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GENDER DIFFERENCES IN MUSCULOTENDINOUS
STIFFNESS AND RANGE OF MOTION AFTER AN
ACUTE BOUT OF STRETCHING
KATHERINE M. HOGE,
1
ERIC D. RYAN,
2
PABLO B. COSTA,
1
TRENT J. HERDA,
1
ASHLEY A. WALTER,
1
JEFFREY R. STOUT,
3
AND JOEL T. CRAMER
1
1
Biophysics Laboratory, Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma;
2
Applied
Musculoskeletal and Human Physiology Laboratory, Department of Health and Human Performance, Oklahoma State
University, Stillwater, Oklahoma; and
3
Metabolism and Body Composition Laboratory, Department of Health and Exercise
Science, University of Oklahoma, Norman, Oklahoma
ABSTRACT
Hoge, KM, Ryan, ED, Costa, PB, Herda, TJ, Walter, AA,
Stout, JR, and Cramer, JT. Gender differences in musculoten-
dinous stiffness and range of motion after an acute bout of
stretching. J Strength Cond Res 24(10): 2618–2626,
2010—The purpose of the present study was to examine
musculotendinous stiffness (MTS) and ankle joint range of
motion (ROM) in men and women after an acute bout of passive
stretching. Thirteen men (mean 6SD age = 21 62 years; body
mass = 79 615 kg; and height = 177 67 cm) and 19 women
(21 63 years; 61 69 kg; 165 68 cm) completed stretch
tolerance tests to determine MTS and ROM before and after
a stretching protocol that consisted of 9 repetitions of passive,
constant-torque stretching. The women were all tested during
menses. Each repetition was held for 135 seconds. The results
indicated that ROM increased after the stretching for the women
(means 6SD pre to post: 109.39°610.16°to 116.63°6
9.63°;p#0.05) but not for the men (111.79°66.84°to
113.93°68.15°;p.0.05). There were no stretching-induced
changes in MTS (women’s pre to postchange in MTS: 20.35 6
0.38; men’s MTS: +0.17 60.40; p.0.05), but MTS was higher
for the men than for the women (MTS: 1.34 60.41 vs. 0.97 6
0.38; p#0.05). electromyographic amplitude for the soleus and
medial gastrocnemius during the stretching tests was un-
changed from pre to poststretching (p.0.05); however, it
increased with joint angle during the passive movements (p#
0.05). Passively stretching the calf muscles increased stretch
tolerance in women but not in men. But the stretching may
not have affected the viscoelastic properties of the muscles.
Practitioners may want to consider the possible gender differ-
ences in passive stretching responses and that increases in
ROM may not always reflect decreases in MTS.
KEY WORDS constant torque, viscoelastic properties, electro-
myography
INTRODUCTION
Stretching is commonly used to improve perfor-
mance (2,49,51,52) and reduce the risk of injury
(5,18,47) before athletic events. It has been
suggested that stretching will decrease the amount
of strain through a range of motion (ROM), thereby reducing
the risk of injury (12,44,53). A stiffer musculotendinous unit
(MTU) is thought to better withstand large and rapid forces
better than a compliant system, thus reducing the likelihood
of injury (9,20,29,35). However, there is little evidence to
support the relationship between increased flexibility and
reduced incidence of injury (25,26,54,55). Yet, a recent study
by Shehab et al. (48) found that stretching routines are still
performed by high-school athletes as an injury prevention
strategy. In addition, there is little research indicating that
stretching improves performance. An acute bout of static
stretching has been found to reduce muscle strength (14,22)
and power (11), impair balance (3), and increase movement
and reaction times (3). In addition, a study by Nelson and
Kokkonen (37) asked subjects before testing whether
stretching would have a beneficial or detrimental outcome,
and all subjects believed that an acute bout of stretching
would result in better performance. However, because of the
limited evidence supporting stretching before competition,
the President’s Council for Physical Fitness and Sports
released a statement concluding that stretching may not
prevent injury and may also compromise performance (27).
