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Training in the Initial Range of Motion Promotes Greater Muscle Adaptations Than at Final in the Arm Curl

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  • Universidade Federal de Santa Maria - UFSM

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Objective: The effects of ROM manipulation on muscle strength and hypertrophy response remain understudied in long-term interventions. Thus, we compared the changes in strength and regional muscle hypertrophy after training in protocols with different ranges of motion (ROM) in the seated dumbbell preacher curl exercise using a within-participant experimental design. Design and methods: Nineteen young women had one arm randomly assigned to train in the initial ROM (INITIALROM: 0°-68°; 0° = extended elbow) while the contralateral arm trained in the final ROM (FINALROM: 68°-135°), three times per week over an eight-week study period. Pre- and post-training assessments included one repetition maximum (1RM) testing in the full ROM (0°-135°), and measurement of biceps brachii cross-sectional area (CSA) at 50% and 70% of humerus length. Paired t-tests were used to compare regional CSA changes between groups, the sum of CSA changes at 50% and 70% (CSAsummed), and the strength response between the training protocols. Results: The INITIALROM protocol displayed a greater CSA increase than FINALROM protocol at 70% of biceps length (p = 0.001). Alternatively, we observed similar increases between the protocols for CSA at 50% (p = 0.311) and for CSAsummed (p = 0.111). Moreover, the INITIALROM protocol displayed a greater 1RM increase than FINALROM (p < 0.001). Conclusions: We conclude that training in the initial angles of elbow flexion exercise promotes greater distal hypertrophy of the biceps brachii muscle in untrained young women. Moreover, the INITIALROM condition promotes a greater dynamic strength increase when tested at a full ROM compared to the FINALROM.
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Sports 2023, 11, 39. https://doi.org/10.3390/sports11020039 www.mdpi.com/journal/sports
Article
Training in the Initial Range of Motion Promotes Greater
Muscle Adaptations Than at Final in the Arm Curl
Gustavo F. Pedrosa 1,2,†, Marina G. Simões 1,†, Marina O. C. Figueiredo 1, Lucas T. Lacerda 1,3, Brad J. Schoenfeld 4,*,
Fernando V. Lima 1, Mauro H. Chagas 1 and Rodrigo C. R. Diniz 1
1 Weight Training Laboratory, School of Physical Education, Physiotherapy and Occupational Therapy,
Federal University of Minas Gerais, Lagoa Santa 31270-901, Brazil
2 Brazilian Air Force, Aeronautical Instruction and Adaptation Center, Lagoa Santa 33400-000, Brazil
3 Department of Physical Education, State University of Minas Gerais, Divinópolis 35501-170, Brazil
4 Department of Health Sciences, CUNY Lehman College, Bronx, New York, NY 10468, USA
* Correspondence: brad.schoenfeld@lehman.cuny.edu
These authors contributed equally to this work.
Abstract: Objective: The effects of ROM manipulation on muscle strength and hypertrophy
response remain understudied in long-term interventions. Thus, we compared the changes in
strength and regional muscle hypertrophy after training in protocols with different ranges of motion
(ROM) in the seated dumbbell preacher curl exercise using a within-participant experimental
design. Design and methods: Nineteen young women had one arm randomly assigned to train in
the initial ROM (INITIALROM: 0°–68°; 0° = extended elbow) while the contralateral arm trained in
the final ROM (FINALROM: 68°–135°), three times per week over an eight-week study period. Pre-
and post-training assessments included one repetition maximum (1RM) testing in the full ROM (0°–
135°), and measurement of biceps brachii cross-sectional area (CSA) at 50% and 70% of humerus
length. Paired t-tests were used to compare regional CSA changes between groups, the sum of CSA
changes at 50% and 70% (CSAsummed), and the strength response between the training protocols.
Results: The INITIALROM protocol displayed a greater CSA increase than FINALROM protocol at 70%
of biceps length (p = 0.001). Alternatively, we observed similar increases between the protocols for
CSA at 50% (p = 0.311) and for CSAsummed (p = 0.111). Moreover, the INITIALROM protocol displayed
a greater 1RM increase than FINALROM (p < 0.001). Conclusions: We conclude that training in the
initial angles of elbow flexion exercise promotes greater distal hypertrophy of the biceps brachii
muscle in untrained young women. Moreover, the INITIALROM condition promotes a greater
dynamic strength increase when tested at a full ROM compared to the FINALROM.
Keywords: muscle hypertrophy; partial angular; partial range of motion; partial angular
displacement; muscle strength
1. Introduction
The effects of manipulating resistance training (RT) variables on muscle hypertrophy
response has been an ongoing focus of investigation [1–3]. Among the RT variables, range
of motion (ROM) was generally overlooked in past studies targeting training prescription
recommendations [3,4]. However, its influence on neuromuscular responses is becoming
increasingly recognized as a potential area of research interest [5,6]. ROM may alter the
length at which the working muscle contracts. At the beginning of a concentric action
(INITIALROM), the muscle length is longer than at the final angles of the action (FINALROM).
Several investigations have reported greater metabolic stress and IGF-1 release after
contractions performed at longer vs. shorter muscle lengths [7–11], which have been
associated with muscle hypertrophy [12,13]. This raises the possibility that training
Citation: Pedrosa, G.F.;
Simões, M.G.; Figueiredo, M.O.C.;
Lacerda, L.T.; Schoenfeld, B.J.;
Lima, F.V.; Chagas, M.H.;
Diniz, R.C.R. Training in the Initial
Range of Motion Promotes Greater
Muscle Adaptations than at Final in
the Arm Curl. Sports 2023, 11, 39.
https://doi.org/10.3390/
sports11020039
Academic Editor: Andrew Hatchett
Received: 9 January 2023
Revised: 31 January 2023
Accepted: 1 February 2023
Published: 6 February 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license
(https://creativecommons.org/license
s/by/4.0/).
Sports 2023, 11, 39 2 of 12
exclusively in the INITIALROM, where the muscle is in a lengthened state, may promote a
greater hypertrophic response than training in the FINALROM.
Several studies have compared the hypertrophic response to training in the
INITIALROM and FINALROM [7,14,15]. For the quadriceps, results showed greater increases
in muscle cross-sectional area (CSA) at the distal muscle regions of the rectus femoris [14]
and vastus lateralis [7,14] for the group that performed the INITIALROM compared to the
FINALROM training group. These findings suggest that the ROM trained may influence
regional muscle growth on quadriceps muscle. Similar to results for the quadriceps, Sato
et al. [16] found a greater increase in muscle thickness of the distal biceps brachii plus
brachialis after preacher unilateral arm curl resistance training at INITIALROM compared
to FINALROM. However, the training occurred two times per week across five weeks,
raising the question as to whether differences would be maintained after a longer training
period. According to Halperin et al. [17], it is possible that the initial improvements were
due to the novel stimulus rather than an inherent superiority of the program. Conceivably,
results may have been different if the study period lasted longer. Therefore, it is necessary
to conduct further research to provide greater insight into the effect of training in various
ROMs on the muscle hypertrophic response over longer time frames.
