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Original Research
Effects of Two Different Preacher Curl Training
Programs on Regional Hypertrophy: An
Experimental Study
Ratanyoo Longrak
Faculty of Sport Science, Burapha University
Abstract: This study explored the regional muscle hypertrophic effect of the preacher curl
training between two distinct program designs. Twenty healthy young males (age: 21.1±0.4
years; height: 174.1±5.1 cm, weight: 69.1±11.3kg) were recruited and randomly allocated to the
6-week programs of either mechanical tension program (MT) or mechanical tension with
metabolic stress program (MTMS). Biceps brachii cross-sectional area (CSA) and thickness at
proximal and distal regions were assessed by magnetic resonance imaging (MRI) and B-mode
ultrasonography (US), respectively. Furthermore, fascia thickness was measured together with
muscle thickness. Results indicated significant increases in biceps brachii CSA at both the
proximal and distal regions in both programs (p < 0.05). Interestingly, muscle CSA at the distal
region exhibited a more pronounced growth with larger effect sizes compared to the proximal
region in both MT (∆12.15%, p = 0.000, ES = Moderate vs ∆8.26%, p = 0.038, ES = Small) and MTMS
(∆16.92%, p = 0.008, ES = Moderate vs ∆9.02%, p = 0.005, ES = Small). Moreover, US further
confirmed these findings, both MT and MTMS showed only significant increases in biceps
brachii thickness at the distal region (∆25.95%, p = 0.000, ES = Large, and ∆21.76%, p = 0.009, ES
= Large, respectively). Interestingly, fascia remodeling interestingly showed that significant
thickness increased at distal region only in MTMS (∆47.27%, p = 0.006, ES = Large). In conclusion,
our study confirmed that the preacher curl exercise per se induced regional hypertrophy
preferentially in the distal region of the biceps brachii muscle, while resistance training program
design had no discernible effect on this hypertrophic pattern.
Keywords: Muscle thickness; Muscle cross-sectional area; Fascia thickness; Preacher curl;
Hypertrophy training
1. Introduction
Resistance training remains highly
popular in contemporary society, with an
increasing number of individuals turning to
gym facilities for bodybuilding purposes.
Consequently, research endeavors have
intensified, focusing on strategies to enhance
muscle mass, commonly referred to as
muscle hypertrophy (Schoenfeld, 2010).
Scientists have looked into various factors
like resistance training intensity: how heavy
should it be? (Campos et al., 2002; Lasevicius
et al., 2018; Lopez et al., 2021), volume: how
many sets should one train? (Baz-Valle et al.,
2022; Brigatto et al., 2022; Schoenfeld et al.,
2019), rest periods: how much should one
rest between set? (Schoenfeld et al., 2016),
range of motion: does full range of motion
*
Correspondence: RL addmuscleclinicz@gmail.com. 0000-0001-6117-7617
Received: 09/06/2024; Accepted: 02/09/2024; Published: 31/12/2024
Longrak
et al.
Citation: European Journal Of Human Movement 2024,
53
:89-100 –
DOI:
10.21134/eurjhm.2024.53.6
always result in better hypertrophy?
(Bloomquist et al., 2013; Kubo et al., 2019),
training frequency: how many times per
week is most effective? (Gentil et al., 2015;
McLester et al., 2000), full or split-training
routine (Evangelista et al., 2021), exercise
order: should it be trained with multi-joint or
single joint exercise first (Gentil et al., 2015),
and exercise techniques: is drop-set a magic
pill for muscle growth? (Goto et al., 2003;
Kelleher et al., 2010) to figure out the most
effective muscle-building strategies, aiming
to elucidate optimal practices for maximizing
training effort (Krzysztofik et al., 2019).
While several studies have shed light
on these interesting variables, comparatively
little attention has been given to the specific
exercise and its impact on regional
hypertrophy (Saeterbakken et al., 2013).
