The Effect of Stretching
Duration on the Flexibility of Lower Extremities in Junior Soccer
Ioannis, Galazoulas Christos, Zakas Nikolaos, Vergou Aikaterini,
University of Thessaloniki
Department of Physical Education
and Sports Sciences
Dr. Galazoulas Christos,
Department of Physical Education and Sports Science,
Aristotle University of Thessaloniki,
Thessaloniki 540 06, Greece.
Tel. +302310 992233
Fax: +302310 992232
effect of different
passive stretching sessions as well as the effect of multiple
stretching sessions in acute stretching protocols has not yet been
thoroughly examined. The purpose of the present study was to
investigate the effect of stretching sessions differing in duration, as
well as the effect of multiple stretching sessions on the lower
extremities range of motion (ROM) in a set total amount of time spent
in stretching of junior soccer players. The subjects comprised of
thirteen junior soccer players aged 14.3 ±1.3 years who
four different passive stretching protocols. All protocols lasted for a
total of 60 seconds each, however, each protocol differed in the
duration of the stretches performed. Three of the stretching protocols
consisted of multiple stretches of different duration each and the
forth protocol comprised of continuous stretching, serving as the
control protocol. ROM was determined during hip flexion, extension, and
abduction, knee flexion and ankle dorsiflexion for both the right and
the left side of the body, using a flexometer and a goniometer. A mixed
within - and between - subjects analysis of variance (ANOVA) with
repeated measures revealed similar ROM values between both sides for
all the examined joints. No significant differences were observed among
the stretching protocols. Further statistical analysis of the data
indicated significant improvements after stretching exercises in all
flexibility protocols. These findings suggest that one 60-second
passive stretch on the lower extremities muscles produced the same
effect as two 30-second, four 15-second and twelve 5-second stretches
over a single flexibility training session in junior soccer players.
Key words: Flexibility,
Stretching duration, Range of motion, junior soccer players.
Flexibility is an indisputable component of fitness, defined as the
ability to move a joint through a normal range of motion without
producing stress to the musculotendinous unit (Chandler et al. 1990).
Stretching is important because it contributes to various physical
benefits, including improved flexibility (Borms et al., 1987; Smith,
1994), athletic performance (Handel et al., 1997; Worrell et al.,
1994), running economy (Godges et al., 1989), injury prevention (Smith,
1994; Worrell et al., 1994; Hartig and Henderson, 1999; Witvrouw et
al., 2001; Witvrouw et al., 2003), promotion of healing, and possibly
decreased delayed-onset of muscle soreness (Buroker and Schwane, 1989).
Although evidence to support the above beliefs is still limited,
stretching is widely used.
Several different stretching protocols have been proposed in scientific
literature in order to regain or retain flexibility and avoid possible
reduction in the range of motion which could impair the functional
activities of the muscle. Numerous researchers have compared stretching
techniques in an attempt to determine which protocol is the most
effective in increasing joint range of motion (Sady et al., 1982;
Thus, three stretching techniques have been developed in order to
enhance flexibility; ballistic stretching, static or passive
stretching, and proprioceptive neuromuscular facilitation. All three
methods have been shown to increase ROM immediately after stretching
(Sady et al., 1982; Smith, 1994). However, ballistic stretching does
not appear to be widely supported in literature and its use is
infrequent (Sady et al., 1982). This is due to the rapid and forceful
nature of the method that could theoretically exceed the extensibility
limits of a muscle (Bandy and Irion, 1994). Moreover, the rapid
increase in tension via myostatic stretch reflex can strain or rupture
Several authors have proposed that the proprioceptive neuromuscular
facilitation techniques are superior to the other stretching methods
for improving flexibility (Shellock and Prentice, 1985; Sady et al.,
1982). However, these techniques may require an experienced
practitioner to administer them safely, reducing their suitability for
most coaches and sports performers.