Despite the discrepancy between knowledge and practice,
stretching is still a major component of preactivity warm-up
routines, and therefore, additional research is necessary
to determine the precise effects of stretching on injury
prevention.
Address correspondence to Dr. Joel T. Cramer, jcramer@ou.edu.
24(10)/2618–2626
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Ó2010 National Strength and Conditioning Association
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Many stretching studies use increases in flexibility as the
primary variable; however, total ROM provides only a fraction
of the information regarding the physiological changes in the
MTU (33). Measures of musculotendinous stiffness (MTS), in
conjunction with ROM, may provide a more comprehensive
understanding of the biomechanical responses of the MTU.
Musculotendinous stiffness is defined as the ratio of change in
passive force in a muscle because of its change in length (35).
It is generally calculated using passive angle-torque or angle–
force curves during a passive stretch (30). The slope of any
tangent to the passive angle-force curve is recorded as the
MTS. Tangential slopes can be calculated at any joint angle to
quantitatively measure the amount of passive resistance
throughout a given ROM. Therefore, stretching-induced
increases in ROM and decreases in MTS imply that not only
is there an increase in ROM, but there are also decreases in
passive stiffness and altered viscoelastic properties of the
MTU.
It is well known that the connective tissues of men and
women differ physiologically (24). However, the mechanisms
contributing to these differen-
ces are not well understood.
Estrogen may play a role, be-
cause estrogen receptors are
present in fibroblasts of tendons
and ligaments, which may alter
collagen synthesis and affect
tissue behavior (24). Other
hormonal fluctuations through-
out the menstrual cycle may
also influence the behavior
of the MTU (13,21,43). Eiling
et al. (13) found significant
decreases in MTS of the knee
flexors during the ovulatory
phase, when estrogen and pro-
gesterone are elevated, com-
pared to all other phases of the
menstrual cycle. In addition,
Ryan et al. (46), using periph-
eral quantitative computed to-
mography, showed a positive
relationship between muscle
size and MTS, providing a pos-
sible explanation for gender
differences in MTS, as men
generally have greater muscle
mass than women.
To our knowledge, only 1
study has compared the MTS
responses to stretching be-
tween men and women (15).
This study used 3, 60-second
constant-angle stretches of the
plantar flexors to measure
viscoelastic stress relaxation and passive elastic stiffness at
each joint angle. However, constant-torque stretches have
been shown to result in greater decreases in MTS and
increases in ROM than constant-angle stretches (56,57).
Therefore, the purpose of this study was to examine the MTS
and ankle joint ROM changes in men and women after an
acute bout of passive, constant-torque stretching.
METHODS
Experimental Approach to the Problem
A repeated-measures design (pre vs. poststretching) that is
depicted in Figure 1 was used to compare the acute effects of
passive stretching of the plantar flexors on MTS and ROM)
in men vs women. Each subject visited the laboratory on 2
separate occasions. The first visit was a familiarization
trial during which the subjects practiced the stretch toler-
ance assessments, and the investigators determined the
maximum tolerable stretching threshold that could be
sustained throughout the entire passive stretching protocol.
This was accomplished by sequentially increasing the
Figure 1. A schematic representation of the experimental design.
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amount of passive torque applied by the dynamometer until
each subject acknowledged discomfort, but not pain elicited
by the stretching protocol. This passive torque setting
was then used during the experimental trial to administer
the stretching protocol. Stretch tolerance, however, was the
maximum amount of passive torque applied by the dyna-
mometer that could be momentarily tolerated by the subject.