Previous research has demonstrated muscle
growth was non-uniform (Zabaleta-Korta et
al., 2023), indicating that hypertrophy did not
occur uniformly along the length of a muscle
(e.g. proximal region versus distal region)
(Nunes et al., 2024). For example, it was
demonstrated that significant increase in
rectus femoris muscle up to 27.9% compared
to only 19.5%, and 17.4% increases of vastus
lateralis and vastus intermedius,
respectively, after training with leg extension
exercise (Narici et al., 1996). On the other
hand, squats had been shown to be highly
effective for inducing vastus medialis
hypertrophy but were ineffective for
targeting the rectus femoris (Kubo et al.,
2019). Moreover, previous study had found
that leg press exercise induced preferential
hypertrophy at the distal region of the
quadriceps than proximal region (Franchi et
al., 2014). From these examples in lower
musculature, therefore, investigating which
exercise induces greater hypertrophy at
which specific region along the muscle length
holds significant practical implications for
practitioners.
Building upon the aforementioned
literature, this study aimed to investigate
regional biceps brachii hypertrophy resulting
from preacher curl exercise with two
different training programs.
2. Materials and Methods
Study design
This study employed a single-blinded
experimental design with two experimental
groups. The training program was
standardized for both groups, starting with 3
sets in the first two weeks, progressing to 6
sets in the next two weeks, and finally 8 sets
in the last two weeks, for a total duration of
six weeks. The training sessions were
conducted in a controlled environment at the
Physiology Laboratory of the Faculty of Sport
Science. Additionally, other training
variables such as execution pattern,
repetition tempo, and rest intervals were
consistently controlled in every training
session. Eligibility criteria required
participants to have no prior resistance
training experience to minimize experience-
related biases. Resistance training was
closely supervised by a certified personal
trainer in a laboratory setting. Baseline
testing included Magnetic resonance
imaging (MRI) and Ultrasonography (US)
assessments for muscle CSA and thickness,
as well as fascia thickness. This study
conformed to the ethical guidelines of the
Declaration of Helsinki and ethical approval
Preacher curl and regional hypertrophy
Citation: European Journal Of Human Movement 2024,
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:89-100 –
DOI:
10.21134/eurjhm.2024.53.6
was granted by the Burapha University
ethics committee (G-HS046/2566(C1).
Participants - Twenty healthy young
untrained males (age: 21.1±0.4 years; height:
174.1±5.1 cm, weight: 69.1±11.3kg) were
recruited from the Faculty of Sports Science.
Utilizing G*power 3.1.9.7 for sample size
calculation (with a priori power analyses
including Effect size = 0.75, α = 0.05, Power =
0.80), the total sample size was 17 with
considering 20% dropout rate allowed;
therefore, the total number of participants in
this study was 20. These input parameters
were following the previous study which
employed the similar experimental design
(Zaroni et al., 2019). Inclusion criteria
ensured participants had 1) no functional
limitations, 2) no history of substance use
affecting muscle metrics, or 3) no resistance
training experience. General health
screenings were conducted by a registered
physician, and written informed consent was
obtained from all participants. Participants
were randomly assigned to mechanical
tension program (MT, n=10) or mechanical
tension with metabolic stress program
(MTMS, n=10) by research randomizer
program to avoid bias.
Preacher curl training programs - Two
different preacher curl training programs,
each utilizing distinct hypertrophic stimuli
differently designed according to different
hypertrophy stimuli (Schoenfeld, 2010), were
implemented over six weeks with one session
per week. The rationale behind employing
two different training programs was to assess
potential variations in regional muscle
hypertrophy despite utilizing the same
exercise
Before the experiment, each
participant's one-repetition maximum (1RM)
was determined according to NSCA
guidelines (Brown, 2016). Participants
performed an aerobic warm-up, followed by
light resistance preacher curls for 8-10
repetitions. After a one-minute rest, the
weight was gradually increased, and
participants performed 3-5 repetitions.
Following a four-minute rest, the weight was
increased by 10%, and participants
attempted a single repetition. This process
continued with three-minute rest intervals
until the highest weight successfully lifted
was recorded as the 1RM.
