Is muscle stiffness a determinant for range of motion in the leg muscles?

Abstract

Previous training studies with comprehensive stretching durations have reported that an increase
in range of motion (ROM) can be related to decreases in muscle stiffness. Therefore, the purpose of this study
was to analyze the association between the passive muscle stiffness of three muscle groups (triceps surae,
quadriceps, hamstrings) to the respective joint ROM. Thirty-six healthy male soccer players volunteered in this
study. After a standardized warm-up, the muscle stiffness was tested via shear wave elastography in six muscles
(gastrocnemius medialis and lateralis, rectus femoris, semitendinosus, semimembranosus, and biceps femoris
long head). The hip extension, hip flexion, and ankle dorsiflexion ROM were also assessed with a modified
Thomas test, a sit and reach test, and a standing wall push test, respectively. We found significant moderate
to large correlations between hip flexion ROM and muscle stiffness for the semimembranosus (rP = –0.43;
P = 0.01), biceps femoris long head (rP = –0.45; P = 0.01), and overall hamstring stiffness (rP = –0.50;
P < 0.01). No significant correlations were found for triceps surae (rP = –0.12; P = 0.51 to 0.67) and rectus
femoris muscle stiffness (rP = 0.25; P = 0.14) with ankle dorsiflexion and hip extension ROM, respectively.
We conclude that muscle stiffness is an important contributor to hip flexion ROM, but less important for hip
extension or ankle joint ROM. Additional contributors to ROM might be tendon stiffness or stretch/pain tolerance

Full text

Biology of Sport, Vol. 41 No2, 2024 115
Marina M Reiner et al. Correlations between muscle stiffness and ROM
INTRODUCTION
Methods such as stretching and foam rolling can increase the range
of motion (ROM) acutely (stretching[1–3], foam rolling[4,5], or
the combination of stretching and foam rolling[6,7]]) as well as in
the long term (stretching[8,9], foam rolling[10]). Two major mech-
anisms have been reported to be involved in the changes in ROM.
On the one hand, an increase in stretch tolerance (i.e., higher toler-
ated torque) seems to be the most common mechanism for ROM
increases after both an acute stretch or foam rolling interven-
tion[11,12] and after long-term interventions with these modali-
ties[13,14]. On the other hand, adecrease in muscle stiffness has
been reported to be another mechanism for an increase in ROM
after acute static and proprioceptive neuromuscular facilitation
stretching (but not after dynamic stretching) interventions of>60s,
as well as after foam rolling[15, 16]. Such decreases in muscle
stiffness have also been observed following several weeks of high-
volume stretching (i.e.,>30min aweek per muscle group)[17],
but not following long-term foam rolling[13]. These training-induced
changes in muscle stiffness after stretching (acute and long term)
and foam rolling (acute) indicate acausal correlation between chang-
es in muscle stiffness and ROM. However, to date, it is not clear if
joint ROM is related to stiffness of the surrounding muscle groups.
While studies have reported acorrelation between some leg muscle
Is muscle stiffness adeterminant for range of motion in the leg
muscles?
AUTHORS: Marina M. Reiner1, Markus Tilp1, Masatoshi Nakamura2, Andreas Konrad1
1 Institute of Human Movement Science, Sport and Health, Graz University, Graz, Austria
2 Faculty of Rehabilitation Sciences, Nishi Kyushu University, Ozaki, Kanzaki, Saga, Japan
ABSTRACT: Previous training studies with comprehensive stretching durations have reported that an increase
in range of motion (ROM) can be related to decreases in muscle stiffness. Therefore, the purpose of this study
was to analyze the association between the passive muscle stiffness of three muscle groups (triceps surae,
quadriceps, hamstrings) to the respective joint ROM. Thirty-six healthy male soccer players volunteered in this
study. After astandardized warm-up, the muscle stiffness was tested via shear wave elastography in six muscles
(gastrocnemius medialis and lateralis, rectus femoris, semitendinosus, semimembranosus, and biceps femoris
long head). The hip extension, hip exion, and ankle dorsiexion ROM were also assessed with amodied
Thomas test, asit and reach test, and a standing wall push test, respectively. We found signicant moderate
to large correlations between hip exion ROM and muscle stiffness for the semimembranosus (rP = –0.43;
P=0.01), biceps femoris long head (rP=–0.45; P= 0.01), and overall hamstring stiffness (rP= –0.50;
P<0.01). No signicant correlations were found for triceps surae (rP=–0.12; P= 0.51 to 0.67) and rectus
femoris muscle stiffness (rP=0.25; P= 0.14) with ankle dorsiexion and hip extension ROM, respectively.
We conclude that muscle stiffness is an important contributor to hip exion ROM, but less important for hip
extension or ankle joint ROM. Additional contributors to ROM might be tendon stiffness or stretch/pain tolerance.
