Muscle Failure Promotes Greater Muscle Hypertrophy in Low-Load but Not in High-Load Resistance Training

Abstract

Lasevicius, T, Schoenfeld,BJ, Silva-Batista, C,Barros, TdS,Aihara, AY,Brendon,H, Longo,AR, Tricoli, V, Peres,BdA, and Teixeira,EL.
Muscle failure promotes greater muscle hypertrophy in low-load but not in high-load resistance training. J Strength Cond Res XX(X):
000–000, 2019—The purpose of this study was to investigate the effects of an 8-week resistance training program at low and high loads
performed with and without achieving muscle failure on muscle strength and hypertrophy. Twenty-five untrained men participated in the
8-week study. Each lower limb was allocated to 1 of 4 unilateral knee extension protocols: repetitions to failure with low load (LL-RF;
;34.4 repetitions); repetitions to failure with high load (HL-RF;;12.4 repetitions); repetitions not to failure with low load (LL-RNF;;19.6
repetitions); and repetitions not to failure with high load (HL-RNF; ;6.7 repetitions). All conditions performed 3 sets with total training
volume equated between conditions. The HL-RF and HL-RNF protocols used a load corresponding to 80% 1 repetitionmaximum (RM),
while LL-RF and LL-RNF trained at 30%1RM.Muscle strength (1RM) and quadriceps cross-sectional area (CSA) were assessed before
and after intervention. Results showed that 1RMchanges were significantly higher for HL-RF (33.8%, effect size [ES]: 1.24) and HL-RNF
(33.4%, ES: 1.25) in the post-test when compared with the LL-RF and LL-RNF protocols (17.7%, ES: 0.82 and 15.8%, ES: 0.89,
respectively). Quadriceps CSA increased significantly for HL-RF (8.1%, ES: 0.57), HL-RNF (7.7%, ES: 0.60), and LL-RF (7.8%, ES: 0.45),
whereas no significant changes were observed in the LL-RNF (2.8%, ES: 0.15).We conclude that when training with low loads, training
with a high level of effort seems to have greater importance than total training volume in the accretion of muscle mass, whereas for high
load training, muscle failure does not promote any additional benefits. Consistent with previous research, muscle strength gains are
superior when using heavier loads.

Key Words: muscular failure, muscle mass, strength, low load and high load

Full text

Original Research
Muscle Failure Promotes Greater Muscle
Hypertrophy in Low-Load but Not in High-Load
Resistance Training
Thiago Lasevicius,
1
Brad J. Schoenfeld,
2
Carla Silva-Batista,
1,3
Talita de Souza Barros,
4
Andr ´e Yui Aihara,
5
Helderson Brendon,
4
Ariel Roberth Longo,
4
Valmor Tricoli,
1
Bergson de Almeida Peres,
4
and
Emerson Luiz Teixeira
1,4
1
School of Physical Education and Sport, University of Sa
˜o Paulo, Sa
˜o Paulo, Brazil;
2
Department of Health Sciences, CUNY Lehman
College, Bronx, New York;
3
School of Arts, Sciences and Humanities, University of Sa
˜o Paulo, Sa
˜o Paulo, Brazil;
4
Paulista University,
UNIP, Sa
˜o Paulo, Brazil; and
5
America‘s Diagnostics S/A, Sa
˜o Paulo, Brazil
Abstract
Lasevicius,T,Schoenfeld,BJ,Silva-Batista,C,Barros,TdS,Aihara,AY,Brendon,H,Longo,AR,Tricoli,V,Peres,BdA,andTeixeira,EL.
