Greater Gastrocnemius Muscle Hypertrophy After Partial Range of Motion Training Performed at Long Muscle Lengths

Abstract

Whether there is an optimal range of motion (ROM) to induce muscle hypertrophy remains elusive, especially for gastrocnemius. This study aimed to compare the changes in gastrocnemius muscle thickness between calf raise exercise performed with full ROM (FULLROM), partial ROM performed in the initial (INITIALROM), and final (FINALROM) portions of the ROM. Forty-two young women performed a calf training program for 8 weeks, 3 d·wk–1, with differences in the calf raise ROM configuration. The calf raise exercise was performed in a pin-loaded horizontal leg-press machine, in 3 sets of 15–20 repetitions maximum. The subjects were randomly assigned to 1 of the 3 groups: FULLROM (ankle: -25º to +25º), INITIALROM (ankle: -25º to 0º), and FINALROM (ankle: 0º to +25º), where 0º was defined as an angle of 90º of the foot with the tibia. The muscle thickness measurements of medial and lateral gastrocnemius were taken via B-mode ultrasound. INITIALROM elicited greater medial gastrocnemius increases than FULLROM and FINALROM (INITIALROM = +15.2% vs. FULLROM = +6.7% and FINALROM = +3.4%; P ≤ 0.009). Furthermore, INITIALROM elicited greater lateral gastrocnemius increases than FINALROM (INITIALROM = +14.9% vs. FINALROM = +6.2%; P < 0.024) but did not significantly differ from FULLROM (FULLROM = +7.3%; P = 0.060). The current results suggest that calf training performed at longer muscle lengths may optimize gastrocnemius muscle hypertrophy in young women. Therefore, when prescribing hypertrophy-oriented training, the inclusion of the calf raise exercise performed with partial ROM in the initial portion of the excursion should be considered.

Full text

Original Research
Greater Gastrocnemius Muscle Hypertrophy After
Partial Range of Motion Training Performed at Long
Muscle Lengths
Witalo Kassiano, Bruna Costa, Gabriel Kunevaliki, Danrlei Soares, Gabriel Zacarias, Ingrid Manske,
Yudi Takaki, Maria Fernanda Ruggiero, Nata
˜Stavinski, Jarlisson Francsuel, Ian Tricoli,
Marcelo A. S. Carneiro, and Edilson S. Cyrino
Metabolism, Nutrition and Exercise Laboratory, Physical Education and Sport Center, State University of Londrina, Londrina, Brazil
Abstract
Kassiano, W, Costa, B, Kunevaliki, G, Soares, D, Zacarias, G, Manske, I, Takaki, Y, Ruggiero, MF, Stavinski, N, Francsuel, J, Tricoli,
I, Carneiro, MAS, and Cyrino, ES. Greater gastrocnemius muscle hypertrophy after partial range of motion training performed at
long muscle lengths. J Strength Cond Res 37(9): 1746–1753, 2023—Whether there is an optimal range of motion (ROM) to induce
muscle hypertrophy remains elusive, especially for gastrocnemius. This study aimed to compare the changes in gastrocnemius
muscle thickness between calf raise exercise performed with full ROM (FULL
ROM
), partial ROM performed in the initial (INITIAL
ROM
),
and final (FINAL
ROM
) portions of the ROM. Forty-two young women performed a calf training program for 8 weeks, 3 days·week
21
,
with differences in the calf raise ROM configuration. The calf raise exercise was performed in a pin-loaded, horizontal, leg-press
machine, in 3 sets of 15–20 repetition maximum. The subjects were randomly assigned to 1 of the 3 groups: FULL
ROM
(ankle: 225˚
to +25˚), INITIAL
ROM
(ankle: 225˚ to 0˚), and FINAL
ROM
(ankle: 0˚ to +25˚), where 0˚ was defined as an angle of 90˚ ofthe foot with the
tibia. The muscle thickness measurements of medial and lateral gastrocnemius were taken by means of B-mode ultrasound.
