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European Journal of Sport Science
ISSN: 1746-1391 (Print) 1536-7290 (Online) Journal homepage: http://www.tandfonline.com/loi/tejs20
Effects of different intensities of resistance
training with equated volume load on muscle
strength and hypertrophy
Thiago Lasevicius, Carlos Ugrinowitsch, Brad Jon Schoenfeld, Hamilton
Roschel, Lucas Duarte Tavares, Eduardo Oliveira De Souza, Gilberto
Laurentino & Valmor Tricoli
To cite this article: Thiago Lasevicius, Carlos Ugrinowitsch, Brad Jon Schoenfeld, Hamilton
Roschel, Lucas Duarte Tavares, Eduardo Oliveira De Souza, Gilberto Laurentino & Valmor
Tricoli (2018): Effects of different intensities of resistance training with equated volume
load on muscle strength and hypertrophy, European Journal of Sport Science, DOI:
10.1080/17461391.2018.1450898
To link to this article: https://doi.org/10.1080/17461391.2018.1450898
Published online: 22 Mar 2018.
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ORIGINAL ARTICLE
Effects of different intensities of resistance training with equated volume
load on muscle strength and hypertrophy
THIAGO LASEVICIUS
1,2
, CARLOS UGRINOWITSCH
2
, BRAD JON SCHOENFELD
3
,
HAMILTON ROSCHEL
2
, LUCAS DUARTE TAVARES
1,2
, EDUARDO OLIVEIRA DE
SOUZA
4
, GILBERTO LAURENTINO
2
, & VALMOR TRICOLI
2
1
Department of Health Sciences, University Ibirapuera, São Paulo, Brazil;
2
Department of Sport, School of Physical Education
and Sport, University of São Paulo, São Paulo, Brazil;
3
Department of Health Sciences, CUNY Lehman College, Bronx, NY,
USA &
4
Department of Health Sciences and Human Performance, The University of Tampa, Tampa, FL, USA
Abstract
The present study investigated the effects of different intensities of resistance training (RT) on elbow flexion and leg press
one-repetition maximum (1RM) and muscle cross-sectional area (CSA). Thirty men volunteered to participate in an RT
programme, performed twice a week for 12 weeks. The study employed a within-subject design, in which one leg and arm
trained at 20% 1RM (G20) and the contralateral limb was randomly assigned to one of the three conditions: 40% (G40);
60% (G60), and 80% 1RM (G80). The G20 started RT session with three sets to failure. After G20 training, the number
of sets was adjusted for the other contralateral limb conditions with volume-matched. CSA and 1RM were assessed at pre,
post-6 weeks, and post-12 weeks. There was time effect for CSA for the vastus lateralis (VL) (8.9%, 20.5%, 20.4%, and
19.5%) and elbow flexors (EF) (11.4%, 25.3%, 25.1%, and 25%) in G20, G40, G60, and G80, respectively (p> .05).
G80 showed higher CSA than G20 for VL (19.5% vs. 8.9%) and EF (25% vs. 11.4%) at post-12 weeks (p< .05). There
was time effect for elbow flexion and unilateral leg press strength for all groups post-12 weeks (p< .05). However, the
magnitude of increase was higher in G60 and G80. In conclusion, when low to high intensities of RT are performed with
volume-matched, all intensities were effective for increasing muscle strength and size; however, 20% 1RM was suboptimal
in this regard, and only the heavier RT intensity (80% 1RM) was shown superior for increasing strength and CSA
compared to low intensities.
Keywords: Low-load, high-load, volume of training, muscle size
Highlights
.Resistance training with intensity ranging 20–80% 1RM are effective to increase strength and muscle hypertrophy.
However, low intensity (20% 1RM) was suboptimal for maximizing muscle hypertrophy.
.A wide spectrum of intensities, from 40–80% 1RM, are viable options to increase muscle mass. It is feasible that employing
combinations of these intensities may enhance hypertrophic results, as well as allow for better recovery by alleviating joint-
related stresses from continuous heavy-load training.
.The initial 6 weeks of training all the studied intensities can produce increases in strength in men with no experience in
resistance training. However, if maximizing strength gains over the long-term training is a primary goal, it is necessary
employ higher training intensities.
