Reps in Reserve or RIR is a method of training in which you control the amount of reps you leave in the tank each set in order to properly manage training intensity. This method of training has far reaching benefits, but it's not without it's downsides. One problem with this method is that many trainees are bad at estimating how many reps they have left in them during a set, leading to inaccurate RIR estimations. This can lead to training intensities that are either higher or lower than what was intended; and sometimes trainees won't even notice because they're convinced that their RIR estimate is accurate.
This can be a huge problem, because without years of training required to know your own body and how you feel as you approach failure on each exercise, you may have a difficult time staying within the optimal RIR ranges to get the desired stimulus from your training sets. Sometimes you may be too far from failure to gain the desired stimulus, while other times you may edge too close to failure and generate a lot of training fatigue too early on in a training cycle, forcing you to need a deload earlier than intended.
Some trainees feel great until they hit their very last rep or two, while others may feel as though they’re going to fail the next rep when they’re really 3-4 reps away from actually failing. This is where periodically training to failure comes into play and can be a great tool.
By training to failure on a given exercise, you know exactly how many reps you can get on that particular exercise with a given load on the bar. This can give you a more objective look at how many reps you should expect to get at a given RIR on that exercise with the same load. So if you perform a set of failure on the bench press with 200 pounds and you are able to get 10 repetitions, you can now use this data to set up your future work sets on the bench press with this particular load while more accurately falling into the desired RIR range.
Extrapolating For Other Loads
While the above method is great for accurately figuring out how to train in the proper RIR range for a specific load, this data can also be extrapolated to estimate your rep maxes with other loads as well, without the need to train to failure with multiple different loads each time you want to change your rep ranges but maintain accurate RIR. This is especially important for the bigger compound movements, since you don’t want to train to failure too often on those movements due to the amount of fatigue that would be generated by doing so.
The best way to do this would be to perform a set to failure in order to calculate your one rep max on a given exercise. The heavier a load you choose, the more accurate the calculation will be. I typically recommend trying to find your true five rep max. Once you have your five rep max, you can estimate what your current one rep max is, and from there use another calculator that estimates how many reps you can get at each percentage of your one rep max. Below is an example of how this would be done:
Step 1: Find your five rep max on the bench press. This can be done by taking a guess at what load you can only get five reps with and then testing it. From there, depending on whether you get more than five reps or less, adjust the load until you find the point where you can only get five reps.
Step 2: Take your five rep max load and use a one rep max calculator to determine what your one rep max is. There are multiple calculators that use slightly different formulas, but I typically use this one.
Step 3: Now that you know your one rep max, use the same chart to determine how many reps you can expect to get at each percentage of that one rep max. For example, the chart says that at 80% of your one rep max, you should expect to get 8 reps when training to failure.
From the above knowledge, you can plan out your training and estimate RIR ranges ahead of time. For example, knowing that 80% of your one rep max allows you to get 8 reps at an RIR of 0, you can use 80% of your one rep max and perform 6 reps to stay at an RIR of 2.
There are a couple of different ways you can implement this strategy into your training. For movements that are more difficult and generate a lot of training fatigue, such as the big compound movements like the bench press, squat and deadlift, I recommend finding your five rep max in order to estimate your one rep max and then use a chart to determine how many reps you can get with a given load. From there you can use this information to choose a load and rep range in order to hit whatever RIR you’re aiming for in your training. This method is better for the compound lifts because you don’t have to train to failure too often in order to get it right.
For other movements such as accessory lifts, it’s safer to train to failure more often. Because of this reason, I recommend periodically taking your last set of each of these exercises and performing an AMRAP (as many reps as possible) to truly gauge how many reps you’re actually capable of getting with that given load. This will allow you to consistently test how many reps you’re capable of and allow you to stay within the desired RIR range.