Muscle failure promotes greater muscle hypertrophy in low-load but not in high-load resistance training. J Strength Cond Res XX(X):
000–000, 2019—The purpose of this study was to investigate the effects of an 8-week resistance training program at low and high loads
performed with and without achieving muscle failure on muscle strength and hypertrophy. Twenty-five untrained men participated in the
8-week study. Each lower limb was allocated to 1 of 4 unilateral knee extension protocols: repetitions to failure with low load (LL-RF;
;34.4 repetitions); repetitions to failure with high load (HL-RF; ;12.4 repetitions); repetitions not to failure with low load (LL-RNF; ;19.6
repetitions); and repetitions not to failure with high load (HL-RNF; ;6.7 repetitions). All conditions performed 3 sets with total training
volume equated between conditions. The HL-RF and HL-RNF protocols used a load corresponding to 80% 1 repetition maximum (RM),
while LL-RF and LL-RNF trained at 30% 1RM. Muscle strength (1RM) and quadriceps cross-sectional area (CSA) were assessed before
and after intervention. Results showed that 1RM changes were significantly higher for HL-RF (33.8%, effect size [ES]: 1.24) and HL-RNF
(33.4%, ES: 1.25) in the post-test when compared with the LL-RF and LL-RNF protocols (17.7%, ES: 0.82 and 15.8%, ES: 0.89,
respectively). Quadriceps CSA increased significantly for HL-RF (8.1%, ES: 0.57), HL-RNF (7.7%, ES: 0.60), and LL-RF (7.8%, ES: 0.45),
whereas no significant changes were observed in the LL-RNF (2.8%, ES: 0.15). We conclude that when training with low loads, training
with a high level of effort seems to have greater importance than total training volume in the accretion of muscle mass, whereas for high
load training, muscle failure does not promote any additional benefits. Consistent with previous research, muscle strength gains are
superior when using heavier loads.
Key Words: muscular failure, muscle mass, strength, low load and high load
Introduction
For many years, high-load resistance training (HL-RT) (i.e., $70%
1 repetition maximum [RM]) has been recommended as the main
strategy to stimulate gains in muscle strength and mass (17).
However, emerging research has challenged this notion from a hy-
pertrophy standpoint, with numerous studies reporting similar
changes in muscle growth between low-load resistance training (LL-
RT) (i.e., ,50% 1RM) and HL-RT (16,18,22,24,33). Alterna-
tively, greater strength gains have been consistently observed for
HL-RT vs. LL-RT (16,18,22,24,33).
It also has been proposed that resistance training performed
until muscle failure is necessary to maximize adaptations in
muscle strength and hypertrophy (7,28,33). This claim is based
on the hypothesis that it is necessary to perform repetitions until
muscle failure for the complete recruitment of high-threshold
motor units, which comprise type II muscle fibers (30,39). Be-
cause type II muscle fibers have a greater potential to increase
strength (35) and are more susceptible to hypertrophy than type I
fibers (12), muscle failure seemingly would be an important
stimulus to maximize muscle adaptations. However, there is ev-
idence that a high level of muscle activity can be achieved by HL-
RT before reaching muscle failure (34), thereby calling into
question the need to train to failure. Findings from longitudinal
studies on the topic are conflicting with some studies showing
advantages for achieving muscle failure (7,29,33) while others
reporting no benefit (21,25,31). A confounding issue in these
studies is that advantages for muscle failure with HL-RT occurred
concomitantly with a greater total training volume, suggesting
that positive results may have been induced by a higher total
training volume rather than muscle failure. Thus, it is difficult to
draw conclusions from the literature as to the role of muscle
failure since studies on the topic performed a similar number of
repetitions in the failure and nonfailure groups (19) or did not
equalize the total training volume (7,21). It is well established that
total training volume plays an important role in muscular
strength and hypertrophy (27,32), and thus, this variable must be
matched between groups to determine causality as to the role of
training to failure in promoting muscular adaptations.
This study aimed to investigate the volume-equated effects of
HL-RT and LL-RT performed with and without muscle failure on
muscle strength and hypertrophy. We hypothesized that muscle
hypertrophy and strength gains would be similar between HL-RT
Address correspondence to Emerson Luiz Teixeira, emerson_teixeira2014@usp.br.