CITATION: Reiner MM, Tilp M, Nakamura M, Konrad A. Is muscle stiffness adeterminant for range of motion
in the leg muscles? Biol Sport. 2024;41(2):115–121.
Received: 2023-05-31; Reviewed: 2023-06-22; Re-submitted: 2023-08-22; Accepted: 2023-08-22; Published: 2023-10-06.
stiffness and ROM, this seems to depend on age, sex, and mus-
cle[18–20]. More specically, Hirata etal.[20] reported asignicant
correlation between gastrocnemius medialis and gastrocnemius late-
ralis muscle stiffness and ankle dorsiexion ROM in young but not
in older participants, measured in a15° dorsiexion position. In
addition, Miyamoto etal.[18] reported such correlations at 0° ankle
angle (gastrocnemius medialis + gastrocnemius lateralis to ankle
dorsiexion ROM) in young male participants but not in young female
participants. Moreover, acorrelation between the hamstring muscles
(semimembranosus, semitendinosus, and biceps femoris long head)
and hip exion ROM was detected in young participants, but without
analyzing sex-specic relationships[19]. This was in line with an
earlier study which reported that hip exion ROM is limited by ham-
string muscle-tendon unit stiffness[21], without distinguishing be-
tween isolated muscle and tendon stiffness, respectively. However,
to the best of our knowledge, no study to date has analyzed the
association between rectus femoris muscle stiffness and hip extension
ROM. Furthermore, no study to date has performed acorrelation
analysis of all joints and related muscles in the leg within one
project.
Additionally, concerning soccer players it is well known that low-
er joint ROM[22] and higher muscle stiffness [23] can lead to
Original Paper
DOI: https://doi.org/10.5114/biolsport.2024.131821
Key words:
Muscle stiffness
Hamstrings
Triceps surae
Rectus femoris
Range of motion
Flexibility
Corresponding author:
Andreas Konrad
Sport and Health University of
Graz, Mozartgasse 14
A-8010 Graz, Austria
E-mail: andreas.konrad@
uni-graz.at
ORCID:
Marina M. Reiner
0000-0002-0332-5244
Markus Tilp
0000-0002-6644-2712
Masatoshi Nakamura
0000-0002-8184-1121
Andreas Konrad
0000-0002-5588-1824

116
Marina M Reiner et al. Correlations between muscle stiffness and ROM
Measurements
Shear wave elastography (SWE)
The SWE values were measured with an ultrasound scanner (Aix-
plorer V12.3, Supersonic Imaging, Aix-en-Provence, France) in com-
bination with alinear transducer array (4–15 MHz, SuperLinear
10-2, Vermon, Tours, France) in the six leg muscles. The measure-
ments were done by aqualied tester with ~4years experience who
tested all subjects. The scanner was used in SWE mode (musculo-
skeletal preset, penetration mode, smoothing level 5, persistence off,
scale 0–300kPa). Per muscle, 3videos with 15seach were obtained.
The SWE values were analyzed with MATLAB R2017b (Math-Works,
Natick USA) and the mean of ve consecutive frames with the low-
est SD within the range of interest within each video was calculat-
ed[25]. The nal values for the muscle stiffness were calculated as
the mean between the two closest values of the three videos and
was divided by 3to convert the shear wave speed to shear modu-
lus[25]. Ahandheld technique without any stabilizing support or
guiding rail was utilized during the measurements [26,27]. The
tester needed to keep the same probe position without any movement
during the whole measurement duration.
To measure the shear modulus of the plantar exor muscles, the
participant was positioned prone in adynamometer (CON-TREX MJ,
CMV AG, Duebendorf, Switzerland) with the hip and knees fully ex-
tended (180°, respectively) and the ankle at neutral position (90°).
The GM was rst measured around the proximal third between the
calcaneus and the popliteal fossa. The gastrocnemius lateralis was
then measured at the same distance between the heel and knee but
on the lateral side of the calf. For the SWE measurements in the rec-
tus femoris, the participant was seated on adynamometer, while the
knee angle was set to 70° and the hip remained at 110°[28]. The
rectus femoris was measured around the distal third of the distance
between the proximal edge of the patella and the iliac spine[29].
For the shear modulus measurement of the hamstring muscles, the
participant was positioned next to the dynamometer in asupine po-
sition with ahip angle of 90° and knee angle of 120° to achieve
aslightly stretched position of the hamstring muscles[28]. The mea-
suring position for the semitendinosus was distal to the tendinous
insertion[25,30] and the measurement of the biceps femoris long
head was performed about half way between the popliteal fossa and
the ischial tuberosity on the lateral side of the back thigh[25,30].
The semimembranosus was measured more medial and more distal
than the measuring position of the semitendinosus[25,30].
