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Triceps brachii hypertrophy is substantially greater after elbow extension training performed in the overhead versus neutral arm position

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Abstract

The biarticular triceps brachii long head (TBLong) is lengthened more in the overhead than neutral arm position. We compared triceps brachii hypertrophy after elbow extension training performed in the overhead vs. neutral arm position. Using a cable machine, 21 adults conducted elbow extensions (90-0°) with one arm in the overhead (Overhead-Arm) and the other arm in the neutral (Neutral-Arm) position at 70% one-repetition maximum (1RM), 10 reps/set, 5 sets/session, 2 sessions/week for 12 weeks. Training load was gradually increased (+5% 1RM/session) when the preceding session was completed without repetition failure. 1RM of the assigned condition and MRI-measured muscle volume of the TBLong, monoarticular lateral and medial heads (TBLat+Med), and whole triceps brachii (Whole-TB) were assessed pre- and post-training. Training load and 1RM increased in both arms similarly (+62-71% at post, P = 0.285), while their absolute values/weights were always lower in Overhead-Arm (-34-39%, P < 0.001). Changes in muscle volume in Overhead-Arm compared to Neutral-Arm were 1.5-fold greater for the TBLong (+28.5% vs. +19.6%, Cohen's d = 0.61, P < 0.001), 1.4-fold greater for the TBLat+Med (+14.6% vs. +10.5%, d = 0.39, P = 0.002), and 1.4-fold greater for the Whole-TB (+19.9% vs. +13.9%, d = 0.54, P < 0.001). In conclusion, triceps brachii hypertrophy was substantially greater after elbow extension training performed in the overhead versus neutral arm position, even with lower absolute loads used during the training.
Triceps brachii hypertrophy is substantially greater after elbow extension
training performed in the overhead versus neutral arm position
Sumiaki Maeo
a
, Yuhang Wu
a
, Meng Huang
a
, Hikaru Sakurai
a
, Yuki Kusagawa
a
, Takashi Sugiyama
a
,
Hiroaki Kanehisa
b
and Tadao Isaka
a
a
Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Japan;
b
National Institute of Fitness and Sports in Kanoya, Kanoya,
Japan
ABSTRACT
The biarticular triceps brachii long head (TB
Long
) is lengthened more in the overhead than neutral
arm position. We compared triceps brachii hypertrophy after elbow extension training performed
in the overhead vs. neutral arm position. Using a cable machine, 21 adults conducted elbow
extensions (900°) with one arm in the overhead (Overhead-Arm) and the other arm in the
neutral (Neutral-Arm) position at 70% one-repetition maximum (1RM), 10 reps/set, 5 sets/
session, 2 sessions/week for 12 weeks. Training load was gradually increased (+5% 1RM/session)
when the preceding session was completed without repetition failure. 1RM of the assigned
condition and MRI-measured muscle volume of the TB
Long
, monoarticular lateral and medial
heads (TB
Lat+Med
), and whole triceps brachii (Whole-TB) were assessed pre- and post-training.
Training load and 1RM increased in both arms similarly (+6271% at post, P= 0.285), while their
absolute values/weights were always lower in Overhead-Arm (-3439%, P< 0.001). Changes in
muscle volume in Overhead-Arm compared to Neutral-Arm were 1.5-fold greater for the TB
Long
(+28.5% vs. +19.6%, Cohensd= 0.61, P< 0.001), 1.4-fold greater for the TB
Lat+Med
(+14.6% vs.
+10.5%, d= 0.39, P= 0.002), and 1.4-fold greater for the Whole-TB (+19.9% vs. +13.9%, d= 0.54,
P< 0.001). In conclusion, triceps brachii hypertrophy was substantially greater after elbow
extension training performed in the overhead versus neutral arm position, even with lower
absolute loads used during the training.
Highlights
.Growing evidence suggests that resistance training at long muscle lengths promotes muscle
hypertrophy, but its practical applications are yet to be explored.
.Triceps brachii muscle hypertrophy was substantially greater after cable elbow extension
training performed in the overhead than neutral arm position, particularly in the biarticular
triceps brachii long head, even with lower absolute loads lifted (i.e. lower mechanical stress
to muscles/joints).
.Cable elbow extension training should be performed in the overhead rather than neutral arm
position if one aims to maximise muscle hypertrophy of the triceps brachii or to prevent atrophy
of this muscle.
KEYWORDS
Bi- and monoarticular
muscles; muscle length;
muscle volume; training load
Introduction
Resistance training is widely recommended for athletic,
general, and clinical populations due to its well-known
benets on physical performance and health (ACSM,
2009; Westcott, 2012). Increasing muscle size is one of
the main goals of resistance training, and several evi-
dence-based hypertrophy-oriented training guidelines
have been established and updated in the past three
decades for various training variables such as load/inten-
sity, volume, and inter-set rest (Evans, 1999; Kassiano
et al., 2022; Kraemer & Ratamess, 2004; Morton,
Colenso-Semple, & Phillips, 2019; Schoenfeld & Grgic,
2019). On the other hand, only relatively recently have
studies begun to examine the inuence of muscle
length/joint angle during exercise on muscle hypertrophy
(Kubo et al., 2006; Alegre, Ferri-Morales, Rodriguez-
Casares, & Aguado, 2014; McMahon, Morse, Burden,
Winwood, & Onambele, 2014; Noorkoiv, Nosaka, & Blaze-
vich, 2014; Stasinaki et al., 2018; Akagi, Hinks, & Power,
2020; Maeo et al., 2021; Pedrosa et al., 2021). Nevertheless,
© 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.