Journal of Strength and Conditioning Research 00(00)/1–6
ª2019 National Strength and Conditioning Association
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protocols with or without muscle failure. Alternatively, we hy-
pothesized that muscle hypertrophy and strength gains would be
greater in the LL-RT protocol performed to muscle failure when
compared with not training to failure.
Methods
Experimental Approach to the Problem
We used a longitudinal design to compare the effects of 8 weeks of
RT at low and high loads performed with and without achieving
volitional failure on muscle strength and hypertrophy. Before the
start of the training program, subjects reported to the laboratory and
were familiarized with performance of the 1RM test performed on
a unilateral leg extension machine. After 72 hours, subjects repeated
the 1RM test and were considered familiarized with the testing
procedures when the interday strength variation was #5%. The
1RM values for all subjects were obtained within 3 visits. At least 72
hours after the last 1RM test, muscle cross-sectional area (CSA) of
the quadriceps was obtained through magnetic resonance imaging
(MRI). After the MRI, each subject’slimbwasallocatedinaran-
domized fashion to 1 of the 2 training protocols based on 1RM and
CSA values: HL-RT leading to repetition failure (HL-RF, 13 limbs);
LL-RT leading to repetition failure (LL-RF, 12 limbs). The contra-
lateral leg was allocated to the same loading protocol of the opposing
leg but without achieving failure: HL-RT not leading to repetition
failure (HL-RNF, 13 legs) and LL-RT not leading to repetition fail-
ure (LL-RNF, 12 limbs). HL-RNF and LL-RNF protocols per-
formed the same total training volume as HL-RF and LL-RF,
respectively. Training was performed twice per week on non-
consecutive days for 8 weeks. After 4 weeks of training, 1RM was
retested 72 hours after the eighth training session to readjust training
load in the ensuing weeks (5–8 weeks). Quadriceps CSA was
assessed 72 hours after completing the last training session, with
subsequent assessment of 1RM 48 hours later. The subjects’rating of
perceived exertion (RPE) was assessed at the end of each training
bout. Subjects were instructed to maintain their usual and customary
dietary practices throughout the course of the study.
Subjects
Thirty-two male individuals volunteered to participate in this study
(age range 19 to 34 years old). Subjects were physically active, but
none had engaged in any kind of regular resistance training or reg-
ular participation in any strength-based sporting activity for the
lower limbs in the past 6 months before study, nor did they partic-
ipate in any parallel program of physical training during the study
period. All subjects were free from cardiovascular and/or neuro-
muscular disorders. Seven subjects withdrew from the study due to
personal reasons; therefore, data from 25 subjects were considered
for analysis. Group characteristics are shown in Table 1. Subjects
were informed about the benefits, discomforts, and possible risks of
the study and signed a free and informed consent term before par-
ticipation. The study was conducted according to the Declaration of
Helsinki, and the University of São Paulo Research Ethics Com-
mittee approved the experimental protocol.
Procedures
Maximum Dynamic Strength Test. Unilateral 1RM knee exten-
sion testing of the right and left lower limbs was performed as per
American Society of Exercise Physiologists recommendations (2).
The test was performed in a leg extension machine (10A-CO12 CAP,
Gervasport, Cotia, SP, Brazil) under isotonic conditions. Subjects
started with a 5-minute warm-up running on a treadmill at 9 km·h
2
1
, followed by 3 minutes of light stretching of the lower limbs. They
then performed a specific warm-up comprising 2 sets: in the first
set, they performed 8 repetitions at approximately 50% 1RM; in
the second set, they performed 3 repetitions at approximately 70%
1RM. A 2-minute rest interval was used between warm-up sets.
Both loads were estimated based on the subject’s familiarization
sessions. Three minutes after the specific warm-up, subjects tested
for their 1RM, herein defined as performance of a complete cycleof
the exercise with the greatest load they could lift. A complete cycle
involved performing a full knee extension (0°) starting from the
initial position of 90° of flexion and then returning to the starting
position while maintaining control throughout the entire move-
ment range. The load was progressively increased from the last set
of the specific warm-up until the subject could not perform the
exercise in the required manner. A 3-minute rest interval was used
between attempts. The greatest load lifted during the trials was
considered as 1RM. Final values were obtained in a maximum of 5
attempts. The coefficient of variation (CV) between 2 measures
performed 72 hours apart was 3.3%.