In mechanical tension program (MT),
participants performed three mechanical-
tension sets of preacher curl exercise, using
pin-loaded bilateral preacher curl machine
(Body-Solid, USA) in the first two weeks. The
set was termed “mechanical-tension set”
because it was customized to be high-
intensity (70%1RM) and maintained
throughout the 6-week program to ensure
maximum mechanical tension which was the
most important stimulus for inducing
hypertrophy from each session (Wackerhage
et al., 2018). Repetitions were performed to
concentric failure to ensure maximal
recruitment of muscle fibers to maximizing
hypertrophic effect (Ruple et al., 2023). Each
set was performed with a fixed repetition
tempo of 2 seconds for each contraction
phase. The execution rhythm was controlled
using a metronome set to a 2-second interval
for each contraction phase, ensuring
consistent timing and cadence throughout
the exercise. 60-second rest between sets was
provided. Participants must keep their
elbows on the supported pad and were
instructed to maintain full range of motion
Longrak
et al.
Citation: European Journal Of Human Movement 2024,
53
:89-100 –
DOI:
10.21134/eurjhm.2024.53.6
during each repetition. Training volume set
was doubled in the third and fourth weeks
and increased to eight sets in the fifth and
sixth weeks.
In Mechanical tension with metabolic
stress program (MTMS), participants
performed two mechanical-tension sets at
70%1RM and one metabolic-stress set at
30%1RM with practical blood flow restriction
in the first two weeks. The purpose of
metabolic-stress set was to induce occlusion
of metabolites and local hypoxia of biceps
brachii (Schoenfeld, 2013). Therefore,
practical blood flow restriction technique
was employed to maximizing these
metabolic-stress stimulus. Practical blood
flow restriction was achieved using elastic
wraps (Grizzly Fitness, Canada) fastened at
the most proximal of upper arms.
Participants were encouraged to fastened
elastic wraps to the tightness at least above
40%AOP. Each participant was familiarized
with perceived AOP level of their own value
by using the adjustable pneumatic cuffs
(H+Cuff, USA) before the study began. The
training volume set increased similarly,
reaching 3 mechanical-tension sets and 3
metabolic-stress sets in the third and fourth
weeks, and 4 mechanical-tension sets and 4
metabolic-stress sets in the fifth and sixth
weeks. All other training variables remained
consistent across both groups.
Regional hypertrophy assessment - All
participants underwent assessment for
muscle CSA and thickness via MRI and B-
mode US of the biceps brachii at 1 week prior
to and 1 week after completion of the training
program. MRI scans (Vantage Elan, Canon,
USA) were conducted by a radiologist using
a 1.5-T scanner, which included standard
axial T1-weighted and T2-weighted fat-
saturated sequences, as well as coronal T1-
weighted and T2-weighted fat-saturated
sequences. Muscle CSA measurements were
taken at two specific regions: proximal region
and distal region, specifically at 50% and 70%
of the humerus length (from the acromion
process to the lateral humeral epicondyle for
the upper arm bone) (Figure 1). Participants
were positioned lying supine with their arms
extended along their sides during the MRI
scans.
Figure 1. Muscle Cross-Sectional Area (CSA) from
Magnetic Resonance Imaging (MRI).
Note. Muscle CSA at proximal region (A) and at distal region
(B) of a random participant
For muscle thickness assessment, a US
device (LOGIQ E10 Series, GE Healthcare,
USA) equipped with a curvilinear probe was
used. Measurements were conducted with
the participants lying supine, and
transmission gel was applied to the skin. The
probe, operating at a frequency range of 4-9
MHz, was used to measure muscle thickness
at the same points along the humerus: the
proximal region at 50% and the distal region
at 70% of the humerus length (Figure 2).
Additionally, a B-mode US was utilized to
measure the fascia thickness above the biceps
thickness measurement points to provide
further understanding of regional muscle
Preacher curl and regional hypertrophy
Citation: European Journal Of Human Movement 2024,
53
:89-100 –
DOI:
10.21134/eurjhm.2024.53.6
complex development. All steps were
conducted by a certified radiologist.
Figure 2. Muscle Thickness (MT) from Ultrasound
Imaging.
Note. Muscle Thickness at proximal region (A) and at distal
region (B) of a random participant
Statistical analysis - The statistical
analysis was calculated to explore the effects
of preacher curl exercise on regional
hypertrophy of the two different preacher
curl training programs. The Shapiro-Wilk
test was used to analyze the normal
distribution of data. Descriptive statistics:
mean and standard deviation, were used to
summarize baseline characteristics. Then,
baseline variables between groups were
initially compared by One-way ANOVA.