To determine stretch tolerance, the passive torque setting
was increased to a supramaximal level, and the dynamometer
was manually stopped by the investigators when the subject
acknowledged the momentary onset of pain during the
ROM. The stretch tolerance test was used to determine each
subject’s maximal ROM and MTS. The second visit was the
experimental trial during which all testing and stretching
took place. Subjects visited the laboratory during normal
hours (8 AM–8 PM). To avoid differences within the menstrual
cycle, the women were all tested during menses, which was
self-reported to the investigators. All subjects were also asked
to refrain from exercise 24 hours before the experimental
trial. Hydration status was not monitored before testing,
which should be noted as a limitation of this study. Figure 1
shows the schedule of assessments for this research design.
Subjects
Thirteen men (mean 6SD age = 20.8 61.8 years; body mass
= 79.0 615.0 kg; height = 176.9 67.2 cm) and 19 women
(age = 20.7 62.5 years; body mass = 60.9 68.9 kg; height =
165.1 67.6 cm) volunteered for this study. None of the
subjects reported any current or ongoing neuromuscular
diseases or musculoskeletal injuries to the foot, knee, or hip.
The women were also required to meet the following criteria:
(a) have consistent, normal menstrual cycles for the past
3 months, (b) report no use of any hormonal contraceptives
for the past 3 months, and (c) have been menstruating for at
least 1 year before the study (13). None of the subjects were
competitive athletes; however, because of their reported
levels of aerobic exercise (mean 6SD men = 3.6 63.9
hwk
21
; women = 3.9 62.6 hwk
21
) and resistance training
(men = 2.6 62.1 hwk
21
; women = 1.1 61.5 hwk
21
), these
individuals might be best classified as normal, recreationally
active participants. This study was approved by the
Institutional Review Board for Human Subjects, and all par-
ticipants completed a written informed consent form and
a Pre-Exercise Testing Health and Exercise Status Question-
naire before testing.
Procedures
Instrumentation. All participants were seated with restraining
straps over the thigh and the tibia just distal to the knee
joint. Each subject’s foot was stabilized in a custom-built
apparatus described and used in previous studies (44) to
measure plantar flexion force equipped with a sensitive load
cell (Omega Engineering Inc., Stamford, CT, USA). Figure 2
shows a picture of a subject situated in the custom apparatus.
The leg flexion angle was kept at 0°below the horizontal
plane (full extension), and a neutral ankle joint angle was
considered 0°(90°between the foot and the leg). The lateral
malleolus of the fibula was aligned with the joint axis of the
custom-built apparatus. The subject’s foot and heel were
stabilized into a thick rubber heel cup and held against the
foot plate with straps over the toes and metatarsals so that
the straps would not impede any passive foot movement
of the ankle joint. The apparatus was also attached to
a calibrated Biodex system 3 isokinetic dynamometer
(Biodex Medical Systems Inc., Shirley, NY, USA) that was
programmed in ‘‘passive’’ mode to stretch the plantar flexor
muscles by passively dorsiflexing the foot at 5°s
21
until the
maximum tolerable torque threshold was met.
Flexibility Assessments and Stretching. Before and after the
passive stretching protocol, 2 stretch tolerance assessments
were performed during which subjects were asked to relax
while their foot was passively and maximally dorsiflexed at
5°s
21
. When the subject acknowledged their maximal ROM
had been reached, the dynamometer was stopped. After the
prestretching flexibility assessments, a 5-minute rest period
was allowed. The stretching protocol was performed in
the same position and in the same fashion as the stretch
tolerance assessments. Nine repetitions of the constant--
torque stretches were performed at the predetermined torque
threshold determined during the familiarization trial. Each
stretch was held for 135 seconds with 10 seconds of rest
between repetitions (22). Immediately after the stretching
protocol, 2 poststretching tolerance assessments were
performed in the same manner as described previously.
The average ROM achieved during the 2 assessments was
used for all subsequent analyses.
Electromyography. Surface electromyographic (EMG) signals
were recorded from bipolar, preamplified electrodes
(EL254S, Biopac Systems, Santa Barbara, CA, USA) placed
over the soleus and medial gastrocnemius muscles. The
Figure 2. Picture of the foot placement in the testing apparatus.
