The Effect of Stretching
Duration on Flexibility During Warming Up in Adolescent Soccer
Athanasios, Galazoulas Christos, Zakas Nikolaos, Vamvakoudis
Efstratios, Vergou Aikaterini
University of Thessaloniki
Department of Physical Education
and Sports Science
Division of Sports, Laboratory of
Dr. Galazoulas Christos,
Department of Physical Education and Sports Science,
Aristotle University of Thessaloniki,
Thessaloniki 540 06, Greece.
Tel. +302310 992233
Fax: +302310 992232
aim of the present study was to examine the effects of different
duration static stretching and multiple stretching sessions on the
passive joint range of motion (ROM) of the lower extremities of
adolescent soccer players, using a general warming up procedure or
stretching alone. Seventeen adolescent soccer players with a mean age
of 15.8 ±0.6 years, height 174.0 ±4.3 cm, body mass 66.4 ±3.4 kg and
5.0 ±0.8 years of training participated in
this study. The subjects
performed, in nonconsecutive days, three static stretching protocols on
the lower extremities muscle groups lasting for 30 seconds each. The
first stretching protocol consisted of one 30 second stretch (1x30s).
The second protocol consisted of two 15 second stretches (2x15s),
whereas the third consisted of six 5 second stretches (6x5s). All
three stretching protocols were performed twice, once after a general
warming up session and once without prior warming up. ROM was
during hip flexion, hip extension, hip abduction, knee flexion and
ankle dorsiflexion for the right and left side of the body, using a
flexometer and a goniometer. A mixed within- and between–subjects
analysis of variance with repeated measures revealed similar ROM values
between both two sides for all measured joints. No significant
differences were observed among the stretching protocols whether
up preceded the experiment or not. Further statistical analysis of the
data indicated significant improvements after all flexibility
protocols. These findings suggest that one 30-seconds static stretch on
the muscle of the lower extremities produced the same effect as two
15-seconds or six 5-seconds stretches over a flexibility training
session and these effects are not affected by warming up
Key Words: Flexibility,
Warming-up, Range of motion, Adolescent soccer players
Muscle shortness and muscle contractures restrict the normal muscle
action and are therefore considered as limiting factors for the range
of motion. Performing stretching systematically could prevent such
detrimental effects. Stretching can positively affect the everyday
functional activities of an individual and narrow the risks for injury
It has been proposed (Garrett 1990) that stretching exercises may alter
the viscoelastic behaviour of the muscle-tendon unit and thereby reduce
the muscle-tendon injury risks. Muscle-tendon extensibility has been
shown to increase during elevated temperatures, thus, it is commonly
recommended that a warm-up session precede any stretching regimen
(Garrett 1990; Smith 1994). Increased tissue temperature can be
achieved relatively soon after the initiation of exercise and 10-min of
warming-up exercise has been suggested as a sufficient preparation for
muscle performance (Astrand and Rodahl 1986). According to
Beaulieu (1981) a minimum of 5 minutes of gradually progressive
muscular exercises such as brisk walking, jogging, or cycling should
precede each stretching session in an attempt to warm the muscles and
the connective tissue prior to stretching. Stretching after warming-up
has been found to increase the ROM of the lower extremities
(Wiktorsson-Moller et al. 1983; McNair and Stanley 1996), however,
according to Wiktorsson-Moller and his associates (1983), warming-up on
the cycle-ergometer for 15 minutes only increases the ankle range of
motion and not the hamstring or the quadriceps ROM.
A short-term stretching program that lasted for 6-weeks (Knight et al.
2001) demonstrated improvements on the ankle dorsiflexion, using a
stretching protocol and active warm-up exercises prior to the
stretching. The Williford et al. (1986) study that lasted for 9 weeks
investigated the effects of jogging prior to stretching compared to
stretching alone on the shoulder, trunk, hamstring, and ankle
flexibility. Researchers concluded that both methods were equally
effective in increasing ROM and flexibility. Although connective
tissue properties have been shown to change with increased temperature
in animal models (Sapega 1981; Warren et al. 1976; Strickler et al.
