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Does Training to Failure Maximize Muscle Hypertrophy?
Article in Strength and conditioning journal · March 2019
DOI: 10.1519/SSC.0000000000000473
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Strength and Conditioning Journal Publish Ahead of PrintDOI: 10.1519/SSC.0000000000000473
Does Training to Failure Maximize Muscle Hypertrophy?
Brad Schoenfeld, PhD, CSCS, FNSCA1, *
Jozo Grgic, MS2
1Department of Health Sciences, Lehman College, Bronx, NY, USA
2Institute for Health and Sport (IHES), Victoria University, Melbourne, Australia
*Corresponding author:
Department of Health Sciences, Lehman College, Bronx, NY, USA
Email: [email protected]
Brad Jon Schoenfeld is an Assistant Professor in Exercise Science and director of the Human
Performance Laboratory at CUNY Lehman College in the Bronx, New York.
Jozo Grgic is a PhD student at the Institute of Sport, Exercise and Active Living, Victoria
University, Melbourne, Australia. ACCEPTED
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Abstract: It has been proposed that training to failure is a necessary strategy to maximize
muscle growth. This paper examines the research behind these claims, and attempts to draw
evidence-based conclusions as to the practical implications for hypertrophy training.
Introduction
Resistance training is well-established as a primary exercise-based strategy to enhance
muscle mass in humans. The manipulation of program variables is believed to be a key factor in
optimizing muscular gains (1, 14). Variables such as volume, load, and frequency have been well
explored in the literature (28-30). One variable that has not received as much attention is the set
endpoint, operationally defined as the point at which a set of repetitions is terminated (34). The
intensity of effort expended during a set is best estimated by how close an individual comes to
reaching muscular failure, which can be defined as the point where the activated muscles are
incapable of completing another complete repetition without assistance (22, 25). Training to
muscular failure has been promoted since the 1940s when Thomas DeLorme, a physician in the
US Army at the time, published a series of papers advocating the use of this method in resistance
exercise (15). While training to failure has long been employed in resistance training programs,
particularly by bodybuilders, the number of well-controlled studies that have explored this topic
is small. Initially, Rooney et al. (21) indicated a benefit for training to failure (versus not training
to failure) for gains in strength; however, these results were not corroborated by others (8).
Recognizing the equivocal body of evidence, Davies et al. (4) recently conducted a meta-analysis
for strength gains, and concluded that similar increases in strength might be attained with both
muscle failure and non-failure training. However, this meta-analysis (as well as the majority of
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original studies) only focused on gains in strength; the effects of training to failure on muscle
hypertrophy have been less explored.
Some researchers have put forth the claim that training to failure is necessary to
maximize muscle growth (2, 7, 38). This contention is at least in part based on the underlying
belief that training to failure elicits full motor unit recruitment, which is considered an essential
component for increases in muscle size (37). However, the applicability of this claim may be
load-specific. High-threshold motor units are recruited almost immediately when lifting very
heavy loads as high levels of force are required from the onset of the exercise (5). This is in
contrast to low-load training, where recruitment of the larger motor units is delayed because a
high level of force is not initially needed to lift the weight; as the set becomes more fatiguing,
higher threshold motor units are then recruited to maintain force output. This physiological
response has been demonstrated in studies showing that fatiguing concentric contractions
produce a corresponding increase in surface electromyography activity during low-load training
(27, 32), but the effect diminishes with the use of progressively heavier loads. It therefore could
be hypothesized that the need to train to failure becomes increasingly less relevant when training
with high intensities of load.
It also has been hypothesized that training to failure augments muscular growth by
increasing metabolic stress. There is some evidence that the buildup of metabolites – byproducts
from anaerobic energy production – enhances the anabolic response to resistance training (26,
35), although this claim remains speculative (36). Research shows that continuing a set to the
point of volitional fatigue heightens energy demands, thereby resulting in a greater metabolite
accumulation (10). This seemingly supports a beneficial metabolic effect of training to the point
of failure. However, it is not clear whether the additional metabolic stress produced during an
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‘all-out’ set leads to a meaningfully greater accretion of muscle proteins compared to a set
stopped short of failure. It is conceivable that a threshold exists for metabolic stress beyond
which no further beneficial effects are realized. The purpose of this column is to (1) review the
current literature as to the effects of failure training on hypertrophic adaptations, and; (2) draw
evidence-based conclusions as to how the strategy should be employed in practice, both in terms
of integration with other resistance training variables and avoiding burnout, for those seeking
maximize muscle growth.
Overview of the Literature
There is surprisingly little longitudinal research investigating the topic of training to
failure. An often-cited study in support of training performed to failure compared muscle growth
in recreationally-trained men performing a multiple set protocol of 10 reps with 60 seconds rest
between sets, whereby one group trained to failure and the other did not (11). Exercises consisted
of the lat pulldown, shoulder press, and leg extension, with 3-5 sets performed per exercise.
Results showed that the group training to failure gained significantly more muscle over the
course of the 12-week study than the group that did not train to muscle failure (+13% vs. +4%).