Kassiano et al. [15] compared changes in muscle thickness of the medial and lateral
heads of the gastrocnemius across an eight-week RT program involving the calf raise
exercise when performed in the INITIALROM vs FINALROM. Results showed the
INITIALROM training elicited greater increases in muscle thickness of the medial and
lateral gastrocnemius compared to the FINALROM, providing evidence that training
exclusively at longer muscle lengths may be superior to training exclusively at shorter
muscle lengths for enhancing muscle hypertrophy of the plantar flexors. However, these
authors assessed hypertrophy at a single point along the muscle, and it is known that
resistance training in different ROM configuration may induce non-homogeneous
hypertrophic adaptations across the length of the muscle [14,18]. Furthermore, the change
in muscle volume analyzed via magnetic resonance imaging (MRI) is considered the gold
standard for estimating muscle hypertrophy [19]. However, this procedure is expensive
[19]. A more economical alternative to analyzing muscle volume by MRI is to assess
muscle CSA by B-mode ultrasound [19], with measurements taken at different sites along
the length of the muscle [14,20]. This approach provides a proxy for muscle volume,
imparting a better comprehension of the influence of ROM manipulation on muscle
hypertrophy.
In addition to its effects on muscle hypertrophy, RT also promotes increases in
maximal strength. Research generally shows that strength increases are specific to the
given ROM trained [21,22]. Accordingly, training in the INITIALROM and FINALROM could
lead to a greater strength increase in the specific angles trained [23]. Taking into account
that the sticking point is a primary determinant of performance in the 1RM test [24], it can
be expected that training in the INITIALROM, which promotes greater strength increases in
this region, would also cause greater increases in the 1RM test performed in full ROM in
comparison to training in the FINALROM. In line with this reasoning, Pedrosa et al. [14]
found that 12 weeks training in the INITIALROM promoted a greater 1RM increase at full
ROM than training in the FINALROM using the knee extension machine. Werkhausen et al.
[2] compared the isokinetic strength after training in the INITIALROM and the full ROM in
the leg press exercise. Results showed similar changes between training in the INITIALROM
and a full ROM, suggesting the strength adaptations across a full ROM are influenced by
the initial training angle. These findings further the rationale that training in the
INITIALROM could be superior to training in the FINALROM in a full ROM strength test.
However, this hypothesis has not yet been objectively tested in other muscles such as the
elbow flexors.
Therefore, this study aimed to compare dynamic strength and regional muscle
hypertrophy changes of the elbow flexors in young women after performing the arm curl
exercise for eight weeks while training in INITIALROM and FINALROM. We hypothesized
Sports 2023, 11, 39 3 of 12
that the INITIALROM protocol would elicit greater increases in dynamic strength and distal
muscle hypertrophy than FINALROM protocol.
2. Methods
We employed a within-participant experimental design whereby the right and left
arms of 21 untrained women trained in INITIALROM or FINALROM for eight weeks. We
chose the seated dumbbell preacher curl exercise to ensure that participants maintained
strict form throughout exercise performance. Pre- and post-study strength was assessed
by the 1RM test in the arm curl, and B-mode ultrasound was employed to assess CSA
changes in the mid- and distal regions of the biceps.
The sample size was estimated a priori following the recommendations of Beck [25]
using the software G*Power (version 3.1.9.2; Heinrich Heine Universität Düsseldorf, DE,
Germany). We used the t-statistic with an alpha of 0.05, power of 0.8, and a relatively
moderate Cohen’s d effect size (ES) of 0.7 and determined that 19 subjects were required
for adequate statistical power. We recruited two additional subjects to account for the
possibility of dropouts, expected to be ~10% of the sample.
Participants were untrained women who had not performed any physical activity for
at least six months prior to the onset of the study. Two participants withdrew for personal
reasons; therefore, 19 women completed the study (mean age = 22.8 ± 10.5 years; mean
body mass = 64.5 ± 8.05 kg; mean height = 164.1 ± 4.7 cm). Each participant’s upper limb
was allocated in a randomized fashion according to upper limb dominance. The order of
training was counterbalanced whereby half of the participants performed the INITIALROM
protocol with their preferred limb, while the other half performed the FINALROM protocol
with their preferred limb. Before participation, written consent was obtained from each
participant after being informed of the procedures, risks, and benefits of the investigation.
The study followed the standards established in the Declaration of Helsinki and was
approved by the ethics committee of the Federal University of Minas Gerais (approval
#CAAE 91438418.4.0000.5149).
In the first pre-training session, after the anthropometric data assessment, we
obtained measures of biceps brachii CSA at 50% and 70% of the distance from the
acromion to the lateral epicondyle of each humerus via B-mode ultrasound (MindRay®
DC-7, Shenzhen, China). It should be noted that muscle hypertrophy assessed by B-mode
ultrasound imaging is highly correlated with MRI, which is considered the gold standard
for measuring changes in muscle mass [26]. Images were acquired at a frequency of 21
frames/s, using a 4–10 MHz linear transducer with a depth ranging from 1 to 6 cm and
gain between 50 and 64 db. The settings were individually adjusted to produce a clear
image of the entire muscle for extended field-of-view, and replication at post-training. The
same trained technician performed all ultrasound scans, moving the transducer in a line
parallel to the humeral epicondyles at a relatively constant speed for approximately 7s at
each site. The images were saved to hard drive and coded for blinded CSA calculation
using the Horos® software. We averaged the two CSA measurements in each region to
obtain the final values used for analyses. Moreover, we summed the CSA at 50%, and 70%
of biceps length (CSAsummed) to produce an estimate of overall biceps hypertrophy.
Previous studies have employed similar formulas in an attempt to produce a hypertrophy
measure more representative of the whole muscle in comparison to a single muscle region
[1,20]. The intraclass correlation coefficients (ICC3,1) in our laboratory for CSA at 50% and
70% of biceps length were 0.94 and 0.92, respectively.
After ultrasound imaging, we assessed participants 1RM in the seated dumbbell
preacher curl exercise. The 1RM test was performed alternately on each arm throughout
a full ROM, with a 3-min recovery interval between the limbs and between attempts. A
final value was obtained within 5 attempts on each arm. Each attempt started with the
elbow fully extended (0°), and the shoulder angle (humerus and trunk) fixed at 45°. The
dumbbell was handed to the participant in this initial position, who then performed a
concentric muscle action until 135° of elbow flexion (forearm perpendicular to the
Sports 2023, 11, 39 4 of 12
ground). The attempt was considered successful if the participant was able to perform the
full range of elbow flexion (0° to 135°) without assistance from auxiliary movements. The
dumbbell load was progressively increased (minimum of 0.5 kg) until the participant was
unable to perform the concentric action with proper form. Hence, the 1RM value corre-
sponded to the weight lifted in the previous successful attempt. This initial test was con-
sidered a familiarization session to the 1RM assessment. The 1RM test was repeated 48h
later (pre-training session 2) and the value obtained in this session was used for statistical
analysis. Between 48 h and 72 h after the last training session, the ultrasound imaging and
the 1RM test in a full ROM were repeated using the procedures previously described.
Training sessions consisted of the seated dumbbell preacher curl performed in a spe-
cific ROM for each limb. The shoulder angle was fixed at 45° (as in the 1RM test). The
INITIALROM protocol was trained from 0° to 68° of elbow flexion, and the FINALROM pro-
tocol was trained from 68° to 135° of elbow flexion (Figure 1). The ROMs were individu-
ally checked by a manual goniometer (axis fixed in the elbow, and the rules fixed in the
arm and forearm) at the beginning of each training session. An elastic cord was placed in
front of the machine to serve as a mechanical stop ensuring training was limited to the
prescribed ROMs (Figure 1). In the INITIALROM, participants began the eccentric muscle
action when their forearm touched the string (68° of elbow flexion) and they continued
lowering the load until full extension. In the FINALROM protocol, the participants began
the concentric action when their forearm touched the string (68° of elbow flexion) and
they continued raising the load until their forearm was perpendicular to the ground (135°
of elbow flexion).