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electrodes had a fixed center-to-center interelectrode distance
of 20 mm and a gain of 350. To reduce interelectrode
impedance, the skin was shaved and lightly abraded, then
cleaned with isopropyl alcohol before electrode placement.
Electrodes were placed in accordance with the recommen-
dations of Hermens et al. (23). The soleus electrode was taped
along the longitudinal axis of the tibia at 66% of the distance
from the medial condyle of the femur to the medial
malleolus, below the base of the medial gastrocnemius.
The electrode for the medial gastrocnemius was taped to
the most prominent bulge of the muscle. A single, disposable,
pregelled, reference electrode (Ag–AgCl, Quinton Quick
Prep, Quinton Instruments Co., Bothell, WA, USA) was
placed on the spinous process of the seventh cervical
vertebrae. All EMG signals were filtered with a passband of
10–500 Hz using a zero-phase shift fourth-order Butterworth
filter. The EMG amplitude values were calculated using
a root-mean squared (RMS)
function and were quantified
with 200-millisecond epochs
corresponding to the same joint
angles used to quantify MTS
(neutral = 0°of dorsiflexion).
These RMS values were then
normalized to each respective
EMG RMS amplitude value
recorded during a maximal
voluntary contraction (MVC)
based on the procedures of
Gajdosik et al. (17). For nor-
malization, the baseline EMG
RMS was subtracted from the
RMS values calculated at each
joint angle and during the
MVC, and then the baseline-
corrected RMS values during
the passive stretches were ex-
pressed as a percentage of the
baseline-corrected MVC value
for each subject.
Signal Processing. The force (kg),
position (°), and EMG (mV)
signals were sampled simul-
taneously at 1 kHz with a
Biopac data acquisition system
(MP150WSW, Biopac Sys-
tems) during each passive
stretch tolerance test. All signals
were recorded and stored on a
personal computer (Dell Inspir-
on 8200, Dell Inc., Round Rock,
TX, USA) to be processed off-
line using custom-written soft-
ware (LabVIEW v. 8.5, National
Instruments, Austin, TX, USA). To calculate MTS, the ankle
joint angle (°) and force (kg) signals were plotted as
angle–force curves (i.e., stress–strain curves) and fit with
a second-order polynomial regression model. Musculotendi-
nous stiffness was calculated at the 3 final joint angles (each
separated by 2°) that were common to both the pre and
poststretching ranges of motion based on the equation
reported by Nordez et al. (38) The force values were gravity
corrected using a cosine function that subtracted the weight
of the foot platform measured at the neutral joint angle.
Statistical Analyses
A 2-way mixed-factorial analysis of variance (ANOVA) (time
[pre vs. poststretch] 3gender [male vs. female]) was used to
analyze the ROM data. A 3-way mixed-factorial ANOVA (time
[pre vs. poststretch] 3gender [male vs. female] 3angle [1 vs. 2
vs. 3]) was usedto analyze the MTS data, and a separate 4-way
Figure 3. Passive range of motion (ROM; °) from pre to poststretching for the men and women. The solid circles
and dark lines are the mean 6SEM values, and the open circles and dashed lines are the individual responses.
*Mean ROM value for the women increased from pre to poststretching (p#0.05).
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mixed-factorial ANOVA (time [pre vs. poststretch] 3gender
[male vs. female] 3angle[1vs.2vs.3]3muscle [soleus vs.
medial gastrocnemius]) was used to analyze the EMG
amplitude data. When appropriate, follow-up analyses were
performed using lower-order ANOVAs and independent and
dependent samples t-tests with Bonferroni corrections. The
assumption of sphericity was not met, so a Greenhouse–
Geisser adjustment was used to
correct for this violation. Pre-
vious test–retest reliability data
for this flexibility assessment in
our laboratory indicated that,
for 15 young men (24 63years)
measured on separate days, the
intraclass correlation coefficient
was 0.94 with a standard error
of measurement of 2.01%. The
SEM for ROM in the present
study was 4.6%, ES = 0.42, and
statistical power = 0.99. An
alpha level of p#0.05 was
considered statistically signifi-
cant for all comparisons. Statis-
tical analyses were performed
using SPSS v. 16.0 (SPSS Inc.,
Chicago, IL, USA).