Contrarily, static stretching has become the most widely used method
for increasing ROM because of the simplicity of execution and the
reduced risks for muscle injury (Sady et al., 1982; Bandy and Irion,
1994). While most of the scientists agree that this method can improve
joint flexibility with the incorporation of passive stretching, limited
research in examining the optimal time a stretch should be sustained,
Numerous studies have investigated the duration required for a static
stretching effort to be effective in the improvement of ROM. According
to Moffatt (1993), the effective duration varies from 5 to 60 sec, but
justifications for these propositions are absent (Entyre and Abraham,
1986). Other studies compared three different techniques of stretching
(dynamic, static, PNF) and Hardy and Jones (1986) performed 6 sec of
stretching whereas Entyre and Lee (1988) suggested that stretching
efforts should last for 9 sec each. Gajdosik (1991) applied the 15 sec
duration in stretching, whereas Raab and his associates (1988) used 20
sec stretching efforts. Smith (1994) based on a review of the
literature suggested that the stretches should be held for 15 to 20
The changes in human muscle flexibility as a result of different
duration static stretching efforts have been investigated in several
studies. Borms and his associates (1987) compared the results of static
stretching on the coxo-femoral flexibility using 10, 20 and 30 sec
efforts. Bandy and Irion (1994) compared the results of static
stretching performing 15, 30 and 60 sec efforts in a program that took
place 5 times a week and lasted for 6 weeks. However, they only
examined the duration of a static stretching in one single stretching
effort and not in multiple efforts. Taylor et al. (1990) suggested that
the largest lengthening in the muscle-tendon unit takes place after 4
stretching repetitions. Further repetitions could only produce little
further improvement in the ROM. Multiple stretching efforts where
examined by Bandy (1997) and Feland (2001) and their associates, using
a 6 weeks program in which the subjects were adults aged 21-39 years
old and people aged more than 65 years old, respectively. Bandy et al.
(1997) managed to find significant improvement in the ROM of the
hamstring muscles, irrespectively of whether the stretching repetitions
were one or three for 30 or 60 sec. Feland et al. (2001) suggested that
when the stretching efforts were applied 4 times and lasted for 60 sec,
ROM was improved significantly more compared to a 4 times repetition of
15 or 30 sec.
However no effort was made in the above research to investigate the
total fit time of the stretching session. This factor may have an
impact on the improvement observed in the ROM, since the duration of a
single stretching effort of 60 sec is greater than one of 10 or 30 sec.
However, the large duration required for the improvement of ROM may be
prohibitive for people performing passive stretching and especially in
athletes, as a lot of time is spent, which eventually might be against
their training program.
Given that athletes and especially soccer players apply passive
stretching in their training, it would prove helpful to examine whether
multiple stretching efforts in a specified time can produce
positive changes in the ROM of either limb of the soccer players, in a
The aim of the present study was to compare the effects of different
duration stretching efforts as well as the effect of multiple stretches
in different total duration, on the passive ROM during hip flexion, hip
extension, hip abduction, knee flexion and ankle dorsiflexion while
controlling the total amount of the time spend in a stretching session
in junior soccer players.
MATERIALS AND METHODS
Thirteen soccer players aged 14.3 ±1.3 years old, (mean height
175.0 ±6.0cm, mean body mass 65.6 ±3.3kg) who had been training for
4.0 ±0.5 years, volunteered to participate as
subjects in the study.
Subjects performed 4 different stretching protocols for the lower
extremities with passive stretching for a total of 60 sec. Τhe first
protocol comprised of one single stretching effort of 60 sec (1x60s).
The second protocol consisted of 2 efforts for 30 sec each (2x30s). Τhe
third protocol comprosed of 4 efforts of 15 sec each (4x15s), while the
last protocol consisted of 12 efforts of 5 sec each (12x5s). The first
protocol served as the control treatment and the next three protocols
as the experimental treatments. The order in which the protocols were
exercised was random so that the results were not affected by the
learning factor. All subjects agreed to maintain their normal exercise
and activity levels for the duration of the study. Subjects were
healthy with no history of musculoskeletal or neurological disease. A
sports medicine accredited doctor examined them physically before the
beginning of the measurements. All subjects as well as their parents
were informed of the nature, purpose and possible risks involved in the
study before giving their informed written consent for participation.