Figure 1. Training protocols range of motion. (A1,A2) = starting and finishing the concentric action
of INITIALROM protocol (0°–68° of elbow flexion), respectively. (B1,B2) = starting and finishing the
concentric action of FINALROM protocol (68°–135° of elbow flexion), respectively.
Each protocol was trained three times per week, in the same session, separated by
48–72 hours over the eight-week study period. We alternated the session-to-session order
in which the training protocols were performed: i.e., if the INITIALROM protocol was the
first to be performed in a given training session, the FINALROM protocol would be trained
first in the next session. If the participant was assigned to start with INITIALROM protocol,
after completing each set, 1 minute interval was allowed before initiating the FINALROM
Sports 2023, 11, 39 5 of 12
protocol with the contra lateral limb. The next set for the starting protocol was only initi-
ated after 3 minutes of the completion of the previous set of the INITIALROM; all recovery
periods were timed with a stopwatch to ensure accuracy.
Participants performed four sets per session in both the INITIALROM and the FI-
NALROM protocols. In an effort to standardize the training stimulus for the development
of hypertrophy and muscle strength, all sets were carried out until volitional failure
[27,28]. When the last set was performed with more than 10 or less than 8 repetitions, the
load was increased or reduced diminished in 1 kg at the next training session, respectively.
Each repetition was performed with a 2s concentric action and a 2s eccentric action (timed
by metronome). Five sets were performed from the fifth week on, following the same pre-
viously described procedures.
The Shapiro–Wilk test confirmed the normality of data distribution, and all variables
presented similar baseline values between training protocols. We analyzed the absolute
difference values (post–pre-values) between training protocols by paired t-test for all var-
iables of interest. We reported 95% confidence intervals (CI) around the point estimate.
Cohen’s d effect sizes (ES) were calculated (post-pre/pooled standard deviation) with the
following interpretation: trivial: <0.20; small: 0.20–0.60; moderate: 0.61–1.20; large: 1.21–
2.0; very large: >2.0) [29]. All statistical procedures were performed using JASP statistics
packages, version 0.14 (Wagenmakers, Amsterdam). We considered statistical signifi-
cance when α < 0.05.
3. Results
When comparing regional CSA between the training protocols, analysis showed the
INITIALROM protocol displayed a greater CSA increase than the FINALROM protocol at 70%
of biceps brachii length (p = 0.001; 95% CI = 0.18 to 0.59 cm2; ES = 0.89), and a relatively
similar CSA increase at 50% (p = 0.331; 95% CI = −0.10 to 0.34 cm2; ES = 0.23). Analysis
showed the CSAsummed increase was not statistically different between the training proto-
cols (p = 0.111; 95% CI = −0.08 to 0.67 cm2; ES = 0.39), as shown in Figure 2. Regarding the
1RM test, analysis showed the INITIALROM protocol presented a statistically greater in-
crease than the FINALROM protocol (p < 0.001; 95% CI = 0.39 to 1.06 kg; ES = 1.05), as shown
in Figure 3.
Sports 2023, 11, 39 6 of 12
Figure 2. The paired mean difference for cross-sectional area in INITIALROM and FINALROM at (a)
50% humeral length; (b) 70% humeral length; and (c) summed values of 50% and 70% humeral
length [30]. The raw data are plotted on the upper axes; each paired set of observations is connected
by a line. On the lower axes, each paired mean difference is plotted as a bootstrap sampling distri-
bution. Mean differences are depicted as dots; 95% confidence intervals are indicated by the ends of
the vertical error bars. ES = effect size. * Significant differences compared with FINALROM protocol.
Sports 2023, 11, 39 7 of 12
Figure 3. The paired mean difference for 1 repetition maximum in INITIALROM and FINALROM [30].
The raw data are plotted on the upper axes; each paired set of observations is connected by a line.
On the lower axes, each paired mean difference is plotted as a bootstrap sampling distribution.
Mean differences are depicted as dots; 95% confidence intervals are indicated by the ends of the
vertical error bars. ES = effect size. * Significant differences compared with FINALROM protocol.
4. Discussion
A primary finding of our study was that training in the INITIALROM elicited greater
increases in CSA at 70% of biceps brachii length and in the 1RM test than the FINALROM
protocol. These results are consistent with our initial hypothesis and provide further evi-
dence that ROM manipulation impacts regional muscular adaptations across a variety of
different muscles and exercises.
To our knowledge, only three previous studies compared regional hypertrophic
changes after training in INITIALROM and FINALROM. McMahon et al. [7] found that the
INITIALROM group achieved greater vastus lateralis hypertrophy than the FINALROM
group only at the distal region after 8 weeks of knee extension training. Similarly, Pedrosa
Sports 2023, 11, 39 8 of 12
et al. [14] showed the INITIALROM group presented greater distal muscle growth of the
rectus femoris and the vastus lateralis muscles than the FINALROM group after 12 weeks
of knee extension training. Moreover, Sato et al. [16] demonstrated the INITIALROM train-
ing elicited greater distal biceps brachii plus brachialis muscle hypertrophy after only five
weeks resistance training. These results corroborate our findings, which suggest that
training in INITIALROM promotes greater distal hypertrophy of the biceps than training in
FINALROM, and a similar hypertrophy response between conditions at the middle region
in young, untrained women. Moreover, our study expands on the findings of McMahon
et al. [7] and Pedrosa et al. [14] and supports those of Sato et al. [16] by providing evidence
that training a muscle at long muscle length has a beneficial effect on muscular adapta-
tions in the upper extremities.
Some other studies have investigated regional muscle hypertrophy between the FI-
NALROM and the FULLROM protocols [14,18,31]. Bloomquist et al. [18] reported greater hy-
pertrophy in the middle and distal regions of the anterior quadriceps femoris in a group
of young men performing the back squat for 12 weeks in a FULLROM group compared to
the FINALROM group. Similarly, McMahon et al. [31] reported greater distal vastus lateralis
hypertrophy in a group of young men and women performing a variety of lower limb
exercises in a FULLROM versus a FINALROM over an 8-week training period. Pedrosa et al.
[14] showed greater distal muscle hypertrophy of rectus femoris and vastus lateralis mus-
cles after training in FULLROM compared to FINALROM. Given that the main difference be-
tween training in FINALROM and FULLROM is that the FULLROM excurses the INITIALROM,
it can be speculated that the greater muscle hypertrophy after training in a FULLROM re-
sults from training at longer muscle lengths.
Although speculative, a possible mechanistic explanation for the heightened regional
hypertrophic response is related to the production of higher amounts of metabolic stress
[10], and insulin-like growth factor (IGF)-1 release [7] when training at longer muscle
lengths in comparison to training at shorter muscle lengths, which in turn may confer
anabolic effects [32]. Additionally, there is evidence suggesting that both metabolic stress
[33] and IGF-1 [34] concentrations may vary between muscle regions after mechanical
overload, and that greater regional muscle hypertrophy occurs in regions demonstrating
greater metabolic stress [35] and IGF-1 concentrations [34]. Thus, we hypothesize that
training in the INITIALROM promotes a heightened physiological response at the distal
portion of the muscle, thereby leading to greater muscle protein increase in this region.
Previous research supports our findings [7,14,18,31]; however, no attempts were made to
explore mechanisms involved, which requires further investigation.
When summing the CSA results of the two regional sites (CSAsummed), hypertrophic
increases were statistically similar between training protocols. This value provides a gen-
eral proxy for hypertrophy of the muscle as a whole. Our findings in this regard are con-
sistent with previous studies on the topic [1,20]. However, although the study lasted eight
weeks and is in line with previous research that aimed to measure muscle hypertrophy
over this time period [7,31], we cannot necessarily infer that results would hold true over
longer-term interventions nor rule out the possibility that other factors may have influ-
enced changes [36]. Therefore, further investigation on topic using longer interventional
period is recommended to confirm or refute the present findings.