INITIAL
ROM
elicited greater medial gastrocnemius increases than FULL
ROM
and FINAL
ROM
(INITIAL
ROM
5+15.2% vs. FULL
ROM
5
+6.7% and FINAL
ROM
5+3.4%; p#0.009). Furthermore, INITIAL
ROM
elicited greater lateral gastrocnemius increases than
FINAL
ROM
(INITIAL
ROM
5+14.9% vs. FINAL
ROM
5+6.2%; p,0.024) but did not significantly differ from FULL
ROM
(FULL
ROM
5
+7.3%; p50.060). The current results suggest that calf training performed at longer muscle lengths may optimize gastrocnemius
muscle hypertrophy in young women. Therefore, when prescribing hypertrophy-oriented training, the inclusion of the calf raise
exercise performed with partial ROM in the initial portion of the excursion should be considered.
Key Words: resistance training, muscle mass, joint excursion, triceps surae, length-tension relationship
Introduction
Range of motion (ROM) can be operationally defined as the de-
gree of movement at a specific joint during the execution of an
exercise (11). Resistance exercise ROM has the potential to
modulate muscular adaptations because depending on the spe-
cific ROM used in each repetition, factors such as internal mo-
ment arm length, the portion of the force-length relationship to
which the stimulus is applied, and muscle activation will be dif-
ferentially affected (6,18). ROM has been classified as full
(FULL
ROM
) when a given movement is performed without re-
striction in the degrees of excursion (13). Notably, ROM may be
intentionally limited in the initial (INITIAL
ROM
) or final
(FINAL
ROM
) portions of a full ROM, taking the concentric action
as reference (13). Despite the widely held belief that FULL
ROM
is
superior to partial ROM to induce muscle hypertrophy;
currently, there is not a definitive consensus on this statement
(12), with findings suggesting the superiority of full ROM over
partial ROM (2), others suggesting similarity (30), and some
others suggesting superiority of partial over full ROM (7,29).
When trying to reconcile the findings, it is possible to notice that
training at longer muscle lengths, through FULL
ROM
or INI-
TIAL
ROM
, frequently elicits greater muscle hypertrophy (13). For
instance, knee extension exercise performed with FULL
ROM
and
INITIAL
ROM
, taking the concentric muscle action as reference
(i.e., at longer muscle length), elicited more favorable muscle hy-
pertrophy in rectus femoris and vastus lateralis than FINAL
ROM
(i.e., at shorter muscle length) (29). Although not unanimous (7), the
superiority of training at longer muscle lengths has been observed in
different studies (20,23,24). Among the mechanisms proposed to
explain these results is the mechanical muscle characteristics, espe-
cially the length-tension relationship (9). Thus, if the fibers of given
muscle work, for example, on the descending limb of the length-
tension relationship, it may experience additional mechanical ten-
sion from passive elements (9). Indeed, this may be the case for the
rectus femoris and vastus lateralis,whichworkontheplateauand
descending limb of the length-tension curve (5,35). If accepted, this
hypothesis implies that optimal ROM is muscle dependent. Con-
sidering that most research has focused on hypertrophy of the
quadriceps (17,23,24,29), findings for other muscles are limited or
nonexistent, as is the case for the gastrocnemius (13).
Submitted for publication August 24, 2022; accepted November 2, 2022.
Affiliation where the research was conducted: Physical Education and Sport Center.
State University of Londrina, Brazil.
Address correspondence to Witalo Kassiano, acc.witalo@gmail.com
Supplemental digital content is available for this article. Direct URL citations appear
in the printed text and are provided in the HTML and PDF versions of this article on
the journal’s Web site (http://journals.lww.com/nsca-jscr).
Journal of Strength and Conditioning Research 37(9)/1746–1753
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The gastrocnemius muscles are biarticular superficial calf
muscles crossing the knee and ankle joints (15). With knees fully
extended and ankle dorsiflexed, the medial and lateral gastroc-
nemius reach longer fascicle lengths than the plantar flexed po-
sition (38–46 mm vs. 26–30 mm) (15). Notably, gastrocnemius
seems to work on the ascending and plateau portions of the
length-tension curve (10,21,39), suggesting that it may produce
reduced active force at shorter muscle lengths (33). Also, it implies
that the gastrocnemius probably needs to reach longer muscle
lengths to produce and experience maximum active force levels
(9,16). Theoretically, gastrocnemius would hypertrophy in a
greater magnitude when trained in INITIAL
ROM
than in
FINAL
ROM
. As a counterargument, the internal moment arm
reduces at longer muscle lengths (21), decreasing the contribution
of these muscles to plantar flexor torque. Thus, it remains elusive
whether there would be superiority of INITIAL
ROM
over
FINAL
ROM
. Therefore, this study compared the effects of calf
training with FULL
ROM
, INITIAL
ROM
, and FINAL
ROM
on me-
dial and lateral gastrocnemius muscle size changes. We hypoth-
esized that INITIAL
ROM
could be superior to FINAL
ROM
, but
similar to FULL
ROM
.
