Yes, to grow muscles you have to train hard. But does that also mean that you have to train every set to the limit – to failure? Or can you also leave some repetitions ‘in the tank’ (RIR training)?
1. Training to muscle failure means that you train a set until you think you can no longer do a decent repetition (volitional failure) or until you cannot complete a repetition and therefore literally fail (momentary failure).
2. If you only did one set for a muscle group, you would have to train to failure for maximum muscle growth. After all, muscle failure provides the maximum growth stimulus. However, in practice you don’t just do one set: you always train in a specific context, where training volume and frequency are especially important.
3. But you can also train to near muscle failure. So it’s heavy, but not all the way to the maximum. The extent to which you train to muscle failure is usually expressed in reps in reserve (RIR). For example, 1 RIR means that you stop the set when you could do one more repetition. So you leave one repetition ‘in the tank’. The amount of RIR you train with is also called relative intensity. Make no mistake: training with one or more RIRs can still be very tough.
4. Most renowned coaches believe that you should use failure training in doses to prevent overtraining. Reaching muscle failure causes great, perhaps disproportionately great, fatigue of the muscle. This can be at the expense of your recovery, causing you to do less productive sets.
5. In general: train with 1-2 RIR for isolation exercises and with 2-3 RIR for compound exercises.
6. You can also occasionally train to complete muscle failure, but only during the last set of an isolating exercise, at the end of a training session and/or before a deload week.
7. Training intensity and training volume are interrelated. If you have little time to train, a high training intensity (for example training everything to muscle failure) with a low training volume (for example only 5 sets per week) can offer a solution.
8. Both beginners and advanced users often have difficulty estimating the correct number of RIR. To this end, it helps to occasionally train to muscle failure, so that you experience what it is like firsthand.
WHAT (REAL) MUSCLE FAILURE IS
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!).
Please note: this concerns fatigue in the muscle, also called local or peripheral fatigue. Sometimes you have to end a set because you are tired in another way, namely centrally and/or cardiovascularly, something that often occurs with very long sets. However, that is different from reaching muscle failure.
By ‘training to muscle failure’ we mean that you train until you are sure that you cannot do any more repetitions (volitional failure), or until you literally fail during the concentric phase of a repetition, for example while raising the barbell during a biceps curl (momentary failure).
The video below shows you what real muscle failure is. That point may be a few reps further than you think, no matter how uncomfortable the set may feel.
The extent to which you train to muscle failure, also called relative intensity, is usually expressed in Reps In Reserve (RIR). For example, 1 RIR means that you stop the set when you could do one more repetition.
ZOOM IN, ZOOM OUT
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. In short: failure training > RIR training .
However, this is viewed purely on a set basis. In practice, you do several sets per muscle group and you usually train your muscle groups twice a week. If we zoom out and consider the complete training program and any nutrition plan, 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. For example, if you do 15 sets per muscle group per week, fatigue will increase very quickly if you train all those sets to complete muscle failure.
The failure issue therefore concerns the context in which the training takes place. More about that in the rest of this article.
STIMULATING REPS AND VOLUME
To grow a muscle group, you have to load it with sufficient ‘stimulating repetitions‘ for a certain period (usually a week). Those are the reps in your sets that are closest to the point of muscle failure. ‘Stimulating’ means that these reps provide significant growth stimuli. You can recognize these repetitions by the fact that they are more difficult and therefore slower than the repetitions at the beginning of your set.
Normally a set should contain at least five of those stimulating repetitions. This is best achieved by training your sets in the range of 6 to 15 repetitions (for practical reasons the best rep range for muscle growth), each time until close to muscle failure. So suppose you use a weight with which you can complete 12 repetitions, then there is little point in only doing 6: only from about the seventh repetition onwards do the reps start to generate serious growth stimuli. Only with heavy compound exercises, such as the barbell squat, the ‘early’ reps in your sets are also quite stimulating.
Assuming about five stimulating reps per set, an average bodybuilder needs to do 10-20 sets per muscle group per week to grow, with a maximum of 10 sets per muscle group per workout.
