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Eects of Active Individual Muscle Stretching on
Muscle Function
Kouichi NaKam ura, PT, MS1,2)*, TaKayuKi Kodama, PT, PhD3), yoshiTo muKai No, MD, PhD2)
1) Department of Physical Therapy, Fukuoka Wajiro Rehabilitation College: 2-1-13 Wajirogaoka,
Higashiku, Fukuoka- city, Fukuoka 811-0213, Japan
2) Faculty of Sports and Health Science, Fukuoka University, Japan
3) Department of Physical Therapy, Faculty of Health Science, Kyoto Tachibana University, Japan
Abstract. [Pur pose] We investigated the effect of active individual muscle stretching (AID) on muscle function.
[Subjects] We used the right legs of 40 healthy male students. [Methods] Subjects were divided into an AID group,
which perfor med stretching, and a control group, which did not. We examined and compared muscle function
before and after stretching in the AID and control groups using a goniometer and Cybex equipment. [Results] A
signicant increase in exibility and a signicant decrease in muscle strength output were obser ved in the AID
group after the intervention. [Conclusion] These results suggest that AID induces an increase in exibility and a
temporary decrease in muscle output strength.
Key words: Active individual muscle stretching, Muscle function, Flexibility
(This article was submitted Aug. 9, 2013, and was accepted Sep. 22, 2013)
INTRODUCTION
Stretching was introduced in a sports coaching program
on TV at the beginning of the 1980s in Japan, which led
to the publication of many stretching-associated books for
the general public and a so-called stretching boom1). Based
on previous studies, the common aims of stretching are to
improve joint range of motion (exibility), decrease mus-
cle tension2–9), improve circulation2 , 10, 11), relieve muscle
pain2, 12 , 13), prevent injury, and improve athletic perfor-
mance1, 2, 13). Stretching using the responses of the nervous
system such as proprioceptive neuromuscular facilitation is
currently attracting attention in the eld of sports. Stretch-
ing is also performed in combination with yoga or Pilates,
which attaches importance to postures and breathing tech-
niques. Thus, various types and purposes of stretching have
been repor ted. However, a number of theories on the asso-
ciation between stretching methods and their effects exist,
and this issue is still controversial.
Individual muscle stretching (ID stretching) developed
by Suzuki et al.2) aims to increase muscle exibility and
extensibility, and improve joint range of motion and dex-
terity associated with muscles. ID stretching has been
widely used in hospitals, clinics, and the eld of sports,
mainly by physical therapists, since 1999. ID stretching is
characterized2) by passive static stretching of individual
muscles using Ib inhibition, detailed anatomical and physi-
ological knowledge, such as that of muscle arrangements
and responses to stimuli, and combination with isometric
contraction, depending on the degree of muscle tension
required. Our previous study14) of ID stretching showed
improvements in exibility, a decrease in muscle strength
output, and psychologically positive changes, which were
better than those of conventional passive static stretching.
However, in the conditioning eld, it is important that not
only physical therapists and trainers perform ID stretching,
but also that patients and athletes control and perform this
stretching by themselves.
Even if the extensibility and exibility of soft tissues rep-
resentative of the muscles improve, they readily decrease
due to posture, exercise, or stress15). Therefore, muscles
treated by ID stretching to reduce muscle tension or pain,
should be continuously stretched by patients or athletes to
maintain soft tissue function15). Unlike passive ID stretch-
ing, which is performed by therapists, active ID stretching
(AID) was developed in 200715) and is performed by pa-
tients and athletes by themselves. AID has since been per-
formed as a bedside or home exercise by patients or athletes
under the management of a physical therapist. However, to
the best of our knowledge, no studies have evaluated the
effects of AID on muscle function. Therefore, this study
was performed to evaluate the effects of AID on muscle
function, using a goniometer (Medica) to determine range
of motion, and an isokinetic dynamometer (Cybex770-
NORM, Medica).
J. Phys. Ther. Sci.
26: 341–344, 2014
*Corresponding author. Kouichi Nakamura (E-mail: naka-
mura@fukuokawajiro-reha.jp)
©2014 The Society of Physical Therapy Science. Published by IPEC Inc.