Methods
Experimental Approach to the Problem
This was a between-group repeated-measures design in which
subjects were randomly allocated to 1 of 3 possible ROM con-
figurations in the calf training: FULL
ROM
(ankle joint: 225° to
125°), INITIAL
ROM
taking the concentric muscle action as ref-
erence (ankle joint: 225° to 0°), or FINAL
ROM
taking the con-
centric muscle action as reference (ankle joint: 0° to 125°)
training groups, where 0° was defined as an angle of 90° of the
foot with the tibia. The current investigation was executed over
12 weeks. Weeks 1, 2, 11, and 12 were used for muscle thickness
measurements, whereas the calf training program was performed
for 8 weeks (weeks 3–10). All experimental groups trained 3 times
a week, totaling 24 training sessions. Each training session was
composed of 3 sets of 15–20 repetition maximum in the bilateral
calf raise exercise. Subjects were assessed at pretraining and
posttraining for medial and lateral gastrocnemius muscle thick-
ness measured with ultrasound imaging.
Subjects
This study sample consisted of apparently healthy adult women
aged between 18 and 35 years. Volunteers were recruited through
dissemination on social media and folders distributed in points of
greater circulation within the campus of the local university. All
volunteers underwent a clinical anamnesis and answered the
physical activity readiness questionnaire (PAR-Q). The inclusion
criteria were not responding "yes”to 1 or more PAR-Q questions;
not having osteomyoarticular problems that could compromise
the performance of the calf training program; not being a user of
dietary supplements or anabolic steroids (self-reported in-
formation); and not being engaged in resistance training for at
least 6 months before participation in this study. Subjects who did
not attend at least 85% of training sessions or missed 2 consec-
utive training sessions were excluded from the analyses. All sub-
jects were instructed to maintain their routines and eating habits
during the intervention. After being informed about the study
proposal and procedures, the subjects signed a written informed
consent form. Written informed consent was obtained from all
subjects after a detailed description of study procedures was
provided. This investigation was conducted according to the
Declaration of Helsinki, and the project was submitted and ap-
proved by the State University of Londrina Research Ethics
Committee (3.930.966). Figure 1 illustrates the sampling process,
with information on the number of subjects recruited and inter-
viewed, allocation to experimental groups, dropouts throughout
the training process, and the final number of subjects who com-
pleted the study and were included in the analyses. Forty-two
young women [FULL
ROM
,n514 (22.0 64.0 years, 69.0 617.6
kg, 165.1 67.7 cm); INITIAL
ROM
,n512 (22.5 62.3 years,
61.3 69.2 kg, 162.2 64.5 cm); and FINAL
ROM
,n516 (22.3 6
3.4 years, 64.8 615.0 kg, 161.7 64.8 cm)] ultimately completed
the study and were included for final analyses.
