Proximity to failure (RIR)
// What the research shows
Robinson et al. (2024) used a series of meta-regressionsMeta-regression A method within a meta-analysis that tests whether the size of an effect depends on a characteristic of the studies. More in the glossary → to look at how many reps you leave in reserve (RIRRIR (reps in reserve) How many more reps you could have done at the end of a set. 0 RIR means failure. More in the glossary →) at the end of a set. Result: hypertrophy increases the closer sets end to failure. Strength gains were similar across a wide range of RIR. The authors note that RIR often had to be estimated from study descriptions and that the analysis is exploratory.
// In practice
- For hypertrophy: end most working sets with roughly 0–3 reps in reserve.
- Go to true failure on safer exercises (machines, isolation work) rather than heavy squats.
- For strength: no need to grind to failure. A heavy enough load matters more.
// Limitations & open questions
Many people overestimate their RIR and are further from failure than they think. The exact shape of the curve is still unclear.
// Sources
// More from Training
Training volume
More hard sets per muscle per week lead to more growth, but each extra set adds a bit less than the one before.
Training frequency
For muscle growth it doesn't matter much how many days you spread your sets over. For strength, practising the lift more often helps.
Load & rep range
Muscles grow similarly with light and heavy loads as long as sets are hard. Maximal strength needs heavy loads.
Range of motion & stretched position
Full range of motion is a good default. Training in the stretched position seems especially important for growth.