Levene’s test assessed the homogeneity of
variances. Changes in muscle thickness,
muscle CSA, and fascia thickness from
baseline to Post-test were calculated, with
95% Confidence Interval. A two-way
repeated measured ANOVA was employed
to compare between-group (MT vs. MTMS)
and between-time (Pre vs. Post) effects. In
addition to the ANOVA, Paired sample t-
tests were conducted to identify within-
group differences from Pre to Post for each
training program separately, aiming to
pinpoint specific changes over time within
each group that the ANOVA might not fully
elucidate. Percentage changes and effect sizes
were calculated using the formula: mean
change /pooled SD, with interpretations
based on conventional criteria of 0.00–0.19
was considered as Trivial, 0.20–0.49 as Small,
0.50–0.79 as Moderate, and ≥0.80 as Large
(Cohen, 1992). Statistical analyses were
performed using IBM SPSS Statis-tics version
20, with a significance level set at α = 0.05.
3. Results
From total 20 participants, 2
participants had dropped out (1 for loss of
interest and 1 for unexpected injury), leaving
8 participants in MTMS and 10 participants
in MT. The results were demonstrated in
Table 1 that participant characteristics of two
groups were not significantly different at
baseline.
For muscle hypertrophy, a main time
effect was found for muscle thickness at only
distal region (F[1,16] = 40.421, p = 0.000,
η!"
#
=
0.716) and for muscle CSA at both proximal
(F[1,16] = 15.358, p = 0.001,
η!
#
= 0.490) and distal
regions (F[1,16] = 38.747, p = 0.000,
"
η!
#"
= 0.708).
However, no main effect group or interaction
was revealed (Table 2).
Specifically, significant increases in
muscle CSA were observed at the proximal
region ∆8.26% (p = 0.038, ES = Small) and
∆9.02% (p = 0.005, ES = Small) in MT and
MTMS, respectively.
Table 1. Participants Characteristics
MTMS (n=8)
(mean±SD)
MT (n=10)
(mean±SD)
F
p-
value
Age (years)
21.3±0.7
21±0
1.270
.276
Height (cm)
173.1±5.5
174.9±5.3
.477
.500
Body mass
(kg)
68.5±11.3
69±11.9
.008
.929
Note. Abbreviations: SD= standard deviation, MTMS = Mechanical
tension with Metabolic stress program, MT = Mechanical tension
program
Longrak
et al.
Citation: European Journal Of Human Movement 2024,
53
:89-100 –
DOI:
10.21134/eurjhm.2024.53.6
Furthermore, more pronounced
percentage increases were noted when
measuring changes at the distal region,
which accounted for ∆12.15% (p = 0.000, ES =
Moderate) and ∆16.92% (p = 0.008, ES =
Moderate) in MT and MTMS, respectively.
Besides, the assessment of muscle
thickness revealed a significant increase in
muscle thickness at only the distal region of
the biceps brachii in both groups. The
significant increases of muscle thickness at
the distal region were ∆25.95% (p = 0.000, ES
= Large) and ∆21.76% (p = 0.009, ES = Large) in
MT and MTMS, respectively. However, no
significant increases were observed at the
proximal region in both programs.
Furthermore, the findings regarding
fascia thickness revealed a main time only at
distal region (F[1,16] = 14.076, p = 0.002,
η!
#""
=
0.468). No main effect group or interaction
was revealed at any region. However, the
sperate analysis revealed only significant
increase at distal fascia thickness within
MTMS (∆47.27%, p = 0.006, ES = Large), but
not MT (p = 0.193). No significant fascia
thickness change was observed at the
proximal region in both training programs.
4. Discussion
This current study provided strong
evidence for regional hypertrophy,
particularly showing how the preacher curl
exercise affected the biceps brachii muscle.