CONTACT Sumiaki Maeo s-maeo@fc.ritsumei.ac.jp Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525
5877, Japan
Supplemental data for this article can be accessed online at https://doi.org/10.1080/17461391.2022.2100279.
EUROPEAN JOURNAL OF SPORT SCIENCE
https://doi.org/10.1080/17461391.2022.2100279
a growing body of evidence suggests that muscle hyper-
trophy is promoted when resistance training is conducted
at long vs. short muscle lengths (see Oranchuk, Storey,
Nelson, & Cronin, 2019 for a recent review), likely attribu-
table, at least in part, to greater metabolic stress (Kooistra,
de Ruiter, & de Haan, 2008) and IGF-1 expression
(McMahon et al., 2014) associated with exercise at long
muscle lengths.
Of the previous studies that compared muscle hyper-
trophy after training at long vs. short muscle lengths,
almost all adopted isometric (Kubo et al., 2006; Alegre
et al., 2014; Noorkoiv et al., 2014; Akagi et al., 2020) or
partial range of motion (ROM) (McMahon et al., 2014;
Stasinaki et al., 2018; Pedrosa et al., 2021) training at
dierent joint angles about the same joint (e.g. knee
extensors trained at knee exed vs. extended positions).
However, resistance training guidelines generally rec-
ommend dynamic exercises with a full ROM when poss-
ible (Evans, 1999; Kraemer & Ratamess, 2004; Morton
et al., 2019). Thus, it is of great practical importance to
compare hypertrophic eects of full ROM exercises
that place the same target muscle(s) under long vs.
short conditions. Based on the characteristics of biarticu-
lar muscles that their lengths are inuenced by two
joints the muscles cross, we recently compared ham-
strings muscle hypertrophy induced by seated (hip-
exed: long) vs. prone (hip-extended: short) leg curl
training performed with a full ROM (Maeo et al., 2021).
The results clearly indicated that hypertrophy was
greater for the seated than prone condition in the
whole and three biarticular hamstrings, but equivalent
in the monoarticular one, providing strong evidence
that muscle length during exercise inuences muscle
hypertrophy. Such a nding can be readily utilised in
the tness and rehabilitation elds, giving a simple
message that seated rather than prone leg curl is the
choice for those aiming to increase hamstrings muscle
size. The same approach can be tested in other major
biarticular muscles in the limbs, the results of which
will greatly contribute to ecient exercise programming
for large populations and future research as well.
The triceps brachii acts as the primary elbow extensor
and is considered to play crucial roles in various sports
and daily life activities such as baseball throws, (Fleisig
& Escamilla, 1996) tennis serves, (Buckley & Kerwin,
1988) and shot puts, (Terzis, Georgiadis, Vassiliadou, &
Manta, 2003) as well as injury prevention from falls
(Dietz, Noth, & Schmidtbleicher, 1981). Of its three con-
stituent muscles, the biarticular triceps brachii long
head (TB
Long
) crosses not only the elbow but also the
shoulder joint, and is lengthened more in the overhead
(shoulder-exed) than neutral arm position (Figure 1)
(Delp et al., 2007). Both overhead (Krings et al., 2016;
Ode L et al., 2012) and neutral (Hussain, Sundaraj, Subra-
maniam, & Lam, 2020; Jurimae, Abernethy, Blake, & McE-
niery, 1996) position elbow extensions are commonly
implemented in the eld and literature (often called
overhead triceps extensionand triceps pushdown,
respectively), but their dierence has rarely been dis-
cussed, particularly for their hypertrophic eects. To
the authorsknowledge, only one study (Stasinaki
et al., 2018) examined the eects of overhead vs.
neutral position elbow extension training on triceps
brachii hypertrophy, which did not nd a signicant
dierence between the two training conditions.
However, some methodological issues should be con-
sidered when interpreting their results. First and most
importantly, their training period (6 weeks) and sample
size (n = 9/condition) were likely insucient, which
appears to be the main reason for not nding a statistical
dierence even though the overhead condition had a
1.5-fold greater increase in a muscle size measure.
Second, the training was conducted with a partial ROM
of the elbow joint in combination with dierent
shoulder joint angles, which itself is not a problem but
contradicts with the general training guidelines as men-
tioned above. These aspects motivated us to reexamine
the hypertrophic eects of overhead vs. neutral position
elbow extension training with a more methodologically
robust and practical approach, although we commend
the previous study (Stasinaki et al., 2018) for its novelty.
