- 2 RIR means you stopped a set when you could have done a maximum of 2 more reps.
- A weight was used to perform 6 repetitions and no more could have been done (complete failure was reached), then 1 RIR would mean using the same weight but performing 5 repetitions instead.
Why use RIR
First of all, when isolated into a single set, training to failure (0 RIR) stimulates muscles growth to a greater extent compared to a few reps away from failure. However, approaching failure causes a disproportionate amount of muscular fatigue and connective tissue damage. Therefore, a wiser approach to training is stopping before reaching complete failure to minimise long term fatigue and improve recovery both between sets and between sessions. In other words, not reaching failure allows you to complete more sets in a session and more sessions in a training cycle.
Having an RIR target instead of following a fixed scheme of weight for a certain number of repetitions is a form of automatic regulation. You can have some days where you feel stronger or weaker than others, so following an RIR target can vastly assist with the adjustment of set difficulty. Additionally, performance naturally declines over a given number of working sets due to fatigue. So if a fixed target percentage of your one rep max is to be used, an RIR target can internally guide the number of repetitions you perform in each set.