We found that performing the preacher curl
for six weeks, with progressive volume,
predominantly increased hypertrophy in the
distal region of the biceps brachii. The
strength of this study was supported by
consistent observations of increased muscle
CSA measured by MRI and muscle thickness
measured by US. Additionally, our
investigation indicated that different
resistance training programs did not
significantly alter the specific hypertrophic
Table 2. Muscle Thickness, Muscle Cross-Sectional Area, Fascia Thickness at Pre and Post
MTMS(n8)
MT(n=10)
Effect p
Pre
(mean±SD)
Post
(mean±SD)
Change
(95%CI)
d
Pre
(mean±SD)
Post
(mean±SD)
Change
(95%CI)
d
Group
Tim
e
Inter-
action
Muscle thickness (cm)
Proximal
2.20±0.26
2.33±0.24
0.13
(-0.07;0.34)
0.53
2.17±0.27
2.28±0.15
0.11
(-0.09;0.31)
0.50
0.642
0.070
0.832
Distal
1.93±0.34
2.35±0.42†
0.43
(0.15;0.70)
1.10
1.85±.20
2.33±0.27†
0.48
(0.28;0.67)
1.96
0.76
0.000
0.709
Muscle cross-sectional area (mm2)
Proximal
723.63
±128.53
788.88
±164.46†
65.25
(26.45;104.04)
0.44
772.60
±131.96
836.40
±146.15*
63.80
(4.40;123.19)
0.46
0.474
0.001
0.965
Distal
797.75
±197.32
932.75
±190.68†
135
(48.88;221.12)
0.70
843.10
±136.89
945.50
±168.13†
102.40
(61.69;143.11)
0.66
0.721
0.000
0.405
Fascia thickness (mm)
Proximal
0.71±0.20
0.76±0.18
0.04
(-0.07;0.05)
0.26
0.70±0.30
0.87±0.14
0.17
(-0.10;0.44)
0.69
0.543
0.152
0.416
Distal
0.55±0.20
0.81±0.17†
0.26
(0.10;0.42)
1.40
0.64±0.17
0.73±0.14
0.09
(-0.05;0.23)
0.57
0.955
0.002
0.085
Note. Abbreviations: SD= standard deviation, MTMS = Mechanical tension with Metabolic stress program, MT = Mechanical tension program, ES = Effect size. d =
Cohen’s d effect size. * p <0.05 compared to Pre, † p <0.01 compared to Pre. and 95% Confidence Interval.
Preacher curl and regional hypertrophy
Citation: European Journal Of Human Movement 2024,
53
:89-100 –
DOI:
10.21134/eurjhm.2024.53.6
patterns induced by the exercise. Both
experimental groups showed similar distal
biceps hypertrophy, regardless of the
hypertrophic stimuli used.
The hypertrophic outcomes observed in
our study aligned with previous research
findings. For instance, Zabaleta-Korta et al.
(2023) reported a significant increase in
muscle thickness following a 9-week regimen
of preacher curl exercise in recreationally
trained women. Their study demonstrated a
notable increase in muscle thickness from
2.68 cm to 2.94 cm, representing a 9.7%
increase (p = 0.017, d = 0.62) in the distal
region. Comparing to our findings, the
relatively larger percentage increase
observed in our investigation, which might
be attributed to the untrained status of our
participants, as novice practitioners often
experience substantial initial gains in
response to training (Arntz et al, 2022).
Moreover, they also reported that the
proximal region of the biceps brachii showed
only a slight, non-significant increase (6.6%,
p = 0.347). The percentage increase in
Zabaleta-Korta’s study was surprisingly
close to the findings in our study, at 5.1% (p =
0.254) in HT and 5.9% (p = 0.156) in MTMS in
the proximal region of the biceps brachii,
supporting the lesser effectiveness of
preacher curl exercise in inducing proximal
hypertrophy.
Additionally, a previous study
investigated how adjusting the range of
motion affects muscle hypertrophy (Pedrosa
et al., 2023). Healthy participants were
instructed to train three times a week, and the
researchers found that focusing on preacher
curls within a specific range of motion, from
0 degree to 68 degree of elbow flexion, led to
more significant distal hypertrophy (d = 0.89)
compared to training at 68 degrees to 135
degrees of elbow flexion (d = 0.23). In our
study, we also employed a full range of
motion as a controlled variable, ensuring all
repetitions passed through 0-68 degrees of
elbow flexion, suggesting a potential
correlation with these findings. Moreover,
the evidence of training at more stretched
position to induce distal hypertrophy was
supported by McMahon et al. (2014). The
researchers found that this approach was
also applicable to leg muscles, demonstrating
that distal vastus lateralis hypertrophy was
greater when exercises like split squats and
leg presses were performed at a larger range
of motion.