Five ROMs of the lower extremities (hip flexion, hip extension, hip
abduction, knee flexion and ankle dorsiflexion with knee flexed) were
measured. The measurements were taken before and immediately after the
performance of each stretching protocol. Hip abduction was measured
with a specially constructed double protractor goniometer, and the
other movements were measured with a Myrin flexometer (Lic Rehab. 17183
Solna, Sweden). This flexometer is a modification of the Leighton
flexometer, and consist of a circular scale with a weighed pointer
controlled by gravity attached to the centre. All flexibility
measurements were made according to the Ekstrand et al. (1982) method.
The coefficient of variation for the method of goniometric measurements
was high (1.9 ±0.7%).
All measurements except ankle dorsiflexion were made on an adjustable
bench. The initial and final positions of each movement were passively
measured starting from a 0 point, as defined by the American Academy of
Orthopaedic Surgeons (1965). Maximal flexibility was defined as the
point where the joint attained to end-range. Two persons performed the
measurements. A tester who was responsible for the maximal passive
movement of the examined joint and an observer who was responsible for
the actual ROM measurement, Throughout the experiment the same
experimenter was assigned the same task. Both tester and observer were
experienced and familiar with the measurement of joint ROM. Ranges were
passively measured in lower extremity joint once on the right-side and
once on the left-side. All pre-test and post-test measurements were
taken at approximately the same time of day. No warming-up exercises
were performed prior to the initial flexibility measurements, and none
of the subjects undertook any training program or other type of
exercise during the 48 hours prior to the measurements. The reliability
coefficient of each measurement was high and has been reported
elsewhere (Zakas et al. 2003).
All subjects performed the 4 flexibility-training protocols in four
different training sessions. Each training session was separated by at
least 1 week from the next, for each subject. The stretching exercises
for all flexibility-training protocols consisted of passive lengthening
of the muscles. Starting from a maximum elongation, passive elongation
of the muscle or muscle groups, without causing pain, maintained for
60, 30, 15 or 5 sec at the position of maximum lengthening
proportionately flexibility-training protocols performed. The working
muscle groups should be adductors, iliopsoas, hamstrings, quadriceps
and soleus for both sides. Prior to the implementation of every
flexibility-training protocol active warming-up took place via
continuous jogging (120-130 bpm) for 10 min, performed in a normal
stride. Briefing sessions were co-ordinated in which visual
demonstrations and individual assistance were provided to ensure all
subjects were confident in the requirements of the program and
competent in the execution of the stretches.
The first flexibility training protocol took place for 60 sec only one
time (1x60s) for both body sides and all examined muscle groups. Τhe
second protocol comprised of 2X30 sec stretches that took place first
for the one side and then for the other side of the body. Τhe third
protocol comprised of 4X15 sec stretches and was also performed for
each side of the body, whereas the fourth protocol consisted of 12X5
sec stretches that were performed for both body sides. Recovery between
the sets in the treatment protocols lasted for 10 sec. All
four treatment protocols performed the warming-up and the stretching
exercises identically, under the direct supervision and guidance of the
investigators. The players that did not complete the treatment
protocols were exempted from the study (2 players).
A mixed within- and between- subjects 4x2x2 ANOVA model with repeated
measurements over the tests was applied for each depended variable. The
first repeated factor was the test which had 2 levels (pre, post). The
second repeated factor was the side which also had 2 levels (right
side, left side). The treatment protocol was set as the between
subjects factor which comprised of 4 levels (1x60s, 2x30s, 4x15s and
12x5s). When significant different values were found, a Scheffe post
hoc analysis was applied to determine the significance of the
relationship of the means. In addition, when significant interactions
were noted, these were further broken down using analysis of simple
main effects. Statistical significance was accepted at the 95% level
The analysis of the main effects revealed no significant differences
between the two body sides or between the treatment protocol groups,
except for the joint flexibility (hip flexion, F1,48=156.89, p=000, hip
extension, F1,48=130.80, p=000, hip abduction, F1,48=65.53, p=000, knee
flexion, F1,48=47.56, p=000, ankle dorsiflexion, F1,48=84.71, p=000),
indicating that the range of motion differs among the joints of the
lower extremities. ROM was higher during knee joint flexion and smaller
during ankle joint dorsiflexion. Additionally, no significant
interactions were observed between the joint x treatment protocol
group, the side x treatment protocol group, the joint x side or the
joint x side x treatment protocol group.
