Training to Failure Produces Greater Muscular Hypertrophy

If you’re in the bodybuilding space and unless you’ve been living under the proverbially rock, you’re certain to have come across the great debate of training to failure. Current school of thought suggests that it is favorable to remain 2 to 3 reps from failure (“Rate of Perceived Exertion” [RPE] of 8 or 7, respectively; also known as “Reps in Reserve” [RIR] of 2 or 3, respectively). However, this has been challenged by many over the years including prominent bodybuilding and athletic figures as well as researchers who claim that this is simply a misguided approach to training. Indeed, as intensity is one of the major predictors of muscle growth, training at a level below maximum intensity would suggest that this approach would be detrimental to muscle growth. There is, of course considerations towards recovery and injury prevention, as if the subject matter couldn’t be muddied any further. So, how do we balance all of this, who’s voice should we be listening to and how do we apply all these conflicting factors? The ultimate question is, how far from failure should an individual train to optimize muscular hypertrophy and strength gains? Thus far, the answer remains to be seen. Previously literature and studies have attempted to answer this question categorically; that is, training to failure versus not training to failure or traditional versus alternative set structures. Muscular and strength adaptations are not however, an all or nothing response.

A new meta-analysis by Robinson et al. (2023)1 attempts to explore this question in a manner that has historically been neglected; that being, investigating the dose-response relationship of muscular hypertrophy and strength adaptions as one approaches failure. The following presents a discussion on the concept of training to failure as well as a summary of the key findings of the study, my own interpretation, and applications for the average lifter.

What is True Failure:

Firstly, we need to define what training to failure is. From a purely definition standpoint, training to failure is repeating an exercise to the point of muscular failure (i.e. the neuromuscular system can no longer produce adequate force to overcome a given load). An example would be completing a barbell curl to the point where you fail to bring the weight back up to any degree (i.e. zero movement from the starting position). Many would argue that this in fact isn’t true failure and that in fact, there are many methods to push beyond this point that would eventually result in true neuromuscular failure.

For example, let’s say you take that same barbell curl, and you complete enough reps to again reach the point where the weight isn’t moving from the starting position whatsoever despite maximum effort. Failure, right? Well, what if you utilize a slight hip swing to cheat the weight into motion and can complete a few more reps in that fashion until you hit failure? Failure, right? What about then dropping the weight and again completing more reps to failure? As you can see, true muscular failure can be quite difficult to obtain and, as you may imagine, produce an intense stimulus when one truly does.

Given the above, I want to preface the rest of the discussion stating that the fear of training to failure for the average gym-goer is misguided. For most individuals, adhering to the 2 to 3 reps from failure dogma for preventing overtraining and injury most likely lands them in them in the 5 to 6 reps from failure camp. That’s a whole lot of opportunity for missed muscular stimulus. If this is you and you aren’t gaining muscle as quickly as you’d prefer, yah ain’t training hard enough.

Current Hypotheses:

As previously mentioned, current consensus in the fitness space would caution individuals to train to around 2 to 3 reps from failure. This is for several reasons including avoiding overtraining, injury, inducing too much stress on the body to the point where it is harmful rather than beneficial, among other camps of thought. The consensus in the fitness community is that pushing beyond the 2 to 3 reps from failure offers no additional benefits in terms of strength or muscular hypertrophy gains while introducing a myriad of negative effects. Indeed, recent research supports this hypothesis. A meta-analysis by Grgic et al. (2022)2 looked at fifteen studies and determined “there were no significant differences between resistance training to failure vs. non-failure on strength and hypertrophy”. Given that result, why would an individual risk overtraining and injury for zero benefit?

Undoubtedly, along my own fitness journey, I have heard this countless times. But as we saw above, true failure is quite difficult to reach. If you are in fact reaching true neuromuscular failure on an exercise, you are likely to have been training long enough to be deemed an advanced trainee, in which case you’re going to require the extra stimulus that training at that intensity offers to promote muscular growth in the first place.

But let’s back up to the average gym-goer who may benefit most from this discussion. What does 2 to 3 reps from neuromuscular failure look like for the typical individual? For many, this would be the point of the exercise where significant difficulty sets in. This is a wildly incorrect assumption. For beginner and intermediate trainees, estimating one’s proximity to failure is extraordinarily difficult. Moreover, previous research3,4,5 has demonstrated that the ability of novice trainees in estimating proximity to failure is poor and produces inaccurate predictions. For these individuals, taking an exercise to mechanical failure (i.e. the point at which the proper form of an exercise breaks down) would be bordering on 2 to 3 reps from true neuromuscular failure and would be a more appropriate recommendation.

Results of the Robinson et al. Study:

The aforementioned study by Robinson and friends (2023).1, not only partially dispels the above hypothesis but also determined the dose-response of training to failure on both strength and hypertrophy. Robinson et al. collected existing studies from relevant meta-analyses and extracted the data to perform a series of exploratory multi-level meta-regressions on outcomes related to strength and hypertrophy. A key part of this study was the adjustment of the produced models to equate for the effects of load, method of volume equating, duration of intervention and training status.