Quadriceps Cross-Sectional Area. Quadriceps CSA was obtained
through MRI (Signa LX 9.1; GE Healthcare, Milwaukee, WI).
Subjects assumed a supine position in the MRI unit with knees
extended and lower limbs straight. Subjects remained lying qui-
etly for 20 minutes before image acquisition. A bandage was used
to restrain limb movements during the test. An initial reference
image was obtained to determine the perpendicular distance from
the greater trochanter of the femur to the inferior border of the
lateral epicondyle of the femur, which was defined as the segment
length. Quadriceps CSA was measured at 50% of the segment
length with 0.8-cm slices for 3 seconds. The pulse sequence was
performed with a field of view between 400 and 420 mm, time of
repetition of 350 ms, eco time from 9 to 11 ms, 2 signal acquis-
itions, and a matrix of reconstruction of 256 3256 mm. The
images were then transferred to a workstation (Advantage
Workstation 4.3; GE Healthcare) to determine quadriceps CSA.
The quadriceps CSA images were traced in triplicate by a trained
researcher, and their mean values were used for further analysis.
The segment slice was divided into skeletal muscle, subcutaneous
fat tissue, bone, and residual tissue. Quadriceps CSA was de-
termined by subtracting the bone and subcutaneous fat area. The
CV between 2 measures performed 72 hours apart was 0.87%.
Resistance Training Protocols. Subjects performed the unilateral
knee extension exercise using a conventional leg extension ma-
chine (10A-CO12 CAP; Gervasport, Cotia, SP, Brazil), with
training performed twice a week for 8 weeks (total of 16 sessions).
Table 1
Subject characteristics by group.*
Baseline values
HL-RF
(n513)
HL-RNF
(n513)
LL-RF
(n512)
LL-RNF
(n512)
Age (y) 23.8 64.9 23.8 64.9 24.3 64.8 24.3 64.8
Height (cm) 176.6 67.2 176.6 67.2 175.4 66.0 175.4 66.0
Body mass (kg) 74.8 612.5 74.8 612.5 73.7 613.3 73.7 613.3
1RM (kg) 75.5 619.2 75.1 618.4 76.1 614.9 75.0 611.8
*HL-RF 5high-load resistance training leading to repetition failure; HL-RNF 5high-lo ad resistance
training not leading to repetition failure; LL-RF 5low-load resistance training leading to repetition
failure; LL-RNF 5low-load resistance training not leading to repetition failure; RM 5repetition
maximum.
Muscle Failure vs. Not Failure (2019) 00:00
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At the beginning of each training session, subjects performed
a general warm-up at 9 km·h
21
on a treadmill for 5 minutes,
followed by a specific warm-up comprising 1 set of 5 repetitions
at 50% 1RM. The general and the specific warm-up were well
tolerated by all subjects, and no one reported tiredness before
starting the experimental protocol. One minute afterward, sub-
jects performed 3 sets of their respective training protocols
(i.e., HL-RF and LL-RF) on one limb until concentric failure. The
mean of total number of repetitions in all sets from HL-RF and
LL-RF was then calculated, and 60% of these values were used to
perform each set of HL-RNF and LL-RNF protocols, re-
spectively, on the opposite limb. Additional sets were performed
in the RNF conditions to equate total training volume between
limbs. Thus, the HL-RNF and LL-RNF protocols performed
fewer repetitions per set but with a greater number of sets to
achieve the same total training volume for HL-RF and LL-RF,
respectively. The HL-RF and HL-RNF protocols used a load
corresponding to 80% 1RM, while LL-RF and LL-RNF proto-
cols trained at 30% 1RM. A 2-minute rest interval was used
between sets. For the muscular failure protocols, repetitions were
performed until subjects were unable to perform a repetition with
a full range of motion using proper form (i.e., starting from 90° of
flexion to full knee extension at 0°).