While on the surface these findings may seem intriguing, the caveat here was that one group
performed all sets continuously to failure while the group that did not train to failure took a 30-
second break at the mid-point of each set. This protocol does not replicate traditional non-failure
training regimens where sets are stopped at a given number of repetitions from fatigue; thus, it
has limited ecological validity.
In a study by Schott et al. (31) one group trained using a low-fatigue training protocol
that included 4 sets of 10 contractions (each contraction lasted 3-seconds followed by 2-seconds
of rest) with 2 minutes of rest between sets while another group trained with high levels of
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fatigue induced by performing 4 sets of 30-second contractions with 1 minute of between-set
rest. Only the latter group experienced significant increases in muscle size after 14 weeks of
training, adding further support for the importance of fatigue for gains in muscle mass. However,
as in the Goto et al. (11) study, the protocol did not mirror resistance exercise performed in the
practical context as it included only isometric muscle actions. Furthermore, the protocol in the
low fatigue group included inter-repetition rest which, again, is not often employed in traditional
resistance exercise.
Sampson and Groellier (22) compared the effects of exercising to muscle failure using a
more traditional resistance training protocol. Twenty-eight untrained young men performed 4
sets of arm curls at 85% one repetition maximum (1RM). Subjects were randomized either to
carry out sets to failure using a 2-second concentric and 2-second eccentric action or to stop
approximately 2 reps short of failure while employing either rapid shortening (explosive
concentric and 2-second eccentric action) or stretch-shortening (explosive movement on both
concentric and eccentric components). After 12 weeks, the average gain in biceps muscle cross-
sectional area was ~11% for all subjects combined, with no significant differences noted between
groups. A key point to keep in mind here is that subjects trained with heavy loads equating to a
6RM. It therefore can be hypothesized that training to failure becomes less important when using
heavy weights, which is consistent with the previously mentioned research on muscle activation.
The study did have a potential confounding issue: the non-failure groups actually performed a
single set to failure at the end of each week to determine the load for the subsequent week of
training. Whether this had a significant effect on the results is not clear.
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Martorelli et al. (16) randomly assigned 89 active women to one of three groups: (1) a
group that performed three sets of repetitions to failure at 70% 1RM; (2) a group that performed
four sets of seven repetitions not to failure, but with volume equalized to the failure condition,
and; (3) a group that performed three sets of seven repetitions not to failure. Training consisted
of free-weight biceps curls performed two days per week for ten weeks. The authors observed
significant main effects for time and for the interaction between the groups. However, the
authors did not perform further post-hoc analyses to determine where the differences between the
groups occurred. The relative changes substantially favored the group training to muscle failure
(17.5% versus 8.5% in the group not training to failure, with equal volume). The magnitude of
differences between groups raises the possibility of a type II error, whereby statistically
significant differences went undetected. The group that performed repetitions not-to-failure
without matching volume to the two other groups did not significantly increase muscle thickness.
Even if there indeed was an advantage favoring the group that trained to failure in the
Martorelli et al. study, it should be noted that the included participants were young women and
therefore, the results cannot be generalized to older adults. Older adults might experience slower
post-exercise recovery and may warrant a different approach to their program design (6). da
Silva et al. (3) essentially used the same study design as Martorelli and colleagues (16) while
including older men (66 ± 5 years) as participants. In this study, the group training to failure and
the group that did not train to failure with equalized volume experienced similar increases in
quadriceps muscle thickness; no significant pre-to-post changes occurred in the group that did
not train to failure and that performed less volume than the two other training groups. These
results may indicate that age (and the age-related recovery from exercise) is an important factor
to consider when prescribing resistance exercise performed to muscle failure. Furthermore, the
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study by da Silva et al. (3) indicates that training to muscle failure may not be needed for
increases in muscle size in older adults. Finally, the totality of findings also suggest that volume
load may be an important variable when considering the relevance of training to failure.
Most recently, Nobrega et al. (18) allocated 32 untrained men to perform 3 sets of leg
extension exercise at either a high load (80% 1RM) or low load (30% 1RM), twice per week.
The study employed a within-subject design whereby each lower limb was randomized to
execute these conditions either to failure or terminated at the point at which participants
voluntarily interrupted training. After 12 weeks, increases in muscle cross-sectional area were
statistically similar between conditions. It should be noted that the differences in volume load
between failure and non-failure training were rather slight in both the high-load conditions
(training to failure: 26,694 kg; training not to failure: 26,042 kg) and in the low-load conditions
(training to failure: 21,114 kg; training not to failure: 20,643 kg), suggesting that the non-failure
condition performed sets at close to full fatigue (likely only one to two repetitions shy of failure).
These results, therefore, may indicate that training close to muscle failure may be similarly
effective for increasing muscle size as training that includes reaching actual muscle failure.