This is an open-access ar ticle dist ributed under the terms of the Cre-
ative Commons Attribution Non-Commercial No Derivatives ( by-nc-
nd) License <ht tp://creativecommons.org /licenses/by-nc-nd/3.0/>.
Original Article
J. Phys. Ther. Sci. Vol. 26, No. 3, 2014342
SUBJECTS AND METHODS
Subjects
The subjects were 40 healthy male students (40 right
lower limbs) with no previous history of disease in their
lower limbs. Their mean age was 20.8 ± 1.6 years, their
mean height was 171.8 ± 5.4 cm, and their mean body
weight was 66.4 ± 7.3 kg.
This study was approved by the Research Ethical Com-
mittee of Fukuoka Hoken Gakuin, and oral and written ex-
planations about the contents and risks of this st udy were
given to all subjects prior to the study. All subjects signed
the consent form after understanding the study contents,
and participated in this study.
Methods
Subjects were randomly and evenly allocated to 2 groups
(20 subjects each) which performed (AID group) or did not
perform AID (control group).
The soleus was evaluated as an ankle plantar exor mus-
cle. Range of motion testing (ROM-T) and measurement of
isokinetic plantar exor muscle strength were performed
before and after stretching. To evaluate exibility, ROM-T
was performed according to the methods established by the
Measurement Standards Committee of the Japanese Asso-
ciation of Rehabilitation Medicine16). The ankle dorsiex-
ion range of motion was measured using a goniometer, per-
pendicularly from the knee-exed position to the bula as
the primary axis, and the 5th metatarsal bone as the move-
ment axis. Two physical therapists (clinical experience, 12.5
± 2.6 years) other than the authors were performed these
measurements. One performed xation, and the other per-
formed the measurement, and after exchanging roles, the
measurement was taken again. An isokinetic dynamometer
(Cybex770-NORM) was used to measure isokinetic muscle
strength output. Based on the study of Yoshino et al.17),
evaluations were performed at low (60 deg/sec), intermedi-
ate (180 deg/sec), and high (300 deg/sec) angular velocities.
A ankle dorsiexion with maximum effort was performed
3 consecutive times, and the mean peak torque achieved at
each angular velocity was calculated14).
Measurements at one angular velocity were taken on 1
day. To avoid order effects, measurements at the 3 angular
velocities were randomly taken on different days.
To stretch the soleus in the AID group, the right forefoot
was bilaterally held with both hands, and the right ankle
was dorsiexed while the center of gravity was posteriorly
moved (Fig. 1). External force applied to the test limb dur-
ing stretching was controlled at 5 kgf using a hand-held
dynamometer (FET-102, Medix Japan) which was used for
the quantitative evaluation of muscle strength14 , 18). The
stretching instructors were 2 physical therapists (clinical
experience, 10.5 ± 2.4 years) other than the authors and the
physical therapists who performed ROM-T. One of the two
physical therapists gave instructions, and the other took the
measurement. The control group did not perform stretch-
ing, and measurements were taken after a resting time simi-
lar to the stretching time of the AID group.
To induce exercise conditions before the evaluation,
all subjects performed an ergometer exercise (5 min,
60 W)19, 20).
Statistical analysis was performed as follows. Flexibility
was analyzed using two-way repeated measures analysis
of variance with the group (2 levels: AID × control) and
the measurement value of the foot dorsiexion range of
motion (2 levels: before × after stretching) as the two fac-
tors. Muscle strength output was analyzed using a 3-way
analysis of variance with the group (2 levels: AID × con-
trol), peak torque values of the two groups (2 levels: before
× after stretching), and the angular velocity (3 levels: 60 ×
180 × 300 deg/sec) as the 3 factors. Fisher’s PLSD was used
for multiple comparison tests. p < 0.05 was regarded as sig-
nicant in all analyses. SPSS 12.0.J for Windows was used
as the statistical software.
RES U LTS
Both the group and ROM value had main effects on ex-
ibility. A comparison between the two groups showed sig-
nicant improvements in exibility in the AID group (Table
1).
A comparison of the ankle dorsiexion range between
before and after the intervention in each group showed a
signicant improvement in exibility in the AID group (p <
0.05), but and no signicant difference in the control group
(p > 0.05) (Table 1).