Besides, the recent study by Nunes et al.
(2020) investigated how preacher curl
exercise performing with cable pulley or free-
weight resistance affected muscle growth.
After 10-week training, they observed
approximately 2mm increase (d = 0.35-0.37)
in the biceps brachii at 50% of the humerus
length, matching our proximal region.
Interestingly, our own findings echoed these
findings, demonstrating 1.3mm increase (d =
0.53) in MTMS and a 1mm increase (d = 0.50)
in MT at proximal region, regardless of
training programs. Nunes' study likely
achieved higher hypertrophy due to longer
training duration and frequency.
Nevertheless, they did not assess muscle
growth at the distal region, making a direct
comparison of regional hypertrophy
challenging at distal region.
In contrast, our study's results differed
from those of Drummond et al. (2016), who
found that after 12 weeks of dumbbell
preacher curl training, uniform biceps brachii
hypertrophy was observed in untrained
participants. Their findings demonstrated a
significant increase in muscle CSA of the
biceps brachii, with approximately 20%
increase in the proximal region and 18%
increase in the distal region, as evaluated via
MRI. The discrepancy in results may be
attributed to differences in measurement
methods. Our current study identified
muscle regions based on anatomical
humerus length, whereas Drummond’s
study used the first, middle, and last MRI
Longrak
et al.
Citation: European Journal Of Human Movement 2024,
53
:89-100 –
DOI:
10.21134/eurjhm.2024.53.6
slices of MRI to represent the proximal,
middle, and distal regions.
From a mechanistic standpoint, Oliveira
et al. (2009) provided evidence that the
preacher curl exercise induced the highest
levels of muscle activation as assessed via
electromyography, particularly at the onset
of the concentric phase, with muscle resting
in stretched position. Additionally,
compared to the standing dumbbell curl,
muscle activation during the latter stages of
the eccentric phase was significantly
elevated. This suggested that the biceps
brachii muscle was maximally engaged when
stretched, potentially contributing to
regional distal hypertrophy.
Furthermore, Nosaka and Sakamoto
(2001) found that reaching maximal
extension (elbow straight) during the
eccentric phase of the preacher curl caused
more muscle damage than keeping the
eccentric phase shorter. From hypertrophic
standpoint, it was previously proposed in the
mechanisms of hypertrophy that muscle
damage, along with mechanical tension and
metabolic stress, was another potential
stimulus for inducing muscle hypertrophy
(Schoenfeld, 2010). Therefore, it was possible
that the preacher curl exercise, by
maximizing muscle activation and inducing
muscle damage during the eccentric phase,
could be particularly effective for promoting
muscle distal hypertrophy.
Besides, previous study further
indicated that training muscles at extended
lengths could potentially lead to an increase
in sarcomere length (Wisdom et al., 2015).
This extension of muscle structure might
promote additional muscle growth
particularly in the distant region. This
phenomenon commonly referred to as
stretch-mediated hypertrophy (Warneke et
al., 2023). This was supported by the
previous study that had found that following
exercising at extended muscle lengths, for
example, there was the significant increase in
fascicle length of vastus lateralis muscle
(∆4.9%, p = 0.001, d = 0.70) after knee
extension exercise which engaged higher
degree of knee flexion during eccentric
quadriceps contraction (Valamatos et al.,
2018).
In addition, the significant increase in
fascia thickness was observed at the distal
region of biceps brachii (p < 0.05) in MTMS,
indicating remodeling of the fascia in
response to the training stimulus (Schleip et
al., 2012). Conversely, in MT, no significant
increase in fascia thickness was observed at
either region. Regarding potential
mechanisms, the effects of practical blood
flow restriction on fascia remodeling may
involve local hypoxic factors, such as hypoxia
inducible factor (HIF). Previous research has
highlighted how blood flow restriction
induced localized hypoxia within working
muscle tissue, consequently activating HIF
pathways and various cellular responses to
low oxygen levels (Torpel et al., 2018). This
activation of HIF signaling pathways could
prompt adaptive changes in fascial thickness
and collagen composition (Valle-Tenney et
al., 2020). Although our study did not deeply
explore molecular level changes in collagen
content expression during training sessions,
existing literature showed the responses of
collagen-related molecular markers
following resistance exercising (Hjorth et al.,
2015; Mackey et al., 2004; Moore et al., 2005).
