goal was a certain effort, reduce the load enough to hit that effort and get the useful work done.
The opposite happens too.
Some days the planned weight flies.
That does not mean turn every good day into a max-out session. It means the system has evidence the athlete may be ready for progression.
RIR only works if you log it honestly
This sounds obvious.
Still worth saying.
If every set gets logged as 2 RIR because that is what the program prescribed, the data is useless.
Log what happened.
The prescribed effort and the actual effort are allowed to disagree.
That disagreement is exactly the information I want.
How Mass in Motion uses it
The program can prescribe a load and an effort target.
Then completed reps, load, and RIR tell us how that dose actually landed.
If a weight keeps showing up easier than expected, progression can move.
If normal weights keep becoming grinders, I want the system looking at that next to recent training and recovery instead of mindlessly adding more weight.
The percentage starts the conversation.
The set finishes it.
If you want to estimate strength from a hard set, use the 1RM calculator.