Procedures
Gastrocnemius Muscle Thickness Measurement. Medial and
lateral gastrocnemius muscle thickness were taken by means of B-
mode ultrasound (FIGLABS, FP - 102, SAEVO, SP, Brazil) with
a 53-mm, 7.5-MHz linear probe model L741. On arrival at the
laboratory, the subject was placed in a prone position on a
stretcher and rested for 10 minutes before the beginning of the
assessment. A generous quantity of water-soluble transmission
gel was applied over the assessed muscle without compressing the
skin. Images were obtained on the right leg with the probe per-
pendicular to the tissue. Image acquisitions of the medial gas-
trocnemius were taken with the probe positioned in the thickest
and more prominent site of the leg from a posteroanterior view
(27). Measurements of the lateral gastrocnemius were taken at the
proximal third between the lateral epicondyle of the femur and
the lateral malleolus of the fibula (27). Two assessors participated
in measurement procedures, with the first handled the probe and
the second responsible for freezing the images. When the quality
of the image was deemed to be satisfactory, the second assessor
obtained muscle thickness dimensions using the machine’s cal-
culation package. The second assessor was blinded to group al-
location. Muscle thickness of medial and lateral gastrocnemius
was defined as the distance from the superficial to deep aponeu-
roses that borders the soleus. Reference lines were drawn on the
subject’s skin with a dermatographic pen on the sites at which
images were obtained and were reinforced and maintained
throughout the study to ensure that the measurement was taken at
the same place at baseline and posttraining. The muscle thickness
assessments were performed in the morning hours (7–11 AM)
before and after training. During baseline assessments, 17 sub-
jects were randomly chosen to be evaluated on 2 days separated
by 72 hours to determine the reliability of the muscle thickness
measurements. The intraclass correlation coefficients for the
medial and lateral gastrocnemius were 0.993 and 0.990; the co-
efficients of variation were 1.4 and 1.6%; the standard errors of
measurement were 0.028 and 0.029 cm, respectively. Posttrain-
ing measurements were performed at an interval of 72–96 hours
after the last training session.
Calf Training Program. The resistance training program was
performed 3 times per week (Mondays, Wednesdays, and Fri-
days) in the afternoon for 8 weeks. The calf raise exercise was
performed bilaterally, in a pin-loaded horizontal leg-press ma-
chine (Ipiranga, Presidente Prudente, SP, Brazil) in 3 sets of 15–20
repetitions, executed until momentary concentric failure
(i.e., when the subject has reached the point where, despite trying
to do so, they cannot complete the concentric muscle action of
their current repetition). This repetition range was chosen based
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on their common inclusion in calf hypertrophy–oriented training
programs (27,31). Whenever the subject reached 20 repetitions in
a given set and reported that they could perform $1 repetition,
the weight was increased by 2–5% for the next set to ensure that
the subjects kept performing the sets to (or very near to) failure in
the established repetition range. The rest period was 60–90 sec-
onds between the sets. The FULL
ROM
group performed calf raise
exercise with no degree of movement restrictions (ankle joint: 2
25° to 125°; 0° 5foot 90° relative to the tibia). INITIAL
ROM
performed calf raise in the partial ROM at the initial excursion of
the concentric muscle action of plantar flexion (ankle joint: 225°
to 0°). FINAL
ROM
performed calf raise in the partial ROM at the
final excursion of the concentric muscle action of plantar flexion
(ankle joint: 0° to 125°). An illustration of the training groups
can be seen in Figure 2. These ROMs were defined from pilot data
collection in which we observed that with overload (i.e., during
calf raise exercise), the complete ROM was approximately 50°,
and initial and final ROMs were approximately 25°. The ankle
joint angles of 225° and 125° were validated through the dis-
placement of the weight stack on the stem. Using an inelastic tape
measure and a goniometer, we identified that 6 cm of weight stack
displacement corresponds to 25° of ankle flexion. This weight
stack displacement was the parameter adopted to validate the
specific ROM. The research assistants confirmed when the sub-
ject had reached the required weight stack displacement during
the calf raise exercise. In the INITIAL
ROM
group, a metallic
structure was placed in the stem where the weight stack of the
machine run to serve as a limiter at the top part of desired plantar
flexion angle (0°). In the FINAL
ROM
group, a step in EVA was
used to serve as a limiter at the bottom part of desired plantar
flexion angle (0°). In INITIAL
ROM
and FINAL
ROM
groups, the
0° angle was identified using a goniometer. The supplementary
material (http://links.lww.com/JSCR/A383) illustrates how the
mechanical stops were used to delimit the ROM excursion. The
Figure 1. CONSORT flow chart. FULL
ROM
5full range of motion, INITIAL
ROM
5initial part of the range of motion, FINAL
ROM
5
final part of the range of motion.
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subjects performed the calf raise exercise at a tempo of 1:2 sec-
onds (concentric and eccentric phases, respectively), with the knee
extended and the foot positioned on the platform supported by
metatarsals. Subjects performed all sessions under specialized
supervision (1:2 subject:supervisor ratio) to ensure safe and
proper execution. All weights and repetitions performed were
recorded. The volume load was calculated as the number of sets 3
number of repetitions 3load lifted. The average volume load of
the first training sessions in week 1 was used as each subject’s
reference value. Thereafter, volume load progression was calcu-
lated based on percentage differences between the average volume
load produced between training sessions 1 and 2–24.