The measurement position of the transducer for each muscle was
determined during the familiarization session and was marked on
areusable foil[16]. The probe was aligned with fascicle orientation
and kept in place for the whole measurement process[31]. Pressure
on the skin was avoided to not inuence tissue or muscle struc-
ture[32]. Aconditioning procedure with passive stretches controlled
in the dynamometer was performed prior to the SWE to guarantee
the same muscle condition in all participants. The angle range of the
conditioning was the same for all participants and was chosen
ahigher injury prevalence. Thus, it would be important to under-
stand the association between lower leg ROM to muscle stiffness es-
pecially in soccer players.
Therefore, the aim of this study was to investigate the correla-
tions between the passive muscle stiffness of three muscle groups
(triceps surae, quadriceps, and hamstrings) and the respective joint
ROM in recreational soccer players. We hypothesized that local mus-
cle stiffness would correlate with the respective joint ROM.
MATERIALS AND METHODS
Participants
An apriori power analysis, based on the results of Hirata etal.[20]
revealed an optimal sample size of 27participants (correlation: bi-
variate normal model, pH1 =0.495, α=0.05, β=0.80). There-
fore, to account for dropout, we recruited 36 healthy male, recre-
ational soccer players from 3rd to 6th Austrian league (training
frequency: 3to 4times per week + 1game at the weekend, age:
23.36 ± 4.11years; height: 181.8 ± 5.2cm; body mass:
81.2 ± 6.8kg) to participate in this study. Minimum 6month prior
the study participants were free of any injuries or neuromuscular
disorders. The participants were asked to avoid strenuous exercises
72hprior to the test and should avoid physical training on the test
day before the test. All participants signed awritten informed consent
form. The study was approved by the Ethics Committee of the Uni-
versity of Graz (approval code: GZ. 39/68/63 ex 2020/21) and was
performed according to the Declaration of Helsinki.
Experimental design
Participants visited the laboratory on two separate days. The rst
appointment was to familiarize the participants with the test proce-
dure. During the second appointment, the data acquisition in the
dominant leg (used for kicking aball) was undertaken. Prior to the
measurements, each participant performed a 5-min warm-up on
astationary cycle ergometer (Monark, Ergomedic 874E, Sweden)
at acadence of 60rev/min[24] and aresistance of 60W. Following
the warm-up and after positioning the participant for the measure-
ment (about 5min in between warm up and start of the rst mea-
surement) shear wave elastography (SWE) of the dominant leg of six
leg muscles (gastrocnemius medialis and gastrocnemius lateralis,
rectus femoris, semitendinosus, semimembranosus, and biceps
femoris long head) was performed to determine muscle shear mod-
ulus as an indicator for muscle stiffness. The ROM of ankle dorsi-
exion (standing wall push), hip extension (modied Thomas test),
and hip exion (sit and reach test) was then tested. During the SWE
measurements, the surface electromyography (sEMG) was visually
monitored on one muscle of each of the three muscle groups of the
leg (gastrocnemius lateralis, vastus lateralis, and biceps femoris long
head), which allowed us to conrm that the participant was in
arested state.

Biology of Sport, Vol. 41 No2, 2024 117
Marina M Reiner et al. Correlations between muscle stiffness and ROM
carefully to not stretch the tissue too much prior the SWE measure-
ment. The range of interest (ROI) during the measuring process was
set centrally and maximized as much as possible, but without in-
cluding any aponeuroses. The participant was asked to relax com-
pletely and avoid any movement during the measurement. This was
conrmed by sEMG, as values up to 5% of maximal isometric con-
traction activation were tolerated. For each muscle, three videos of
15seach were recorded. For the analysis, the mean of ve consec-
utive frames with the lowest standard deviation of the averaged shear
modulus of the ROI within each video was considered. To calculate
the mean passive stiffness of amuscle, the two closest mean values
out of the three videos were taken[25]. The reliability of all the SWE
assessments in any muscle was confirmed in previous experi-
ments[4,16,33]. Furthermore, the mean SWE values of all the re-
spective muscle groups where more than one muscle was assessed
(i.e., plantar exors (gastrocnemius medialis + gastrocnemius late-
ralis), hamstrings (semitendinosus + semimembranosus + biceps
femoris long head)) were also calculated as aproxy for overall mus-
cle group stiffness.