The purpose of this study was therefore to examine
the eects of elbow extension training performed in
the overhead vs. neutral arm position on triceps
brachii muscle hypertrophy. To this end, we designed
a 12-week training intervention study using a within-
participant comparison model, a powerful approach
for comparing hypertrophic responses induced by two
types of interventions (MacInnis, McGlory, Gibala, & Phil-
lips, 2017). A sample size of 21 (i.e. n = 21 arms per con-
dition) was deemed well sucient based on our recent
study (Maeo et al., 2021) using the same training inter-
vention model on the hamstrings (n = 20 legs per con-
dition). We hypothesised that 1) hypertrophy of the
TB
Long
and consequently the whole triceps brachii
(Whole-TB) would be greater, but 2) that of the monoar-
ticular lateral and medial heads (TB
Lat+Med
) would be
equivalent, when elbow extension training is performed
in the overhead vs. neutral arm position.
Methods
Participants and study overview
Twenty-one healthy young adults (14 males, age: 23.0 ±
1.4 y, height: 1.73 ± 0.07 m, body mass: 70.0 ± 11.1 kg; 7
2S. MAEO ET AL.
females, age: 24.3 ± 1.6 y, height: 1.61 ± 0.07 m, body
mass: 53.6 ± 6.3 kg) participated in this study, which
was approved by the Ethics Committee of Ritsumeikan
University (BKC-IRB-2018-087). Written informed
consent was obtained from each participant. The partici-
pants were all healthy, but none had been involved in
any type of systematic resistance training programme
in the past 12 months. They conducted 12-week unilat-
eral elbow extension training with one arm in the over-
head position (Overhead-Arm) and the other arm in the
neutral position (Neutral-Arm). All participants attended
three measurement sessions; two sessions before the
training period (Pre 1 and Pre 2) separated by 27
days, and one session after the training period (Post) 2
4 days after the nal training session. Participants
were instructed to avoid any intensive and unfamiliar
physical activities for the arms within 2 days before Pre
1 and throughout the experimental period. Each
measurement session involved MRI scans and one-rep-
etition maximum (1RM) measurements. Training and
measurements were conducted as follows.
Training programme
Each arm was assigned to Overhead-Arm or Neutral-
Arm, with the dominant and non-dominant arms coun-
terbalanced using a computer-generated list. Both
arms were trained unilaterally with the assigned training
condition in a standing position by using a cable
machine (Signature Series Dual Adjustable Pulley, Life
Fitness, Chicago, IL) with the shoulder joint xed at
180° exion for Overhead-Arm and for Neutral-Arm
(0° = anatomical position) (Figure 1). The elbow joint
ROM was 90 for both conditions, which we dened
as the full ROM, with the wrist kept supinated (to help
keep the shoulder adducted). Each training session com-
menced with 510 warm-up repetitions at 50% of the
load prescribed for that session (detailed below) with
the assigned training condition. Participants then per-
formed the elbow extensions 10 repetitions/set for 5
sets, taking 2 s for each of the concentric (elbow extend-
ing) and eccentric (elbow exing) phases without a
pausing phase with the guide of a metronome (60
bpm). 2-min rest intervals were taken in between sets.
Figure 1. Postures of the shoulder and elbow joints (A and B) and operating ranges of each triceps brachii muscle on the normalised
forcelength curve (CE) during the elbow extensions performed in the overhead and neutral arm positions. These were obtained
using the OpenSim Arm26 model, (Delp et al., 2007) with the shoulder joint exed at 180° and for the overhead and neutral con-
ditions, respectively, and the elbow joint angle ranging 90 for both conditions as conducted in this study. It can be clearly seen
that the TB
Long
operates at longer muscle lengths in the overhead than neutral condition, while there is no dierence between the
conditions in the TB
Lat
and TB
Med
. TB
Long
= triceps brachii long head; TB
Lat
and TB
Med
triceps brachii lateral and medial heads,
respectively.
EUROPEAN JOURNAL OF SPORT SCIENCE 3
After training one arm (5 sets), the other arm was
trained. The preceding arm was counterbalanced in
the rst training session among participants, and it
was switched every session for each participant. Training
was conducted twice per week on nonconsecutive days.
Training load was gradually increased at the rst,
second, and third sessions from 50, 60, and 70% of
1RM measured pre-training (detailed below), respect-
ively, and 70% of 1RM was used thereafter. This protocol
was the same as for our previous study (Maeo et al.,
2021) targeting the hamstrings, and similar to those of
previous studies (Stasinaki et al., 2018; Kawakami, Abe,
Kuno, & Fukunaga, 1995; Sugisaki et al., 2015; Wakahara,
Fukutani, Kawakami, & Yanai, 2013) targeting the triceps
brachii, which all found typical hypertrophy for the tar-
geted muscles (see Discussion). At least one examiner
always supervised the training sessions and provided
verbal encouragement, and corrected the joint positions
and/or movement speed of the exercise when necessary.