Statistical Analysis
Data distribution and variance homogeneity were verified
through Shapiro-Wilk and Levene’s tests, respectively. The one-
way analysis of variance (ANOVA) was used to compare the
baseline characteristics between the groups. The comparison of
different ROM configurations (FULL
ROM
vs. INITIAL
ROM
vs.
FINAL
ROM
) effects on gastrocnemius muscle thickness was made
using an analysis of covariance (ANCOVA) of the raw difference
between baseline and posttraining measures with the baseline
score as a covariate. When the F-ratio was significant, Bonfer-
roni’s post hoc test was used to identify the differences between
pretraining and posttraining raw data. The pvalues for group
comparisons were also presented. The interpretation of the effect
of time was made from the 95% confidence interval (95% CI) of
the mean difference from pretraining to posttraining (i.e., there
was a significant difference when the inferior and superior con-
fidence limits did not cross zero). The effect size (ES) was calcu-
lated as posttraining group mean minus the pretraining mean,
divided by the groups-pooled pretraining standard deviation (4).
The one-way ANOVA was used to compare the initial volume
load between the groups. The volume-load progression slopes
were generated using linear regression and compared through an
F-test. For all statistical analyses, significance was accepted at p,
0.05. The data were stored and analyzed using JASP software
(version 0.14.1, Amsterdam, NL). The data are presented as mean
and standard deviations.
Results
No significant between-group differences for subject char-
acteristics or dependent variables were detected at baseline (p
$0.265). Session attendance was 93.4 65.7% for the
FULL
ROM
, 91.0 65.6% for the INITIAL
ROM
,and92.06
5.8% for the FINAL
ROM
with no difference between the
groups.
Table 1 displays the pretraining and posttraining values of
gastrocnemius muscle thickness. There were significant increases
in muscle thickness of the medial gastrocnemius for FULL
ROM
and INITIAL
ROM
(p#0.001) but not for FINAL
ROM
(p5
0.053). A significant group effect was observed for the changes in
the medial gastrocnemius muscle thickness (F59.254; p,
0.001). There was a greater increase for INITIAL
ROM
than for
FULL
ROM
[mean
diff
50.13 cm (95% CI: 0.03, 0.23), p50.009]
and greater increases for INITIAL
ROM
than for FINAL
ROM
[mean
diff
50.17 cm (95% CI: 0.07, 0.27), p,0.001], but no
difference was observed between FULL
ROM
and FINAL
ROM
[mean
diff
50.04 cm (95% CI: 20.05, 0.13), p50.892]. Figure 3
shows the relative changes on muscle thickness of medial gas-
trocnemius (FULL
ROM
516.7%; INITIAL
ROM
5115.2%; and
FINAL
ROM
513.4%).
There were increases in muscle thickness of the lateral gas-
trocnemius for FULL
ROM
, INITIAL
ROM
, and FINAL
ROM
(p#
0.005). A significant group effect was observed for the changes in
the lateral gastrocnemius (F54.464; p50.018). There was a
greater increase for INITIAL
ROM
than for FINAL
ROM
[mean
diff
50.13 cm (95% CI: 0.02, 0.25), p50.024], but not significant
difference was observed between INITIAL
ROM
and FULL
ROM
[mean
diff
50.12 cm (95% CI: 20.01, 0.24), p50.060] and
between FULL
ROM
and FINAL
ROM
[mean
diff
50.01 cm (95%
CI: 20.10, 0.12), p50.999]. Figure 3 shows the relative changes
on muscle thickness of lateral gastrocnemius (FULL
ROM
5
17.3%; INITIAL
ROM
5114.9%; and FINAL
ROM
516.2%).
The groups started the training program with similar volume
load (FULL
ROM
52,696.4 6460.9 kg, INITIAL
ROM
52,687.0
6467.8 kg, FINAL
ROM
52,696.4 6460.9 kg; F50.78, p5
0.469). Volume load progression slopes differed significantly
between FULL
ROM
and INITIAL
ROM
(F563.61; p,0.001) and
between FULL
ROM
and FINAL
ROM
(F521.86; p,0.001) but
not between INITIAL
ROM
and FINAL
ROM
(F52.019; p5
0.162). Figure 4 shows the volume load progression from session
to session in the FULL
ROM
, INITIAL
ROM
, and FINAL
ROM
groups.