Introduction
Resistance training (RT) is the primary mode of exer-
cise to increase muscle strength and hypertrophy in
humans. These increases can positively impact the
ability to carry out daily activities (FitzGerald et al.,
2004;Rantanenetal.,2002)aswellassignificantly
improve overall health and wellness. Additionally, RT
has been shown to be an important strategy for enhan-
cing physical performance in athletics (Los Arcos et al.,
2014; Markovic, Jukic, Milanovic, & Metikos, 2007;
Pareja-Blanco, Rodríguez-Rosell, Sánchez-Medina,
Gorostiaga, & González-Badillo, 2014).
Variables of an RT programme such as rest inter-
val, frequency, volume, and intensity can be
© 2018 European College of Sport Science
Correspondence: Thiago Lasevicius, Department of Health Sciences, University Ibirapuera, C/Av. Interlagos, 1329, Chácara Flora –São
Paulo PC 04661-100, São Paulo, Brazil. E-mail: lasevicius.thiago@gmail.com
European Journal of Sport Science, 2018
https://doi.org/10.1080/17461391.2018.1450898
manipulated to induce muscular adaptations (Amer-
ican College of Sports Medicine, 2009; Schoenfeld,
Grgic, Ogborn, & Krieger, 2017). With respect to
intensity, training with loads equating to 65–85% of
maximum dynamic strength (1RM) has been rec-
ommended to increase strength and muscle mass
(American College of Sports Medicine, 2009). Alter-
natively, several studies have shown that low to moder-
ate intensities (30–50% 1RM) promote similar gains
in muscle mass compared to training with higher
intensities (Lamon, Wallace, Leger, & Russell, 2009;
Leger et al., 2006;Mitchelletal.,2012; Ogasawara,
Loenneke, Thiebaud, & Abe, 2013;Schoenfeld,
Peterson, Ogborn, Contreras, & Sonmez, 2015).
Mitchell et al. (2012) found that leg extension exercise
performed at 30% 1RM until failure similarly
increased quadriceps muscle volume compared to
high-intensity exercise (80% 1RM) and was superior
to a 30% 1RM non-failure condition. The authors
speculated that this finding was due to complete
recruitment of the motor unit pool when low-intensity
exercise is performed to volitional failure and with a
large volume of training (VT). Alternatively, high-
intensity RT resulted in superior strength gains com-
pared to low-intensity exercise (Mitchell et al.,
2012). Intriguingly, electromyography research
shows greater muscular activation in high- versus
low-intensity RT (Schoenfeld, Contreras, Willardson,
Fontana, & Tiryaki-Sonmez, 2014), suggesting that
full spectrum of motor units may not be fully stimu-
lated when training at lower intensity.
Many studies have sought to compare muscular
adaptations with low- versus high-intensity RT.
Some have found greater increases in muscle hyper-
trophy with heavier intensity (Campos et al., 2002;
Holm et al., 2008; Schuenke et al., 2012), while
others showed no significant differences between
low and high intensity (Lamon et al., 2009; Leger
et al., 2006; Mitchell et al., 2012; Ogasawara
et al., 2013; Popov et al., 2006; Schoenfeld et al.,
2015; Tanimoto et al., 2008; Tanimoto & Ishii,
2006). A confounding issue in the majority of
these studies is that VT was not equated between
groups, and the few studies that endeavoured to
do so all used the VT of the high-intensity group
as the standard for the low-intensity group, which
resulted in lower volumes for both groups and
thus potentially limited muscular adaptations. It is
well established that the VT plays an important
role in muscular adaptations, with evidence of a
dose–response relationship between volume and
hypertrophy (Schoenfeld, Ogborn, & Krieger,
2017). Thus, when different intensities of RT are
performed, VT must be matched at sufficiently
high levels to help ensure maximal responses for
each training condition.
The present study aimed to investigate the effect of
different intensities of RT across a wide spectrum of
loading zones with matched VT on 1RM and
muscle cross-section area (CSA) in response to 12-
weeks of RT. We hypothesized that intensities
between 40% and 80% 1RM would produce similar
hypertrophic responses and 20% would be below
the intensity threshold needed to maximize adap-
tations. Moreover, it was hypothesized that higher
intensities (60–80% 1RM) would have greater
effects on muscle strength when compared to lower
intensities (20–40% 1RM) of RT.
Methods
Experimental procedures
To determine the effect of different intensities of
RT on increases 1RM and CSA of the vastus later-
alis (VL) and elbow flexors (EF), a within-subject
design was employed in which one leg and arm
was set at 20% 1RM (G20) for all participants and
the contralateral limb was randomly assigned to
one of the three possible conditions: 40% 1RM
(G40); 60% 1RM (G60), and 80% 1RM (G80).