1990), stretching alone appears to improve maximal joint ROM in humans
(Taylor et al. 1995; Knight et al. 2001). However, it still remains
unclear whether stretching alone can alter ROM in human subjects during
Improvements in flexibility have also been associated with the amount
and the duration of the applied force during stretching (Sapega
1981). Several authors have made suggestions regarding the
appropriate duration a stretch should be maintained, in order to be
effective (Beaulieu 1981; Sady et al. 1982). Nevertheless, little
scientific research exists on the duration and the number of
repetitions of stretches needed to exert beneficial effects. Madding et
al. (1987) examined hip abduction range of motion as a result of
stretching for 15 seconds, 45 seconds, or 2 minutes. All those who
underwent stretching exhibited significant improvements in flexibility
over controls that did not stretch, but stretching for longer than 15
seconds did not continue to improve flexibility. Borms et al. (1987)
compared the results of static stretch on hip flexibility for 10, 20
and 30 seconds. All three experimental groups increased hip flexibility
but exhibited no significant between-group differences. Bandy and Irion
(1994) recorded no increments in flexibility when stretching lasted
from 30 to 60 seconds.
However, all the above scientists experimented with the duration of
static stretching in one single effort and not in multiple ones. Taylor
and his associates (1990) reported that maximal benefit on flexibility
occurs when each muscle group was stretched for four times; further
stretching did not result in significant increases in muscle length. In
an attempt to determine the most effective method for improving joint
flexibility, Wiktorsson-Moller et al. (1983) suggested that five to six
repetitions are sufficient to increase hip, knee, and ankle ROM.
Multiple repetitions were also used by Bandy et al. (1997) in adults
aged 21-39 years old, as well as by Feland et al. (2001) in elders aged
more than 65 years old, in a stretching protocol that lasted for 6
weeks. The first experiment revealed significant improvements in ROM
whether stretching was repeated three times for 30 seconds each or
three times for 60 seconds each. Feland et al. (2001) recorded
significant improvements in ROM when stretching was performed four
times for 60 seconds each, compared to four times for 15 or 30 seconds
each. However, no effort was done in these studies to control the total
stretching time, while manipulating stretch duration. This factor could
have a different impact in the improvement of joint ROM during passive
Considering that many athletes and especially soccer players tend to
perform stretching without prior warming up, and given that the time
spent in each stretch is the minimum for most athletes, it would be
interesting to examine the effects of passive stretching on the
improvement of joint ROM, when multiple stretching efforts are
performed in the same duration during active warming up procedures
prior to stretching or when stretching is performed alone.
The aim of the present study was to investigate the effects of passive
stretching duration, and multiple stretches in different duration, on
the ROM during hip flexion, hip extension, hip abduction, knee flexion
and ankle dorsiflexion while controlling the total amount of the time
spent in a stretching session, in adolescent soccer players with
stretching exercises being performed after and without a general
MATERIALS AND METHODS
Seventeen adolescent soccer players aged 15.8 ±0.6 (Mean ±SD) years old with 5.0 ±0.8 years of training volunteered to act
as subjects for the present study. Subjects’ height was 174.0 ±4.3cm and their body mass was 66.4 ±3.4kg.
The experimental protocol consisted of three different passive
stretching programs of the lower limbs, of total duration 30 seconds
each. All three programs were performed twice, the first time without
any warming up procedure and the second time after a general warming up
session. Τhe first stretching program consisted of one 30-second
stretch (1x30s). The second stretching program consisted of two
15-second stretches (2x15s), whereas the third consisted of six
stretches that lasted for 5-seconds each (6x5s). The stretching
programs were performed solo as the control measurements and the
stretching programs preceded by warming up sessions formed the
experimental measurements. Between each set of the last two stretching
programs there was a 10 second rest interval. All three programs were
performed in exactly the same manner, whether warming-up preceeded
stretching or not. The active warming-up session in the flexibility
training programs lasted for 20 minutes and comprised of continuous
jogging at a normal stride with a mean heart rate of 120-130 bpm.
Intensity was estimated for all subjects via telemetry (Sport Tester,
Finland). All the stretching groups performed the stretching exercises
identically, under the direct supervision and guidance of the
The programs were performed in random order so as to eliminate the
effects of familiarity on the results. The subjects agreed to maintain
their normal exercise and activity levels for the duration of the
study. All 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. Before
participating in the study, 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.