The examiners also assisted (spotted) the participants in
executing the exercise when they could no longer
repeat the repetitions up to 10 in each set. This was
done in such a way that the participants could complete
the task in a controlled manner with their continuous
(maximum) eorts. If the participants could complete
all the prescribed protocol without examinersassist at
the third session and thereafter, +5% of 1RM was
added at the subsequent sessions.
1RM
1RM was measured in each arm with the assigned train-
ing condition using the same cable machine as for the
training. At Pre 1, participants were familiarised with
the exercise by performing 35 repetitions with a light
load, which was gradually increased (35 stages) with
a short rest period (1020 s) until the participants felt
it somewhat heavy. Thereafter, only 1 repetition was per-
formed at each increasing load by increments of 1.25 kg,
with 2 min rest in between trials. 1RM was dened as
the maximum load lifted with the proper joint positions,
which was checked by the examiner(s). At Pre 2, partici-
pants performed 5, 3, and 1 warm-up repetitions at 50%,
75%, and 90% of 1RM of Pre 1, respectively, with 30 s
rest, and tried the same 1RM load of Pre 1 after 2
min rest. 1RM was determined by increasing or decreas-
ing the load thereafter. At Post, the warm-up and 1RM
assessment were similarly conducted but based on the
1RM of Pre 2. The training load and its increments in
the training sessions described above were also based
on the 1RM of Pre 2. The mean within-participant coe-
cient of variation (CV) between the two pre-training ses-
sions were 8.0% and 10.5% for the Overhead-Arm and
Neutral-Arm 1RM, respectively. Data from Pre 2 was
used for further analysis as the Pre value.
MRI
Preceding the 1RM measurement, longitudinal relax-
ation time-weighted cross-sectional MRIs of the upper
arm were obtained for each arm using 18-channel
body array and spine coils (Body 18 and CP Spine
Array Coil, Siemens Healthineers, Germany) with the fol-
lowing parameters (modied based on previous studies
Kawakami et al., 1995; Wakahara et al., 2013 [e.g. slice
thickness and gap were reduced from 10 mm to 2.5
mm for a more precise analysis]): eld of view, 250*250
mm; matrix, 448*336; pixel size, 0.56*0.74 mm; in-plane
resolution, 0.42 mm; TR, 700 ms; TE, 9.4 ms; ip angle,
120°; gap, 2.5 mm; slice thickness, 2.5 mm; number of
slices, 32*2 blocks (Figure 2). Participants lay supine
with their arms extended and muscles relaxed in a 3T
magnet bore (MAGNETOM Skyra, Siemens Healthineers,
Germany), and 2 series of blocks were taken with the
most proximal slice set at the widest part of the
humerus head to cover the whole triceps brachii for
each arm.
Images were analysed by using image analysis soft-
ware (Horos, Horos Project), with the MRI data anon-
ymised and investigators blinded to the training
conditions. Anatomical cross-sectional areas (ACSAs) of
the individual triceps brachii muscles were manually
outlined in every other image from the most proximal
to the most distal image in which the muscle was
visible. Care was taken to exclude visible adipose and
connective tissue incursions. ACSAs for the skipped
images and gaps were estimated based on linear interp-
olation between the images in which ACSAs were out-
lined (Maeo, Shan, Otsuka, Kanehisa, & Kawakami,
Figure 2. Example images of the right arm MRIs at 50% of the
whole length of the triceps brachii taken at Pre (A) and Post (B).
Anatomical cross-sectional areas of the Long, Lat, and Med
heads of the triceps brachii are drawn. Lat = lateral; Long =
long; Med = medial; Post = post-training; Pre = pre-training.
4S. MAEO ET AL.
2018). The volume of individual muscle was determined
by summing all ACSAs for that muscle multiplied by the
slice thickness. Due to diculty in separating the mono-
articular lateral and medial heads in the distal regions in
some participants, the muscle volumes of these muscles
are reported as the sum of these muscles (i.e. TB
Lat+Med
).
The Whole-TB volume was calculated by summing the
volumes of TB
Long
and TB
Lat+Med
. The mean within-par-
ticipant CVs between the two pre-training sessions for
the muscle volume were as follows: TB
Long
, 2.5%; TB
Lat
+Med
, 1.6%; Whole-TB, 1.5%. Data from the two pre-train-
ing sessions were averaged and used for further analysis
as the Pre value.
Statistical analysis
All data were analysed using SPSS software (version 25,
IBM Corp, USA) unless otherwise noted. Statistical signi-
cance was set at P< 0.05. Residuals were checked for
normality and homoscedasticity by ShapiroWilks test
and Levenes test, respectively, and all data set were
conrmed by the tests except for relative increase in
1RM and relative training load (explained below).
Changes in muscle volumes from Pre to Post were com-
pared between arms by an ANCOVA with the Pre values
as covariates and the Post values as the dependent vari-
ables. A linear mixed-eects model was used with a
subject as a random eect and an arm (training con-
dition) as a xed eect. Eect sizes of between-condition
dierences were calculated as Cohensdvalues based on
absolute change values, and were interpreted as trivial <
0.2; small 0.20.49; moderate 0.5-0.79; and large 0.8
(Cohen, 1988). To improve statistical inference, mean
dierence from baseline with their bootstrap 95% con-
dence interval (CI) was calculated for each condition by
using estimation statistics (Ho, Tumkaya, Aryal, Choi, &
Claridge-Chang, 2019).