Range of motion (ROM)
The ROM measurements of the dorsiexion and hip extension were
tracked with a3D motion capture system (Qualisys, Gothenburg,
Sweden). Eight cameras were used, and reective markers (diameter:
1cm) were positioned on the participant’s hip and dominant leg
according to the Qualisys Gait module “CAST lower body marker
set”. Two additional markers were positioned on the right and left
iliac crest to ensure proper tracking during the hip extension ROM
in supine position. Firstly, the dorsiexion ROM was tested with the
standing wall push exercise. The exercise was repeated three times
for 5seach time. The starting position was standing upright in front
of awall. The hands were positioned on the wall at shoulder height
and width. After the start command, the participant was asked to
move the dominant leg behind the body as far as possible and posi-
tion it with extended leg and the heel touching the ground. The toes
of both legs were front facing. To reach the maximum dorsiexion
ROM at the point of discomfort in the stretched calf muscles of the
dominant leg, the knee of the other leg could also be exed. To test
hip extension ROM, the participant was asked to perform three
modied Thomas tests[34] with the dominant leg, each for 5s(inthe
end position). In each test, the participant lay supine on amedical
bed, with the gluteal fold right behind the edge of the bed, and the
hip was exed to 90° with knees xed by hands with extended elbow
joints. The extended elbows ensured the same positioning for each
participant and also helped to maintain the contact of the lumbar
spine with the medical bed during the test to avoid pelvic tilt during
the movement[35]. The participant was asked to relax their legs
completely. The contralateral leg was held in position with both hands
while the dominant leg was lowered unassisted toward the oor
until the end position in arelaxed state was reached. Moreover, to
test hip exion ROM, the participant performed three sit and reach
tests with the help of aSit n’ Reach trunk exibility box (Fabrication
Enterprises; Baseline Model 12-1086, New York, USA). The par-
ticipant was positioned sitting on the ground in front of the exibil-
ity box with the whole sole of each foot touching the box and the
knees fully extended and relaxed. For the starting position, the trunk
was kept upright and the arms were held parallel to the ground. The
task was to move the slider on top of the exibility box slowly as far
in the direction of the toes (and further) as possible. The knees were
kept in acompletely extended position during the forward bend
procedure. Moreover, both hands were on top of each other during
the pushing phase to minimize possible trunk rotation during the hip
exion. The value reached in the maximum forward bend position
was noted.
The camera system was calibrated at the beginning of each test
day and the data of each trial was controlled for completeness after
the measurement. Only trials with clear visibility of all markers dur-
ing the ROM movement were taken for analysis. If the data of atri-
al was not complete (i.e., markers were missing) one more trial was
conducted. For the analyzing procedure, the data points of the re-
ective markers were labeled within Qualisys and then exported to
Visual 3D, abiomechanical modeling software (Velamed GmbH –
Science in Motion, Köln, Germany) to calculate the joint angles with-
in the single ROM-tests. These joint angles were exported to aspread-
sheet and the best attempt out of the three was then chosen for
further analysis. If an evasive movement in any joint in any of the
tests was detected, the attempt was repeated.
Surface electromyography (sEMG)
SEMG (Myon320, myon AG, Zurich, Switzerland) was used to mon-
itor the muscle activation during SWE testing. Skin preparation and
surface electrode positioning (BlueSensor N, Ambu, A/S, Ballerup,
Denmark) were performed according to SENIAM recommenda-
tions[36] on the muscle belly of the vastus lateralis, biceps femoris
long head, and gastrocnemius lateralis. The signal was sampled at
2000Hz and normalized by amaximal voluntary isometric contrac-
tion. If any muscle activation was detected during the SWE assess-
ments (exceeding 5% of maximal muscle contraction, [37]), the
trial was repeated. The data were checked live during the SWE as-
sessment. If any abnormality was found during the SWE assessment
in the raw sEMG the data was further processed by performing
ahigh-pass ltered (10Hz Butterworth) and root-mean square (RMS,
50ms window).
Statistics
For the statistical analysis, SPSS (version 28, SPSS Inc., Chicago,
Illinois) was used and the normal distribution was tested with the
Kolmogorov-Smirnov test. In the case of anormal distribution, Person’s
correlation coefcient (rP) was used to determine the correlations
between the ROM and SWE variables of the respective joints. If the
values showed no normal distribution (semitendinosus shear modulus
data only), Spearman’s rho (rS) was calculated. The effect size of the

118
Marina M Reiner et al. Correlations between muscle stiffness and ROM
Correlation analysis of hamstring muscle shear modulus (i.e.,
stiffness) and hip flexion range of motion
The correlation analysis revealed asignicant moderate negative
relationship between the shear modulus of the semimembranosus
(rP= –0.43; P =0.01; 95% CI =–0.67 to –0.12) and biceps
femoris long head (rP =–0.45; P=0.01; 95% CI =–0.68 to
–0.14) and hip exion ROM. However, there was no correlation
between the semitendinosus (rS=–0.10; P=0.57; 95% CI
=–0.42 to 0.25) and hip exion ROM.
Moreover, asignicant large correlation was detected between
the mean shear modulus of the hamstring muscles (semimembra-
nosus + semitendinosus + biceps femoris long head) and the hip
exion ROM (rP=0.50; P<0.01; 95% CI =–0.71 to –0.21).
The scatter plots for all the correlations of the hamstring muscle
SWE to hip exion ROM are presented in Figure1.