All participants performed two sessions per week
of unilateral elbow flexion (arm curl) and unilateral
leg press 45° for 12 weeks. Participants performed
three sets of G20 first each workout, with each set
taken to volitional failure. VT (sets × repetition ×
load) for G20 was recorded and used to match
the VT for the higher intensity condition in the
contralateral limb (i.e. G40, G60, and G80).
Unilateral arm curl and unilateral leg press 45°
1RM, as well as CSA of the VL and EF were
assessed at pre, post-6 weeks, and post-12 weeks
of training.
Subjects
Thirty health young men (age = 24.5 ± 2.4 years;
height = 180.0 ± 0.7 cm; body mass = 77 ± 16.5 kg)
volunteered to participate in this study. The sample
was determined by a post hoc power analysis based
on the previous research from our lab using VL
CSA as the outcome measure with a target effect
size difference of 0.6 and an alpha of 0.05, resulting
in a power of 0.82. Participants were recreationally
active with no experience in RT. All participants
were made aware of the procedures, benefits and
potentialsrisks,andthensignedaninformed
consent document to participate in this investi-
gation. This study was conducted according to the
Declaration of Helsinki, and the Institution’s
Research Ethics Committee approved the exper-
imental protocol.
2T. Lasevicius et al.
Muscle CSA
Muscle CSA was determined for the EF and VL
using B-mode ultrasonography with a 7.5 MHz
linear-array probe (SonoAce R3, Samsung-
Medison, Gangwon-do, South Korea). A researcher
experienced in muscle ultrasound testing performed
all measurements. To measure EF CSA, the
researcher first identified the midpoint between the
head of the humerus and the lateral epicondyle of
the humerus, which was then marked with semiper-
manent ink for reference. Thereafter, the skin was
transversally marked every 1 cm from the reference
point along the medial and lateral aspects of the
upper arm to orient ultrasound probe placement.
For the VL CSA, the researcher identified the mid-
point between the greater trochanter and the lateral
epicondyle of the femur. The skin was then transver-
sally marked every 2 cm from the reference point
along the medial and lateral aspects of the thigh to
orient probe placement.
For measures of both EF and VL, sequential ultra-
sound images were acquired by aligning the head of
the probe with each mark on the skin following a
middle-to-lateral direction. A generous amount of
gel was applied to the probe to enhance conductivity
and care was taken to avoid depressing the skin
surface while scanning. After collecting this data,
the EF and VL images were digitally reconstructed.
Specifically, the images were sequentially opened in
power point (Microsoft, USA), and then each image
was manually rotated until the fascia of the EF and
VL muscles were modelled (Lixandrão et al.,
2014). CSA of the resulting EF and VL images
were then measured using computerized planimetry
(i.e. the VL and EF muscles CSA were contoured
following the muscle fascia using an 800 dpi
mouse) (Magic Mouse, Apple, USA) in two differ-
ent days, 72 h apart (intra-researcher reproducibil-
ity). The planimetry software was calibrated with
fixed distance scales displayed in the ultrasound
images. Test–retest reliability of CSA measurements
using intra-class correlation coefficient (ICC),
typical error (TE), and coefficient of variation
(CV) for EF were 0.99, 0.43 cm
2
, and 3.2% and
for vastus lateralis were 0.99, 0.59 cm
2
, and 2.5%,
respectively.
Maximal dynamic strength (1RM)
Unilateral elbow flexor and unilateral leg press 45°
1RM testing were performed as per American
Society of Exercise Physiologists recommendations
(Brown & Weir, 2001). Briefly, participants ran for
5 min on a treadmill (Movement Technology;
Brudden) at 9 km h
−1
, followed by two warm-up
sets of the unilateral EF exercise and unilateral leg
press 45°. In the first set, the participants performed
eight repetitions with an intensity corresponding to
50% of their estimated 1RM obtained during the
familiarization sessions. In the second set, they per-
formed three repetitions with 70% of their estimated
1RM. A 3-min rest interval was afforded between
warm-up sets. After the completion of the second
set, participants rested for 3 min and then had up to
five attempts to achieve their unilateral EF and unilat-
eral leg press 45° 1RM. A 3-min rest interval was
afforded between attempts (Brown & Weir, 2001).