We also explored if there were any dierences in 1RM
and training load between the arms (training con-
ditions). Absolute 1RM at Pre and Post and absolute
training load at each training session were compared
between arms by a paired t-test at each time point. Rela-
tive increase in 1RM at Post and relative training load at
each session, both expressed as % 1RM of Pre, were
compared between arms by the Wilcoxon signed-rank
test because most of the data at the early training ses-
sions were not normally distributed due to prescribing
the training loads based on % 1RM values. The main stat-
istical results were the same when the relative data were
compared by paired t-tests, or when absolute data were
z-scored and compared by paired t-tests. Descriptive
data are presented as means ± SDs.
Results
Training load
Training load gradually increased in both Overhead-Arm
and Neutral-Arm (Figure 3). In the relative values, there
were signicant but only minor dierences between
arms at some of the rst half sessions (P= 0.0250.044
at sessions 4, 7, 9, 10, 12), and no signicant dierences
existed at the second half sessions (P= 0.1950.876). On
the other hand, absolute training load was always lower
for Overhead-Arm than Neutral-Arm at all sessions (P<
0.001), as can be clearly seen from Figure 3.
1RM
Absolute 1RM was lower for Overhead-Arm than
Neutral-Arm at both Pre (7.2 ± 3.7 vs. 11.5 ± 4.7 kg, P<
0.001) and Post (12.0 ± 5.8 vs. 18.3 ± 6.9 kg, P< 0.001).
Relative increases in 1RM did not signicantly dier
between the arms (71.4 ± 46.8% vs. 62.3 ± 29.2%, P=
0.285).
Muscle volume
There were signicant dierences in mean muscle
volume changes between the arms in each of the
TB
Long
, TB
Lat+Med
, and Whole-TB (Figure 4; see Table for
details, Supplementary data 1). The increases in muscle
volume were greater for Overhead-Arm than Neutral-
Arm in the TB
Long
(ANCOVA-adjusted mean change:
+28.5% vs. +19.6%, 1.5-fold dierence, P< 0.001,
Cohensd= 0.61 [medium] based on absolute changes
of 50.6 ± 30.6 vs 34.5 ± 21.2 cm
3
), TB
Lat+Med
(+14.6%
vs. +10.5%, 1.4-fold dierence, P= 0.002, d= 0.39
[small] based on absolute changes of 42.1 ± 33.4 vs
30.4 ± 26.9 cm
3
), and Whole-TB (+19.9% vs. +13.9%,
1.4-fold dierence, P< 0.001, d= 0.54 [medium] based
on absolute changes of 92.8 ± 58.1 vs 64.9 ± 45.2 cm
3
).
Discussion
The primary nding of this study was that hypertrophy
of the triceps brachii was greater after elbow extension
training performed in the overhead vs. neutral arm pos-
ition, not only in the TB
Long
and Whole-TB but also in the
TB
Lat+Med
. This supported our rst hypothesis on the
TB
Long
and Whole-TB, but refuted the second hypothesis
on the TB
Lat+Med
for which we had presumed equivalent
hypertrophic eects of the overhead and neutral con-
ditions. Nevertheless, the observed clearly greater
hypertrophy of the overall triceps brachii after overhead
vs. neutral position elbow extension training would be
EUROPEAN JOURNAL OF SPORT SCIENCE 5
highly useful in exercise prescription and designing
future studies.
Muscle hypertrophy
Changes in the Whole-TB volume induced by the 12-
week twice-weekly training intervention of this study
were +19.9% for the Overhead-Arm and +13.5% for
the Neutral-Arm, which correspond to +0.83% and
+0.58% per session, respectively. These are in the
range of the reported gains (+0.551.19% per session)
in the Whole-TB volume or ACSA after traditional iso-
tonic resistance training for the triceps brachii per-
formed 23 times per week for 616 weeks (Stasinaki
et al., 2018; Kawakami et al., 1995; Sugisaki et al., 2015;
Wakahara et al., 2013). Thus, it appears that typical
triceps brachii hypertrophy was induced in this study
as well, although a direct comparison is dicult given
dierent methodology used by this study vs. previous
ones such as training frequency and period to name a
few. It may be worth mentioning that these studies
adopted various triceps brachii exercises such as stand-
ing (Kawakami et al., 1995) or lying (Sugisaki et al.,
2015) elbow extension using a dumbbell, and lying
dumbbell press (Wakahara et al., 2013). It is beyond
the scope of this study to discuss which or any combi-
nation of these is more eective than others in promot-
ing triceps brachii muscle hypertrophy. Nevertheless,
given that the hypertrophy pattern was the same for
both Overhead-Arm and Neutral-Arm in a sense that
both had greater hypertrophy in the TB
long
than TB
Lat
+Med
(Figure 4), there may be no need to combine
these to optimise Whole-TB hypertrophy (i.e. only the
overhead condition is ne). On the other hand, there is
some evidence that single-joint (Maeo, Shan, Otsuka,
Kanehisa, & Kawakami, 2018) and multi-joint (Kubo, Ike-
bukuro, & Yata, 2019) exercises preferentially train biarti-
cular and monoarticular muscles, respectively, the
former of which is supported by this study. Thus, a com-
bination of overhead elbow extension (single-joint exer-
cise) and lying dumbbell press (multi-joint exercise) may
further promote hypertrophy of the Whole-TB. Further
Figure 3. Relative (A) and absolute (B) training load used in the training sessions. Training load was gradually increased at the rst,
second, and third sessions from 50%, 60%, and 70% 1RM measured pre-training, respectively, and 70% of 1RM was used thereafter. If
the participants could complete all the prescribed protocol at the third session and thereafter without repetition failure, +5% 1RM was
added at the subsequent sessions. *P< 0.05, between conditions. Neutral-Arm = the arm that trained in the neutral position; Over-
head-Arm = the arm that trained in the overhead position.