RESULTS
Range of Motion
There was a significant time 3
gender interaction for ROM
(p= 0.020). Range of motion
increased from pre to post-
stretching for the women
(p,0.001), but not the men
(p= 0.066) (Figure 3).
Musculotendinous Stiffness
There was no 3-way interaction
(time 3angle 3gender, p=
0.258), no 2-way interactions
for time 3angle (p= 0.796) or
time 3gender (p= 0.144), but
there was a 2-way interaction
for angle 3gender (p= 0.019)
and no main effect for time (p=
0.590). The marginal means for
MTS (collapsed across time)
increased such that joint angle
1,joint angle 2 ,joint angle 3
for both the men and women
(p,0.001), and MTS was
greater for the men than the
women at all joint angles (p=
0.008) (Figure 4).
Electromyographic Amplitude
There was no 4-way interaction (time 3angle 3gender 3
muscle, p= 0.262), no 3-way interactions for time 3angle 3
gender (p= 0.168), angle 3muscle 3gender (p= 0.733),
time 3angle 3muscle (p= 0.186), or time 3muscle 3
gender (p= 0.073), no 2-way interactions for time 3gender
(p= 0.249), angle 3gender (p= 0.481), muscle 3gender
Figure 4. Musculotendinous stiffness (MTS; kg°
21
) plotted over the ankle joint angles used to calculate the MTS
values. The open circles represent the mean 6SEM for the women, whereas the solid circles represent the mean 6
SEM for the men. The solid lines represent the prestretching condition, whereas the dashed lines were
poststretching values. *Indicates that the mean MTS values increased from joint angle 1 to joint angle 2 to joint
angle 3 (p#0.05). †Mean MTS values were greater for the men than for the women (p#0.05).
Figure 5. Electromyographic amplitude (mean 6SD) values of the soleus and medial gastrocnemius from pre to
poststretching. Electromyographic amplitude values are presented as a percentage of maximal voluntary
contraction. MG denotes medial gastrocnemius and SOL denotes soleus. *Significant difference from pre to
poststretching.
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(p= 0.841), or time 3angle (p= 0.644), but there were
significant 2-way interactions for time 3muscle (p= 0.039)
and angle 3muscle (p= 0.034). The marginal means for
soleus EMG (collapsed across time) increased such that joint
angle 1 ,joint angle 3 (p= 0.040) and joint angle 2 ,joint
angle 3 (p= 0.028); however, the soleus EMG amplitude did
not increase from joint angles 1 to 2 (p= 0.320). The marginal
means for medial gastrocnemius EMG (collapsed across
time) increased such that joint angle 1 ,joint angle 2 (p=
0.025) and joint angle 1 ,joint angle 3 (p= 0.019); however,
the medial gastrocnemius EMG amplitude did not increase
from joint angles 2 to 3 (p= 0.345). The EMG amplitude for
the soleus (p= 0.611) and medial gastrocnemius (p= 0.096)
was unchanged from pre to poststretching.
DISCUSSION
The main findings of the present study were that the ROM
increased after 20 minutes of passive stretching for the women
but not the men. Furthermore, there were no stretching-
induced changes in MTS, but MTS was higher for the men
than for the women throughout the study. These findings
were generally consistent with those of Magnusson et al.
(31,34) in that MTS at fixed joint angles was unchanged after
an acute bout of stretching. Magnusson et al. (31) examined
the effects of static and cyclic stretching of the hamstrings
and reported increases in ROM after both stretching
protocols, but no changes in MTS. The authors attributed
these findings to an increase in stretch tolerance, rather than
to a change in the viscoelastic properties of the MTU (31).