All subjects performed the flexibility-training protocols in 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 without causing pain maintained for 30, 15 or 5 sec at the
position of maximum lengthening according to the flexibility program
performed. The working muscle groups should be adductors, hip flexors,
hamstrings, quadriceps and soleus of both body sides. Briefing sessions
were co-ordinated in which visual demonstrations and individual
assistance was provided to ensure all subjects felt confident with the
experiment and competent in the execution of the stretches.
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 performed prior to and immediately
after each stretching protocol. Hip abduction was measured with a
specially constructed double protractor goniometer, and the rest of the
movements were measured with a Myrin flexometer (Lic Rehab. 17183
Solna, Sweden). This flexometer is a modification of the Leighton
flexometer, and consists of a circular scale with a weighed pointer
controlled by gravity attached to the centre. All flexibility
measurements were performed according to the Ekstrand et al. (1982)
method. The coefficient of variation for the method of goniometric
measurements was high (1.9
All measurements except for ankle dorsiflexion were held 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 examiners
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 familiarized with the measurement of
joint ROM. Ranges were passively measured in the lower extremity joints
first on the right-side and then on the left-side of the body. All
pretest and posttest measurements were taken at approximately the same
time of day. Νo warning-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.,
A mixed within and between subjects 3x2x2x5 ANOVA model with repeated
measurements over tests was applied for each depended variable. The
first repeated factor was the joint and this had 5 levels (hip flexion,
hip extension, hip abduction, knee flexion and ankle dorsiflexion). The
second repeated factor was the leg and this had 2 levels (right and
left leg). The third repeated factor was the warm-up and this had 2
levels (stretching alone and stretching preceded by warm-up). The
between subjects factor was the treatment protocols and this had 3
levels (1x30s, 2x15s, and 6x5s). When significant differences 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 broken down further by
using analysis of simple main effects. Statistical significance was
accepted at the 95% level (p<.05).
The analysis of the main effects revealed no significant differences
between the two legs, for either control or experimental measurements
(p>0.05), indicating that the range of motion did not differ between
the two body sides in the three testing programs. Additionally, no
significant interactions were noted for joint x treatment protocol
group, for leg x treatment protocol group, for joint x leg or for joint
x leg x treatment protocol group.
A further analysis by paired t-test that used 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 players. Thus, only the results of the right side will be
A significant increase was observed in all joint ROMs (p<0.01 to
p<0.001) immediately after flexibility training protocol in all
three-flexibility treatment protocols, when warming up preceded
stretching (Table 1) and without warming up (Table 2). The increments
in degrees were similar with or without warming up. During hip flexion
the increments varied from 8.4 to 10.1 degrees, during hip extension
from 5.9 to 6.6 degrees, during hip abduction from 4.9 to 5.4 degrees,
during knee flexion from 4.0 to 4.2 degrees and during ankle
dorsiflexion the increments varied from 2.8 to 4.0 degrees.
Our study was designed in order to obtain a more thorough understanding
of whether elongation of a warmed-up muscle improves ROM, when the
passive stretching lasts for half a minute or when the stretches are
repeated more times in the same total duration, as well as how joint
ROM is affected when stretching is performed with and without warming
up. According to the data, in the treatment that lasted for 30 seconds
or less, active warm-up prior to stretching or stretching alone
achieved similar results in increasing ROM in all measured joints of
the lower extremities.
In unpublished findings we found similar results during acute
flexibility training conditions in adolescent soccer players when after
a general warming up subjects performed static stretching for 30
seconds one time, 15 seconds for two times and 5 seconds for six times.
Regarding the 30 second stretch that was performed once, the results of
our study are in conjunction with previous results obtained in
sort-term flexibility training programs. Borms and his colleagues
(1987) demonstrated significant increases in hip flexibility ROM when
subjects performed 30, 20 and 10 seconds single static stretching for
10 weeks, twice per week. Bandy and Irion (1994) as well as Bandy et
al. (1997) found significant improvements in the ROM, when static
stretching of the femoral lasted for 30 seconds.
Scientific data is conflicting regarding the ideal number of stretches
needed in order to obtain the maximum gains in joint ROM. The present
study demonstrated similar increments in joint ROM when the stretches
were performed once, twice or six times in a total duration of 30
seconds. Similar results have been published elsewhere (Bandy et al.