Number of Sets, Repetitions, and Total Training Volume. We
calculated the average number of sets and number of repetitions
performed per set throughout training period (16 training ses-
sions). The total training volume was calculated as the sum of the
training volume (number of sets 3number of repetitions 3ex-
ternal load) performed throughout training period.
Perceptual Response. Thirty minutes after the end of each ex-
perimental condition (i.e., RF and RNF), subjects reported RPE
using the CR10 scale (1). All subjects were given standardized
instructions as to perceptual response of exertion according to the
recommendations of Borg (1). Subjects were asked to give
a number corresponding to their perceived intensity of effort,
strain, and/or fatigue experienced during the exercise session. A
value of “0”represented “absolutely nothing”from an exertion
standpoint and “10”represented a “maximal exertion.”
Statistical Analyses
Data are presented as mean values and SDs. Data normality was
tested by the Shapiro-Wilk test and the visual inspection of box
plot to observe the presence of outliers. After confirming data
normality, a mixed model for repeated measures was applied with
2 factors: experimental protocols (HL-RF, HL-RNF, LL-RF, and
LL-RNF) and time (pre and post) for the quadriceps CSA. To rule
out confounding of lower-limb dominance on strength gains, we
used an ANCOVA with dominant and nondominant limbs as
covariates. For RPE, a mixed model for repeated measure was ap-
plied, assuming experimental protocols (HL-RF, HL-RNF, LL-RF,
and LL-RNF) and times (1–16 sessions) as fixed factors and subjects
as a random factor. Four different structures of covariance matrices
were tested, and the Bayesian information criterion (lowest BIC)
was used to select the model that best fit each individual data set.
The total number of sets, repetitions, and total training volume were
compared by a one-way analysis of variance (ANOVA). In all
analyses, the Tukey post hoc was used for multiple comparisons
when a significant F value was found. The effect size (ES) was cal-
culated as the post-training mean minus the pre-training mean di-
vided by the pooled pre-training SD (23), where the following
categories were used to evaluate the magnitude of the change for
1RM and quadriceps CSA: #0.49 small; 0.50–0.79 medium and
$0.80 large (5). The significance level was set a priori at p#0.05.
Data were analyzed using the SAS 9.3 statistical package.
Results
Quadriceps Cross-Sectional Area
There was a significant time 3condition interaction in quadriceps
CSA (p50.002). Quadriceps CSA increase significantly pre- to post-
test in HL-RF (85.0 612.1 to 91.7 611.4 cm
2
,ES:0.57,p50.001),
HL-RNF (85.1 610.9 to 91.5 610.4, ES: 0.60, p50.001), and LL-
RF (85.7 614.3 to 92.3 614.8 cm
2
, ES: 0.45, p50.001), with no
significant differences between these protocols (HL-RF vs. HL-RNF,
confidence interval [CI] 522.25 to 1.80, p50.81; HL-RF vs. LL-
RF, CI 522.25 to 1.80, p5081; HL-RNF vs. LL-RF, CI 520.51
to 1.38, p50.331). However, no significant increase in quadriceps
CSA was noted from pre- to post-test for LL-RNF (85.8 614.7 to
88.0 614.6 cm
2
, ES: 0.15, CI 521.9561 to 3.533, p50.994)
(Figure 1A). In addition, quadriceps CSA increases at post-test in HL-
RF, HL-RNF, and LL-RF were significantly higher when compared
with LL-RNF (CI 52.094–9.152, p50.004; CI 52.172–6.039, p
50.001; CI 52.802–7.905, p50.001, respectively).