The differences between these studies were that Magnusson
et al. (31) used 1, 90-second stretch for the left and right
hamstrings, whereas the pres-
ent study used a constant-
torque stretching protocol
(22) consisting of 9, 135-second
stretches of the right triceps
surae. Therefore, based on the
hypothesis of Magnusson et al.
(31) that longer stretching du-
rations may elicit viscoelastic
changes in the MTU (i.e.,
decreases in MTS) rather than
simple increases in stretch tol-
erance, it is unclear why the
longer durations of stretching
in the present study did not
elicit changes in MTS.
We propose 4 potential ex-
planations as to why the longer
stretching durations in the pres-
ent study did not decrease
MTS, but improved ROM in
the women compared to pre-
vious studies: (a) differences
between the muscles examined,
(b) different stretching intensities, (c) different stretching
treatments, and (d) gender differences. For example, it is
possible that muscle-specific responses to stretching may
exist when comparing the hamstrings (31) and the triceps
surae. Ryan et al. (45) suggested that the smaller, distal
muscle groups such as the triceps surae may require longer
durations of stretching to elicit stretching-induced decreases
in muscle activation. It is possible that a similar principle
could be applied to changes in MTS. To illustrate, in another
study, Ryan et al. (44) showed that a minimum stretching
duration of 2 minutes was required to elicit decreases in MTS.
Because the duration of stretching in the present study was
longer than the minimum duration recommended by Ryan
et al. (44), our findings may also have been influenced by
stretching intensity.
The subjects’ pain tolerance may also have affected the
ROM and MTS results of the present study if they could
not tolerate higher stretching intensities. In theory, if the
stretching intensity of the present study was less than that of
previous studies that have demonstrated decrease in MTS
(33,36,38,44), then this may have contributed to the lack of
decrease in MTS in the present study. However, Behm et al.
(4) reported no changes in ROM after 3 separate stretching
protocols of varying intensities. The authors (4) suggested
that this may be attributed to either an increase in passive
tension because of delayed-onset muscle soreness from the
stretching or a greater myotatic stretch reflex at higher
stretching intensities that increased the active stiffness of the
muscle. Because EMG amplitude increased with joint angle
in the present study (Figures 5 and 6), our findings supported
the hypothesis of Behm et al. that the myotatic reflex
Figure 6. Electromyographic amplitude (mean 6SD) values of the soleus and medial gastrocnemius by joint angle.
Electromyographic amplitude values are presented as a percentage of maximal voluntary contraction . MG denotes
medial gastrocnemius and SOL denotes soleus. *Joint angle was significantly different from joint angle 1. †Joint
angle was significantly different from joint angle 2. ‡Joint angle was significantly different from joint angle 3.
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activation may have limited our ability to measure the
decreases in MTS if indeed they did exist. Thus, our findings
should be used as cautionary notes for future studies to ensure
that the myotatic reflex is quiescent while assessing MTS.
It is also possible that differences in the stretching protocol
could affect changes in MTS and ROM. Ryan et al. (44)
suggested that a constant-torque stretching protocol will
increase the work performed on the MTU, as compared
to a traditional static stretching protocol or constant-angle
stretch, which may not be as demanding. Yeh et al. found that
a constant-torque stretching protocol resulted in greater
decreases in MTS than a constant-angle stretching protocol
of the calf in hypertonic patients, which may have been
because of increased strain relaxation or muscle creep during
the constant-torque stretching (56,57). However, Magnusson
et al. (31) reported increases in ROM but no changes in MTS
after cyclic and static stretching of the hamstrings. Therefore,
the increases in ROM reported by Magnusson et al. (31) and
those reported in the present study may be because of
increases in stretch tolerance, rather than changes in the
viscoelastic properties of the muscle.