FATIGUE AND RECOVERY
More is better doesn’t always count when it comes to muscle growth. After all, for every stimulus there is also fatigue. We have already seen that there are different types of fatigue: central fatigue (in the central nervous system), cardiovascular fatigue (in the heart) and peripheral or local fatigue (in the muscle).
The more stimulus, the greater the fatigue, the more your recovery capacity is demanded. And the recovery capacity of natural bodybuilders is quite limited.
Therefore, always strive for the most favorable Stimulus Fatigue Ratio (SFR) possible in your training: as much growth stimulus as possible with as little fatigue as possible.
TRAINING TO MUSCLE FAILURE
For optimal muscle growth, should you train your sets to the limit, i.e. to muscle failure? Or is it better to stay a bit away from that, by leaving a few reps ‘in the tank’ (i.e. by training with Reps In Reserve)? The answer to these questions is not that simple and certainly not black and white: training to muscle failure is perhaps the most controversial topic in natural bodybuilding.
PRO AND CON
Proponents of failure training say that you will only achieve maximum growth if you give your sets the maximum effort, which means that you train them to muscle failure. This view stems from bro science, based on older scientific studies. But according to coach Layne Norton, these studies failed to correct training volume.
Later studies assumed equal training volume and showed that training to near failure produced the same muscle gains as training to failure when the volume was equal. Norton mentions the following studies: 33343066, 29577974, 28713535 and 31809457. In other words, you don’t have to go all the way for optimal muscle gains.
In fact, training to muscle failure can even be detrimental. According to opponents, training to muscle failure causes disproportionate fatigue, which is at the expense of your recovery capacity and thus also of the quality of the rest of your training(s).
The alternative: if you train with RIR, you may create slightly fewer stimulating repetitions per set, but because less fatigue occurs, you can do more (productive) sets, and thus – on balance – achieve more stimulating repetitions. And so you will grow more, is the thought.
Another argument against training to muscle failure is that it promotes poor technique and therefore injuries.
META-ANALYSES
In a meta-study (2020), hypertrophy expert Brad Schoenfeld tries to find an answer through an analysis of 15 scientific studies, all conducted among young adults.
The answer? In general, training to muscle failure is not a prerequisite for maximum muscle growth and/or strength increase. Only advanced athletes would benefit from training a few sets regularly to muscle failure.
On the other hand, training to muscle failure does not appear to be detrimental to muscle growth, at least not in the short term. It should be noted that long-term studies in the field of bodybuilding are scarce and it is therefore not excluded that failure training will eventually lead to overtraining. There is some evidence for that.
A second meta-analysis (2021) shows that it is better to stay somewhat removed from muscle failure. Based on twenty relevant studies, the authors conclude that the training stimulus is associated with relatively much fatigue. Training to muscle failure significantly increases muscle damage and thus recovery time, neuromuscular fatigue and metabolic disruption. This compares to training with RIR, but with the same number of repetitions in total.
A third study, a scoping review of no less than 38 studies, states that training to muscle failure is probably not superior to non-failure for maximizing hypertrophy. The optimal proximity to failure in strength training for muscle growth is unclear and may be moderated by other training variables, such as absolute intensity and training volume. Also, training to failure is likely to cause greater neuromuscular fatigue, muscle damage and perceived discomfort than not training to failure.
A fourth meta-analysis, again by Brad Schoenfeld and others, is based on fifteen studies. The review concludes that training to muscle failure is not a prerequisite for optimal muscle growth. However, it does not seem to have any adverse effects here either. More research is needed to determine the long-term effects of failure training.
Finally, there is a fifth analysis, a so-called meta-regression, and it shows a somewhat different picture: training to (near) muscle failure is relatively important for muscle growth, is the main conclusion. But in a roundtable with coaches Mike Israetel and Eric Helms, among others, the necessary nuances are introduced. The most important thing is that the training in studies is very different from reality. For example, in the studies only one muscle group is often trained and/or for a short period and/or for a low training volume. The fatigue factor therefore plays a much less important role in the laboratory than is actually the case with natural bodybuilders.
WHAT PRACTICE TEACHES US
Of course, science doesn’t say everything. The practical experience of renowned bodybuilding coaches such as Mike Israetel, Eric Helms, Steve Hall, Menno Henselmans, and Sean Nalewanyj may be just as important. And these coaches all believe that failure training should be used in moderation to avoid disproportionate fatigue — the unfavorable SFR we already talked about.