Discussion
The purpose of this study was to examine the effects of 3 different
ROM configurations (FULL
ROM
, INITIAL
ROM
, and FINAL-
ROM
) on the muscle thickness of gastrocnemius muscles in un-
trained young women. The main finding of this study is that
ROM can influence the magnitude of increases in muscle
Figure 2. Illustration of 3 experimental groups. FULL
ROM
5full range of motion, INITIAL
ROM
5initial part of the range of motion,
FINAL
ROM
5final part of the range of motion.
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thickness of the gastrocnemius. Specifically, the INITIAL
ROM
induced greater gains on the medial and lateral heads compared
with the FINAL
ROM
. Moreover, INITIAL
ROM
elicited greater
increases in the medial gastrocnemius than FULL
ROM
. This in-
dicates that partial ROM training at longer muscle lengths can
optimize hypertrophy of the gastrocnemius muscles. Our initial
hypothesis that INITIAL
ROM
would be superior to FINAL
ROM
was confirmed. Conversely, the assumption that there would be
similar gains between INITIAL
ROM
and FULL
ROM
was not
confirmed, given that there was more favorable gastrocnemius
muscle hypertrophy for INITIAL
ROM
configuration. Potential
mechanisms and explanations for our findings are discussed
following.
In this study, we observed more favorable medial and lateral
gastrocnemius hypertrophy for the INITIAL
ROM
, especially when
contrasted with FINAL
ROM
(between-group ES: 0.48–0.66). A
possible explanation for this superiority may lie in the muscle
length at which the gastrocnemius muscles were trained. Growing
evidence suggests that resistance exercises performed at long
muscle lengths promote superior muscle hypertrophy (19,20,32).
In this study, the calf raise exercise was performed with the knees
extended and, specifically in INITIAL
ROM
, the ankle moved ex-
clusively in dorsiflexion angles, in which the gastrocnemius heads
reach longer muscle lengths (15). Given that gastrocnemius work
on the ascending and plateau portions of the length-tension curve
(10,21), it is possible to propose that the gastrocnemius fibers may
have produced maximum active force levels from contractile el-
ements (i.e., actin and myosin filaments) in the INITIAL
ROM
configuration to reach longer muscle lengths (9,16). Thus, gas-
trocnemius muscle fibers probably experienced optimal me-
chanical tension that resulted in a more favorable muscle
hypertrophy stimulus (38). Conversely, the gastrocnemius fibers
in the FINAL
ROM
group may not have produced maximum active
force because of the shorter muscle length in this ROM configu-
ration (15,16). Thus, experiencing reduced mechanical tension
and less favorable muscle hypertrophy stimulus (38). This con-
ceivably helps to explain the greater muscle hypertrophy in the
INITIAL
ROM
group.
Still based on the length-tension relationship, it is possible
to suggest that gastrocnemius fibers in the INITIAL
ROM
configuration potentially experienced additional passive ten-
sion from elastic elements (e.g., titin), and this may have
contributed to eliciting superior muscle growth because of the
potential additive effects of stretch and contraction (3,13,25).
This phenomenon has been called stretch-mediated hyper-
trophy (24). Indeed, it has been suggested that there is an in-
crease in titin stiffness (especially in the PEVK segment) in the
active muscle when reaching longer muscle lengths that result
in further passive tension in the sarcomere (25). Thus, this
would result in greater overall mechanical tension, a primary
hypertrophic stimulus (38). Importantly, it has been argued
that only muscles that work in the descending limb of the
length-tension curve appear to experience stretch-mediated
hypertrophy (13,28). Although there are findings from a ca-
daver study suggesting that gastrocnemius may work in the
descending limb (5), it remains questionable whether, in fact,
the sarcomeres of the gastrocnemius muscle fibers reach the
descending limb in vivo human muscles (10,21,39). There-
fore, it remains to be determined whether gastrocnemius fibers
work in descending limb of the length-tension curve and may
experience stretch-mediated hypertrophy.