Gender differences in the extensibility of the plantar flexor
muscles have been reported by Gajdosik et al. (15) and
Riemann et al. (42). These studies showed that the MTS was
greater through the entire ROM (15) and at 10°dorsiflexion
(42) for the men than for the women, respectively. The
present findings are unique, however, in that only 1 previous
study has examined the passive musculotendinous properties
and responses to an acute bout of stretching in men and
women (15). Our study further delineated the gender
differences by controlling for birth control and menses in
the women. Therefore, our results extended the findings of
Gajdosik et al. (15) and Riemann et al. (42) and suggested
that gender differences can be observed in ROM measure-
ments after a bout of stretching, which may be related to
fundamental hormonal differences.
A few hypotheses have been proposed to explain the
gender differences in neuromuscular properties and visco-
elastic changes. These include fluctuations in hormone levels,
discrepancies in muscle cross-sectional area (CSA) and
anthropometry, and differences in passive properties such
as viscoelastic stress relaxation or viscoelastic creep. Many
studies have examined the effect of estradiol and progesterone
on active MTS and anterior cruciate ligament (ACL) laxity
throughout the menstrual cycle with equivocal findings
(13,21,41,43,50). When a change in MTS or ACL laxity was
observed across the menstrual cycle, it was generally at or
near ovulation when estradiol levels peak (13,21,41,43,50).
Therefore, because we tested during menses when estradiol
levels are lowest, the observed gender differences may have
been even greater if we had tested at or near ovulation.
Several studies also have reported strong positive correla-
tions between muscle CSA and MTS (7,10,16,32,46). Men
generally have a greater muscle mass than do women, which
is believed to result in higher MTS values. In agreement with
our findings, many authors have shown that before or
without stretching intervention, men have higher passive
and active MTS values than do women (6–8,10,19,39,40,42).
However, after accounting for body weight, body mass, or
limb size, no differences were observed in MTS between
genders (7,8,19,39,40). In addition, it has been suggested that
the viscoelastic creep response differs between genders (28),
which is a tissue response that occurs during constant-torque
stretching. Similarly, Gajdosik et al. (15) reported gender
differences in viscoelastic stress relaxation during a 60-second
static stretch, which suggested that men and women may
respond differently to stretching.
Overall, the results of the present study indicated that
an acute bout of passive stretching increased ROM for the
women, but not for the men. In addition, there were no
changes in MTS, which is commonly used to assess the
viscoelastic properties of the muscle. It has been suggested
that a decrease in MTS reduces the total amount of strain
through a given ROM, which may reduce the risk of strain
injuries (44). If the goal of the stretching intervention is to
increase ROM and decrease MTS, the findings of this study
indicated that men may have to stretch at a higher intensity
or longer duration to achieve the same increases in ROM as
women. In contrast, a stiffer MTU is thought to be advan-
tageous, because it can better withstand rapid and large forces
compared to a compliant system, thus reducing the likelihood
of ligamentous injury (42). For women, who are at a 2–8 times
greater chance of sustaining an ACL injury than men (1),
maintaining MTS may be an important factor in reducing this
risk. Because MTS was not decreased after stretching, these
findings indicate that, although it is unknown if stretching
affects the risk of injury, it may be a safe treatment before
competition. However, future research is necessary to de-
termine when the stretching is applied before performance
and how long the changes in ROM may last.
PRACTICAL APPLICATIONS
The findings of this study suggested that passive stretching
increased ROM for the women but not for the men, but there
were no changes in MTS. Thus, the women experienced
increases in stretch tolerance but not changes in muscle
stiffness. Practitioners who use stretching may want to
consider the possible gender differences in passive stretching
responses and that increases in ROM may not always reflect
decreases in MTS. Therefore, men may have to stretch for
a longer duration or at a greater intensity to achieve similar
increases in ROM as women. It is important for coaches and
athletes to know that this type of stretching may not always
result in the desired effects (increases in ROM or decreases in
MTS).
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