In regard to the 1RM results, our study shows that training in the INITIALROM elicits
greater dynamic strength improvements in a full ROM test compared to training in the
FINALROM; these results were observed despite the use of heavier absolute loads when
training in the FINALROM. To our knowledge, only one study to date has compared
changes in dynamic strength at a FULLROM after training in the INITIALROM versus FI-
NALROM. Pedrosa et al. [14] reported the INITIALROM group showed greater 1RM test in-
crease at a FULLROM compared to the FINALROM after 12 weeks of knee extension training,
lending support to our results.
Several studies indicate a ROM-specific strength increase after training in a FULLROM,
FINALROM [18,21,22], and INITIALROM [14]. Bloomquist et al. [18] found that the training
Sports 2023, 11, 39 9 of 12
groups (FULLROM and FINALROM) presented greater 1RM increases in the trained ROM.
Similarly, Martínez-Cava et al. [21] reported ROM-specific strength adaptations after 10
weeks of training in the bench press exercise at a full ROM, two-thirds ROM, and one-
third-ROM). In addition, Pedrosa et al. [14] showed the INITIALROM and FINALROM groups
presented greater 1RM increases in the ROM trained. Although the present study did not
compare the strength performance in different ROMs, previous findings [14,18,21–23]
support the rationale that a ROM-specific strength increase may also have occurred in the
present study, and therefore influenced the results of the 1RM test in a full ROM. Accord-
ingly, the INITIALROM training would allow a greater strength enhancement at the begin-
ning of the concentric action of a full ROM compared to training in the FINALROM [14]. We
speculate that this specific joint-angle strength adaptation (from the INITIALROM protocol)
was fundamental to overcoming the sticking point and thus resulted in a superior increase
in 1RM.
Changes in muscle morphology may help to provide a mechanistic explanation for
the observed angular specific differences in strength increase between conditions [37]. Ev-
idence indicates a positive association between greater increases in distal muscle CSA re-
gions and increases in torque angles where the muscle is elongated [37]. Thus, the greater
muscle hypertrophy response at 70% in the INITIALROM condition may have enhanced
strength performance in a full ROM 1RM test to a greater extent than training in FI-
NALROM. This hypothesis needs further investigation.
Additionally, it is known that the increase in maximum dynamic strength is related
to alterations in neural factors, such as an increase in the number of activated motor units,
improvement in inter and intra muscular synchronization, and a reduction in the activa-
tion of the antagonist muscles during exercise performance [38]. Thepaut-Mathieu et al.
[39] reported that resistance training performed exclusively at a short muscle length pro-
moted greater neural adaptations (as assessed by surface electromyography) near or at
the trained angles, and this adaptation coincided with the greater observed increases in
muscle strength near or at the trained angles; the response did not occur in the group that
trained in long muscle length. This finding is supported by Noorkoiv et al. [37], who
demonstrated a positive and significant correlation between the force increase at short
muscle length angles and the increase of the surface electromyographic signal only in the
group that trained at the short muscle length compared to the long length group. It there-
fore could be hypothesized that the contribution from the improvement of neural factors
to increase the performance of the 1RM test was smaller in the FINALROM group compared
to INITIALROM group. The present study did not attempt to assess neural factors; hence,
further investigations are needed to better elucidate the mechanisms of strength increases
associated with ROM manipulation.
This study has several limitations that should be taken into account when attempting
to draw practical conclusions. First, although performing sets to volitional fatigue helps
to ensure that all individuals receive a comparable hypertrophic stimulus [27], its imple-
mentation influences other variables, such as the number of repetitions performed. Future
studies should seek to study ROM-induced muscular adaptations with different configu-
rations of RT variables. Second, we only tested dynamic strength in a full ROM using the
knee extension machine and thus cannot extrapolate findings to specific partial ROMs,
isometric strength at different joint-angles or the transfer of these results to the activities
of everyday life. Third, the findings are specific to dynamic elbow flexion exercise and
thus cannot necessarily be generalized to other exercises or muscle groups. Fourth, we
measured hypertrophy at only two points along the length of the biceps brachii; it would
be interesting to analyze other regions or even the muscle volume to obtain a more robust
perspective of hypertrophic changes. Fifth, our findings are specific to young, healthy,
untrained women and thus cannot necessarily be generalized to other populations.
Finally, we chose to employ a within-participant design, which affords the benefit of
enhancing statistical power by reducing the amount of between-participant variability
[40]. While this experimental model can provide keen insights into skeletal muscle
Sports 2023, 11, 39 10 of 12
adaptations in longitudinal RT investigations [40], a potential limitation of this design is
the possibility of a cross-education effect. There is evidence indicating that the cross-edu-
cation effect, if it indeed occurs, would be restricted to neural parameters and muscle
strength gains; morphological changes (e.g., CSA) are not materially influenced by this
effect [41]. Hence, any muscle strength gains achieved in the contralateral limb should
conceivably evolve from an increase in motor neuron activation without contribution
from morphological adaptations. Moreover, previous studies investigating the cross-ed-
ucation effect for EMG amplitude have shown inconclusive results [42,43]. For example,
Hortobágyi, et al. [42] found that changes in the EMG amplitude of the untrained limb
depend on the training mode performed (e.g., type of muscle action). The neuromuscular
changes were similar to the changes in muscle strength. Moreover, other researchers
found that the cross-education effect contributes to approximately 7.8% of the muscle
strength gain of the contralateral limb [44]. In the present study, the mean relative increase
in the INITIALROM and FINALROM groups was 42.8 ± 14.8% and 19.0 ± 10.3%, respectively;
these differences would be outside of any potential confounding from cross-education.
Furthermore, it has been argued that, when both limbs of an individual are trained with
different protocols, the cross-education effect is minimal or non-existent [44,45]. Thus,
based on the magnitude of influence presented by Munn et al. [44], it seems likely that
any difference in the strength responses between limbs would be due to training protocols
with minimal confounding from cross-education.
5. Conclusions
In conclusion, the seated dumbbell preacher curl performed in the INITIALROM elic-
ited greater biceps brachii hypertrophy at 70% length, but not at 50% nor for the CSAsummed
in untrained women. Moreover, the INITIALROM protocol promoted a greater increase in
the 1RM test in full ROM compared with training in the FINALROM. These findings add to
the body of literature indicating that training at long muscle lengths promotes increases
in hypertrophy at the distal muscle region, and these findings occur in both the upper and
lower extremity musculature.
Author Contributions: Conceptualization, R.C.R.D., F.V.L. and M.H.C.; methodology, R.C.R.D.,
L.T.L. and M.G.S.; formal analysis, G.F.P., M.O.C.F., B.J.S. and M.G.S.; writing—original draft prep-
aration, G.F.P., M.G.S. and R.C.R.D.; writing—review and editing, G.F.P., B.J.S. and R.C.R.D. All
authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement: The study was conducted in accordance with the Declara-
tion of Helsinki, and approved by the Ethics Committee of Federal University of Minas Gerais (pro-
tocol code CAAE - 91438418.4.0000.5149 and august 09, 2018)
Informed Consent Statement: Informed consent was obtained from all subjects involved in the
study. Written informed consent has been obtained from the patient(s) to publish this paper.