Table 1
Medial and lateral gastrocnemius muscle thickness (in
centimeters) before and after 8 wk of the calf raise training with
different ROM configurations.*
Muscle thickness FULL
ROM
INITIAL
ROM
FINAL
ROM
Medial gastrocnemius
Pre 1.65 60.29 1.58 60.26 1.75 60.27
Post 1.76 60.30† 1.82 60.27
†,‡,§
1.81 60.29
Mean
diff
0.10 (0.04, 0.17) 0.23 (0.16, 0.31) 0.06 (20.01, 013)
ES 0.40 0.88 0.22
Lateral gastrocnemius
Pre 1.65 60.32 1.61 60.29 1.62 60.27
Post 1.77 60.34† 1.85 60.34
†,‡
1.72 60.25†
Mean
diff
0.12 (0.04, 0.20) 0.24 (0.15, 0.32) 0.10 (0.03, 0.18)
ES 0.41 0.82 0.34
*Note . ROM 5range of motion; FULL
ROM
5full range of motion (n514); INITIAL
ROM
5initial
part of the range of motion (225˚ to 0˚) (n512); FINAL
ROM
5final part of the range of motion
(0˚ to 125˚) ( n516); ES 5effect size. Pretraining and posttraining data are presented as
mean and standard deviation, whereas mean
diff
as mean and 95% confidence intervals.
†p,0.05 vs. baseline.
‡p,0.05 vs. FINAL
ROM
.
§p,0.05 vs. FULL
ROM
.
Figure 3. Changes from pretraining to posttraining period for
medial and lateral gastrocnemius muscle thickness.
†
p,0.05
vs. FINAL
ROM; ‡
p,0.05 vs. FULL
ROM
. The horizontal lines
represent mean and 95% confidence intervals, whereas each
circle represents a subject. FULL
ROM
5full range of motion;
INITIAL
ROM
5initial part of the range of motion; FINAL
ROM
5
final part of the range of motion.
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Notably, other factors such as internal moment arm and
muscle activation play an important role in muscle capacity for
producing force and then potentially influence the hypertrophic
stimulus (13). Theoretically, the longer the internal moment
arm length, the greater the capacity of muscle in producing a
turning force at a specific joint (36). Some research has found
that internal moment arm lengths increase with increasing
plantar flexion angle, thereby being greater at shorter muscle
lengths (21,22). This could result in greater force production at
a more flexed plantar position and then a more favorable hy-
pertrophic stimulus for the FINAL
ROM
configuration. How-
ever, our results do not support this notion. Thus, it is possible
to suggest that the change in the internal moment arm length at
different ankle joint angles may not be sufficient to sub-
stantially affect the gastrocnemius production of plantar flex-
ion torque. Importantly, investigations have been less devoted
to understanding potential differences in the internal moment
arm lengths of each muscle and how these might alter with
changing ankle joint angles. Thus, further research is needed to
determine the internal moment arm lengths of individual
muscles and explore the potential influence of this factor on
muscle hypertrophy.
Regarding muscle activation at different ankle positions,
findings are divergent. For example, there is a report suggest-
ing that surface electromyographic (sEMG) amplitude is subtly
greater for lateral gastrocnemius, but not for medial gastroc-
nemius, at a more dorsiflexed ankle position (i.e., longer
muscle lengths) compared with a more plantar flexed position
(i.e., shorter muscle lengths) (1). Conversely, other studies
found no differences in sEMG amplitude when comparing a
more dorsiflexed versus a more plantar flexed ankle position
(8,34). Interestingly, studies consistently observe greater
plantar flexion torque in more dorsiflexed position (1,8,21).
Based on greater gastrocnemius hypertrophy in the INI-
TIAL
ROM
group observed in this study, and not consistent
findings on sEMG, it is possible to suggest that the muscle
activation, per se, may not indicate the hypertrophic potential
when comparing training at different muscle lengths (37). In
fact, torque production across a range of joint angles creates
discordant muscle sEMG amplitudes (37). By contrast, greater
hypertrophy is commonly observed when training at longer
compared with shorter muscle lengths (12,13). Importantly,
because of the divergent findingsonmuscleactivationatdif-
ferent ankle positions, further studies are needed to charac-
terize this aspect and investigate the potential relationship
between muscle activation and gastrocnemius muscle hyper-
trophy. In addition, other techniques (e.g., magnetic resonance
imaging, ultrasonography) have been used to infer the mag-
nitude of the stimulus in a given muscle and should be
explored.