DISCUSSION
The purpose of this study was to investigate if passive muscle stiff-
ness of three muscle groups (triceps surae, quadriceps, and ham-
strings) is related to the respective joint ROM. We found asignicant
small to large negative correlation between hip exion ROM and the
stiffness of the semimembranosus (rP=–0.43), biceps femoris long
head (rP=–0.45), and the overall hamstrings (rP=–0.50), which
indicates that higher stiffness causes lower hip flexion ROM.
correlation coefcients was assessed according to the suggestions of
Hopkins[38], i.e., trivial (0–0.1), small (0.1–0.3), moderate
(0.3–0.5), large (0.5–0.7), very large (0.7–0.9), and nearly perfect
or perfect (0.9–1). The 95% condence intervals (CIs) for the cor-
relations were also calculated. The alpha level was set to 0.05.
RESULTS
Correlation analysis of plantar flexor muscle shear modulus (i.e.,
stiffness) and ankle dorsiflexion range of motion
The correlation analysis revealed no signicant relationship between
the muscle shear modulus of the gastrocnemius medialis (rP=–0.12;
P= 0.51; 95% CI =–0.43 to 0.22) or gastrocnemius lateralis
(rP=–0.07; P=0.67; 95% CI =–0.39 to 0.26) and the dorsi-
exion RoM.
Moreover, no correlation was detected between the mean shear
modulus of the gastrocnemii (gastrocnemius medialis +gastrocne-
mius lateralis) and the dorsiexion ROM (rP=–0.12; P=0.51;
95% CI =–0.43 to 0.22).
Correlation analysis of rectus femoris muscle shear modulus (i.e.,
stiffness) and hip extension range of motion
The correlation analysis revealed no signicant relationship between
the muscle shear modulus of the rectus femoris (rP=0.25; P=0.14;
95% CI =–0.09 to 0.53) and the hip extension ROM.
FIG. 1. Scatter plots of the correlation between hamstring muscles stiffness assessed with shear wave elastography and hip exion
range of motion. * indicates asignicant correlation.

Biology of Sport, Vol. 41 No2, 2024 119
Marina M Reiner et al. Correlations between muscle stiffness and ROM
However, in the third hamstring muscle, the semitendinosus, we did
not nd such acorrelation. Moreover, there was no signicant cor-
relation between ankle dorsiexion ROM and gastrocnemius media-
lis or gastrocnemius lateralis stiffness. Similarly, there was no sig-
nicant correlation between rectus femoris stiffness and hip extension
ROM.
Since previous studies have reported asignicant correlation be-
tween gastrocnemius medialis and gastrocnemius lateralis stiffness
assessed via SWE and dorsiexion ankle ROM in young men[18,20],
it was surprising that we could not conrm this result in the present
study. Differences cannot be explained by the participants as all the
studies included young males of asimilar age ( Hirata etal.[20] age
=22; Miyamoto etal.[18] age =21.6; current study age =23).
However, the previous studies did not specify whether their partici-
pants were athletes or not. We recruited recreational soccer players
of the 3rd to 6th Austrian league, and hence it can be assumed that,
besides age[20] and sex[18], the training status of the participants
may have also affected the correlation between gastrocnemius me-
dialis or gastrocnemius lateralis stiffness and ankle dorsiexion ROM.
This was conrmed in previous studies which reported lower mus-
cle stiffness in untrained participants compared to their athlete
peers[39]. Although the muscle stiffness might be higher in ath-
letes, arecent meta-analysis showed that regular strength training
can increase the ROM of a joint[40]. Consequently, mechanisms
other than muscle stiffness, such as stretch tolerance, may be re-
sponsible for the relatively high ankle dorsiexion ROM found in our
sample (36.99 ± 5.37)[41]. Another explanation for the difference
in results may be the assessment of the gastrocnemius medialis and
gastrocnemius lateralis stiffness, which was performed in aneutral
ankle joint position in the present study. Miyamoto etal.[18] and
Hirata etal.[20] assessed gastrocnemius medialis and gastrocne-
mius lateralis stiffness in aslightly stretched position (Miyamoto
etal.[18] 14° ankle angle; Hirata etal.[20] 15° ankle angle). When
Miyamoto etal.[18] assessed stiffness at aneutral position, the sig-
nicant correlation with ROM only remained in the gastrocnemius
lateralis but not in the GM. No signicant correlation was observed
below slack length. Consequently, it is likely that such acorrelation
is dependent on the muscle-tendon unit length.