Maximum Dynamic Strength Test (1 Repetition Maximum)
There was significant time 3condition interaction in unilateral
leg extension 1RM (p50.0001). The 1RM values increased pre-
to post-test in all training protocols (p,0.0001). However,
values for HL-RF (75.5 619.2 to 99.3 619.0 kg, ES: 1.24) and
HL-RNF (75.1 618.4 to 99.4 620.4 kg, ES: 1.25) were signif-
icantly greater when compared with the LL-RF and LL-RNF
protocols (76.1 614.9 to 89.2 616.9 kg, ES: 0.82, CI 5
8.728–24.73, p50.001 and 75.0 611.8 to 86.5 613.7 kg, ES:
0.89, CI 59.273–28.45, p50.001, respectively). No significant
differences in pre- to post-test 1RM values were detected between
protocols of the same intensity (HL-RF vs. HL-RNF, CI 524.79
to 4.96, p50.972 and LL-RF vs. LL-RNF, CI 529.20 to 3.87,
p50.383) (Figure 1B).
Number of Sets, Repetitions, and Total Training Volume
The average number of sets and repetitions performed by HL-RF,
HL-RNF, LL-RF, and LL-RNF were 3.0 60 sets and 12.4 63.1
reps, 5.5 60.5 sets and 6.7 61.6 reps, 3.0 60 sets and 34.4 67.7
reps, and 5.4 60.6 sets and 19.6 64.1 reps, respectively. Total
training volume values were similar among HL-RF, HL-RNF, LL-
RF, and LL-RNF (34,853 68,020 kg, 34,803 67,857 kg, 34,576
616,372 kg and 34,592 616,326 kg, p.0.05, respectively).
Rating of Perceived Exertion
There was a significant time 3condition interaction for RPE (p,
0.05). The RPE was significantly greater in all training sessions
for protocols performed until muscle failure (HL-RF and LL-RF)
compared with protocols without muscle failure (HL-RNF and
LL-RNF) (p,0.05) (Figure 2).
Discussion
This study investigated the effects of volume-equated LL-RT and
HL-RT with and without muscle failure on muscle strength and
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hypertrophy in untrained, physically active men. Our main
findings were as follows: (a) When performing low-load re-
sistance training, training with a very high level of effort is nec-
essary to increase muscle hypertrophy; (b) muscle failure with
HL-RT confers no additional benefits on muscle strength and
hypertrophy; (c) RPE is greater when training to failure as op-
posed to stopping short of failure, independent of load.
It has been suggested that low-load resistance training only
promotes similar muscle hypertrophy to high load resistance
training when the low load condition is performed to muscle
failure (10,22,24,26). Support for this hypothesis is based on
acute findings showing that low-load resistance training pro-
moted a greater increase in myofibrillar protein synthesis only
when performed until muscle failure and with a high volume of
training (3,4). Moreover, low-load training with blood flow re-
striction (BFR) to failure has been shown to produce superior
hypertrophy compared with a repetition-matched control per-
forming the same exercise without BFR (20); alternatively, when
low-load training without BFR is taken to failure, hypertrophy is
similar to the BFR condition (9). Our findings provide longitu-
dinal confirmation for this hypothesis with direct measures of
long-term hypertrophy in untrained men. These results were seen
regardless of training volume given that only LL-RF increased
muscle CSA despite total training volume being equated between
conditions. Taken as a whole, these findings indicate that when
engaging in low-load resistance training, performing sets with
a high level of effort is more important than a higher training
volume when the objective is to increase muscle hypertrophy.
Training to failure may heighten metabolic stress due to pro-
longed energy use from the glycolytic system, and the associated
buildup of metabolites could enhance the anabolic milieu, po-
tentially leading to greater muscle hypertrophy (13,19,28).
Consistent with the size principle, higher threshold motor units
are recruited early during a set of heavy load training, whereas the
initial repetitions in a low-load set primarily involve recruitment
of lower threshold motor units; only when a low-load set con-
tinues to the point where greater levels of force are needed to
sustain contractions do higher threshold motor units become
activated. Accordingly, it has been hypothesized that the fatigue
associated with training to muscle failure results in the progressive
recruitment of a greater number of high-threshold motor units,
which conceivably could enhance muscle hypertrophy (29,38).