Muscle strength output was signicantly lower after
stretching in the AID group than in the control group. A
comparison of muscle strength output between before and
after the intervention in each group revealed a signicant
decrease after the intervention in the AID group only (p <
Fig.1. Active individual muscle stretching of the so-
leus
Tab le 1. Range of motion before and af ter the inter-
vention
Group Before After
AID 19.5 ±3.6 25.2± 3.0*
Control 19.7± 3. 5 20.1±3.2
AID: Active Individual Muscle Stretching
Before: Before stretching After: Af ter stretching
n=40, the values shown are angles (°)
Mean ± standard deviation *p<0.05
343
0.05) (Table 2). Muscle strength output here means muscle
strength of plantarexion.
A comparison of the peak torque between before and af-
ter the intervention at each angular velocity showed a sig-
nicant difference only at an angular velocity of 60 deg/sec
in the AID group (p < 0.05). No signicant differences were
observed between before and after the intervention in the
control group (p < 0.05) (Table 2).
DISCUSSION
This study evaluated the effects of AID on muscle func-
tion in terms of exibility and isokinetic muscle strength
output.
A signicant improvement in exibility after stretch-
ing was observed in the AID group, but not in the control
group. This nding together with those of previous studies
indicates the responses of the nervous system to stretching.
Helda et al.21) reported that a prolonged stretch of muscle
spindles inhibited their afferent activity, which resulted
in a decrease in muscle tension. Fowles et al.22) reported
that prolonged static stretching induced responses in Golgi
tendon organs and nociceptors, which inhibited muscle ten-
sion. These responses of the nervous system can also be ex-
plained by a delay and decrease in the integral value21, 23)
of the stretch reex, and a decrease in muscle tension may
also have resulted in improvements in exibility. We specu-
late that these responses by the nervous system occur red in
the body since, AID can also be classied as static stretch-
ing, and results similar to those in previous studies were
obtained. The reason why a few improvement trends were
seen in the control group was same position has range of
motion measurement and AID and thinks that a temporary
stretching effect was given.
Muscle strength output after the intervention was lower
in the AID group than in the control group. This result to-
gether with those of previous studies suggests the involve-
ment of the physical properties of muscle tissue. Morse et
al.7) reported a decrease in the elasticity of muscle connec-
tive tissue (increased extensibility) as acute changes imme-
diately after stretching. Cramer et al.25) demonstrated that
the sarcomeres of muscle bers were stretched by stretch-
ing and Teramoto et al.26) reported that tendons were also
stretched. These studies suggest that muscle bers are lon-
ger after stretching than before, due to the physical charac-
teristics of the muscle. Based on the muscle tension-length
relationship, a certain muscle length is necessary to exert
maximum contraction tension27). Since muscle length was
reported to be longer after stretching than before, even at
the same joint angle, due to sarcomere/tendon elongation,
muscle strength may decrease after stretching28). This in-
crease in muscle length may have caused decrease in mus-
cle strength output which was observed as an acute change
immediately after stretching in the present as well as previ-
ous studies.
An evaluation of isokinetic muscle strength output ex-
erted at each angular velocity revealed a decrease after
the intervention only at an angular velocity of 60 deg/sec
in the AID group. Nelson et al.29) reported that the effects
of stretching were marked at 60 deg/sec because this low
angular velocity resembles the velocity of isometric exer-
cise, and muscle contraction occurs at a lower velocity. AID
as well as ID stretching, in which an individual muscle is
selected for stretching, was more susceptible to Ib inhibi-
tion, which had inhibitory effects on muscle tension. Mus-
cle tension may have been associated with the decrease in
muscle strength output at the low angular velocity in the
AID group.
The results of this study suggest that AID as self stretch-
ing, as well as passive static stretching2–9), improves ex-
ibility and decreases muscle strength output, showing
potential in the self-conditioning eld. In this study, the
expression “a decrease in muscle strength output” was
used; however, changes in muscle tension and the inhibi-
tory effects of muscle tension, which may be present in the
background, were not evaluated. Neurophysiological stud-
ies using electromyography30, 31) should be performed in the
future to more thoroughly evaluate the inhibitory effects
of muscle tension. In addition, an evaluation that assesses
performance using basic and sport actions24) is required,
because many muscles are involved in actual joint exercise.
An evaluation of the duration of effects28) of home exercise
utilizing AID is also needed.
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