An experienced researcher conducted all the tests,
and strong verbal encouragement was provided
during the test. Test–retest reliability of 1RM
measurements using ICC, TE and CV for unilateral
EF were 0.99, 0.45 kg, and 1.86% and for unilateral
leg press 45° were 0.99, 4.77 kg, and 2.48%,
respectively.
Training programme
The RT was carried out twice per week for 12
weeks using unilateral elbow flexion and unilateral
leg press 45° exercises. The study employed a
within-subject design whereby one leg and arm
was set at 20% 1RM (G20, n= 30) for all partici-
pants and the contralateral limb was randomly
assigned to one of the three possible conditions:
40% 1RM (G40, n= 10); 60% 1RM (G60, n=
10), and 80% 1RM (G80, n= 10). The training pro-
tocol for G20 consisted of three sets of elbow
flexion and leg press exercise carried out to the
point of momentary concentric muscular failure
(i.e. the inability to perform another concentric
repetition while maintaining proper form). Total
VT performed by G20 was recorded and then
equatedinthecontralateral limb. In this case,
G40, G60, and G80 groups performed how
many sets and repetitions necessary to complete
the VT from G20, with repetitions performed
until to volitional failure and the training load
was adjusted every 4 weeks to ensure the target
intensity was achieved. The initial exercise per-
formed was altered in each session; in other
words, if one day, the subject started the session
with the unilateral elbow flexion, the other day,
he started with the unilateral leg press. All proto-
cols were performed with a 120-s rest period
between sets and cadence of repetitions was
carried out with a controlled concentric and
eccentric cycle of approximately 2-s each. Partici-
pants were instructed to refrain from performing
any additional resistance-type training throughout
the duration of the study.
Effects of different intensities of resistance training with equated volume load on muscle strength and hypertrophy 3
Statistical analyses
Data were analysed quantitatively and visually to
verify normality (Shapiro-Wilk) and existence of out-
liers (box-plots). For measures of reproducibility,
test–retest for CSA and 1RM employed the ICC,
absolute agreement, and TE which was calculated
as standard deviation of the difference between day
1 and day 2 measurements/√2 and the CV which
was calculated as the (TE of the difference between
day 1 and day 2/means of the day 1 and day 2
values) × 100. A mixed model analysis was per-
formed for each dependent variable (CSA and
1RM), assuming the conditions (G20, G40, G60,
and G80) and time (pre, post-6 weeks and post-12
weeks) as fixed factors, and the participants as a
random factor. Whenever a significant F-value was
obtained, a post hoc test with a Tukey’s adjustment
was performed for multiple comparison. ES was cal-
culated as the post-training mean minus the pre-
training mean divided by the pooled pre-training
standard deviation (Morris, 2008), where 0.2 =
small, 0.5 = medium, and 0.8 = large (Cohen,
1988). In addition, we presented the mean value
and confidence intervals from absolute difference
between groups (CIdiff). Positive and negative confi-
dence intervals that did not cross zero were con-
sidered significant. The significance level was set at
p< .05, and all analyses were made with statistical
software package SAS 9.2.
Results
No significant differences in any variables of interest
were observed between groups at baseline. The VT
for all groups was similar for unilateral elbow
flexion and unilateral leg press 45° exercises through-
out the study. The description of training variables is
depicted in Table I.
EF and VL cross-sectional area
There was significant main effect of time in EF and
VL CSA for all conditions following RT intervention
(p= .0001). EF CSA increased significantly in all
conditions from pre- to post-12 weeks (G20: 11.4%
ES: 0.63, G40: 25.3% ES: 2.10, G60: 25.1% ES:
1.40, and G80: 25% ES: 1.39). When the mean
value of differences between conditions were ana-
lysed at post-12 weeks, EF CSA in G80 was greater
than G20 (95%CI
diff
= 0.32 to 4.25, F= 3.74, d:
0.49, p= .01), but similar to G40 (95%CI
diff
=
−1.66 to 3.15, F= 1.47, d: 0.78, p= .85) and G60
condition (95%CI
diff
=−1.92 to 2.88, F= 1.47, d:
0.78, p= .95) (Figure 1).