However, when performing repetitions in proximity to failure,
but not going to failure, muscle activity seems to be the same as
when repetitions are taken to failure (25,34). To date, only one
study has investigated the effect of muscle failure in LL-RT and
HL-RT. N ´
obrega et al. (25) randomized untrained men to per-
form resistance training using either muscle failure or volitional
interruption at low and high loads (e.g., 30 and 80% 1RM, re-
spectively). After 12 weeks, similar increases in muscle thickness
Figure 1. A) Quadriceps cross-sectional area (CSA) and (B) maximum dynamic strength (1RM) (mean 6SD) evaluated before
(pre) and after 8 weeks (post). High-load resistance training leading to repetition failure (HL-RF); high-load resistance training
not leading to repetition failure (HL-RNF); low-load resistance training leading to repetition failure (LL-RF); and low-load
resistance training not leading to repetition failure (LL-RNF). *Significantly different compared with pre (p,0.002); #Signifi-
cantly different when compared with LL-RF and LL-RNF (p,0.002). RM 5repetition maximum.
Figure 2. Ratings of perceived exertion (RPE) (mean 6SD) evaluated in each training session.
High-load resistance training leading to repetition failure (HL-RF); high-load resistance training not
leading to repetition failure (HL-RNF); low-load resistance training leading to repetition failure (LL-
RF); and low-load resistance training not leading to repetition failure (LL-RNF). #Significantly dif-
ferent when compared with HL-RNF and LL-RNF (p,0.05).
Muscle Failure vs. Not Failure (2019) 00:00
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were observed both with and without muscle failure independent
of the load used. Our results conflict with those of N´
obrega et al.
(25), given that we showed significantly greater muscle growth
when low-load training was performed to failure versus not to
failure. A possible explanation for these discrepancies is that in
the study by N ´
obrega et al. (25), the subjects in the volitional
interruption condition terminated a set when they felt sufficiently
fatigued. This approach resulted in performance of a comparable
number of repetitions between conditions, indicating the voli-
tional interruption group was in close proximity to failure. Al-
ternatively, our study showed substantial differences in the
number of repetitions performed between the low-load failure
and nonfailure conditions (34.4 vs. 19.6 repetitions, respectively).
Combined, the literature suggests that a high level of effort is
required to elicit hypertrophy during low-load training, and
simply increasing volume will not augment results if the effort
expended is low.
As opposed to our findings regarding low-load resistance
training, muscle failure did not provide additional benefits on
muscular adaptations when training at high resistance training
loads in untrained men. This result is largely in agreement with
the prevailing body of literature on the topic. Sampson and
Groeller (31) found similar increases in elbow flexors CSA after
12 weeks of regimented HL-RT (85% 1RM) performed either
until failure or not to failure. Martorelli et al. (21) also showed
similar increases in elbow flexors CSA after 10 weeks of HL-RT
between the failure group and the nonfailure group, indicating no
advantage in performing sets to muscle failure. Taken as a whole,
it can be inferred that muscle fibers are sufficiently stimulated to
hypertrophy when HL-RT sets are stopped short of concentric
failure, and that further repetitions do not elicit additional ben-
efits (25,34).
Regarding muscle strength, we found that muscle failure is not
obligatory to maximize muscle strength, independent of training
load in untrained men. Although all groups increased muscle
strength, HL-RF (33.8%) and HL-RNF (33.4%) elicited greater
increases when compared with the LL-RF and LL-RNF protocols
(17.7 and 15.8%, respectively). Our data are consistent with
previous studies showing that heavier loads are required to
maximize gains in dynamic strength (18,22,26,33). Of the studies
that have investigated the effect of muscle failure in HL-RT on
muscle strength, our results are in agreement with those of Fol-
land et al. (11), who compared high and low fatigue protocols and
found no difference between groups after 9 weeks of training.