6S. MAEO ET AL.
research is needed to directly explore this issue, and the
approach and results of this study would be an informa-
tive guide for developing such work.
Based on our recent nding (Maeo et al., 2021) that
muscle hypertrophy was greater after seated than
prone leg curl training exclusively in the biarticular
hamstrings (i.e. equivalent in the monoarticular one),
we hypothesised greater hypertrophy of the overhead
than neutral condition to occur in the TB
Long
(and
Whole-TB) but not in the TB
Lat+Med
. However, the over-
head condition induced greater hypertrophy than the
neutral condition not only in the TB
Long
but also in the
Figure 4. Changes in muscle volume of the TB
Long
(A), TB
Lat+Med
(B), and Whole-TB (C) after the training. In each subgure/muscle(s),
the raw data is plotted on the upper axes for Overhead-Arm (left) and Neutral-Arm (right); each paired set of observations at Pre and
Post is connected by a line. On the lower axes, each paired mean dierence is plotted as a bootstrap sampling distribution. Mean
dierences are depicted as dots with horizontal dashed lines; 95% condence intervals are indicated by the ends of the vertical
error bars. ***P< 0.001 and **P< 0.01, dierence between arms (conditions) based on a baseline-adjusted ANCOVA. dvalues indicate
Cohensdeect sizes of between-group dierences based on absolute change values. The bar graphs in the summary gure (D) are
based on the ANCOVA-adjusted mean changes for each muscle(s). TB
Long
= triceps brachii long head; TB
Lat+Med
= triceps brachii
lateral and medial heads; Neutral-Arm = the arm that trained in the neutral position; Overhead-Arm = the arm that trained in the over-
head position; Whole-TB = whole triceps brachii.
EUROPEAN JOURNAL OF SPORT SCIENCE 7
TB
Lat+Med
(Figure 4). This suggests that factors other the
muscle length dierence during exercise inuenced the
degree of hypertrophy of the monoarticular muscles, in
contrast to our previous study on the hamstrings (Maeo
et al., 2021). A potential reason may be related to the
muscle length of the TB
Long
and its associated force con-
tribution to the elbow extension task. More specically,
as can be seen from the simulation data in Figure 1,
the TB
Long
is lengthened in the overhead condition,
operating at around the edge of the descending limb
of the force-length curve, to the point where it can
only produce a small force. This would result in propor-
tionally greater force contribution from the TB
Lat+Med
to
the elbow extension task in the overhead vs. neutral
condition due to reduced contribution from the TB
Long
,
which is supported by a recent simulation study (Kho-
linne et al., 2018). This was likely not the case for the
seated vs. prone leg curl training, in which the biarticular
muscles operated at much wider regions (i.e. not around
the edge) of the descending limb in the seated condition
(see Figure 1 of Maeo et al., 2021) compared to the case
for this study, with other synergists such as the sartorius
and gracilis also collaboratively contributing to the knee
exion task (Maeo et al., 2021).
Another explanation for greater hypertrophy found
not only in the TB
Long
but also in the TB
Lat+Med
may be
due to reduced muscle blood ow concomitant with
maintaining the overhead arm position, (Tschakovsky &
Hughson, 2000) which may have increased the meta-
bolic stress within the muscle and promoted hypertro-
phy, (Pearson & Hussain, 2015) likely irrespective of bi-
and monoarticular muscles. Again, this was perhaps
not the case for the seated vs. prone leg curl training
(Maeo et al., 2021), in which the legs were approximately
in a horizontal position when extended in both con-
ditions. Unfortunately, it is unknown how much of
these potential mechanisms alone or in combination
inuenced the degree of muscle hypertrophy, so we
cannot rule out the possibility that training at long
muscle length in the overhead condition per se had no
inuence on the hypertrophy of the TB
Long
. However,
it is worth noting that the dierence between the con-
ditions (overhead > neutral) in the degree of hypertro-
phy was slightly more pronounced in the TB
Long
vs.