A further analysis using a paired t-test for each treatment protocol
group in each flexibility joint movement, showed no significant
differences in the joint ROM between the two body sides of the junior
players. Thus, only the results of the right side will be
A significant increment was observed for all joint ROMs (p<.01 to
p<.001) immediately after the performance of all four flexibility
training protocols of the treatment groups (Table 1). Hip flexion was
increased by 8.3 to 10.2 degrees, hip extension by 5.9 to 6.8 degrees,
hip abduction by 2.7 to 5.5 degrees, knee flexion by 3.3 to 4.7 degrees
and in ankle dorsiflexion the increments varied from 1.8 to 4.6
According to the results, significant improvement in the ROM of the
lower extremity joints is produced after the muscles undergo passive
lengthening for a total of one minute irrespectively of whether this
lengthening is performed once or using multiple stretches in sets of
This study cannot be directly compared to the results of others due to
the differences in methodology. However, the increases in ROM after the
completion of acute condition stretching exercises in different
duration concurs with the findings of Madding et al. (1987) who
compared passive strengthening of 15, 45 and 120 sec during hip
abduction to one single stretching session. Madding and his associates
also found improvements in joint ROM irrespectively if the passive
lengthening of the muscles lasted for 15 or 120 sec. It seems that
under acute conditions the critical factor for the increment in joint
ROM might be the lengthening of the muscles and not the time that they
should be kept in the lengthening position or the number of the
In short-term flexibility conditions Bandy et al. (1997) found
significant improvement in the hamstring flexibility whether the
passive stretching was performed one time or three times for half or
one minute in a 6 week stretching program, that took place 5 times per
week. Important improvements were also suggested by Roberts and Wilson
(1999) in the passive ROM of hip flexion, knee flexion and extension
irrespectively of whether the passive stretching was repeated 9 times
for 5 sec or 3 times for 15 sec a 5 weeks program.
It is accepted that during stretching exercises joint flexibility is
affected by the extensibility of connective tissue. Sapega et al.
(1981) as well as Warren et al. (1976) demonstrated that tissue
temperature can significantly influence the extensibility of connective
tissue and, therefore, affect joint flexibility. Until now, research
has focused on the influence of the increased temperature of muscles on
the improvement of flexibility as a result of stretching exercises. It
is believed that a general 5-min warming-up session should take place
first during every training session in order to make the best of all
(Beaulieu, 1981), due to its viscosity decrement (Shellock and
Prentice, 1985). In the present study the soccer players performed
several stretching exercises after a 10-min warming-up procedure.
Therefore, it is reasonable to assume that the improvements in joint
flexibility immediately after each stretching protocol were due to the
muscle elongation that occured during stretching, especially since the
general training session proceeded. However, further investigation is
required in order to completely clarify the warming up contribution to
the increments of joint ROM during stretching.
No data collected in the present study could suggest a specific
mechanism explaining the results. Connective tissue is comprised of
collagen, elastin, and ground substances which are the structures that
to limit ROM (Wright and Johns, 1960). Among these myogenic restrictive
factors, neurogenic constrains, joint constraints, skin, subcutaneous
connective tissue, and frictional constraints are included (Hutton,
1992). During stretching, only neurogenic and myogenic restrictions
might exist during voluntary control in the acute setting. Most of the
emphasis on stretching exercises used in rehabilitative medicine and
athletic training has been placed on the neurogenic component by
employing stretching techniques that are presumed to promote the level
of inhibition to the muscle undergoing stretch. It seems that in the
acute stretching session, the gains on flexibility might be due to
neurogenic and myogenic adaptations, whereas during short-term
stretching programmes, the gains on flexibility might be due to
myogenic adaptations. However, further research is necessary to provide
information on the exact mechanisms involved in improving flexibility
during acute stretching settings.
We propose that a stretching session with passive lengthening lasting
for 60 sec can constitute an important stimulus for the improvement of
lower extremity joints ROM in junior soccer players. All stretching
efforts appear effective whether they are performed only once or in
sets. Results from the present study might prove useful for players who
desire to increase their flexibility, as well as for clinicians who
incorporate passive stretching sessions in rehabilitation programs and
for coaches who incorporate the same type stretching exercises as part
of their training sessions.
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