For the VL CSA, all conditions showed significant
increases from pre- to post-12 weeks (p< .0001). VL
CSA increased significantly in all conditions from
pre- to post-12 weeks (G20: 8.9%, ES: 0.62; G40:
20.5%, ES: 1.16; G60: 20.4%, ES: 2.02; and G80:
19.5%, ES: 2.28). When mean value of differences
between conditions were analysed post-12 weeks,
VL CSA was greater in G80 than G20 (95%CI
diff
=
0.48 to 7.21, F= 3.09, d: 0.35, p= .01), but similar
to G40 (95%CI
diff
=−2.97 to 5.27, F= 1.32, d:
1.55, p= .88) and G60 condition (95%CI
diff
=
−2.71 to 5.53, F= 1.32, d: 1.59, p= .81) (Figure 2).
Maximal dynamic strength (1RM)
There was a significant time × condition interaction
for unilateral elbow flexion and unilateral leg press
45° 1RM (p= .0042). Unilateral elbow flexion 1RM
increased significantly from pre- to post-6 weeks in
the G20 (16.5%, ES: 0.93), G60 (30%, ES: 1.30),
and G80 (31.6%, ES: 1.96) conditions (F= 268.30,
p≤.05). In addition, unilateral elbow flexion 1RM
increased significantly from pre- to post-12 weeks
for all conditions (G20: 23.3%, ES: 1.25; G40:
26.7%, ES: 1.33; G60: 33.6%, ES: 1.41; and G80:
54.1%, ES: 4.56) (p< .0001). Elbow flexion 1RM
at post-12 weeks increase in G80 condition was sig-
nificantly higher when compared to G20 (95%CI
diff
= 2.35 to 10.98, F= 11.86, d: 1.49, p= .001), G40
(95%CI
diff
= 2.31 to 12.88, F= 11.86, d: 1.69, p
= .001), and G60 conditions (95%CI
diff
= 1.51 to
12.08, F= 11.86, d: 1.32, p= .001) (Table II).
Unilateral leg press 45° 1RM increased signifi-
cantly from pre- to post-6 weeks in G20 (15.8, ES:
0.75), G40 (27.9%, ES: 1.24), G60 (32.1%, ES:
1.42), and G80 (25.6%, ES: 1.42) conditions (F=
242.40; p< .0001). Additionally, unilateral leg press
45° 1RM increased significantly from pre- to post-
12 weeks for all conditions (G20: 22.1% ES: 1.14;
G40: 30.4%, ES: 1.43; G60: 55.4%, ES: 2.99; and
G80: 45.7%, ES: 3.27) (p< .0001). Finally, leg
press 45° 1RM increases at post-12 weeks in the
G60 and G80 conditions were significantly higher
when compared to G20 and G40 (G60 vs. G20:
95%CI
diff
=−0.65 to 73.66, F= 10.82, d: 1.00, p
= .04; G80 vs. G20: 95%CI
diff
= 3.34 to 77.66, F=
10.82, d: 1.11, p< .05; G60 vs. G40: 95%CI
diff
=
−4.37 to 3.87, F= 10.82, d: 1.59, p= .02; and G80
vs. G40: 95%CI
diff
= 8.49 to 99.51, F= 10.82, d:
1.74, p< .05) (Table II).
Discussion
The present study investigated the effects of different
intensities of RT (20–80% 1RM) with equated
4T. Lasevicius et al.
volume on muscular strength and hypertrophy fol-
lowing 12 weeks of regimented training. Our main
findings were: (a) all intensities of RT increased the
EF and VL CSA; (b) all intensities of RT increased
elbow flexion and leg press 1RM. The magnitude of
increases in muscle CSA and 1RM of the upper
and lower body when training at 80% 1RM were
greater than at 20% 1RM.
The findings of this study call into question the
American College of Sports Medicine guidelines
stating that the use of loads ≥65% 1RM are required
to promote hypertrophic adaptations (American
College of Sports Medicine, 2009). Alternatively,
our findings corroborate the results from other
studies that demonstrated low-intensity RT per-
formed until volitional failure can increase muscle
mass to a similar extent as high-intensity RT at least
with loads ≥40% 1RM, even when volume is
equated between conditions (Mitchell et al., 2012;
Ogasawara et al., 2013; Schoenfeld et al., 2015).
Some researchers have proposed that it is necessary
to perform a higher volume of low-intensity training
to achieve the magnitude of increase in muscle size
observed with high-intensity training (Burd et al.,
2010; Burd, Mitchell, Churchward-Venne, & Phil-
lips, 2012; Mitchell et al., 2012). In general, a
majority of studies that investigated the topic
employed a substantially higher training volume for
the low-intensity condition (Mitchell et al., 2012;
Ogasawara et al., 2013; Schoenfeld et al., 2015),
which conceivably could have affected the hyper-
trophic response.