TB
Lat+Med
(mean change dierence: 1.5-fold vs. 1.4-fold,
Cohensd: 0.61 [medium] vs. 0.39 [small], overlaps in
the 95% CI: smaller vs. larger, Figure 4). Thus, we con-
sider that the hypertrophy of the TB
Long
was at least
partly promoted by being more lengthened in the over-
head than neutral condition during the exercise, while
either or both mechanisms mentioned above may also
have played some roles in promoting hypertrophy of
the TB
Lat+Med
.
Training load and 1RM
Here, we discuss the training loads used and their shifts
as well as changes in maximum strength, together with
the hypertrophy results, to provide practical information
and a novel aspect of associations among them found in
this study. Relative training load (% 1RM of Pre)
increased similarly for both training conditions although
there were some minor albeit signicant dierences
between conditions in the rst half sessions (Figure
3A). After the intervention, relative increases in 1RM
did not signicantly dier between the overhead vs.
neutral conditions. These indicate that relative training
load and improvement in muscle strength were equival-
ent between the two training conditions. Given that the
hypertrophy was greater for the overhead than neutral
condition as discussed above, the similarity of strength
improvement might seem inconsistent. However, it is
well documented that strength improvement induced
by a relatively short (e.g. 12 weeks) resistance training
intervention is mainly attributable to neural factors such
as increased neural drive although increases in muscle
size could also contribute to the strength gain (Maeo
et al., 2018). This study did not measure any neurophy-
siological parameters to assess neural changes induced
by the training since the focus of this study was to
compare changes in muscle size. Nevertheless, we rec-
ommend future studies measure both neural and
muscle size parameters to better understand how each
of these contributes to training-induced strength
gains, ideally by multiple measurements over the time
course of long-term intervention (e.g. > 6 months).
Absolute training load (kg) was always lower for the
overhead than neutral condition (Figure 3B) because
absolute 1RM was lower for the overhead condition at
both Pre and Post. This is likely at least partly attributable
to the TB
Long
operating at around the edge of the des-
cending limb of the force-length curve (i.e. lower
force-generating capacity) in the overhead condition
(Figure 1). Taken together with the hypertrophy
results, this indicates that absolute training load is not
a determinant of training-mediated hypertrophic gains.
Although such a nding is already reported by previous
studies (Mitchell et al., 2012; Schoenfeld, Peterson,
Ogborn, Contreras, & Sonmez, 2015) that showed
similar hypertrophy after high vs. low load resistance
training performed to repetition failure, they used the
same exercise and body position for both conditions,
indicating that both absolute and relative load were
dierent between the conditions. It is important to
note that low (relative) load, compared to traditional
high load, resistance training performed to failure
requires substantially greater number of repetitions
8S. MAEO ET AL.
and is more time-consuming, which may limit its practi-
cal use. In contrast, relative training load in this study
was equivalent between conditions (or we intentionally
matched them, at least at the initial sessions, Figure 3A),
and the number of repetitions and therefore total time
were the same for both conditions throughout the inter-
ventions. Thus, this study supports the previous studies
(Mitchell et al., 2012; Schoenfeld et al., 2015) and adds
that the environment within the muscle such as
muscle length during exercise, rather than absolute or
even relative training load, can be a strong determinant
of training-induced muscle hypertrophy. This aspect
would be particularly relevant in rehabilitation and per-
iodisation since lower absolute load indicates lower
mechanical stress on muscles and joints.
Limitations and future perspectives
This study provided further evidence with a practical
model that training at long vs. short muscle lengths pro-
motes muscle hypertrophy (Maeo et al., 2021), which
may be partly attributable to greater metabolic stress
(Kooistra et al., 2008) and IGF-1 expression (McMahon
et al., 2014) associated with exercise at long muscle
lengths. However, it was also found that other factors
such as body position-related changes in muscle blood
ow may also have inuenced the degree of muscle
hypertrophy, likely irrespective of bi- and monoarticular
muscles. Thus, future studies comparing hypertrophic
eects of resistance training at dierent joint angles/
muscle lengths, especially when manipulating an angle
of one of two joints biarticular muscles cross (as con-
ducted in this study), should consider/examine the
inuence of body position-related changes in muscle
blood ow. It is also necessary to explore the mechan-
isms underpinning greater hypertrophy after training
at long vs. short muscle lengths as well as its dose
response relationship using both basic science and prac-
tical approaches. Specically, it is currently unknown
whether muscles should be lengthened as much as
possible during exercise, or there is an optimal length-
ened state, to achieve maximum hypertrophy. Clarifying
these will largely contribute to rening eective and safe
exercise prescription.