Data Availability Statement: All data generated or analyzed during this study will are included in
the published article as Table(s) and Figure(s). Any other data requirement can be directed to the
corresponding author upon reasonable request
Acknowledgments: Supported by the FAPEMIG; CAPES (Brazil); and PRPq of Universidade Fed-
eral de Minas Gerais.
Conflicts of Interest: B.J.S. serves on the scientific advisory board for Tonal Corporation, a manu-
facturer of fitness equipment. The other authors declare no conflicts of interests, financial or other-
wise.
Sports 2023, 11, 39 11 of 12
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... The effects of manipulating range of motion (ROM) during RT have been extensively studied, with many investigations focusing on training at longer muscle lengths (Wolf et al., 2023). While generally lacking ecological validity, five studies have compared longer vs. shorter muscle length isometric contraction (Akagi, Hinks & Power, 2020;Alegre et al., 2014;Hinks et al., 2021;Kubo et al., 2006;Noorkõiv, Nosaka & Blazevich, 2014), and nine studies have compared partial ROM at longer muscle lengths (referred to as lengthened partials and abbreviated as LPs) vs. shorter muscle lengths (referred to as shortened partials and abbreviated as SPs) on muscle hypertrophy (Kassiano et al., 2022a;Larsen et al., 2024a;Maeo et al., 2020Maeo et al., , 2022Mcmahon et al., 2014b;Pedrosa et al., 2022Pedrosa et al., , 2023Sato et al., 2021;Stasinaki et al., 2018) 1 . Additionally, a recent study compared employing LPs following momentary failure using full ROM vs. full ROM alone and found that the former intervention resulted in greater muscle hypertrophy vs. full ROM (Larsen et al., 2024b) 1 . ...
... Research on LPs vs. full ROM RT has used single-exercise interventions, which are not representative of typical RT routines that involve multiple exercises, limiting the ecological validity of these findings (Kassiano et al., 2022b). Additionally, most studies have focused on lower-body muscles (quadriceps, plantar flexors, hip extensors), with fewer studies on upper-body muscles (e.g.: elbow flexors and extensors) (Pedrosa et al., 2023;Goto et al., 2019). Moreover, these studies typically train muscles through the central 75% of a joint's ROM, not at maximal muscle lengths, leaving it unclear if the benefits of longer muscle length training extend to the extremes of muscle length. ...
... Additionally, it appears that the inclusion of shorter-muscle length training by the full ROM condition did not enhance muscle hypertrophy, suggesting that the inclusion of the lengthened range of motion should be the primary consideration when it comes to range of motion during RT for muscle hypertrophy. This hypothesis is consistent with much of the previous research on the topic, showing a hypertrophic superiority of training at longer vs. shorter muscle lengths (Akagi, Hinks & Power, 2020;Alegre et al., 2014;Bloomquist et al., 2013;Burke et al., 2024;Goto et al., 2019;Hinks et al., 2021;Kassiano et al., 2022a;Kinoshita et al., 2023;Kubo et al., 2006;Kubo, Ikebukuro & Yata, 2019;Larsen et al., 2024aLarsen et al., , 2024bMaeo et al., 2020Maeo et al., , 2022McMahon et al., 2014aMcMahon et al., , 2014bNoorkõiv, Nosaka & Blazevich, 2014;Pedrosa et al., 2022Pedrosa et al., , 2023Sato et al., 2021;Valamatos et al., 2018). Importantly, the similar magnitude of muscle hypertrophy observed may be a result of the multi-exercise, multi-modality approach employed in the present study. ...
Article
Full-text available
Purpose Resistance training using different ranges of motion may produce varying effects on musclular adaptations. The purpose of this study was to compare the effects of lengthened partial repetitions (LPs) vs . full range of motion (ROM) resistance training (RT) on muscular adaptations. Methods In this within-participant study, thirty healthy, resistance-trained participants had their upper extremities randomly assigned to either a lengthened partial or full ROM condition; all other training variables were equivalent between limbs. The RT intervention was an 8-week program targeting upper-body musculature. Training consisted of two training sessions per week, with four exercises per session and four sets per exercise. Muscle hypertrophy of the elbow flexors and elbow extensors was evaluated using B-mode ultrasonography at 45% and 55% of humeral length. Muscle strength-endurance was assessed using a 10-repetition-maximum test on the lat pulldown exercise, both with a partial and full ROM. Data analysis employed a Bayesian framework with inferences made from posterior distributions and the strength of evidence for the existence of a difference through Bayes factors. Results Both muscle thickness and unilateral lat pulldown 10-repetition-maximum improvements were similar between the two conditions. Results were consistent across outcomes with point estimates close to zero, and Bayes factors (0.16 to 0.3) generally providing “moderate” support for the null hypothesis of equal improvement across interventions. Conclusions Trainees seeking to maximize muscle size should likely emphasize the stretched position, either by using a full ROM or LPs during upper-body resistance training. For muscle strength-endurance, our findings suggest that LPs and full ROM elicit similar adaptations.
... The findings for strength outcomes in ROM studies are not unexpected due to the principle of specificity; however, more nuance is needed regarding hypertrophy and resistance training ROM. Specifically, the muscle length (i.e., shortened or lengthened position) at which an exercise is performed (5,6,7,23,24) may affect muscle growth and temporal recovery (8,22). Additionally, the muscle length at which peak torque (i.e., the point in the ROM where force demand is highest due to the relationship between internal and external moments) is experienced in an exercise (25) may be crucial to consider. ...
... Indeed, various studies (5,6,7,23,24) have compared training at different muscle lengths and found that training at long muscle lengths may enhance hypertrophy, with fewer studies (35,39) reporting no substantial differences in hypertrophy when training through different muscle lengths. Maeo et al. (6,7) observed greater hypertrophy in biarticular muscles when training through a full ROM at a longer muscle length compared to a shorter muscle length. ...
... versus +13.9%, respectively, d = 0.54, p < 0.001). Importantly, regional hypertrophy within the same muscle (5,23) may also be affected by the length a muscle is trained. For example, Pedrosa et al. (5) found that performing partial ROM leg extensions for 12 weeks at a longer muscle length led to greater distal rectus femoris growth at 70% of femur length compared to training through only the final ROM or varied ROM (short and long) in untrained women. ...
... Likewise, a recent systematic review demonstrated that performing RT exercises in a longer muscle length leads to greater muscle hypertrophy when compared to shorter muscle lengths (Kassiano, Costa, Nunes, et al., 2023a). Such a finding is supported by several studies that compared initial pROM (that is, longer muscle length) to final pROM (shorter muscle length) and fROM and found superior results for initial pROM in muscle hypertrophy and strength of lower-limbs (Kassiano, Costa, Kunevaliki, et al., 2023a;Pedrosa et al., 2022) andupper-limbs (Goto et al., 2019;Pedrosa et al., 2023). ...
... The fROM was determined as a knee flexion of 90-0°, and final pROM as a flexion of 45-0° ( Figure 1b). To ensure that the ROM was respected during the scott bench curls and seated leg extension exercises, a resistance band and a metal structure were used to serve as references for the correct ROM, as previously standardized for the same exercises (Pedrosa et al., 2022;Pedrosa et al., 2023). A metal goniometer (Staline®, USA) was used to accurately define joint angles. ...
... Recently, Pedrosa et al. (2023) measured the muscle hypertrophy of the elbow flexors after eight weeks of RT using an initial ROM (0-68°) and a final ROM (68-135º) in scott bench curls on untrained women. As result, the arm that trained in the initial pROM condition significantly increased the distal muscle hypertrophy of the elbow flexors. ...