For the hamstrings, we found signicant correlation between hip
exion ROM and the stiffness of the semimembranosus (rP=–0.43),
biceps femoris long head (rP=–0.45), and overall hamstrings
(rP=–0.50), but not for the semitendinosus (rS=–0.10). In con-
trast, Miyamoto etal.[19] found a signicant correlation between
the sit and reach score and all three tested hamstring muscles (semi-
membranosus (rP=–0.25), biceps femoris long head (rP=–0.263),
semitendinosus (rP =–0.299)) and overall hamstring stiffness
(rP=–0.331). The slightly less pronounced correlation compared
to the present study could be explained by the female participants
included in the study by Miyamoto etal.[19]. Previous studies have
reported that young males, but not females, showed asignicant
correlation between gastrocnemius medialis and gastrocnemius
lateralis stiffness to ankle dorsiexion[19]. Consequently, it can be
speculated that the correlation between hamstring stiffness and hip
exion ROM might also be sex-dependent. However, Miyamoto
etal.[19] did not distinguish between sex in their study, so this re-
mains an open question Another possible explanation for the more
pronounced correlations compared to Miyamoto etal.[19] could be
that the participants in the current study were recreational male soc-
cer players. All in all, the correlations found in the study of Miyamo-
to etal.[19] and in the current study range from 0.25 to 0.5, and
hence the effect sizes can be considered as small to large. Thus, only
6% to 25% of the variation in ROM can be explained by the varia-
tion in muscle stiffness, according to these ndings. Consequently,
the remaining variation might be explained by other mechanisms,
such as stretch tolerance, tendon stiffness, or nerve stiffness.
To the best of our knowledge, this study was the rst to explore
the correlation between rectus femoris stiffness and hip extension
ROM. However, no signicant correlation was found between those
two variables. Although previous studies have found an increase in
ROM following asingle bout of foam rolling, no changes in rectus
femoris elongation (i.e., indication for stiffness) were reported[42].
Consequently, due to this lack of correlation found by Vigotsky
etal.[42], as well as the lack of correlations found in this study, oth-
er structures such as the iliopsoas muscle, ligaments, or the joint
capsule rather than the rectus femoris muscle could likely explain
hip extension ROM.
This study does have some limitations. Firstly, we did not assess
tendon stiffness. Since it is not recommended to assess tendon stiff-
ness with SWE, due to the technical restrictions of the device[43],
this parameter was not included. It is likely that Achilles tendon stiff-
ness and patellar tendon stiffness might be related to ankle dorsi-
exion and hip extension ROM, respectively. Consequently, future
studies should aim to assess tendon stiffness via force-elongation
curves[24] or other reliable methods such as the use of aMyoton-
Pro device[44]. Additionally, through pilot studies we recognized
that it was not possible to assess muscle stiffness with SWE of deep
lying muscles such as the iliopsoas as well as the soleus muscle with
high reliability. Consequently, we decided not to include these mus-
cles into that study. Furthermore, we did not assess stretch toler-
ance, which is another likely candidate for a correlation with
ROM[21]. Finally, we did not include female participants. Since
there have been differences reported in the correlation between ROM
and muscle stiffness between males and females in anon-athlete
population[18], future studies should take this into account.
CONCLUSIONS
It can be concluded that asmall to large correlation exists between
hip exion ROM and the stiffness of the semimembranosus, biceps
femoris long head, and overall hamstrings (but not in the semiten-
dinosus). However, it has to be noted that amaximum of 25% of
the variation in hip exion ROM can be explained by muscle stiffness.
Moreover, we did not nd a signicant correlation between ankle

120
Marina M Reiner et al. Correlations between muscle stiffness and ROM
Acknowledgements
This study was supported by agrant (Project P32078-B) from the
Austrian Science Fund FWF.
Conict of Interest declaration
The authors declare no conict of interest.
dorsiexion ROM and gastrocnemius medialis or gastrocnemius late-
ralis stiffness. In addition, there was no signicant correlation between
rectus femoris stiffness and hip extension ROM. Consequently, oth-
er structures such as tendon stiffness or stretch tolerance might be
factors which can be related to ankle dorsiexion ROM and hip exten-
sion ROM.
1. BehmDG, BlazevichAJ, KayAD,
McHughM. Acute effects of muscle
stretching on physical performance,
range of motion, and injury incidence in
healthy active individuals: asystematic
review. Appl Physiol Nutr Metab.
20131(1):1–11.
2. BehmDG, KayAD, TrajanoGS,
BlazevichAJ. Mechanisms underlying
performance impairments following
prolonged static stretching without
acomprehensive warm-up. Eur JAppl
Physiol. 202121(1):67–94.
3. KonradA, MočnikR, TitzeS,
NakamuraM, TilpM. The Inuence of
Stretching the Hip Flexor Muscles on
Performance Parameters. ASystematic
Review with Meta-Analysis. Int JEnviron
Res Public Health 20218(4):1936
4. ReinerMM, TilpM, GuilhemG,
Morales-ArtachoA, KonradA.
Comparison of ASingle Vibration Foam
Rolling and Static Stretching Exercise on
the Muscle Function and Mechanical
Properties of the Hamstring Muscles.
JSports Sci Med. 20221(2):287–297.
5. WilkeJ, MüllerAL, GiescheF, PowerG,
AhmediH, BehmDG. Acute Effects of
Foam Rolling on Range of Motion in
Healthy Adults: ASystematic Review
with Multilevel Meta-analysis. Sports
Med. 20200(2):387–402.
