Reps in reserve and rate of perceived effort are two useful ways of measuring the potential effectiveness of a set. These tools can be especially useful for trainers when ascertaining how a performed set was received and whether a progression or regression is needed.

R.I.R

Reps in reserve are used to determine how many theoretical repetitions could be performed before failure was achieved, for example, if 8 repetitions were achieved and it was established that 10 would have led to task failure then a total of 2 repetitions were left in reserve, this would be termed 2 reps in reserve. It’s accepted that when the goal is strength or hypertrophy, sets must be taken close to or to failure. This is because as a set approaches failure, there is an involuntary slowing of velocity and the high threshold motor units of the muscle are called into action. These motor units have the highest potential to signal hypertrophy. This pertains partly to the Henneman size principle which states that as more force is needed, motor units are recruited in a precise order according to the magnitude of their force output, with small units being recruited first, thus exhibiting task-appropriate recruitment. From this, we can state that it is beneficial or even required to take sets towards failure and by using R.I.R, we can establish if that task was achieved.

R.P.E

Rate of perceive effort is another useful tool that can aid in ascertaining the effectiveness of a set or session. Typically used as a grade of 1-10 this is another great way for trainers to effectively plan progression or regression intra workout. An example of this in action would be asking a client to grade the difficulty of a performed set or workout with 1 being very easy and 10 being task failure. A trainer would use the information given to plan the next set or session to facilitate progression. 

Potential flaws with these tools can include an individual incorrectly calculating their true number of reps in reserve as there is often an underestimate in how many reps would truly lead to task failure or a client purposefully giving a lower or higher RPE to misdirect a trainer. This considered, it’s good practice to utilize other points of reference to corroborate, such as speed of movement, (velocity will reduce as failure is approached), form and technique, (this will usually break down as failure is approached), and facial expressions, (involuntary grimacing or becoming flushed is common when a task is difficult).



We know that for progress to be facilitated, effort and intensity must be periodically high, simply going through the motions is not enough to shift the needle. The tools above are some of the best we have for ensuring efforts put forth are adequate and provide the loudest possible signal for adaptation.