The figure below clarifies this and suggests that as a rule you should train with 1-3 RIR and that you should therefore only use failure training in moderation. The 0 RIR stands for volitional failure, -1 RIR for momentary failure.
The best Stimulus:Fatigue Ratio (SFR) is approximately two repetitions from muscle failure. (Source: Mike Israetel / Renaissance Periodization)NUANCES
According to Schoenfeld, this issue is mainly about the nuances. In other words, the context we already talked about:
There are a number of limitations to the current body of literature that impair the ability to draw strong conclusions on the matter, and various factors must be considered from a programming standpoint.
In a blog post and Instagram post, he explains the findings of his meta-studies in more detail and draws the following conclusions:
- For muscle growth you need to create a stimulus that challenges your body beyond its current capabilities;
- For beginning strength athletes, it is probably not necessary to train to muscle failure: an RIR of 2 to 3 is generally sufficient to stimulate growth. For more experienced strength athletes, it is probably beneficial to do some failure training: the need for failure training is likely to increase as you get closer to your genetic ceiling;
- As an advanced athlete you may have to train a few sets to muscle failure. However, older strength athletes should use this sparingly, due to their more limited recovery capacity;
- Training all your sets to muscle failure at a regular training volume is strongly discouraged — this may lead to overtraining in the long term;
- If you use a high training frequency (i.e. if you train your muscle groups three times a week or more) it is better not to train too much to the point of muscle failure;
- If you train in high rep ranges (i.e. with low weights), you may have to train closer to muscle failure than when you train in low rep ranges (i.e. with high weights), although the question remains whether you should train to complete muscle failure;
- Although not yet clearly proven by research, failure training is probably best used only for isolation exercises (e.g. side raises) and not for compound exercises (e.g. deadlifts). The latter is due to the great central fatigue that failure training causes with these types of exercises, as well as because of the risk of injury.
According to Menno Henselmans, training to muscle failure can be especially useful in these situations:
- To experience what muscle failure is so that you can better estimate your RIR;
- To create maximum growth stimulus when you have little time to train (such as with High Intensity Training). More about that in the next paragraph.
Henselmans also advises his clients to only train the last set of an exercise to muscle failure.
Finally, coach Steve Hall of Revive Stronger advocates making a difference in the type of exercise: train isolating exercises close to muscle failure (1-2 RIR) and compound exercises a little further away (2-3 RIR).
INTENSITY VERSUS VOLUME
How hard you train (relative intensity) also depends on how many sets you do weekly (training volume). More of one means less of the other.
Some people have little time and, for example, only train a muscle group once or twice a week, for a total of three workouts per week. Then you can safely train a few sets to muscle failure, for example every last set of an exercise.
If your schedule allows you to train a lot and often, and you want to get maximum results, it is best to train with 1-3 RIR as standard, at 10-20 sets per muscle group per week. You only train to muscle failure occasionally, for example at the end of your training or before a deload week.
IN CONCLUSION
Should you train to muscle failure or not? Fortunately, you don’t have to choose. After all, real life is not a scientific study in which one half trains exclusively to muscle failure and the other half never. The point is that you apply failure training with some policy.
In principle, training to muscle failure is not necessary to achieve maximum gains. In fact, it’s better to keep a few reps ‘in the tank’ to avoid disproportionate fatigue. Therefore, train on average with 1-3 RIR, to be more precise 1-2 RIR for isolation exercises and 2-3 RIR for compound exercises.
Probably the more experienced you are (i.e. the closer you are to your genetic potential), the closer you should train to muscle failure. As an advanced athlete, therefore, also do a few sets until muscle failure, but with caution: only with isolating exercises, only in the last set of an exercise, or in the last week for a deload.
Remember: natural bodybuilding is about training smart and that is not necessarily the same as training as hard as possible. Training to muscle failure must be done carefully and therefore in doses. Referring to the figure below: you train at least ‘Hard’, sometimes ‘Hard AF’ and occasionally until ‘Failure’. Training with RIR certainly does not mean easy training.
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Last updated on September 20, 2023.