Article
Full-text available
Purpose: The present study aimed to compare final partial range of motion (final pROM) vs. full range of motion (fROM) in muscle hypertrophy and maximal strength development in physically active young men. Methods: Ten physically active young men (age=22.90±2.47 years; body mass=83.85±11.67 kg; height=176.30±6.22 cm) participated in a randomized, intra-subject experimental design in which RT was performed using the upper- and lower-limbs with final pROM or fROM three times per week for six weeks. For all subjects, an arm or thigh was randomly selected and assigned for the final pROM condition, and the contralateral limb for the fROM condition. The subjects performed three sets of 12 repetitions at 60% of one-repetition maximum (1-RM), with two-minute rest interval between the sets and between limbs. The muscle hypertrophy of the elbow flexors and the knee extensors and the 1-RM test in the specific ROM that has been trained was measured before and after the intervention. An analysis of covariance was used to compare the different conditions on muscle hypertrophy and the maximal strength development. Results: The results showed that there was no statistically significant difference between the conditions for elbow flexors muscle hypertrophy (p=0.920; Cohen’s d=0.046) and knee extensors muscle hypertrophy (p=0.291; Cohen’s d=0.152). Similarly, there was no statistically significant difference between the conditions for 1-RM of the arm (p=0.161; Cohen’s d=0.898) and 1-RM of the thigh (p=0.276; Cohen’s d=0.533). Conclusions: Therefore, these findings suggest that there was no statistically significant difference between the different ROM, however, the moderate-large effect size (leg=0.533 and arm=0.898) in favor of final pROM in the maximal strength development, may indicate a potential direction for future research in physically active young men.
... The relative difference in CSA between the preand post-training protocol measurements was indicative of muscle swelling and employed for groups comparison. For the reliability measurement of CSA, we computed the ICC 3,1 for the two CSA measurements taken during the third experimental session (n = 64 images with ICC 3,1 = 0.99), as previously conducted (19,21). In these sessions, another researcher assessed 35% of all the images, resulting in an also high measurement reliability (ICC 3,1 = 0.98) between them, procedure performed previously (22). ...
... The study's results indicated that muscle swelling was greater when the muscles were electro stimulated at the 100° angle. It is worth mentioning that previous studies have shown that training in the lengthened (dynamic (19) or isometric (27)) position was superior to training in the shortened position for promoting muscle hypertrophy. These collective results emphasize the importance of analyzing swelling from a predictive perspective regarding hypertrophic potential. ...
... The 1RM value represented the maximum weight lifted in the last successful attempt. Similar procedures for achieving 1RM have been previously documented for the preacher curl exercise(19,20). ...
Article
Full-text available
SUMMARY Background. It is still not clear what physiologically differentiates trained individu­als from untrained individuals regarding the ability to hypertrophy, with speculation that these individuals may present different swelling levels in response to the same training load. Objective. This study aimed to compare the response of muscular swelling between eight adults from the More Experienced Group (MEG) and eight participants from the Less Experienced Group (LEG). Methods. The swelling response in the biceps brachii muscle was assessed by measur­ing the variation in cross-sectional area at 50% of the arm length (pre vs post) using B-mode ultrasound through a paired t-test. This comparison was conducted after the completion of four sets to failure at 70% of the one maximum repetition test in the preacher barbell curl exercise. Additionally, the mean values for the maximum number of repetitions (MNR), time under tension (TUT), and the rate of perceived exertion (RPE) for the four sets were also compared using a paired t-test. Results. LEG exhibited greater muscle swelling compared to the MEG (22.59 ± 7.05%; 15.71 ± 5.40%, respectively: p < 0.001), although no significant differences were observed in MNR, TUT, and RPE. Conclusions. Experience level appears to influence the response of muscular swell­ing, indicating that individuals with less experience tend to have greater swelling than those with more experience in strength training. Thus, more trained individuals should seek to implement training strategies, such as an increase in training load, if maintain­ing muscular swelling is desired.
... The effects of manipulating range of motion (ROM) during resistance training (RT) has been extensively studied, with many investigations focusing on training at longer muscle lengths (Wolf et al., 2023). While generally lacking ecological validity, five studies have compared longer versus shorter muscle length isometric contraction (Akagi et al., 2020;Alegre et al., 2014;Hinks et al., 2021;Kubo et al., 2006;Noorkõiv et al., 2014), and nine studies have compared partial ROM at longer muscle lengths (referred to as lengthened partials and abbreviated as LPs) versus shorter muscle lengths (referred to as shortened partials and abbreviated as SPs) on muscle hypertrophy Maeo et al., 2020Maeo et al., , 2022Pedrosa et al., 2021Pedrosa et al., , 2023Sato et al., 2021;Stasinaki et al., 2018) 1 . Additionally, a recent study compared employing LPs following momentary failure using full ROM versus full ROM alone and found that the former intervention resulted in greater muscle hypertrophy versus full ROM 1 . ...
... This hypothesis is consistent with much of the previous research on the topic, showing a hypertrophic superiority of training at longer versus shorter muscle lengths (Akagi et al., 2020;Alegre et al., 2014;Bloomquist et al., 2013;Burke et al., 2024;Goto et al., 2019Goto et al., , 2019Hinks et al., 2021;Kinoshita et al., 2023;Kubo et al., 2006Kubo et al., , 2019Maeo et al., 2020Maeo et al., , 2022Noorkõiv et al., 2014;Pedrosa et al., 2021Pedrosa et al., , 2023Sato et al., 2021;Valamatos et al., 2018). ...
... Additionally, it has been shown by imaging techniques that muscle hypertrophy in response to resistance training may not be homogeneous along different muscle regions (15). This regional hypertrophy response, when a non-uniform increase in CSA along the muscle occurs, has been demonstrated for the triceps brachii (13,16) biceps brachii (17,18), and quadriceps femoris (19,20). Nonetheless, anthropometric-based equations proposed in the literature are not specific for different muscle regions and describe a limited number of muscles. ...
... The settings were adjusted for each volunteer to produce the clearest images of the analyzed muscles. In previous studies from our laboratories using the same ultrasound device and similar procedures, we have obtained good inter-evaluator reliability values (ICC 3.1 ≥ 0.92) (18,32,33). A procedure bed was installed at the side of the US device to accommodate the participant during the image acquisition procedure, which took approximately 45 minutes per individual. ...
... 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). ...
Article
Full-text available
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.
... Consult the following studies for the evidence. [15][16][17][18][19][20][21][22] From these studies we can infer that hypertrophy is either equal or greater when exercises are performed at lengthened partials instead of full ROM or shortened partials. This corresponds to the condition of peak stretch with mechanical tension. ...
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The aim of this systematic review and meta-analysis was to examine how mean muscle length during resistance training (RT) influences regional muscle hypertrophy. We included studies that manipulated muscle length through range of motion (ROM) or exercise selection and evaluated regional muscle hypertrophy (i.e., changes at proximal, mid-belly, and/or distal sites). After systematically searching through three databases with additional secondary searches 12 studies were included in a meta-analysis. The meta-analysis was performed within the Bayesian meta-analytic framework. Standardized mean changes indicated trivial hypertrophic effects estimated with relatively high precision between proximal (25% muscle length; SMD: 0.04 [95%QI: -0.07, 0.15]; Exponentiated lnRR: 0.48% [95%QI: -1.99%, 3.13%]), mid-belly (50% muscle length; SMD: 0.07 [95%QI: -0.02, 0.15]; Exponentiated lnRR: 1.14% [95%QI: -0.84%, 3.13%]), and distal (75% muscle length; SMD: 0.09 [95%QI: -0.01, 0.19]; Exponentiated lnRR: 1.8% [95%QI: -0.52%, 4.26%]) sites. While the effects of training at longer muscle lengths showed an increasing trend from proximal to distal sites, the percentage of posterior distributions falling within ROPE was high from proximal to distal sites suggesting that effects are practically equivalent when contrasting “shorter” and “longer” mean muscle lengths at the typical differences employed in the current body of literature (i.e., an average difference of 21.8% mean muscle length). In summary, our results indicate that training at longer mean muscle length does not seem to produce greater regional muscle hypertrophy compared to shorter mean muscle lengths. However, due to small contrast in muscle lengths employed between conditions/groups, our findings should be considered limited to the contrasts typically employed in the literature.