6. KonradA, NakamuraM, BernsteinerD,
TilpM. The Accumulated Effects of Foam
Rolling Combined with Stretching on
Range of Motion and Physical
Performance: ASystematic Review and
Meta-Analysis. JSports Sci Med.
20210(3):535–545.
7. KasaharaK, KonradA, YoshidaR,
MurakamiY, SatoS, KoizumiR,
BehmDG, NakamuraM. The comparison
between foam rolling either combined
with static or dynamic stretching on knee
extensors’ function and structure. Biol
Sport. 20230(3):753–760.
8. BorgesMO, MedeirosDM, MinottoBB,
LimaCS. Comparison between static
stretching and proprioceptive
neuromuscular facilitation on hamstring
exibility: systematic review and
meta-analysis. Eur JPhysiother.
20180(1):12–19.
9. MedeirosDM, MartiniTF. Chronic effect
of different types of stretching on ankle
dorsiexion range of motion: Systematic
review and meta-analysis. Foot (Edinb).
20184(1):28–35.
10. KonradA, NakamuraM, TilpM, DontiO,
BehmDG. Foam Rolling Training Effects
on Range of Motion: ASystematic Review
and Meta-Analysis. Sports Med.
20222(10):2523–2535.
11. MagnussonSP. Passive properties of
human skeletal muscle during stretch
maneuvers. Areview. Scand JMed Sci
Sports. 1998(2):65–77.
12. NakamuraM, OnumaR, KiyonoR,
YasakaK, SatoS, YahataK, FukayaT,
KonradA. The Acute and Prolonged
Effects of Different Durations of Foam
Rolling on Range of Motion, Muscle
Stiffness, and Muscle Strength. JSports
Sci Med. 20210(1):62–68.
13. KiyonoR, OnumaR, YasakaK, SatoS,
YahataK, NakamuraM. Effects of 5-Week
Foam Rolling Intervention on Range of
Motion and Muscle Stiffness. JStrength
Cond Res. 20226(7):1890–1895.
14. KonradA, TilpM. Increased range of
motion after static stretching is not due to
changes in muscle and tendon structures.
Clin Biomech (Bristol, Avon).
20149(6):636–642.
15. KonradA, StalidisS, TilpM. Effects of
acute static, ballistic, and PNF stretching
exercise on the muscle and tendon tissue
properties. Scand JMed Sci Sports.
20177(10):1070–1080.
16. ReinerMM, GlashüttnerC, BernsteinerD,
TilpM, GuilhemG, Morales-ArtachoA,
KonradA. Acomparison of foam rolling
and vibration foam rolling on the
quadriceps muscle function and
mechanical properties. Eur JAppl
Physiol. 202121(5):1461–1471.
17. NakamuraM, YahataK, SatoS,
KiyonoR, YoshidaR, FukayaT, NunesJP,
KonradA. Training and Detraining Effects
Following aStatic Stretching Program on
Medial Gastrocnemius Passive Properties.
Front Physiol. 20212(1):656579.
18. MiyamotoN, HirataK,
Miyamoto-MikamiE, YasudaO,
KanehisaH. Associations of passive
muscle stiffness, muscle stretch
tolerance, and muscle slack angle with
range of motion: individual and sex
differences. Sci Rep. 2018(1):8274.
19. MiyamotoN, HirataK, KimuraN,
Miyamoto-MikamiE. Contributions of
Hamstring Stiffness to Straight-Leg-Raise
and Sit-and-Reach Test Scores. Int
JSports Med. 20189(2):110–114.
20. HirataK, YamaderaR, AkagiR.
Associations between Range of Motion
and Tissue Stiffness in Young and Older
People. Med Sci Sports Exerc.
20202(10):2179–2188.
21. MagnussonSP, SimonsenEB, AagaardP,
BoesenJ, JohannsenF, KjaerM.
Determinants of musculoskeletal
exibility: viscoelastic properties,
cross-sectional area, EMG and stretch
tolerance. Scand JMed Sci Sports.
1997(4):195–202.
22. BradleyPS, PortasMD. The relationship
between preseason range of motion and
muscle strain injury in elite soccer
players. JStrength Cond Res.
20071(4):1155–1159.
23. WatsfordML, MurphyAJ, McLachlanKA,
BryantAL, CameronML, CrossleyKM,
MakdissiM. Aprospective study of the
relationship between lower body stiffness
and hamstring injury in professional
Australian rules footballers. Am JSports
Med. 20108(10):2058–2064.
24. KayAD, Husbands-BeasleyJ,
BlazevichAJ. Effects of Contract-Relax,
Static Stretching, and Isometric
Contractions on Muscle-Tendon
Mechanics. Med Sci Sports Exerc.
20157(10):2181–2190.