Similarly, Izquierdo et al. (15) reported no additional strength
benefits from training to failure in lower- and upper-body exer-
cise. In an attempt to provide clarity on the body of literature,
Davies et al. (6) performed a meta-analysis that found similar
strength increases when high-load resistance training was per-
formed to failure versus not to failure.
Only one study has endeavored to investigate the effect of
muscle failure on muscle strength in low-load resistance training.
N´
obrega et al. (25) found that muscle failure did not increase
muscle strength over and above that achieved by the volitional
interruption group. However, as previously mentioned, the
number of repetitions completed in the volitional interruption
group was similar to the muscle failure group, obscuring the
ability to draw inferences about the importance of muscle failure
on low-load strength gains. When taken in conjunction with our
findings, it can be inferred that muscle failure is not a significant
factor for increasing muscle strength in low-load resistance
training. Given the design of our study, the evidence suggests that
achieving a certain amount of volume of training may be more
important to maximize muscle strength than performing repeti-
tions until muscle failure.
The RPE was significantly greater in all training sessions for
protocols performed until muscle failure. This suggests that
training to muscle failure in beginners may not only induce un-
necessary exertion, but also may impair muscle recovery due to
the higher metabolic and neuromuscular impact. In addition,
training with a high level of unnecessary effort could reduce ex-
ercise enjoyment, ultimately resulting in a lower adherence to the
resistance training program (36).
This study is not without limitations. First, although subjects
were instructed to maintain their usual and customary diet, we
did not attempt to monitor nutritional intake, which may have
influenced results between conditions. However, the within-
subject design as well as the randomization process would have
helped to minimize any potential variations attributed to this
variable. Second, the findings are specific to untrained young
men; it is not clear whether training to failure may be necessary to
promote a growth response in women, the elderly, or those who
are resistance trained. Third, findings are specific to performance
of a single-joint lower-body exercise and thus cannot necessarily
be generalized to upper-body and multijoint exercises. Fourth, we
cannot rule out the possibility that a cross-education effect may
have influenced our results since muscle failure condition always
was performed first. However, our results are in accordance with
other studies (21,31) showing that performing repetitions to
failure is not the major issue to development of muscle strength;
thus, if the cross-education did in fact occur, it was not sufficient
to confound results. Fourth, our training protocol used only the
leg extension exercise, limiting generalizability to hypertrophic
changes associated with failure training using other exercises and
in regions of the body other than the quadriceps. Finally, although
we used a gold-standard assessment for hypertrophy (MRI),
measurements of CSA were taken at the midpoint of the thigh.
Research shows that the quadriceps femoris often hypertrophies
in a nonuniform manner along the length of the muscle with
persistent resistance training (8,14,37). It is possible that training
to failure may induce regional specific hypertrophy in the proxi-
mal or distal region that would not have been accounted for in our
testing protocol, although it is difficult to envision a rationale as
to why such an effect would occur.
Practical Applications
Based on our findings, we propose that a high level of effort is
required to elicit hypertrophic adaptations in low-load re-
sistance training in beginners, even with total training volume
matched. Alternatively, muscle strength increases in total
training volume-equated low load are similar independent of
whether training is performed to failure in untrained men.
When performing resistance training at high loads, muscle
failure does not confer any additional strength or
hypertrophy-related benefits compared with stopping well
short of failure provided total training volume is equated be-
tween conditions in novice trainees.
Acknowledgments
This manuscript is original and not previously published, nor is it
being considered elsewhere until a decision is made as to its
acceptability by the JSCR Editorial Review Board. No funding
was received for this study from National Institutes of Health
Muscle Failure vs. Not Failure (2019) 00:00 |www.nsca.com
5
Copyright © 2019 National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.

(NIH), Welcome Trust, or Howard Hughes Medical Institute
(HHMI). The authors declare they have no conflict of interest.
The results of this study do not constitute endorsement by the
authors or the National Strength and Conditioning Association
(NSCA).
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