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Resistance exercise range of motion (ROM) influences muscular adaptations. However, there are no consistent practical guidelines about the optimal ROM for maximizing muscle hypertrophy. The objective of the present paper was to systematically review the literature for studies that compared the effects of full ROM (fROM) and partial ROM (pROM) on muscle hypertrophy. PubMed/MEDLINE, Scopus, and Web of Science databases were searched to identify articles from the earliest record up to and including April 2022. We calculated the effect size (ES) scores of the variables of interest. Eleven studies were included in the review. fROM and pROM performed in the initial part of the ROM elicited greater muscle hypertrophy of the rectus femoris, vastus lateralis, biceps brachii and brachialis distal sites (between-groups ES: 0.20–0.90) than pROM performed in the final part of the ROM. fROM elicited greater muscle growth on the gluteus maximus and adductors than pROM in the final part of the ROM (between-groups ES: 0.24–0.25). Initial pROM produced more favorable proximal rectus femoris hypertrophy than fROM (between-group ES: 0.35–0.38). pROM in the middle part of the ROM elicited greater triceps brachii hypertrophy than fROM (between-groups ES: 1.21). In conclusion, evidence suggests that when training at a longer muscle length—through either a pROM or fROM—some muscles, such as the quadriceps femoris, biceps brachii and triceps brachii tend to experience optimal growth. Thus, the use pROM in the initial part of the excursion in combination with fROM training should be considered when prescribing hypertrophy-oriented resistance training programs.
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The present study compared two unilateral arm curl resistance exercise protocols with a different starting and finishing elbow joint angle in the same ROM for changes in elbow flexors strength and muscle thickness of the trained and non-trained arms. Thirty-two non-resistance trained young adults were randomly assigned to one of the three groups: extended joint training (0°–50°; EXT, n = 12); flexed joint training (80°–130°; FLE, n = 12); and non-training control (n = 8). The exercise training was performed by the dominant arms twice a week for 5 weeks with gradual increases in the training volume over 10 training sessions, and the non-dominant (non-trained) arms were investigated for the cross-education effect. Maximal voluntary contraction torque of isometric (MVC-ISO), concentric (MVC-CON), and eccentric contractions (MVC-ECC), and thickness (MT) of biceps brachii and brachialis of the trained and non-trained arms were assessed at baseline and 4–8 days after the last training session. The control group did not show significant changes in any variables. Significant (P < 0.05) increases in MVC-ISO torque (16.2 ± 12.6%), MVC-CON torque (21.1 ± 24.4%), and MVC-ECC torque (19.6 ± 17.5%) of the trained arm were observed for the EXT group only. The magnitude of the increase in MT of the trained arm was greater (P < 0.05) for EXT (8.9 ± 3.9%) than FLE (3.4 ± 2.7%). The cross-education effect was evident for MVC-ISO (15.9 ± 14.8%) and MVC-CON (16.7 ± 20.0%) torque of the EXT group only. These results suggest that resistance training at the extended elbow joint induces greater muscle adaptations and cross-education effects than that at flexed elbow joint.
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Background Nowadays, there is a lack of consensus and high controversy about the most effective range of motion (ROM) to minimize the risk of injury and maximize the resistance training adaptations. Objective To conduct a systematic review and meta-analysis of the scientific evidence examining the effects of full and partial ROM resistance training interventions on neuromuscular, functional, and structural adaptations. Methods The original protocol (CRD42020160976) was prospectively registered in the PROSPERO database. Medline, Scopus, and Web of Science databases were searched to identify relevant articles from the earliest record up to and including August 2020. The RoB 2 and GRADE tools were used to judge the level of bias and quality of evidence. Meta-analyses were performed using robust variance estimation with small-sample corrections. Results Sixteen studies were finally included in the systematic review and meta-analyses. Full ROM training produced significantly greater adaptations than partial ROM on muscle strength (ES=0.56, P=0.004) and lower-limb hypertrophy (ES=0.88, P=0.027). Furthermore, although not statistically significant, changes in functional performance were maximized by the full ROM training (ES=0.44, P=0.186). Finally, no significant superiority of either ROM was found to produce changes in muscle thickness, pennation angle, and fascicle length (ES=0.28, P=0.226). Conclusion Full ROM resistance training is more effective than partial ROM to maximize muscle strength and lower-limb muscle hypertrophy. Likewise, functional performance appears to be favored by the use of full ROM exercises. On the other hand, there are no large differences between the full and partial ROM interventions to generate changes in muscle architecture.
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The study compared changes in strength and regional muscle hypertrophy between different ranges of motion (ROM) in the knee extension exercise. Forty-five untrained women were randomized to either a control group or to perform the exercise in one of the following 4 groups (0°=extended knee): Full ROM (FULLROM: 100°-30° of knee flexion); Initial Partial ROM (INITIALROM: 100°-65°); Final Partial ROM (FINALROM: 65°-30°); Varied ROM (VARROM: daily alternation between the ROM of INITIALROM and FINALROM). Pre- and post-training assessments included one repetition maximum (1RM) testing in the ROM corresponding to the initial, final and full ROM, and measurement of cross-sectional areas of the rectus femoris and vastus lateralis muscles at 40%, 50%, 60% and 70% of femur length in regard to regional muscle hypertrophy. Results showed that the INITIALROM group presented a greater relative increase than all groups at 70%, and at 50% and 60% the increases were greater than FINALROM, FULLROM, and non-training control (CON) groups. Moreover, FINALROM group presented similar changes compared to the CON group at 60% and 70%. In regard to 1RM, FINALROM and INITIALROM groups presented greater relative increases at the ROM trained, and no group showed greater increases than VARROM or INITIALROM, regardless the ROM tested. In conclusion, partial ROM training in the initial phase of the knee extension exercise promoted greater relative hypertrophy in certain muscle regions than training in other ROM configurations, and no group promoted a greater 1RM increase than VARROM group, which showed similar 1RM increases in the different ROMs tested.
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We tested whether explosive resistance training with partial range of motion (ROM) would be as effective as full ROM training using a noninferiority trial design. Fifteen subjects with strength training experience took part in an explosive –concentric only– leg press training program, three times per week for 10 weeks. One leg was randomly assigned to exercise with partial ROM (i.e. 9º) and the other leg to full ROM. Before and after training, we assessed leg press performance, isokinetic concentric and isometric knee extension torque, and vastus lateralis muscle architecture. Overall, both training modalities increased maximal strength and rate of force development. Training with partial ROM yielded noninferior results compared to full ROM for leg press peak power (+69 ±47% vs. +61±64%), isokinetic strength (4‐6±6‐12% vs. 1‐6±6‐10% at 30, 60, and 180˚s‐1), and explosive torque after 100 (47±24 vs. 35±22) and 150 ms (57±22% vs. 42±25%). The comparison was inconclusive for other functional parameters (i.e. isokinetic peak torque (300˚s‐1), joint angle at isokinetic peak torque, explosive torque after 50ms, and electrically evoked torque) and for muscle fascicle length and thickness, although noninferiority was established for pennation angle. However, partial ROM was not found statistically inferior to full ROM for any measured variable. Under the present conditions, the effects of explosive heavy resistance training were independent of joint ROM. Instead, these data suggest that the distinct timing of muscle work in explosive contractions confers more influence to the starting joint angle than ROM on adaptations to this type of training.