The researchers discovered two unique patterns that were separately applicable to strength gains and muscular growth. Firstly, we’ll focus on the strength outcomes. The results showed that strength gains are minimally influences by proximity to failure; that being, strength outcomes did not seem to significantly improve when taken closer to failure versus farther away. In fact, there was a marginal improvement in strength when sets were taken farther from failure however, this observation was only seen under heavy loads and low repetition sets. This is congruent with current dogmas in strength training, which state that strength gains are primarily influenced by neuromuscular adaptation and the principle of specificity. Of course, as you may know, strength gains are also mediated by muscle cross-sectional area and improvements in connective tissue, but the primary driver is neuromuscular adaptation and improvements in lifting technique (i.e. practicing the same lift over and over and over again). In this light, training slightly away from failure makes sense as this would allow a lifter to focus on perfecting technique versus exhausting the muscle to force adaptation. This would also allow the lifter to train in this fashion repeatedly throughout the week over long training sessions without inducing overtraining or resulting in injury.

A completely alternate pattern was seen for the results related to muscular hypertrophy. The researchers demonstrated that muscular hypertrophy in fact improves non-linearly as sets are terminated closer to failure. So, what is happening here exactly? The observed relationship may be able to be explained mechanistically. Specifically, as sets are taken closer to failure, there is an increased and sequential recruitment of motor units and the muscle fibers that they innervate based on the muscle fiber size and type. As type II fibers have a greater potential for hypertrophy and higher threshold motor units innervate more type II fibers, one would expect that pushing closer to failure then would result in increased promotion of muscular growth. Furthermore, as one continues to train in this fashion and at a high intensity, there is a habituation to this stimulus (i.e. the trainee is able to effectively handle intense training sessions and reap the inherent benefits described above).

Conclusions and Applications:

There are many applications for the above research and results. Paramount to applying these results is addressing the issue of overtraining, fatigue management and staving off injury which can present detrimental setbacks to a trainee’s progress. While I agree that this demands focus, I believe the current approach is erroneous and requires a re-examination. Instructing trainees to keep sets 2 to 3 reps from failure is too broad and doesn’t account for specific intensities of unique exercises (think of the demands of a barbell squat versus a dumbbell curl). This approach treats all exercises as equal in terms of intensity and fatigue, which is utterly illogical. Secondly, training 2 to 3 reps from failure on a consistent basis may fail to produce the desired stimulus that is required for muscular hypertrophy.

I propose the following as an alternative. Particularly, for complex compound exercises (such as the squat, deadlift, bench press), I would suggest that these be taken 1 rep from mechanical failure on a consistent basis, leaving still a few potential reps to true neuromuscular failure. Everything else should be taken to neuromuscular failure (provided it can be done safely). Then, to adequately manage fatigue and prevent overtraining and injury, a de-load week should be included in a trainees program every 4 – 6 weeks (listen to your body here as well). During the de-load week, one would still train with high intensity however, sets would be significantly reduced by at least half. For example, if you were previously doing 3 sets of a compound exercise you would do 1 during that week. If you were previously doing 4 sets on an isolation exercise you would do 2 sets. I would also suggest that rest times be increased during this week and recovery be prioritized. This week is not about setting PRs or pushing the envelope either, so it is crucial to ensure that one is not attempting to increase the load during this week.

In this way, the body is periodically permitted to rest and recover. Furthermore, outside of the de-load week, an individual would be training with sufficient intensity to ensure that the maximum stimulus for muscular growth is being elicited. It is important to note that the above protocol applies to anyone with at least 1 year of training under their belt. The reason being is that training at such a high intensity is taxing for novice lifters and would likely result in significant muscle soreness which may derail a training program or lead to a loss of motivation for training. The overarching point here is to avoid using current training protocols of sticking 2 to 3 reps from failure as an excuse to be lazy in the gym. I guarantee any prominent figure in the fitness industry didn’t get there by avoiding training to failure, train hard!

References:

1. Robinson ZP, Pelland JC, Remmert JF, Refalo MC, Jukic I, Steele J, and Zourdos MC, (2023). Exploring the Dose-Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions.

2. Grgic, J., Schoenfeld, B. J., Orazem, J., & Sabol, F. (2022). Effects of resistance training performed to repetition failure or non-failure on muscular strength and hypertrophy: A systematic review and meta-analysis. Journal of Sport and Health Science, 11(2), 202–211. https://doi.org/10.1016/j.jshs.2021.01.007

3. Armes C, Standish-Hunt H, Androulakis-Korakakis P, Michalopoulos N, Georgieva T, Hammond A, Fisher JP, Gentil P, Giessing J, Steele J. "Just One More Rep!" - Ability to Predict Proximity to Task Failure in Resistance Trained Persons. Front Psychol. 2020 Dec 23;11:565416. doi: 10.3389/fpsyg.2020.565416. PMID: 33424678; PMCID: PMC7785525.

4. Mansfield, Sean K.1,2; Peiffer, Jeremiah J.1,2; Hughes, Liam J.1,2; Scott, Brendan R.1,2. Estimating Repetitions in Reserve for Resistance Exercise: An Analysis of Factors Which Impact on Prediction Accuracy. Journal of Strength and Conditioning Research ():, August 31, 2020. | DOI: 10.1519/JSC.0000000000003779

5. Pelland, J.C., Robinson, Z.P., Remmert, J.F. et al. Methods for Controlling and Reporting Resistance Training Proximity to Failure: Current Issues and Future Directions. Sports Med 52, 1461–1472 (2022). https://doi.org/10.1007/s40279-022-01667-2