Ours is the first study to match the VT between a
wide range of intensities (e.g. 20–80% 1RM) based
on VT in the lowest intensity condition. This strategy
was adopted in order to avoid potentially misleading
interpretations when the VT between training proto-
cols are different and thus isolate the effects of inten-
sity on muscular adaptations. For example, the VT
performed in other studies that use low-intensity
RT (30% 1RM) was higher than those shown with
high-intensity RT (80% 1RM) (Mitchell et al.,
2012; Ogasawara et al., 2013; Schoenfeld et al.,
2015). It is possible that muscle hypertrophy in the
heavier intensity conditions in these studies may
have been blunted by the lower amount of volume
performed compared to the lighter-intensity con-
ditions. However, our study indicates that volume
was not a significant factor in this regard, at least
with respect to intensities of ≥40% 1RM. This
suggests that there is a threshold of volume needed
to promote marked increases in muscle hypertrophy
with intensities between 40% and 80% 1RM.
Although upper and lower body CSA were
increased in all conditions, the highest intensity con-
dition (80% 1RM) presented greater gains compared
with the lightest intensity condition (20% 1RM).
Consistent with these findings, data from Holm
et al. (2008) found a higher increase in quadriceps
CSA when training at 70% vs. 15.5% 1RM with the
VT equated between the conditions. However, sub-
jects in the study did not train to failure in the low-
intensity condition, confounding the ability to draw
causality on the hypertrophic effects of the different
loading schemes. Our findings suggest that there is
a minimum intensity necessary to trigger important
mechanisms involved in increasing muscle size
(Holm et al., 2008; Kumar et al., 2009), and it
appears that 20% 1RM falls below this threshold.
Given that we did not study intensities between
20% and 40% 1RM, it is not clear where the
minimum threshold lies along this continuum.
Hypertrophy-oriented routines are often designed
to raise mechanical tension and/or metabolic stress
(Goto, Ishii, Kizuka, & Takamatsu, 2005; Schoen-
feld, 2010; Seynnes, de Boer, & Narici, 2007).
Given that the increase in CSA in this study was
similar between intensities of 40% and 80%, it can
be inferred that protocols designed to maximize
metabolic stress (i.e. high number of repetitions and
low to moderate intensities) and protocols designed
to maximize mechanical tension (low number of
Table I. Training variables for the unilateral elbow flexion and unilateral leg press 45° exercises.
Unilateral elbow flexion
Training variables G20 G40 G60 G80
Sets 3 ± 0 3.7 ± 1 4.5 ± 1.2 4.2 ± 1
Repetitions 67.7 ± 18.7∗28.2 ± 10.5∗∗ 14.5 ± 4.7 10.2 ± 2.8
Volume load 21,674.1 ± 2952.7 21,919.1 ± 3028.1 20,822 ± 3644.1 20,543 ± 3479.5
Unilateral leg press 45°
Training variables G20 G40 G60 G80
Sets 3 ± 0 2.5 ± 0.4 3.4 ± 1.4 3.1 ± 0.9
Repetitions 61.1 ± 29.9∗30.8 ± 8.0 18.8 ± 5.9 14.0 ± 4.6
Volume load 163,043.0 ± 34,695.2 153,946.2 ± 28,285.5 160,900 ± 30,997.9 169,095.4 ± 36,054.5
∗Significant difference from G40, G60 and G80 (p< .05).
∗∗Significant difference from G80 (p< .05).
Effects of different intensities of resistance training with equated volume load on muscle strength and hypertrophy 5
repetitions and high intensities) would promote
similar hypertrophic increases when the VT is
matched. Thus, these findings suggest that VT
plays an important role in increasing muscle mass
as opposed to inherent aspects of the protocol itself
or training stimulus.
There were significant increases in strength for all
groups following 6 and 12 weeks of RT. The
increases in strength levels in the initial weeks of
training have been attributed to neural mechanisms
(Gabriel, Kamen, & Frost, 2006; Sale, 1988), and
this appears to be the case even with the very low-
intensity condition (20% 1RM) employed in our
study. Holm et al. (2008) found that an intensity of
15.5% 1RM was insufficient for increasing muscle
strength following regimented RT. However, as pre-
viously mentioned, the sets in this condition were not
taken to muscular failure. In contrast to the findings
by Holm et al. (2008), our results showed G20
increased 1RM in the arm curl and leg press through-
out the training period. Discrepancies in results may
in part be attributable to differences in the manipu-
lation of total training volume in combination with
the level of effort expended (i.e. proximity to
failure) in the low-intensity condition. Specifically,
the total VT for all groups in our study was based
on G20 and all the volume of all other conditions
(G40, G60, and G80) was matched to the volume
load achieved in G20, with repetitions performed
until to volitional failure.