Conclusion
In summary, elbow extension training performed in the
overhead vs. neutral position produced greater hyper-
trophy in the biarticular triceps brachii as expected,
which appears to be at least partly attributable to the
between-condition dierence in its muscle length
during exercise. On the other hand, greater hypertrophy
of the overhead condition was also found in the mono-
articular muscles, in which muscle lengths do not dier
between the conditions. This may suggest involvement
of muscle length-related proportionally greater force
contribution from the monoarticular muscles due to
reduced contribution from the biarticular one, and/or
arm position-related reduced muscle blood ow, as
additional hypertrophy-promoting factors in the over-
head condition. In either case, hypertrophy of the
overall triceps brachii was consequently much greater
after overhead vs. neutral elbow extension training,
even with lower absolute loads lifted (i.e. lower mechan-
ical stress on muscles/joints). Thus, we recommend
elbow extension training should be performed in the
overhead rather than neutral arm position if one aims
to maximise muscle hypertrophy of the triceps brachii
or to prevent atrophy of this muscle.
Acknowledgments
This work was supported by a research grant from the Des-
cente and Ishimoto Memorial Foundation of Sports Science
to SM. We thank Professor Jonathan Folland at Loughborough
University for his comments on the interpretation of the hyper-
trophy of the monoarticular muscles and Mr. Takahiro Tanaka
at Ritsumeikan University for his support with the OpenSim
simulation analysis.
Disclosure statement
No potential conict of interest was reported by the author(s).
Funding
This work was supported by Descente and Ishimoto Memorial
Foundation for the Promotion of Sports Science: [Grant
Number 2019-20].
ORCID
Sumiaki Maeo http://orcid.org/0000-0003-0919-4799
Yuki Kusagawa http://orcid.org/0000-0003-4446-4723
Takashi Sugiyama http://orcid.org/0000-0001-9391-0633
Tadao Isaka http://orcid.org/0000-0002-8190-3281
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EUROPEAN JOURNAL OF SPORT SCIENCE 11
... Similar results were found by both Sato et al. (2021) in the elbow flexors [47]. A further study by Maeo et al. (2022) featured a within-subject design comparing "neutral-arm" and "overhead-arm" elbow extensions and showed greater hypertrophy in all 3 heads of the triceps brachii in the longer muscle length condition [48]. This finding is noteworthy, since only the long head of the triceps brachii was trained at longer muscle lengths during the "overhead" condition; yet the lateral and medial heads of the triceps brachii also saw greater hypertrophy. ...
... Similar results were found by both Sato et al. (2021) in the elbow flexors [47]. A further study by Maeo et al. (2022) featured a within-subject design comparing "neutral-arm" and "overhead-arm" elbow extensions and showed greater hypertrophy in all 3 heads of the triceps brachii in the longer muscle length condition [48]. This finding is noteworthy, since only the long head of the triceps brachii was trained at longer muscle lengths during the "overhead" condition; yet the lateral and medial heads of the triceps brachii also saw greater hypertrophy. ...
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It has been proposed that training to failure is a necessary strategy to maximize muscle growth. This paper examines the research behind these claims, and attempts to draw evidence-based conclusions as to the practical implications for hypertrophy training.
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We evaluated the effects of differential muscle architectural adaptations on neuromuscular fatigue resistance. Seven young males and 6 females participated in this study. Using a longitudinal within-subject design, legs were randomly assigned to perform isometric training of the tibialis anterior (TA) 3× per week for 8 weeks at a short (S-Group) or long muscle-tendon unit length (L-Group). Before and following training, fascicle length (FL) and pennation angle (PA) of the TA were assessed. As well, fatigue-related time-course changes in isometric maximal voluntary contraction (MVC) torque and isotonic peak power (20%MVC resistance) were determined before, immediately, 1, 2, 5, and 10 min following task failure. The fatiguing task consisted of repeated maximal effort isotonic (20%MVC resistance) contractions over a 40° range of motion, until the participant reached a 40% reduction in peak power. Although there was no clear improvement of neuromuscular fatigue resistance following training in both groups (P = 0.081; S-Group: ~20%, L-Group: ~51%), the change in neuromuscular fatigue resistance was related positively to the training-induced increase in PA (~6%, P < 0.001) in the S-Group (r = 0.739, P = 0.004) and negatively to the training-induced increase in FL (~4%, P = 0.001) in the L-Group (r = −0.568, P = 0.043). Both groups recovered similarly for MVC torque and peak power after the fatiguing task as compared to before training. We suggest that the relationships between the changes in muscle architecture and neuromuscular fatigue resistance depend on the muscle-tendon unit lengths at which the training is performed.
Article
Resistance exercise training (RET)-induced increases in voluntary 1RM strength are greater with higher loads and training by replicating (or close) the strength test. In contrast, RET-induced muscular hypertrophy is primarily mediated by intensity of effort, which is achieved by performing RET to volitional fatigue and with an internal focus on contracting a muscle throughout the exercise range of motion. In addition, RET-induced muscular hypertrophy is augmented by increasing training volume, but with diminishing returns. Other training variables such as volume-load, inter-set rest, and time under tension have negligible effects on RET-induced changes in muscle size or strength. We conclude that an uncomplicated, evidence-based approach to optimizing RET-induced changes in muscle size and strength follows the FITT principle: frequency, intensity (effort), type, and time.