25. Morales-ArtachoAJ, LacourpailleL,
GuilhemG. Effects of warm-up on
hamstring muscles stiffness: Cycling vs
foam rolling. Scand JMed Sci Sports.
20177(12):1959–1969.
26. HugF, TuckerK, GennissonJL, TanterM,
NordezA. Elastography for Muscle
Biomechanics: Toward the Estimation of
Individual Muscle Force. Exerc Sport Sci
Rev. 20153(3):125–133.
27. LacourpailleL, HugF, BouillardK,
HogrelJY, NordezA. Supersonic shear
imaging provides areliable measurement
of resting muscle shear elastic modulus.
Physiol Meas. 20123(3):19–28.
28. LacourpailleL, NordezA, HugF,
DoguetV, AndradeR, GuilhemG. Early
detection of exercise-induced muscle
damage using elastography. Eur JAppl
Physiol. 201717(10):2047–2056.
29. HamS, KimS, ChoiH, LeeY, LeeH.
Greater Muscle Stiffness during
Contraction at Menstruation as Measured
by Shear-Wave Elastography. Tohoku
JExp Med. 202050(4):207–213.
30. LLe SantG, AtesF, BrasseurJL,
NordezA. Elastography Study of
Hamstring Behaviors during Passive
Stretching. PLoS One.
20150(9):e0139272.
REFERENCES

Biology of Sport, Vol. 41 No2, 2024 121
Marina M Reiner et al. Correlations between muscle stiffness and ROM
31. Le SantG, NordezA, AndradeR, HugF,
FreitasS, GrossR. Stiffness mapping of
lower leg muscles during passive
dorsiexion. JAnat.
201730(5):639–650.
32. KotBC, ZhangZJ, LeeAW, LeungVY,
FuSN. Elastic modulus of muscle and
tendon with shear wave ultrasound
elastography: variations with different
technical settings. PLoS One.
2012(8):e44348.
33. ReinerM, TilpM, GuilhemG,
Morales-ArtachoA, NakamuraM,
KonradA. Effects of aSingle
Proprioceptive Neuromuscular Facilitation
Stretching Exercise With and Without
Post-stretching Activation on the Muscle
Function and Mechanical Properties of
the Plantar Flexor Muscles. Front Physiol.
20212(1):732654.
34. AslanH, BuddhadevHH, SuprakDN,
San JuanJG. Acute Effects of Two Hip
Flexor Stretching Techniques on Knee
Joint Position Sense and Balance. Int
JSports Phys Ther. 20183(5):846–859.
35. VigotskyAD, LehmanGJ, BeardsleyC,
ContrerasB, ChungB, FeserEH. The
modied Thomas test is not avalid
measure of hip extension unless pelvic tilt
is controlled. PeerJ. 2016(1):e2325.
36. HermensHJ, FreriksB, MerlettiR,
StegemanD, BlokJ, RauG,
Disselhorst-KlugC, HäggG. European
Recommendations for Surface
ElectroMyoGraphy. Roessingh Res Dev
1999(2):13–54
37. GajdosikRL, Vander LindenDW,
McNairPJ, WilliamsAK, RigginTJ.
Effects of an eight-week stretching
program on the passive-elastic properties
and function of the calf muscles of older
women. Clin Biomech (Bristol, Avon).
20050(9):973–83.
38. HopkinsWG. ANew View of Statistics.
Sportsscience. 2001(1)1
39. HobaraH, KimuraK, OmuroK, GomiK,
MuraokaT, SakamotoM, KanosueK.
Differences in lower extremity stiffness
between endurance-trained athletes and
untrained subjects. JSci Med Sport.
20103(1):106–111.
40. AlizadehS, DaneshjooA, ZahiriA,
AnvarSH, GoudiniR, HicksJP, KonradA,
BehmDG. Resistance Training Induces
Improvements in Range of Motion:
ASystematic Review and Meta-Analysis.
Sports Med. 20233(3):707–722.
41. MoseleyAM, CrosbieJ, AdamsR.
Normative data for passive ankle
plantarexion--dorsiexion exibility. Clin
Biomech (Bristol, Avon).
20016(6):514–21.
42. VigotskyAD, LehmanGJ, ContrerasB,
BeardsleyC, ChungB, FeserEH. Acute
effects of anterior thigh foam rolling on
hip angle, knee angle, and rectus femoris
length in the modied Thomas test.
PeerJ. 2015(1):e1281.
43. RyuJ, JeongWK. Current status of
musculoskeletal application of shear
wave elastography. Ultrasonography.
20176(3):185–197.
44. ChenG, WuJ, ChenG, LuY, RenW,
XuW, XuX, WuZ, GuanY, ZhengY,
QiuB. Reliability of aportable device for
quantifying tone and stiffness of
quadriceps femoris and patellar tendon at
different knee exion angles. PLoS One.
20194(7):e0220521.