Additionally, cells within the fascia layer,
such as satellite cells, are pivotal in muscle
repair and regeneration (Johnson et al., 2023).
Thus, we suggested that the process of fascia
remodeling might significantly link to
enhancing satellite cell function and the
overall adaptive capacity of skeletal muscle.
Last but not least, the findings of this
study supported the thought process of
hypertrophy program design, that
practitioners aiming to maximize muscle
growth across all regions of a muscle should
incorporate multiple exercises targeting the
muscle (Baz-Valle et al., 2019). Our results
revealed that exclusively performing
preacher curls may not fully optimize the size
Preacher curl and regional hypertrophy
Citation: European Journal Of Human Movement 2024,
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:89-100 –
DOI:
10.21134/eurjhm.2024.53.6
of the proximal region of the biceps brachii.
Costa et al. (2021) similarly demonstrated
that incorporating a variety of exercises, such
as standard biceps curls, preacher curls, and
inclined dumbbell curls, across training
sessions resulted in superior absolute
increases in the percentage of muscle
regional hypertrophy across proximal,
middle, and distal regions.
This was further reinforced by previous
studies which showed that engaging in
various exercises targeting a specific muscle
led to different patterns of muscle activation,
potentially contributing to hypertrophy
across various regions of the muscle (Finni et
al, 2008; Wakahara et al., 2013). Furthermore,
another work by Zabaleta-Korta et al. (2021)
demonstrated about the role of various
exercises, such as smith machine squats and
leg extensions, leading to distinct regional
hypertrophy in the legs. Their findings
showed that even with identical volume and
intensity protocols, both exercises produced
different patterns of muscle growth.
Specifically, squats led to more significant
increases in the vastus lateralis, while leg
extensions primarily enhanced the rectus
femoris. This indicated that different
exercises targeted muscle growth in different
areas.
Thus, we proposed that future research
should explore other specific exercises on
regional hypertrophy, with a focus on
identifying elbow flexor exercise that
promoted greater growth in the proximal
region. This information could inform the
development of training protocols, designed
to maximize biceps brachii hypertrophy by
strategically pairing exercises such as the
preacher curl with those targeting the
proximal region. Moreover, this study
utilized a relatively small sample size,
determined based on an effect size of 0.75 as
reported by Zaroni et al. (2019). However, it
was important to acknowledge that effect
sizes could vary across different studies. This
variability could potentially influence the
outcomes and generalizability of the
findings. Therefore, future studies should
consider the potential variability in effect
sizes when designing their sample sizes and
interpreting the results.
5. Practical Applications.
This study demonstrated that
performing the preacher curl exercise
effectively promoted regional hypertrophy,
particularly in the distal region of the biceps
brachii. However, it was important to note
that since these participants did not have a
regular resistance training routine, their
initial trainability might have influenced the
observed outcomes. Moreover, we suggested
that relying solely on preacher curls might
result in suboptimal hypertrophy of the
proximal region of the biceps. Practitioners
aiming to design comprehensive training
programs for complete biceps brachii
development should incorporate preacher
curls alongside other curl variations to
ensure balanced and maximal muscle
hypertrophy.
6. Conclusions
In conclusion, this study
demonstrated that biceps brachii regional
hypertrophy was affected by the selected
exercise per se, but not resistance training
programs. Preacher curl exercises were
found to particularly promote hypertrophy
in the distal region of the biceps brachii.
Further research into the effects of specific
exercises, such as those targeting the
proximal region of the biceps brachii, as well
as other muscle groups, is warranted to
inform the development of more effective
hypertrophy program designs.
Funding: This research received no external
funding.
Acknowledgments: Thank everyone for supports
throughout my Ph.D. journey.
Conflicts of Interest: The authors declare no
conflict of interest.
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