One interesting aspect of our findings is that
strength appeared to plateau after 6 weeks in the
lower intensity conditions and, after 12 weeks,
higher training intensities resulted in greater strength
increases compared to lower intensities. These results
are in agreement with previous studies on the topic
that demonstrated an advantage for higher intensities
on muscle strength performance (Campos et al.,
Figure 1. Elbow flexor CSA values from pre-test to post-6 weeks and post-12 weeks for G20, G40, G60, and G80 conditions (mean ± SD).
∗Significant difference from pre-test (p< .05).
#
Significantly greater than G20 group at post-12 weeks (p< .05).
Figure 2. VL CSA values from pre-test to post-6 weeks and post-12 weeks for G20, G40, G60, and G80 conditions (mean ± SD). ∗Significant
difference from pre-test (p< .05).
#
Significantly greater than G20 group at post-12 weeks (p< .05).
6T. Lasevicius et al.
2002; Mitchell et al., 2012; Ogasawara et al., 2013;
Schoenfeld et al., 2015). Untrained individuals parti-
cipating in the initial stages of RT generally have a
low level of fitness and lack the coordination to
perform exercises in a fluid manner. Thus, all
loading schemes provided a sufficient stimulus to
produce increases in muscular strength (Harris,
Debeliso, Spitzer-gibson, & Adams, 2004).
However, it can be speculated that over time
heavier intensities are necessary to continue making
gains. This is consistent with evidence that resist-
ance-trained individuals require higher intensities to
improve muscle strength (Peterson, Rhea, & Alvar,
2004; Rhea, Alvar, Burkett, & Ball, 2003).
Although we did not attempt to elucidate the
mechanisms responsible for our findings, it seems
plausible that neural adaptations may explain the
different strength responses between intensities.
Specifically, high-intensity RT may promote greater
effects on motor unit recruitment, motor unit firing
rates, and/or alterations in agonist-antagonist co-acti-
vation ratios compared to training at lower intensities
(Gabriel et al., 2006; Sale, 1988). Alternatively, other
factors related to the principle of specificity may be
involved in the process, whereby high-intensity train-
ing has greater similarities to 1RM testing versus low-
intensity training (Aagaard, Simonsen, Trolle,
Bangsbo, & Klausen, 1996; Cronin, McNair, & Mar-
shall, 2001). Further research is needed to determine
mechanistic explanations.
The present study is not without limitations. First,
the study was performed in young men with no pre-
vious experience in RT. Thus, our findings cannot
be generalized to other population including
women, elderly, and/or resistance-trained individ-
uals. Second, it is possible that differences in training
status, hormonal influence, and other factors could
influence muscular adaptations when training at
different intensities. Third, we cannot rule out the
possibility that the cross-education effect may have
influenced strength results given the within-subject
design. However, the fact that the highest intensity
condition showed the greatest changes in strength
indicates that any influence of cross-education, if
such a phenomenon did in fact occur, was not suffi-
cient to counteract the effects of heavier loading on
this outcome. Lastly, we did not attempt to deter-
mine nutritional intake, which may have influenced
results between conditions. However, the within-
subject design would have helped to minimize any
potential variations attributed to this variable.
In conclusion, our results demonstrated that inten-
sities ranging from 20% to 80% 1RM are effective for
increasing muscle strength and hypertrophy in men
with no experience in RT. However, our findings
indicate that the lowest RT intensity (20% 1RM)
was suboptimal for maximizing muscular adap-
tations. With regards to strength gains, our results
indicate that over the initial 6 weeks of training all
the studied intensities can produce increases in
1RM. However, if maximizing strength gains over
the long-term training is a primary goal, it is necessary
employ higher training intensities.
Disclosure statement
No potential conflict of interest was reported by the authors.
ORCID
Hamilton Roschel http://orcid.org/0000-0002-9513-
6132
Lucas Duarte Tavares http://orcid.org/0000-0003-
0941-6224
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