1997) in the hamstring muscles ROM, irrespectively of whether the
stretches were performed once, or three times for 30 or 60 seconds.
Other studies (Roberts and Wilson 1999) also demonstrated similar
increments in passive ROM during hip and knee flexion and extension,
irrespectively of whether the static stretches were performed three
times for 15 seconds or nine times for 5 seconds each, in a 5 week
static stretching program. Taylor and his associates (1990) recorded
the greatest gains in ROM of animal subjects with 4 repetitions of the
stretches, whereas Wiktorsson-Moller et al. (1983) suggested that five
to six repetitions are sufficient to increase hip, knee, and ankle ROM.
On the contrary, a study on elderly subjects (Feland et al. 2001)
concluded that a 60 seconds stretch was more effective in increasing
knee extension ROM than a 15 or 30 second stretch of the same total
duration. This might be due to the fact that elderly people need longer
duration stretches in order to improve ROM, since joint mobility
declines with increasing age, acknowledging that the results should be
applied only to a similar age group. Hence, it appears that the
increments in joint ROM is irrespective to the frequency of the
elongation performed by the muscles during static stretching, however,
further research is needed in order to clarify the issue.
The results of the present study demonstrated similar increases on the
flexibility when static stretching was performed after or without a
general active warming-up session. Similar results have been published
in previous studies conducted either in acute stretching conditions or
after a short-term stretching program. Taylor et al. (1995) reported
increments on hamstring ROM when the stretching protocol was performed
without prior stretching but with passive warn compresses on the
hamstring muscles. McNair and Stanley (1996) also demonstrated
increases on the dorsiflexion ROM using a stretching protocol without
warming up and a stretching protocol that included running prior to the
stretches. Increases in hip flexion, hip extension, hip abduction, knee
flexion and ankle dorsiflexion ROM were demonstrated by
Wiktorsson-Moller et al. (1983) after a stretching protocol that was
preceded by a 15-min warming-up session on the cycling ergometer. In a
short-term-stretching program, Knight et al. (2001) demonstrated
increases on ankle dorsiflexion ROM when a 6-weeks program was
performed with stretching alone and with active exercise warming-up
prior to the stretching. Similar results were also published by
Williford et al. (1986) concerning shoulder, trunk, hamstring and ankle
flexibility, when a 9-week stretching program was performed with and
The increased muscle temperature during warming-up does not appear to
improve flexibility when it is not associated with stretching exercises
or when it does not include active muscle elongation (Zakas et al.
2003) hence, passive heat alone cannot cause any increase in hip range
of motion (Henricson et al. 1984). Shrier and Gossal (2000) reported
that contrary to popular belief, warming-up performed without
stretching does not increase range of motion. Most of the research in
this area has been performed on animals using passive warming devices
such as heat lamps, whereas in human studies, physical activity is the
most popular means for warming the muscles. The belief that warming-up
is associated with improvements in flexibility derives from animal
experiments in vitro. These studies have demonstrated that tissue
temperature can significantly alter the extensibility of connective
tissue and, therefore, affect joint flexibility (Sapega et al. 1981;
Warren et al. 1976). The impact of connective tissue as a stimulus for
stretching seems however overestimated, whereas the myogenic
constraints in determining ROM appears to be underestimated (Hutton
1992). It has been suggested (Hill 1968; Magid and Law 1985) that in
still sartorius muscles of the frog a proportion of the cross-bridges
are connected and during the muscle’s elongation these are detached.
The improved joint flexibility of the soccer players performing the
stretching exercises only, could be attributed to the myogenic
constraints instead of the connective tissue lengthening, since similar
improvements in the ROM have occurred when warming up preceded the
stretches. These improvements appear to be the results of static muscle
lengthening. According to Van der Poel (1998) muscle length is
completely dependent on how the muscle is used during movement.
However, further research is needed in this area in order to further
identify the mechanisms involved in improving flexibility, since the
role of connective tissue in affecting flexibility appears to be
The results of the present study suggest that the improvements in joint
ROM of the lower extremities appear to be irrelevant to the frequency
of muscle elongation via passive stretching. Warming-up the muscles
prior to stretching does not necessarily improve flexibility in
adolescent soccer players. These findings could be helpful to players
who desire to increase their flexibility, as well as to the coaches who
incorporate static stretching activities in their training programs.
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