Interestingly, the INITIAL
ROM
group elicited significantly
greater increases in medial gastrocnemius muscle size than
FULL
ROM
(between-group ES: 0.48), and although we did not
observe significance for the lateral gastrocnemius, the ES fa-
vored the INITIAL
ROM
(between-group ES: 0.41). Our find-
ings are in accordance with a recent study, which found more
favorable muscle hypertrophy of the vastus lateralis and rectus
femoris in the INITIAL
ROM
than in the FULL
ROM
when per-
forming the knee extension exercise (29). A potential expla-
nation for such INITIAL
ROM
-favorable findings over
FULL
ROM
may be an interaction between muscle length and
volume load progression (which influences mechanical ten-
sion). In fact, higher rates of volume-load progression seems to
result in greater muscle hypertrophy (26). The analysis of the
training loads in this study showed that both partial ROM
groups (INITIAL
ROM
and FINAL
ROM
)progressedmorethan
the FULL
ROM
(see Figure 4). Notably, the INITIAL
ROM
ach-
ieved greater increases in gastrocnemius muscle thickness than
the other 2 ROM configurations. Because the magnitude of
volume load progressions was similar for the INITIAL
ROM
and
FINAL
ROM
, this seems to indicate that muscle hypertrophy
seems to be optimized through an interaction between volume-
load progression—thus, overload—and training at longer
muscle lengths.
Certainly, our study has limitations that need to be
addressed. First, dietary intake and daily physical activity
levels were not assessed and remain uncertain whether these
factors could exert some influence on muscular adaptations.
Importantly, the subjects were instructed to maintain their
nutritional habits and not perform any additional exercise on a
Figure 4. Volume load progression per session for the FULL
ROM
, INITIAL
ROM
, and FINAL
ROM
configurations, with slopes (continuous straight lines) and 95% confidence intervals (dotted
lines). FULL
ROM
5full range of motion; INITIAL
ROM
5initial part of the range of motion; FINAL
ROM
5final part of the range of motion.
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systematic basis. Second, the training intervention in this study
lasted8weeks;itwouldbeinteresting to have longer training
periods to verify the effects of different ROM configurations
on muscular adaptations. Third, because our study exclusively
investigated the medial and lateral gastrocnemius muscle hy-
pertrophy, future investigations should consider examining
the influence of ROM on the architectural (e.g., fascicle length
and pennation angle) and functional (e.g., maximum voluntary
isometric contraction and 1 repetition maximum) parameters,
as well as the effects of specific ROM on muscle size changes of
the soleus and other muscles with limited or nonexistent
findings such as the hamstrings and pectoralis major. More-
over, given that a resistance training program comprises a
variety of exercises (14), it is necessary to investigate the effect
of different ROM configurations on other exercises that target
the calf muscles (e.g., seated calf raise). Finally, this experiment
was performed on untrained young women and therefore re-
mains to be determined whether such findings are also ob-
served in other populations of different ages, sex, and training
status.
Practical Applications
Although FULL
ROM
configuration significantly increased
both gastrocnemius heads, INITIAL
ROM
elicited more
favorable muscle hypertrophy, especially compared with
FINAL
ROM
configuration. Therefore, from the results of
our study, it is possible to suggest that calf raise exercise
performed with partial ROM in the initial portion of the
movement (i.e., training at longer muscle lengths) may
induce greater hypertrophy of the gastrocnemius muscles
following 8 weeks of resistance training in untrained
young women. These results add to the growing evidence
suggesting that resistance training performed at long
muscle lengths promotes superior muscle hypertrophy.
From a practical perspective, strength and conditioning
professionals and practitioners aiming to optimize medial
and lateral gastrocnemius muscle growth should consider
including this strategy in the hypertrophy-oriented train-
ing program.
Acknowledgments
The authors express thanks to all the subjects for their
engagement in this study, the Coordination of Improvement of
Higher Education Personnel (CAPES/Brazil) for the scholarship
conferred to WK, BC, GK, NS, JF, IT, and the National Council of
Technological and Scientific Development (CNPq/Brazil) for the
grants conceded to ESC.
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