Practical Implications
A primary issue when attempting to draw evidence-based conclusions on the topic is
qualifying the alternative endpoint to failure. Specifically, if failure is not the chosen option, then
at what point should a set be terminated? One option may be to use the “repetitions in reserve”
(RIR) scale proposed by Zourdos et al. (39), whereby a RIR of 0 equates to training to failure, a
RIR of 1 equates to stopping one repetition short of failure, a RIR of 2 equates to stopping two
repetitions short of failure, etc. However, as indicated by Hackett et al. (12) individuals may
underestimate the number of repetitions to failure during the earlier sets and the accuracy of
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prediction may increase with subsequent sets. Other researchers also show that resistance
training experience may increase the ability to accurately predict repetitions to failure (33) and
therefore, when using this scale, a period of familiarization should be incorporated in the study
design in order to keep the comparison between the groups valid.
A potential issue with continuous training to failure is that it may increase the potential
for overtraining and psychological burnout (9). This hypothesis was supported by a study from
Izquierdo et al. (13), who randomized members of the Spanish Basque ball team to perform 3
sets of 8 resistance exercises targeting the body’s major muscle groups either to failure or non-
failure using 70-80% of 1RM. Training was carried out twice a week for 16 weeks. Results
showed that training to failure blunted resting levels of anabolic hormones (IGF-1 and
testosterone); an outcome indicative of non-functional overreaching (9). Thus, if failure training
is employed in a program, it seems prudent to do so judiciously. There is no research on the
topic, but one strategy would be to limit its use to the last set of an exercise. For example, if
muscle failure is incorporated in the first set of a given exercise, it is likely that the performance
(concerning the total number repetitions) would be hindered on subsequent sets (24). By limiting
the use of a muscle failure only on the last set of a given exercise we may ensure that sufficient
volume is achieved, although the effects of failure training on volume remain somewhat
equivocal (24). As with all resistance training variables, failure training could also be periodized
so that it is used more extensively in a short training block (i.e. the peaking phase of a mass-
building program) and less so during other training cycles.
Based on the limited available evidence, it would appear that stopping several repetitions
short of failure when training with moderately heavy loads (6-12 RM) does not seem to
compromise hypertrophy, at least when training volume is equated. The paucity of research with
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light loads makes it difficult to extrapolate a specific recommendation, but a logical case (from a
motor unit recruitment perspective) can be made that RIR values would need to be in the range
from 0 to 2 in order to fully stimulate the highest threshold motor units, and thus maximize
hypertrophic adaptations. More research is needed to strengthen evidence-based conclusions.
Other more advanced methods, such as the assessment of velocity loss also require
attention in this context (23). In one study, Pareja-Blanco et al (19) randomized resistance-
trained men to one of two protocols that differed only in the amount of repetition velocity loss
allowed in each set: 20% vs. 40% of velocity loss. The 40% velocity loss group trained in close
proximity to muscle failure while the 20% velocity loss group performed approximately half of
the maximum number of repetitions. After the 8-week training intervention, greater hypertrophy
in the vastus lateralis and intermedius was observed in the 40% velocity loss group. These
findings suggest that training to failure (or very close to it) might be indeed of importance for
maximizing increases in muscle size. One limitation here is that the groups were not matched for
total volume in terms of the total number of performed repetitions as the 40% velocity loss group
also performed more total repetitions. This may be relevant given the linear dose-response
relationship between volume and muscle hypertrophy (28). It would be interesting for future
studies to use a similar protocol while adding more sets to the small velocity loss group in order
to equate the volume load comparison.
An important limitation with the current body of literature is that the majority of studies
to date have been carried out in untrained subjects. A case can be made that as a lifter gains more
training experience, there is an increasing need to challenge the neuromuscular system with
higher levels of effort. Support for this hypothesis can be inferred in the results of the study by
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Pareja-Blanco and colleagues (19), but additional research is needed to draw stronger
conclusions.
Ultimately, training to failure also needs to be considered in the context of the whole
resistance training program (see Figure 1). One variable that is likely important to take into
account here is training frequency. In a recent study, training to failure in each set using a 3 x 10
repetitions protocol (compared to training without reaching failure using a 6 x 5 repetitions
protocol) slowed down the recovery up to 24-48 h post-exercise (17). This attenuated post-
exercise recovery will not likely be of practical importance if the training program is performed
with a low weekly training frequency per muscle group (e.g., training each muscle group once
per week). However, when training with a higher training frequency (e.g., training a muscle
group +4 times week), training to failure should likely be used sparingly to allow a better
neuromuscular condition before the subsequent training session. Slower rates of recovery may be
more pronounced when exercising with a higher number of repetitions, which is another
component that needs to be taken into account in program design (20).
It also is important to consider the specific exercises performed. Multi-joint movements,
particularly those performed using free weights and of a structural nature, are substantially more
taxing on the neuromuscular system than single-joint exercises. It therefore seems pragmatic to
limit the use of training to failure in exercises such as squats, deadlifts, presses, and rows.
Alternatively, failure can be employed more liberally when performing single-joint exercises as
they are much less physically and mentally demanding.
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Figure 1: Key aspects to consider when incorporating training to muscle failure in
resistance exercise.
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