To fail or not to fail? New insights

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For optimal muscle growth, should you train every set to the limit, i.e. to muscle failure?


If you try to do as many reps as possible in a set, sooner or later there will come a point where you can’t go any further: with the best will in the world, you won’t be able to squeeze out another full rep. In short, you have reached muscle failure. That’s the point at which the muscle is so fatigued that it can no longer produce the force to complete a repetition (properly!).

If you do not train a set to complete muscle failure, but still keep a few repetitions ‘in the tank’, we call this training with Reps In Reserve (RIR). For example, 2 RIR means that you stop at the point where you could do two more repetitions.


Prerequisite: a set trained to complete muscle failure always provides a greater stimulus for muscle growth than a set where you keep a few repetitions in the tank. However, this is viewed purely on a set basis. In practice, you do several sets per muscle group and you probably train your muscle groups two to three times a week.

If we zoom out and consider the complete training program, the question remains whether training to complete muscle failure is better for your gains than RIR training. After all, heavy training also leads to fatigue, especially if you do many sets.

In short, the issue of muscle failure or RIR is about the context in which the training takes place.


What is better for muscle growth: training your sets to muscle failure or with RIR? A lot of research has been done on this topic, but there is no clear winner. It is clear that you have to train your sets at least to near muscle failure if you want to be able to grow. The question remains whether it makes sense to train until complete muscle failure.

Following a new study, a so-called meta-regression, Revive Stronger colleagues held a roundtable with coaches Eric Helms and Mike Israetel, and the creator of the study, Zac Robins.

The study shows that training to complete muscle failure can be beneficial. However, Israetel and Helms comment on this. For example, scientific studies usually involve small training programs, in which, for example, only one muscle group is trained, or in which training is only done two or three times a week. In such situations, fatigue is limited and you can safely train a few sets to muscle failure. Revive Stronger host Steve Hall:

If you’re not limited by fatigue, training to failure makes more sense.

The practice of the average natural bodybuilder is very different: often 10 to 20 sets are completed per muscle group, spread over two to three weekly training sessions. In that context, fatigue is much higher and it is wise to train with RIR: 1-2 RIR for isolating exercises, 2-3 RIR for compound exercises. Purely on a set basis, the growth incentive is slightly less, but because you do a larger number of sets, the muscle growth is greater on balance.

Please note: sets of 1-3 RIR are still heavy sets! You just don’t go all the way, which gives you a better stimulus-to-fatigue ratio.


Fortunately, in practice you don’t have to choose. You can safely train sets with 1-3 RIR on the one hand and some sets to complete muscle failure on the other, for example the last set of an isolating exercise. Another option, which coach Israetel recommends, is to build up the relative intensity during a mesocycle, culminating in a deload. So for example 3 RIR in week 1, building up to 1-0 RIR in week 6.


In a podcast with Steve Hall, researcher Zac Robinson concludes as follows:

Conclusion is that proximate failure seems to be pretty meaningful for hypertrophy, but there’s a lot of other things that need to be kind of contexualized when we future go to prescribed training for an individual.

In other words: training to the point of muscle failure is necessary to seriously build muscle. But whether you train most sets completely to muscle failure or with RIR is a conscious choice you have to make, especially based on the volume of training you complete in a week.

If you train like an average bodybuilder with 10-20 sets per muscle group per week, then basically train with RIR, with the possible exception of the last sets of your isolation exercises (which you train until complete muscle failure). The number of RIR is as follows: 1-2 RIR for isolation exercises, 2-3 RIR for compound exercises.

If you train with a maximum of 10 sets per muscle group per week, you can safely train almost all your sets to muscle failure. ‘Almost’, because with the large compounds, such as the barbell squat, it is better not to go all the way. The latter partly from an injury perspective.

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