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Magnetic resonance imaging (MRI) is the current gold standard for measuring changes in muscle size (cross-sectional area [CSA] and volume) but can be cost-prohibitive and resource-intensive. We evaluated the validity of B-mode ultrasonography (US) as a low-cost alternative to MRI for measuring muscle hypertrophy and atrophy in response to resistance training and immobilization, respectively. Fourteen young men performed 10wk of unilateral resistance training (RT) to induce muscle hypertrophy. In the final two weeks of the 10wk, the subjects' contralateral leg was immobilized (IMB). The cross-sectional area of the vastus lateralis (VLCSA) was measured at the mid-thigh before and after each intervention using MRI (VLCSAMRI ) and US (VLCSAUS ). The relationship and agreement between methods were assessed. Reliability of US measurements ranged from good to excellent in all comparisons (ICC >0.67). VLCSA significantly increased after 10 weeks of RT (VLCSAUS : 7.9 ± 3.8%; VLCSAMRI : 7.8 ± 4.5%) and decreased after 2 weeks of IMB (VLCSAUS : -8.2%±5.8%; VLCSAMRI : -8.7 ± 6.1%). Significant correlations were identified between MRI and US at each time point measured (all r > 0.85) and, importantly, between MRI- and US-derived changes in VLCSA. Bland-Altman analysis revealed minimal bias in US measurements relative to the MRI (-0.5 ± 3.0%) and all measurements were within the upper and lower limits of agreement. Our data suggest that B-mode ultrasonography can be a suitable alternative to MRI for measuring changes in muscle size in response to increased and decreased muscle loading in young men.
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Objective We aimed to perform a systematic review and meta-analysis of the effects of training to muscle failure or non-failure on muscular strength and hypertrophy. Methods Meta-analyses of effect sizes (ESs) explored the effects of training to failure vs. non-failure on strength and hypertrophy. Subgroup meta-analyses explored potential moderating effects of variables such as training status (trained vs. untrained), training volume (volume equated vs. non-equated), body region (upper vs. lower), exercise selection (multi- vs. single-joint exercises (only for strength)), and study design (independent vs. dependent groups). Results Fifteen studies were included in the review. All studies included young adults as participants. Meta-analysis indicated no significant difference between the training conditions for muscular strength (ES = –0.09; 95% confidence interval (CI): –0.22 to 0.05) and for hypertrophy (ES = 0.22; 95%CI: –0.11 to 0.55). Subgroup analyses that stratified the studies according to body region, exercise selection, or study design showed no significant differences between training conditions. In studies that did not equate training volume between the groups, the analysis showed significant favouring of non-failure training on strength gains (ES = –0.32; 95%CI: –0.57 to –0.07). In the subgroup analysis for resistance-trained individuals, the analysis showed a significant effect of training to failure for muscle hypertrophy (ES = 0.15; 95%CI: 0.03 to 0.26). Conclusion Training to muscle failure does not seem to be required for gains in strength and muscle size. However, training in this manner does not seem to have detrimental effects on these adaptations, either. More studies should be conducted among older adults and highly trained individuals to improve the generalizability of these findings.
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Purpose This study aimed at determining through MRI investigations, force and soreness assessments whether the modulation of muscle length is a relevant strategy for minimising neuromuscular electrical stimulation (NMES)-induced muscle damage in young healthy participants. Methods Comparison of 2 NMES sessions (40 isometric electrically-evoked contractions of the knee extensors) was randomly performed on 1 knee flexed at 50° (short muscle length) and the contralateral at 100° (long muscle length) in a single group of healthy participants. Indirect markers of muscle damage including changes in maximal voluntary isometric contraction (MVC) force, muscle volume and transverse relaxation time (T2) were measured before, 2 days (D2), 4 days (D4) and 7 days (D7) after the NMES sessions in each limb of the ten participants. Results Although stimulation intensity was similar during the NMES session on both limbs, significantly lower force production was recorded at long muscle length (peak at 30 ± 5% MVC force) as compared to short muscle length (peak at 61 ± 12% MVC force). In the following days, MVC force at long muscle length was decreased from D2 to D7, whereas no significant change occurred at short muscle length. Increases in muscle volume and T2 were found at each time point in stimulated muscles at long muscle length, whereas no change was found at short muscle length. Conclusion For the same stimulation intensity, NMES-induced isometric contractions generate higher knee extension force output and result in lower muscle tissues alterations that could be related to a lower intramuscular shear strain when exercise is performed at short muscle length.
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The manipulation of the muscle action duration (MAD) can influence the instantaneous torque along the range of motion, which can lead to adaptations of regional muscle hypertrophy. The aim of this study was to compare the effects of matched resistance training (RT) on the knee extension machine with different MAD in the cross-sectional area (CSA) responses within the quadriceps femoris (QF) and its muscles. Forty-four subjects were allocated into a control and 3 experimental groups. For a period of 10 weeks, subjects in the experimental groups performed the training protocols that were different only by the MAD: group 5c1e (5s concentric action [CON] and 1s eccentric action [ECC]; group 3c3e (3s CON and 3s ECC) and group 1c5e (1s CON and 5s ECC). Magnetic resonance imaging was performed (before and after the intervention) to determine the relative change (%) in CSA of the QF muscles along proximal (30%), middle (50%), and distal regions (70% distal of the femur). The change in CSA of the rectus femoris at the middle region are greater in 5c1e (6.8 ± 6.5%) and 1c5e (7.4 ± 6.0%) groups than 3c3e (3.4 ± 6.6%) and control groups (0.2 ± 1.8%). In addition, vastus lateralis at the distal region (5c1e = 15.9 ± 11.8%; 1c5e = 14.4 ± 10.0%) presenting greater increases in change of CSA than the others vastus only 5c1e (vastus lateralis [VI] = 5.0 ± 4.7%; vastus medialis [VM] = 4.2 ± 3.2%) and 1c5e groups (VI = 4.7 ± 3.6%; VM = 3.4 ± 3.1%). In conclusion, this study showed that matched RT protocols with different MAD resulted in different region-specific muscle hypertrophic across the individual muscles of QF.
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Participation in resistance exercise is encouraged throughout the lifetime, offering such benefits as improved strength and muscle mass accretion. Considerable research has been completed on this topic within the past several decades, with the current narrative dictating that increased muscle size yields further increases in muscle strength. However, there remain unanswered questions relating to the observation that certain training interventions yield only one specific adaptation (strength or size). Studies investigating resistance training often include either bilateral or unilateral exercise programs. Unilateral exercise programs are often used as they allow for comparison between two separate training interventions within the same individual. This is viewed as an advantage, relating to statistical power, but a limitation insofar as one intervention could be confounded by the intervention within the opposing limb. For example, when only one limb is trained both limbs often get stronger (albeit to differing magnitudes), termed the cross-education effect. However, we propose that when both limbs are trained that the cross-education effect may not occur and that the adaptations produced are reflective of the contraction history of the muscle. Herein, we discuss ways to test the idea that strength change may be dictated by the contraction history of the muscle. If each limb responds only to the contraction history within each limb (as opposed to the opposite limb), then this would have immediate ramifications for research design. Furthermore, this would certainly be of importance among injured populations undergoing rehabilitation, seeking to find the most efficacious exercise regimens.